Sunday, August 31, 2008

Turf - Biostimulants and Stress

Use of biostimulants in turf has been shown to have some positive effects in research. The following is some basic information on how they work to reduce stress.

Plant Stress and Biostimulants

Under favorable growing conditions, plants synthesize hormones in sufficient amounts and do not require additional supplements. However, when plants are subjected to various stresses (i.e., mechanical, chemical or environmental) the normal production of these important plant hormones can be compromised. Research studies have shown that biostimulants improve plant quality, especially when they are under harsh, stressful conditions.

Research at Penn State and Virginia Tech have shown that root growth enhancement (root length and root dry weight) of plants supplemented with biostimulants occur during the greatest stress periods of the summer. In addition, improved root strength appears to be a major benefit of biostimulants. Improved mechanical stress tolerance can be of particular value on athletic fields. Further studies have also shown that biostimulants have increased chlorophyll content and photosynthetic capacity of plants, especially during periods of stress.

Tests have shown the common turf disease Dollar Spot can be suppressed by up to 50% by some biostimulants. However, it is important to be aware that during non-stress periods, control plots (where no biostimulants were added) showed no significant differences in the above tested qualities when compared to plants receiving biostimulants. Therefore, biostimulants can prove most important to plants when their functional processes are disrupted by less than favorable growing conditions. They can be particularly important when managing high valued ornamentals.

Some typical examples where biostimulants are most practical include golf courses, sod farms, athletic fields, and during the transplanting of small trees and shrubs. They are also of use when managing exclusive residential and commercial turf areas when the quality of turf needs to be maintained during stressful periods. In many respects, biostimulants and turf endophytes are similar in their abilities to perform as “insurance policies” by improving stress tolerances of the grass plants. Little value is gained when all conditions are optimal, but when less than ideal situations occur, then the endophytes and biostimualnts can enhance plant functions and reduce the loss of turf/plant quality.

Reprinted in part from "Unraveling Some of the Mysteries of Plant Biostimulants" by Steven K. Rettke, Ornamental IPM Program Associate, in the September 7, 2008 edition of the Plant and Pest Advisory, Lanscape, Nursery, and Turf Edition, from Rutgers University.

Turf - Biostimulants

The following is summary of some research from Virginia on the use of biostimulants in turf as well as basic information on biostimulants.

Biostimulants, plant biochemical regulators, and plant growth regulators are terms used to describe materials other than fertilizer, that when applied to plants in small quantities effect biochemicals that influence the physiological processes within plants. Examples are materials that contain high percentages of hormones. Hormones are designated organic compounds such as auxins, cytokinins, gibberellins, abscisic acid, and ethylene that influence plant function. Auxins, gibberellins and cytokinins stimulate growth while abscisic acid and ethylene are inhibitors of growth. The use of these stimulating hormones as foliar-applied materials to manipulate plant conditioning is currently pursued in cultural aspects of turfgrass management.

The biostimulant studies at Virginia Tech initially were attempts to enhance cool season turfgrass sod production. Results from research concluded in 1979 in our department showed applications of a synthetic cytokinin at 24 gm per acre, significantly increased soybean seed yield generated interest in evaluating cytokinin treatments in our on-going turfgrass sod enhancement project.

After several attempts to utilize commercial seaweed products as the source of cytokinins, positive results were realized when seaweed extracts were obtained from seaweed processes at low temperatures. Results from these seaweed extracts gave more consistent results that the synthetic cytokinins. It was concluded that in addition to cytokinins, seaweed supplied other compounds such as auxins and amino acids to provide more positive responses. More consistent results were eventually obtained when humic acid was applied with seaweed extracts, indicating that the auxin activity of the humic acid enhanced the hormone activity supplied by seaweed.

In the mid-1980’s, Dr. Petrovic of Cornell University, indicated that enhanced rooting of Kentucky bluegrass was observed when a triazole fungicide was applied. Our subsequent research confirmed this observation. Since then we have documented that in addition to treatments with seaweed, humic acid, and triazole fungicide, applications of amino acid or trinexapae ethyl have biostimulant effects. Most recently we have detected biostimulant effect when silicate was applied to creeping bentgrass.

Various graduate student projects over the past ten years showed that application of seaweed, and humic acid to cool season turfgrass, conditioned the grass to enhance toleration of salinity, drought, nematode invasion, disease infestation, herbicide toxicity, and shade. One doctoral student obtained data showing that bermudagrass was affected less by chilling temperatures when treated with cytokinin and iron.

The measurements of turfgrass growth provided strong evidence that, indeed, plant growth regulators did condition turfgrass to better tolerate stressful environments.

The antioxidant content of turfgrasses can be stimulated with applications of biostimulants. The application of humic acid (HA) plus seaweed extract (SE) to creeping bentgrass will significantly enhance the antioxidant, superoxide dismutase (SOD), activity. The enhance vigor of bentgrass associated with antioxidant content can be demonstrated. Infection of Dollarspot disease is
decreased with the increase of antioxidant content of the bentgrass leaves.

Results of our studies strongly suggest that the benefits derived from applications of biostimulant materials to turfgrass results from the stimulation of antioxidant produced in the grass. Biostimulants enhance gene expression under different environmental stresses. As more is learned about he biostimulant influence on turf, the better cultural tools the turfgrass manager has at his disposal.

Extracted in part from "BIOSTIMULANT PRODUCTS: WHAT RESEARCH HAS SHOWN: HOW THEY WORK", by R. E. Schmidt, Professor, Dep. of Crop and Soil Environmental Sciences, Virginia Tech, Blacksburg, Virginia.

Saturday, August 30, 2008

Landscape - Pictures of Drought Effects on Landscape Plants

The following are pictures of landscape plants with severe drought symptoms.

Leaf scorch and leaf drop on Japanese maple.

Leaf scorch on dogwood.

Leaf senescence and drop on Virburnum

Gordon Johnson, Extension Horticulture Agent, UD, Kent County

Landscape - Drought Effects on Landscape Plants

The following are some comments on the current drought effect on landscape plants in the Region from the University of Maryland TPM/IPM weekly report.

We had major droughts in 2006 and 2007. Now we are experiencing a drought again in August. There are parts of the Eastern Shore that are claiming the drought this summer is even worse than last summer’s drought (Delaware is not as bad as last year but we still have a serious drought in most of the state). We are getting reports of Leyland cypress with trunk cracking and oozing from cankers. Leyland cypress commonly shows these problems under severe drought stress. Carroll County and Baltimore County have many red maples that are showing premature red color of foliage. (many trees in Delaware are also starting to go into senescence early this year). This is very common in a lot of neighborhoods. Several sites I have visited showed severe scorching of foliage. I visited a new home community in Carroll County to look at dying maples. The site had a large planting of maples and conifers on embankments. The plants were under severe stress and many of the plants were well on their way to death. The planting was installed over the last 3 years and the plants were not being watered and left to fend for themselves. This is a good way to guarantee the death of the trees. In central Maryland we are seeing many scorched leaves on oaks, zelkova, London plane, red maples, and Japanese maples. Cherry trees have whole trees that are turning pre-maturely yellow and dropping foliage in August from the drought. (Similar comments can be made for Delaware). Plants in parking lot islands are really suffering with a lot of leaf scorch and dieback. Red oaks, white oaks, and pin oaks are showing branch dieback and in some cases death of trees from 3 years of drought stress. We visited a site in Wheaton and viewed large American beeches, red oaks and white oaks with severe branch dieback from drought injury. The impact of the drought can be devastating to large old, mature oaks. It is rather late to start watering at this point in the season but if the drought period continues I would suggest getting water into the root zones of valuable trees using a trickle irrigation system. The long range prediction is for a colder than normal winter and if the plants go into the winter under drought stress we can expect winter injury.

Reprinted with added comments from the August 29, 2008 edition of the TPM/IPM Weekly Report for Arborists, Landscape Managers & Nursery Managers from the University of Maryland Cooperative Extension.

Friday, August 29, 2008

Plants for Delaware Landscapes - Summersweet Clethra

Summersweet Clethra is a native shrub well adapted for Delaware landscapes. The following is more information.

Clethra alnifolia, summersweet clethra, is a native shrub that grows 3 to 8 feet tall depending on the varieties and the soil moisture. As a native, this shrub lives on the edges of the woods near streams and other wet areas. It can remain a single shrub or it can sucker and become an island of shrubs. The fragrant flowers in pure white, pale pink to bright pink are the biggest draw, but the rich green foliage that turns golden yellow in the fall is also an important element in design. Color, texture and fragrance aside, the summersweet clethra is very pest and disease free. In the modern landscape, the summersweet clethra is great in a shrub border in the sun and shade. It still prefers moist soil conditions, so an irrigation system or soaker hoses in the shrub border would be important to the health of the plants, especially for the plants in the sun. The smallest cultivar is ‘Hummingbird’, growing only 3 feet tall and forming colonies of plants. The flowers are pure white and very fragrant. The leaves a dark rich green that turn to gold in the fall. Other excellent white flowering fragrant cultivars include ‘September Beauty’, ‘Paniculata’, and ‘Chattanooga’. The lightest pink is ‘Fern Valley Pink’, the brightest pink is ‘Ruby Spice’, and ‘Hokie Pink’ is a medium pink.

Information from Ginny Rosenkranz, Extension Educator, Wicomico/Worcester/Somerset Counties, University of Maryland, in the August 10, 2007 edition of the TPM/IPM Weekly Report for Arborists, Landscape Managers & Nursery Managers, University of Maryland Cooperative Extension.

Turf and Landscape - Some Mole Control Products

The following is information on some mole control products available on the market.

Most products tend to work as a repellent based on castor bean oil as the active ingredient. Many have been tested on the Eastern mole and appear effective on that species, which is our predominant species. These products need to be sprayed (garden hose-end applicator) or granule applied (through a spreader) at regular intervals to maintain a barrier that repels these small mammals to your neighbor. The repellent type products are marketed as natural and safe, but information about effectiveness is mixed. Mole-Med may have changed its name to Chase due to new ownership and is available in both liquid and granular form. Other repellents include Scoot Mole, Shotgun Mole & Gopher Repellent, Mole Max, Mole-Out, Whole Control, Schultz Garden Safe Mole Repellent and many others. All are based on some percentage of caster bean oil as the active ingredient. Formulations vary with each, sprayable or granular. These products will generally treat 5,000 to 10,000 square feet and last one to three months. Many of the ready-to-use products are costing around $15 to $20 per item.

More recent products include several baits that seem to be very effective if applied properly to active feeding runways. See below on how to locate active feeding runways. Wear rubber gloves whenever handling and placing baits in tunnels.

Two products called Kaput Mole Control (Lesco) and Moletox Baited Gel (Bonide) are water-based gels containing warfarin (0.025 percent) as the active ingredient and flavored like their primary food, earthworms. It is best to locate the active runways as you would for trapping (next page) before placement of the bait. They are both packaged in syringe-type applicators with which the bait is injected into the tunnels. Usually figure around $20 per syringe.

The latest registered mole bait is Talpirid (Bell Laboratories), a bromethalin-based product that actually looks, feels and tastes (so they say) like earthworms. Each worm contains a lethal dose of bromethalin. It is the only mole bait that has submitted efficacy studies to EPA. This product appears to be a higher cost item at around $50 per box 20 worms.

MOTOMCO Mole Killer is a bait similar to Talpirid, but in a more affordable package of eight worms for around $18 to $22. Gemplers, QC Supply and MFA are carrying this product.

We can also find some poisonous granular baits of a different class as compared to the previous baits mentioned. These include Moletox II and Mole-Nots, both of which are cracked corn baits laced with two percent zinc phosphide. One teaspoon of material will treat an active tunnel. While some results indicate excellent control with these products, keep in mind that moles do not prefer grains in their diet.

Another granular bait is Mole Patrol Bait. Mole Patrol is a ready-touse, pelletized bait highly palatable with unique attractants. This product cont a ins chloropha c inone , a historically sound anticoagulant of the rodenticide industry. Some studies indicate 100 percent control of moles. A one-pound container can be purchased for less than $10.

Trapping is still one of the most efficient means of controlling moles and anyone can be successful by following a few simple steps. If you have the network of shallow runways used for feeding, then you can do some effective trapping. First, you need to locate active feeding runways. Second, select a tunnel to set your trap. There are several types of traps to choose from and simply follow the instructions of the manufacturer to set the trap. The Nash trap (wire hoop type) and the Victor Out O' Sight trap (scissors type) do work, but seem to be more diffi cult to set. The Victor Harpoon or Gig type trap has been the most successful trap for us at the MU Turfgrass Research Center.

Information from "Dealing with Those Pesky Moles and Voles" in the Missouri Environment and Garden News for Missouri's Gardens, Yards and Resources, March 2007

Thursday, August 28, 2008

Landscape - Late Summer Premature Leaf Fall

Late summer premature leaf fall is a common occurance in some trees and shrubs. The following is more information.

Tuliptrees (Liriodendron tulipifera) are exhibiting yellow leaves at this time – far earlier than the typical fall defoliation. This phenomenon occurs in a number of species, but tuliptree and river birch are two plants in which late summer leaf drop is common.

Leaf drop in tulip tree. Photo courtesy of Janna Beckerman, Purdue University.

The leaf drop is a response to low soil moisture levels near the end of the growing season. When soil moisture levels are low, there is not enough water to support all of the leaves on the tree. Rather than create a situation where all the leaves are supplied with a limited amount of water, trees and shrubs will often “self-prune” or “self-thin” their canopies so the remaining leaves are supplied with adequate water. This keeps the tree in overall better health than it would be if it tried to retain all of its leaves.

Early yellowing or other coloration could be a result of environmental stress or pest or disease, so it is important to check your plants thoroughly. However, trees that partially defoliate are not necessarily in trouble.

Adapted from "Late Summer Leaf Fall in Trees" by Mike Mickelbart, Dept. of Horticulture & Landscape Architecture and Janna Beckerman, Dept. of Botany & Plant Pathology, Purdue University, Purdue Plant and Pest Diagnostic Laboratory.

Landscape and Nursery - Glyphosate Mistakes This Year Can Show Up Next Year

Glyphosate herbicide (Roundup and and may others) is a systemic that is very good for controlling weeds around woody plants. However, there is a potential for woody plants to take up glyphosate in certain situations. A fall mis-application may not show any affect until next year at leaf out. The following is some more information.

Herbicide application must be done very carefully around landscape plants. Special care must be taken with broad-spectrum herbicides (those that will kill a wide range of plants). Roundup (glyphosate) is a broad-spectrum, systemic herbicide. Simply put, this means that Roundup can kill a lot of plants because the plant takes up the herbicide and transports it to the roots and other parts of the plant. This is why Roundup is such an effective herbicide. While many herbicides do damage to the parts of the plant they come in direct contact with, Roundup actually “penetrates” the entire plant and kills it to the roots. This is great if you are trying to control dandelions, but not so great if you accidentally spray your trees and shrubs with Roundup.

In one nursery, crabapple trees were slow to leaf out and when they did, the leaves were small and distorted. These symptoms are classic herbicide damage symptoms. Roundup is used at this nursery to control a wide range of weeds within the rows. However, the nursery manager hadn’t sprayed any herbicides since last year. So what happened? Most likely, the trees took up the Roundup last year, but underwent fall dormancy, and didn’t show symptoms right away. The Roundup would have been transported to various parts of the plant, including the roots. When the trees leafed out the following year—that’s when the damage became evident.

There are several potential entry points for herbicides such as glyphosate. If spraying is done on a windy day, herbicide might drift onto the leaves. When looking around the nursery, however, most trees were not affected. If drift was the problem, you would expect to see many different species showing symptoms. In the nursery in question, species in two genera were showing very dramatic symptoms - Prunus and Malus. Why only these two species? These species have a tendency to send up suckers. If Roundup was sprayed in late summer or fall when suckers were present, the herbicide could have been taken up, transported around the plant, and when the trees break dormancy, the damage is apparent. Green bark is a point of entry and suckers often have green bark. Prunus and Malus species also have thin bark, especially on young trees. It is therefore plausible that young trees with thin bark might be susceptible to this point of entry. Certainly, trees with fresh damage to the bark or recent prunning wounds will also take up glyphosate. It is important to think about all potential entry points for herbicides when spraying.

Adapted from "Residual Roundup Damage" by Michael Mickelbart and Mike Dana, Horticulture & Landscape Architecture, Purdue University and Janna Beckerman, Botany & Plant Pathology, Purdue University.

Wednesday, August 27, 2008

Landscape - European Hornets Very Active Now

We have had samples of European hornets come into the office recently. This is the time of the year that these hornets change their feeding habits and can attack plants in the landscape. The following is more information.

The European hornet is a large brown heavy-bodied wasp with yellow and orange markings. It prefers to nest in hollow trees. Normally, European hornets feed on other insects - caterpillars, grasshoppers, flies, etc. At this time of year, they look for carbohydrates and begin to attack fruit and trees and bushes (especially ash and lilac). The hornets can chew into fruit and chew off the bark and girdle branches as they create wounds from which they collect sap. European hornets have a long workday, they will continue to fly into early evening so damage occurs over a short period of time.

Control is difficult and involves finding nests in the area. If nests are found, they can be treated with insecticides such as Sevin or numerous pyrethroids. Landscape sprays are usually ineffective.

Adapted from "EUROPEAN HORNETS HITTING FRUIT AND TREE BARK" By Lee Townsend in the current edition of the Kentucky Pest News from the University of Kentucky, College of Agriculture.

Landscape - Watering Trees and Shrubs

With the current drought in mid-state it is critical to water trees and shrubs to prevent premature defoliation

While many homeowners are diligent to keep their lawns watered and green, trees and shrubs often get ignored. Reducing stress to trees and shrubs this time of year is critical. As we go into the fall, trees are shifting internal resources and undergoing physiological changes that will enable them to withstand the rigors of the winter to come. If plants are subjected to severe stresses now, they will be more predisposed to various winter injuries. With this in mind, irrigating trees and shrubs is important in landscapes.

Give good, long soakings rather than frequent light waterings. A typical rule of thumb is to provide at least one inch of irrigation per week. How many gallons of water this translates into depends on the size of the tree. If we measure the width of crown spread of a tree we can calculate the area under the drip line. We can then figure the volume of water needed to cover this area with one inch of water.

Increase the irrigation amount as temperature soar. The one inch per week is a good rough guide but peak evaporative demand can approach three inches per week in Delaware during extremely hot summer weather.

Apply mulch properly. Mulching is the best way to conserve precious soil moisture in the landscape.

Use irrigation bags on newly established trees. Gator bags are designed to provide about 15 gallons of water over several hours, providing an easy way to ensure a slow steady watering. Gallons of water needed to provide 1 inch of irrigation under the dripline of trees of various sizes

Don’t allow water to run-off. Water that runs off is wasted water. If you’re watering by hand and notice water running off, move from tree to tree to allow water to soak in before resuming watering.

Wilting leaves, leaf scorch, dropping leaves and drooping leaders in conifers are signs of water stress. If using overhead sprinklers, some experts argue against watering late in the evening due to possible disease problems associated with wet foliage. Morning is the best time to water.

Adapted from the Michigan State University Landscape Alert Newsletter.

Tuesday, August 26, 2008

Greenhouse, Nursery, and Landscape - Great Publication With Conversion Tables

The University of Georgia Extension has a great publication with conversion tables for horticultural applications. The following is more information and a link.

Conversion Tables, Formulas and Suggested Guidelines for Horticultural Use

By, Bodie V. Pennisi, Gary L. Wade, Melvin P. Garber, Paul A. Thomas and James T. Midcap, Horticulture Department, University of Georgia

Pesticide and fertilizer recommendations often are made on a pounds-per-acre or tons-per-acre basis for field production. However, greenhouse and nursery operators, landscape professionals and orchardists often must convert these recommendations to smaller areas, such as row feet or square feet per tree or per pot. Pints, cups, ounces, tablespoons and teaspoons often are the common units of measure. Metric units of measure can further complicate conversion. This publication is designed to help growers make these calculations and conversions and to provide other data useful in the management, planning and operation of horticultural enterprises. A number of formulas for calculating fertilizer application rates on a parts-per-million basis are given. Tables for fertilizer injector calibration using a conductivity meter, as well as pre-plant application rates for various soil mix components and amendments, also are provided. A brief explanation of how each table is used is provided.

Link to the publication:

Greenhouse and Nursery - Check your Fertilizer Injectors

You should check your fertilizer injectors before each growing cycle for proper function. The following is some more information.

This is also a good time to check your fertilizer injector to be sure it is working correctly. To do this, take a fertilizer sample from the end of the hose the next time you fertilize and put it in a clean plastic container for testing. Test the sample using a conductivity meter or send a sample to the University of Delaware Soil Test Lab.

1) Test and record the conductivity of the water to be mixed with the fertilizer.

2) Test the conductivity of the fertilizer and water mixture.

3) Subtract the water conductivity determined in #1 above.

4) The result is an accurate indication of how much fertilizer is present (the higher the conductivity means more fertilizer).

Fertilizer companies and suppliers often can provide a chart relating conductivity to parts per million concentrations of their various fertilizers. Ask your fertilizer company for their electrical conductivity chart and compare your fertilizer reading to the chart.

For example, a 100 ppm solution of 20-20-20 from company A had a corresponding meter reading of 0.41, from company B the meter reading was 0.46. A 100 ppm 15-0-15 solution was 0.69 with one company and 0.76 with another company.

Information taken in part from Floriculture Timely Topics from UMASS Extension.

Monday, August 25, 2008

Drought Stressed Trees and Shrubs

We are seeing signs of drought effects on trees and shrubs across mid-state now. The following are some thoughts on the current situation.
  • Premature leaf drop is occurring in drought stressed trees and shrubs due to the drought condition. With the drought in 2007 and now stress in 2008, expect long lasting effects. Trees and shrubs that have been severely stressed for two years in a row will have much reduced food reserves due to lowered photosynthesis. Winter survival may be affected and you may see more trees and shrubs that do not leaf out properly in the spring.
  • Drought also reduces the amount of defensive chemicals that stressed trees and shrubs can produce making them more prone to damage from insects and diseases. Late season borer damage would be an example.
  • We have very limited subsoil moisture reserves in many areas. This will be a concern as we go into the fall. Root death may occur and this can lead to increase in root rots over the winter when rains do occur.
  • It is critical to water stressed trees and shrubs before leaf drop occurs. Water deeply - shallow watering will not help plants recover sufficiently. Limited rainfall (less than 0.5 inch) also will not be enough and additional water will be needed.

Gordon Johnson, Extension Horticulture Agent, UD, Kent County

Full Drought in Kent and Sussex Counties

We are now in full drought in Kent and Sussex counties with little rain in sight. Weather patterns have not been conducive even for scattered thundershowers. The following are some August rainfall totals across Midstate Delaware.

Smyrna 0.05 inches
Dover 0.14 inches
Kitts Hummock 0.35 inches
Viola 0.84 inches
Sandtown 0.21 inches
Harrington 0.48 inches
Milford 0.23 inches
Ellendale 0.11 inches
Blackbird 1.03 inches
Townsend 0.22 inches
Bridgeville 0.01 inches

Trees and shrubs that are not being irrigated are dropping their leaves, non-irrigated turf is dormant.

Gordon Johnson, Extension Agent, UD, Kent County

Sunday, August 24, 2008

Plants to Consider for Delaware Landscapes - Offered in the Fall UDBG Plant Sale - Bulb crops

The fall UDBG plant sale is coming up in two weeks. The following are some bulbing perenials that are well adapted to Delaware landscapes that are being offered at the sale.

Allium schubertii, ornamental onion, sun, moist to dry soils, 15", rose-purple 10-12" globe shaped flower in late spring, attracts butterflies

Sternbergia lutea, autumn daffodil, sun to part shade, 6-8", foliage appears in fall with yellow flowers, deer resistant, prefers moist soils with good drainage

Saturday, August 23, 2008

Landscape - Redheaded Sawfly on Pine

Redheaded sawfly is now active on pines. The following is information on this pest from the University of Maryland landscape IPM report.

Redheaded Pine Sawfly, Neodiprion lecontei

In mid to late August redheaded pine sawfly eggs begin to hatch. Female sawflies have been laying eggs into needles over the last couple of weeks. The larval stage of this insect will feed on mugo pine, red pine, scotch pine and several other species of pines. If you examine foliage now you may see the yellowish colored eggs inserted in a row into the needles of the pine. When the eggs hatch the larvae will feed in clusters, usually on tip growth of the host pine. This group feeding of larvae can defoliate whole sections of a pine very rapidly in late August to early September.

Physical control: Prune out the needles that have eggs present. This action is the easiest preventative measure for control. Once the larvae hatch you can prune off the tip growth while the larvae are small.

Chemical control: Horticultural oil sprayed onto the larvae will give control. Neem products can also be used to control early instar larvae. Spinosad (Conserve) will also give control.

Information and photo from the August 22, 2008 edition of the TPM/IPM Weekly Report for Arborists, Landscape Managers & Nursery Managers from the University of Maryland Cooperative Extension.

Friday, August 22, 2008

Landscape - Woody Vining Weed Control

Woody vining weeds can be difficult to control in the landscape. The following are some recommendations.

Woody-vine control in landscape plantings

No selective herbicides exist that allow you to chemically control woody vines growing among broadleaf ornamentals. Cultural controls include hand weeding and repeated cultivation. Cutting the stems at the soil line does not control these weeds due to re-growth from rootstocks. Cutting the vine at the soil line and then treating the young re-growth with a systemic herbicide is an option when you cannot easily spray the weed's foliage without contacting foliage of desirable plants.

Spraying a contact herbicide such as diquat or pelargonic acid will affect the foliage but will not eliminate underground portions of the vine. (Repeated application gradually can deplete the root reserves of a perennial if you continually spray the re-growth.) A physical barrier such as black plastic or a landscape fabric suppresses establishment of these weeds from seed. However, mulches are ineffective for controlling perennial vines that already are established. Therefore, chemical control is limited to non-selective post-emergence herbicides such as glyphosate (Monsanto's Roundup Pro) and glufosinate ammonium (AgrEvo's Finale).

Roundup Pro, a systemic herbicide, is the compound of choice for most situations because it translocates to roots of perennial vines. However, you may need to make repeated applications to completely kill a perennial vine with a deep, well-established root system. Finale is a contact herbicide with limite translocation in plants. You can expect regrowth from the rootstock following an application with this product, and you'll probably need repeat treatments for long-term control.

To avoid injury to nearby ornamentals when you spray with Roundup or Finale, use a shielded spray. When using directed sprays, avoid contacting the bark of young trees or species with thin or green bark. Both Roundup and Finale can cause bark injury to such plants. Wiper applications of Roundup are another way to apply this herbicide near sensitive ornamentals. You'll need to use higher concentrations of Roundup with wipers-check the label for specific use directions.

You can apply Finale anytime weeds are actively growing. In general, the optimum time to apply Roundup is in late summer to early fall (this range of times is greater in warmer climates), but before frost. One exception is greenbrier, where spring applications are necessary because its older leaves apparently do not readily absorb the chemical. You also can apply Roundup to cut stems or stumps, or inject it into stems, for controlling individual plants. You should make such treatments to actively growing vines immediately after cutting the stem.

Information from Jeffrey Derr, Associate Professor of Weed Scienc, Virginia Polytechnic Institute and State University.

Landscape - Some Woody Vine Weeds

Several woody-vine species occur frequently in landscapes and other non-crop areas. Below are some of the most common types.

Poison ivy. Poison-ivy stems can trail along the ground or climb up trees, poles and other structures by clinging with aerial roots. However, poison ivy can also grow as a shrub. Its leaves are trifoliate -you may have heard the phrase "leaflets of three, let it be" as a reminder to avoid these plants. The leaves, which have alternate arrangement turn bright red in fall, and the fruit are greenish to grayish-white berries. Approximately one-half to two-thirds of the human population are sensitive to the toxin in poison ivy, which causes a contact dermatitis. The toxin is present in all parts of the plant at all times of the year, even in overwintering stems. Never burn this plant because the toxin may be present in the smoke and can cause lung damage if you inhale it. Poison ivy spreads by seed, creeping rootstocks and rooting of stems into soil.

Virginia creeper and wild grape. Virginia creeper grows in the same range and habitat as poison ivy, and people sometimes confuse the two. However, the palmate leaves of Virginia creeper generally have five to seven coarsely toothed leaflets. This plant climbs by tendrils and, like poison ivy, its stems will root into soil. Birds spread its seed, and the fruit are blue or black.
Virginia creeper is in the same family as wild grape and, like Virginia creeper, various wild-grape species can be serious weed problems. Grape leaves are simple (no leaflets, just one whole leaf) but are sometimes deeply lobed. Grapes climb by tendrils and often grow rampantly over trees and fences. Both wild grapes and Virginia creeper exhibit alternate leaf arrangement.

Trumpet creeper. Trumpet-creeper leaves are compound, pinnate and alternate, with seven to eleven toothed leaflets per leaf. It climbs by aerial roots, which can damage siding on buildings to which they attach. Trumpet creeper has showy orange, trumpet-shaped flowers that produce a pod containing winged seed. Hummingbirds are attracted to trumpet creeper. One possible way to manage this weed is to dig it up, plant it in pots and sell it as hummingbird vine (a name nurseries often use for this plant)!

Honeysuckle. Japanese honeysuckle has simple, opposite leaves, which distinguishes it from the vines I've described so far. The flowers are yellowish-white and fragrant, and the plant is deciduous to evergreen, depending on the region. You may be able to take advantage of the evergreen characteristic of the plant by applying a foliar-absorbed herbicide in fall when it is still in leaf but after desirable deciduous trees and shrubs have dropped their leaves. Importersintroduced Japanese honeysuckle to the United States from Asia as an ornamental (for which it still is used) but it has escaped cultivation and become a significant weed.

Information from Jeffrey Derr, Associate Professor of Weed Science, Virginia Polytechnic Institute and State University

Thursday, August 21, 2008

Landscape - Winter Annual Weed Control in Landscape Beds

It is time to apply premergence herbicides to control winter annual weeds in landscape beds (before the end of August). The following is some information.

Winter annual weeds start to germinate in late summer when soil temperatures have cooled down. Soil temperatures are usually cool enough by the end of August to get some germination, especially in irrigated beds. Common winter annuals include chickweed, henbit, purple deadnettle, field violet, annual speedwells and mustard family weeds including bittercress. Winter annual grasses include annual bluegrass, annual ryegrass, and downy brome. Several short lived perennials and biennials will also be germinating at this time such as mouseear chickweed and marestail (horseweed). To prevent winter annual weed germination, apply preemergence herbicides to landscape beds before the end of August. OH2 and Rout are examples of preemergence materials highly effect in landscapes on mustard family weeds, speedwells, Lamiums (henbit and purple deadnettle), horseweed, and annual bluegrass. They are weak however on chickweed which is better controlled with herbicides containing isoxaben (Snapshot, Gallery), pendamethalin (Pendulum, others), trifluralin (Snapshot, others), or prodiamine (Barricade). Preemergence herbicides can be effective in reducing late summer germinating winter annuals; however, many of these weeds germinate from fall through spring requiring long residual materials or repeat applications. Check with each product label for compatibility with specific landscape plants and efficacy on specific winter annual weeds. Most of these herbicides will require some irrigation to activate them.

Gordon Johnson, Extension Horticulture Agent, UD, Kent County.

Landscape - Sawflies on Pines

Sawflies can cause significant damage to pines in the late summer. The following is more information.

Sawflies are members of the same insect order (Hymenoptera) that includes ants, bees, and wasps. The larval stage has a caterpillar-like body that may be brightly marked with stripes or spots. Some species change significantly in appearance as they grow, making identification confusing. Large numbers of sawflies can strip the needles from a tree in a short period. Several species can be found on pines in Delaware.

Feeding is most severe in the crown to upper half of the tree but heavily infested trees can be completely defoliated. If this occurs after the winter buds have formed, many branches or even the entire tree can be killed. There are two generations each year in some sawflies. The second generation feeds on both old and new needles during August and September.

Sawfly populations are usually controlled by combinations of natural enemies, predators, starvation, disease, or unfavorable weather. Outbreaks can occur when natural control does not produce high mortality. Regular inspection of pines will help to detect sawfly infestations before the larvae reach a size that can cause significant defoliation. Since eggs are laid in clusters, feeding by groups of larvae can cause unsightly damage to ornamental or landscape plantings, as well as nursery trees.

If only a small number of colonies are present and accessible, they can be handpicked, shaken off, or pruned from the tree and destroyed. Some of the insecticides that can be used for sawfly are acephate, bifenthrin, carbaryl, esfenvalerate, and permethrin. Although sawflies look like caterpillars, they are not susceptible to Bt sprays.

Adapted from "SAWFLIES - LATE SEASON PINE DEFOLIATORS" By Lee Townsend in the August 18, 2008 edition of the Kentucky Pest news from the University of Kentucky, College of Agriculture.

Wednesday, August 20, 2008

Greenhouse - Iron Deficiency in Pansies

Iron deficiency is a common problem in growing fall pansies. The following is some information and recommendations.

In pansy, symptoms of iron deficiency are interveinal chlorosis (yellowing) of primarily the youngest leaves, followed by marginal burning in severe cases. The first step in treating iron
deficiency is assuring the substrate pH is within the recommended range. If the media pH is too high, lower it to 5.4 to 5.8 using iron sulfate. Not only will this treatment lower the pH, it will also increase the iron supply in the substrate solution. If further treatment is needed, use a foliar spray of 10% iron chelate at 4 oz per 100 gallons.

Information from "COMMERCIAL PANSY PRODUCTION" by Douglas A. Bailey, Professor, North Carolina State University, Department of Horticultual Science.

Greenhouse - Managing Greenhouse Insects

The following is a good summary on insect management in greenhouses from Michigan State University.

Do not carry-over insects from one crop to another. Keep thrips numbers down to less than 10 per card per week in the fall and winter on poinsettias and Dracaena. Avoid keeping houseplants or allowing weeds to grow in the greenhouse. When each batch of media arrives for a new crop, check it for fungus gnats by filling a one gallon zip-lock bag half-full with moist soil. If fungus gnat adults emerge within two weeks, consider applying a fungus gnat treatment at planting time. Check incoming plant material carefully. If insects are found, treat them with an appropriate product listed below to start with as clean a crop as possible.


Monitor thrips and whiteflies with yellow sticky cards. Change cards once per week. Use at least one card per house or one per 2,000 square feet. Check the first plants to flower for thrips. For spider mites and aphids, check susceptible plants like marigold (mites) and pepper (aphids), weekly. Potato wedges can be stuck in soil and checked 24 hours later for fungus gnat larvae.

Systemic insecticides

Use Marathon, Tristar, Flagship, Safari, or Aria in poinsettia pots, lily pots, or in hanging baskets prone to problems with whiteflies, aphids, mealybugs or soft scales. Note: Aria does not work on silverleaf whitefly. Tristar and Safari also suppress thrips.

Preventing outbreaks

If yellow sticky cards or scouting indicates an increase in aphids, mites, thrips, fungus gnats or whiteflies, apply the following materials once per week until populations decrease to acceptable levels.

Thrips: Avid, Mesurol, Orthene 97, Safari, Sanmite, Tristar, and Conserve. (Note: some thrips populations may be resistant to Conserve.)

Aphids: Aria, Azatin, BotaniGard, Celero, Decathlon, Discus, Distance, Endeavor, Enstar II, Flagship, Marathon, Ornazin, Orthene 97, Precision, Safari, Talstar, Tristar.

Whiteflies: Azatin, BotaniGard, Celero, Decathlon, Distance, Endeavor, Enstar, Flagship, Marathon, Ornazin, Orthene 97, Precision, Safari, Sanmite, Talus, Judo, Tame, Tristar (Note: many populations of silverleaf whitefly are resistant to Marathon, and some may also be resistant to Flagship, Tristar, Safari, Distance and Talus.)

Mites: Akari, Avid, Floramite, Hexygon, Judo, Ovation, ProMite, Pylon, Sanmite, Shuttle, Tetrasan.

Broad mites: Avid, Akari, Judo, Pylon, SanMite.

Fungus gnats: Azatin XL, Adept (not on poinsettias), Distance, Marathon, and (drenches) (perhaps other nicotinoids; not yet tested), Mesurol.

Mealybugs: Aria, Celero, Flagship, Orthene, Safari, Talus and Tristar.

Reprinted from "Managing greenhouse insects: by David Smitley, Entomology in the December 21 edition of the Greenhouse Alert Newsletter from Michigan State University.

Tuesday, August 19, 2008

Greenhouse and Nursery - More Mum Diseases and Control

The following are control recommendations for several common foliar disease problems in mums.

Alternaria, Botrytis and Septoria are common fungal diseases of mums that affect foliage and flowers. These diseases can be managed using thiophanate methyl (Cleary's 3336), iprodione (Sextant), chlorothalonil (Daconil Ultrex, Pathguard 6F), chlorothalonil & thiophanate methyl (Spectro 90 WDG) or fludioxonil (Medallion). As the plants grow rapidly in August and develop a dense canopy of leaves, treatments may be necessary.

Bacterial leaf spot, caused by Pseudomonas cichorii often occurs during hot humid weather in August. This disease tends to be problematic during years of heavy rains or where overhead watering is practiced. Plants with this disease have large black spots concentrated at the base of the plant. The spots often begin at the leaf margin but may also occur randomly. From the leaf, the bacterium can move through the petiole and into the stem resulting in a canker. The sepals of infected flower buds will become brown to black and up to several inches of pedicel may be killed. Copper hydroxide sprays such as Kocide 101 77 WP or Phyton 27 will help protect against this disease. These materials do not cure the disease, they limit spreading to uninfected plants. Also there are differences in cultivar susceptibility. Make notes when you see susceptible varieties and avoid growing them in the future.

Bacterial leaf spot and foliar diseases are spread by splashing water, which is why we see more of these diseases during rainy years. Drip irrigation helps to prevent foliar diseases. If overhead watering, foliage should always be dry before evening hours.

Information from "Garden Mums - Past Crop Problems and Production Tips" by Tina M. Smith, Extension Floriculture Program, UMASS.

Greenhouse - Caterpillars on Ornamental Cabbage and Kale

Caterpillars need to be controlled on ornamental cabbage and kale. Several caterpillars will attack these plants this time of year, but the most common is the Imported Cabbage Worm. The following is some information.

The familiar imported cabbage worms adults can be seen fluttering above ornamental cabbage and kale. The adult is a white butterfly tinged with yellow on the underside of its wings.

Females have two black spots on their wings, but males have only one black spot. Look on the upper leaf surface for the bullet shaped eggs with fine parallel lines. Eggs hatch into slow moving velvety-green larvae that is easily missed as it blends into the green leaf color. Larger caterpillars have a delicate yellow line that runs lengthwise down the center of their bodies. Look for the larvae and signs of their feeding damage (irregular holes in the leaves, and dark green droppings) on ornamental kale and cabbage.

Many different materials are labeled including various formulations of Bacillus thuringiensis B. T) var. kurstaki (Biobit HP, Deliver, Dipel Pro DF, or Javelin WG) can be used against the small actively feeding caterpillars. Conserve is also labeled for many lepidoptera larvae including the imported cabbageworm. Many pyrethroids, Orthene, and Spintor are also effective and may be preferred when large worms are found.

Information taken in part from the New England Greenhouse Update.

Monday, August 18, 2008

Greenhouse - Prepare for the Upcoming Heating Season by Improving Insulation

Heating season in greenhouses will be here before you know it. While there is still some down periods, take time to work on houses to reduce heat losses later on. The following is some information on insulation.

Maximize the Insulation Endwalls - Insulate the endwalls of the greenhouse, especially the north endwall. In most parts of Virginia, the north endwall provides very little light for crop production. This wall can actually be constructed of a solid material like wood. Plywood (1/2-inch thick) will lose about the same amount of heat as a double poly wall. At least, insulate this wall for winter production. Reflective (foil backed) insulation boards provide better insulation than other rigid foam boards. Place them with the reflective side facing into the greenhouse. If possible, add windbreaks outside the greenhouse along the north wall. These may be conifers planted for screening or a temporary fence material to divert the wind over the greenhouse. The south endwall can be insulated with an extra layer of plastic.

Foundations on new construction - On new construction, foundation heat loss can be reduced by half through the installation of 1 to 2 inches of polyurethane or polystyrene insulation. This insulation should be installed 1.5 to 2 feet deep around the foundation wall with care given not to leave gaps or openings. This is especially important when installing any type of floor heating system.

Existing foundation and side walls - If the foundation of the greenhouse was not insulated during construction, make sure that all gaps or holes below the foundation board are filled or repaired. If the greenhouse has a concrete kneewall, insulating the inside of it with insulation board can significantly reduce heat loss. Reflective insulation boards can be added to the inside of any flat greenhouse wall but should not extend above the crop or bench height. Leave a small airspace between the insulation and the sidewall to prevent freezing of the greenhouse wall. Be sure that the reflective surfaces are not in contact with perimeter heating pipes where they are a part of the heating system. Sidewall insulation can reduce annual heating costs 5% to 10%.

Information from "Dealing with the High Cost of Energy for Greenhouse Operations" by Joyce G. Latimer, Extension Specialist, Greenhouse Crops; Virginia Tech

Greenhouse - Stretch Control in Ornamental Cabbage and Kale

Along with mum and fall pansies, greenhouse growers have added ornamental cabbage and kale for fall sales. Controlling stretch in these crops can be difficult due to high temperatures during late summer. The following is information on height control using growth regulators in ornamental cabbage and kale.

Chemical growth regulators are required to control plant height of ornamental cabbage and kale. Sumagic foliar sprays between 8 and 16 ppm were effective in controlling height at a cost of $0.02 and $0.04, respectively. B-Nine at 2500 ppm also provided comparable control in limiting unnecessary stretch, with a cost of $0.01 per pot when sprayed twice. A B-Nine rate of 5000 ppm is also recommended at a cost of $0.01 per pot. Although effective in controlling height, it is not economically feasible to apply Bonzi or Sumagic as drenches, because the costs are 3 to 6 times that of Sumagic foliar sprays or B-Nine foliar sprays.

Information from "Ornamental Cabbage and Kale Growth Control with B-Nine, Bonzi and Sumagic Foliar Sprays" vby James L. Gibson and Brian E. Whipker in the Floriculture Research Series No. 142 from North Carolina State University.

Sunday, August 17, 2008

Greenhouse - Boron Deficiency in Fall Pansy

Boron deficiency is a common problem in pansies. The following is information on this subject.

Boron deficiency can be a serious problem with pansies. Symptoms are initially expressed on the new leaves and stems, with the young growth being thick texture strap-like. With advanced conditions, death of the growing point can occur, thus resulting in axillary shoot growth. It is important to prevent B deficiency before symptoms appear because growing point death or distorted leaves can not be reversed. If deficiency symptoms are severe, it is rarely economical to try to reverse the damage. It is more economical to dispose of the crop and start over. Excessive levels of Ca can have an antagonistic effect on B availability and growing the crop at substrate pHs above 6.2 can tie up B. Make sure your fertilizer or irrigation water contains ample levels of B. Limit excessive Ca applications by avoiding calcium nitrate based fertilizers. Maintain the pH within the acceptable range of 5.4 to 5.8 to assure B is readily available to the plant. Some growers are supplying a weekly B drench application to the plants for the first three to four weeks of the crop as a preventative measure. For a 0.25 ppm B rate, mix 0.85 g borax (11% B) or 0.48 g solubor (20% B) per 100 gallons of water.

Photos of boron deficiency in pansies from NC State University.

Information from "Managing Fall Pansy Fertilization" by Brian E. Whipker, Todd J. Cavins, and James L. Gibson, Department of Horticultural Science, North Carolina State University.

Plants to Consider for Delaware Landscapes - Offered in the Fall UDBG Plant Sale: Ferns

This is a continuation of the series on plants for Delaware landscapes featuring those being offered in the Fall UDBG plant sale. In this post we feature some hardy ferns.

Thelypteris decursive-pinnata, japanese beech fern, shade to part shade, moist soils, 12-24", vigorous spreader, graceful fronds, great as a groundcover.

Cheilanthes lanosa, hairy lip fern, native plant, shade to part shade, 6-8",10 soft textured with fuzzy green leaflets along brown stipes, great in containers

Saturday, August 16, 2008

Landscape - Capturing Rainwater

With water conservation a continuing concern, one potential way to reduce water usage from municipal sources or wells is collecting rain water for later use. The following is an article on the subject.

Capturing rainwater during the wetter times of the year and storing it could be an ideal source for a supplemental supply. This is often referred to as rainwater harvesting and has been used for thousands of years to provide people with water for drinking, cooking, sanitation, agriculture, and many other uses. Its use all but disappeared in developing nations during the twentieth century because of centralized water supplies, deeper wells, and other technologies. However, with consistent droughts in many parts of the U.S., people are looking to the skies once again for its free water.

A rainwater harvesting system can work in two ways depending on someone’s needs and location. The first method is ground catchment systems. This involves collecting water in open air areas, such as a pond, or storing the water underground in the aquifer. It is done by slowing down the runoff of water and directing it to the desired location. This method is good to store large amounts of water for uses such as irrigation, livestock watering, fire protection, or even recreation.

The second method of rainwater harvesting is to collect rooftop runoff into tanks or cisterns for later use. This is the more practical form of collection if the intended use is domestic supply. The main components include a catchment area (usually an established roof), a conveyance system (gutters and downspouts), and storage (tank). Because most people already have the roof and gutters in place, installing a rainwater harvesting system may be as simple as putting in a storage tank.

Tanks can be homemade, ranging in variety from reused barrels to large steel-reinforced cement cisterns. They can also be installed by professionals who specialize in rainwater harvesting. Either way, it is essential that every tank includes certain components to be low-maintenance and long-lasting. These include a filter, inlet, vent, overflow, access opening, and tap or inside pump.

With this in mind, it is important to mention just how much water can be collected from the rain. With one inch of rain, a roof with 1000 square feet can collect up to 620 gallons of water. With the average rainfall in Delaware around 45 inches per year, this amounts to nearly 28,000 gallons! Certainly, this amount could supplement well or municipal water for watering important landscape plants in dry conditions.

Adapted from the August 2008 Agricultural Newsletter, Prince Edward County, Virginia, Virginia Tech Extension.

Turf - New Materials for Surface Feeders

Over the last few years several new products have become available for the control of surface feeding insect pests in turfgrass. Some of these new products are simply combinations of previously available active ingredients, others are new members of already available insecticide classes, and two actually belong to new insecticide classes.

Clothianidin (Arena) and thiamethoxam (Meridian) are two new neonicotinoids that, like imidacloprid (Merit), are primarily white grub products but can also be effective against billbugs by killing the younger larvae when feeding inside the grass stems. Both also claim chinch bugs on their label, although thiamethoxam with the caution that it only provides suppression. However, both would not exactly be my first choice for chinch bug control. Among the neonicotinoids, clothianidin has the best environmental profile as it is (based on EPA standards) ‘practically non-toxic’ to mammals, birds, and fish, and also has the lowest water solubility. Thiamethoxam is ‘slightly toxic’ to mammals and birds, ‘practically non-toxic’ to fish, but has a fairly high water solubility. Therefore, it has to be used carefully in situation where groundwater contamination potential exists. In comparison, imidacloprid is ‘moderately toxic’ to mammals, ‘practically non-toxic’ to birds and fish, and is only slightly more water soluble than clothianidin.

Two newer products are combinations of the pyrethroid bifenthrin and a neonicotinoid: Allectus (bifenthrin + imidacloprid) and Aloft (bifenthrin + clothianidin). These combination products simultaneously provide control of white grubs (through the neonicotinoid) and surface feeding insects (through bifenthrin). Both provide control of almost all the common turfgrass insect pests. However, along the same lines, they will also be very ‘effective’ against most non-target insect in turfgrass such as predators and parasites of turfgrass pests. Before applying these combinations, consider how likely both white grubs and surface insect pests are to occur in the same turfgrass area, let alone damage it. If a turfgrass area has the potential for problems with white grubs and surface feeders, make sure not to apply the combination more than 3–4 weeks before the surface feeders should be controlled to avoid the loss of bifenthrin activity. These combinations can be considered ‘moderately toxic’ to mammals and ‘practically non-toxic’ to birds. Because the bifenthrin component is ‘very highly toxic’ to fish but essentially not water soluble, these products have to be applied with care wherever there is a chance of surface water contamination.

Another recent addition to the turfgrass insecticides is the oxadiazine insecticide indoxacarb (Provaunt) which is highly effective against caterpillar pests (sod web-, cut-, armyworms) and annual bluegrass weevil larvae (Table 1). Indoxacarb also has a good environmental profile being ‘slightly toxic’ to mammals, ‘practically non-toxic’ to birds and fish, and essentially not soluble in water.

The anthranilic diamide insecticide chlorantraniliprole (Acelepryn) just received registration. It is not only highly effective against all the important white grub species, but also controls the caterpillars (sod web- , cut-, armyworms) and larvae of billbugs and annual bluegrass weevil. Against chinch bugs it only provides suppression. Ongoing research indicates that chlorantraniliprole will control caterpillars for 2-3 months, i.e., cover at least two generations. Chlorantraniliprole has an exceptional environmental profile being ‘practically non-toxic’ to mammals, birds, fish, and honey bees, and essentially not soluble in water.

Reprinted from "New Products for Surface Feeding Insect Pests in Turfgrass" by Albrecht M. Koppenhöfer, Ph.D., Turfgrass Entomology, Rutgers University in the July 24, 2008 edition of the Plant and Pest Advisory, Landscape, Nursery, and Turf Edition, Rutgers University.

Friday, August 15, 2008

Greenhouse - Avoid Overdosing with PGR's

Plant growth regulators (PGR's) are used to control stretch and increase flower breaks in greenhouse plants. This time of year, they are used in pansies, ornamental kale, ornamental cabbage, and other fall flowering crops to reduce stretch in the hot weather. Overdoses can be an issue. The following is an article on the subject.

A grower sometimes must deal with PGR overdose situations. Overdosing with PGRs can happen in several ways including miscalculation during mixing, applying specific chemicals to ultra-sensitive species, selecting a PGR rate that is too high for the species, stage of development or prevailing environmental conditions, or applying a PGR too frequently. In addition, inadvertent spray drift and inadvertent overlap during treatment can also result in overdose.

Once an overdose is suspected, a grower has a number of options to mitigate the effects. If an overdose spray of Cycocel or B-Nine (or the generic equivalents of these compounds) is applied and the mistake is discovered before the spray dries (usually within 30 minutes of initial application), the material can be washed off with a hose and the damage avoided. This is not an option with materials like Bonzi, Sumagic, Topflor or A-Rest. If the range of overdose is only modestly high, for example 25-50% too high a rate, then environmental conditions that minimize stress may be enough to allow the plant to recover without further intervention. In this scenario, adequate sunlight combined with increased temperatures, increase fertilization, and reduced water stress will all favor rapid growth and allow the plant to out grow the adverse effects of the overdose. In circumstances where the dose is too high to mitigate in this way, a gibberellic acid treatment can be used to reverse the effect of the PGR. Remember, growth retardants (Cycocel, B-Nine, Bonzi, Sumagic, Topflor & A-Rest) inhibit gibberellic acid (GA) activity in the plant. Therefore applying GA products such as Fascination (or the generic equivalent) will produce a plant response just the opposite of the PGR.

For bedding plants, spray Fascination as soon as the error is discovered. Use a starting rate in the range of 1-to-3 ppm (but rates as high as 25 ppm may be needed). Evaluate plant response after 5-to-7 days. Then adjust the application rate based on observed plant response, and reapply as needed at this time. The full effect of a single application should be evident within 1-week.

Reprinted from the New England Greenhouse Update Website.

Greenhouse and Nursery - Avoid Phytotoxicities

It is important to avoid phytotoxicities on greenhouse and nursery plants by pesticides. The following is an article on the subject.

Pesticide phytotoxicity can often be distinguished from pest problems by the pattern and timing of symptom development. Although the damage may take up to several days or more to occur, pesticide damage symptoms often occur all at once and often have a regular distribution on the crop. Symptoms caused by pathogens usually develop over an extended period of time in random or grouped patterns. Pesticide phytotoxicity can be expressed by a number of different symptoms, including leaf speckling, cupping and twisting and other leaf distortions or even plant death. Pesticides with hormone-type activity such as the insect growth regulator Distance and herbicides containing 2,4-D tend to produce leaf cupping and twisting. Other pesticides that have caused twisted growth include Judo applied to dracaena plugs and Botanigard ES applied to tomato plants.

Phytotoxicity can also be caused by the solvents in a formulation (EC formulation vs WP), impurities in spray water, using a higher rate of pesticide than is listed on the label, tank-mixing or inadequately mixing the spray solution. Environmental conditions such the temperature, humidity, and light can also influence phytotoxicity. High temperatures can speed up pesticide degradation and volatilization, but may also result in increased phytotoxicity for some products. Plants that are stressed are more susceptible to pesticide injury.

Poinsettias become more sensitive to spray injury as bracts turn color. Pesticide applications to poinsettia bracts are risky since there are so many variables. Differences in cultivars, culture and environmental conditions may increase or decrease bract sensitivity to pesticides. If you are inexperienced with a particular pesticide, always test a small portion of your crop before treating your entire crop.

To prevent injury due to pesticides, be sure to follow label directions exactly. See the company's website to read any technical bulletins about the product or call the company's technical representative before using a product for the first time.

If minor phytotoxicity is suspected from foliar applications of an insecticide, miticide or fungicide, watch the new growth as it emerges. Plants will often grow out of one-time spray damage. As plants grow, the damage will remain on the oldest leaves and the new growth will appear healthy.

Information from the New England Greenhouse Update Newsletter.

Thursday, August 14, 2008

General - Useful Conversion Factors for Small Measurements

The following are useful conversion factors for small measurements of fertilizers, pesticides, or growth regulators when using backpack or small scale sprayers or application equipment.

1 gallon (gal) = 128 fluid ounces (fl oz)
1 fl oz = 30 milliliters (ml)
1 gal = 3785 ml = 3.785 liters
1 cup = 48 teaspoons
1 tablespoon = 3 teaspoons
1 fl oz = 2 tablespoons = 6 teaspoons

1 ounce (oz) = 28.3 grams (g)
1 pound (lb) = 16 oz = 454 g

1% = 10,000 ppm
1 ppm = 1 milligram (mg) per liter

Greenhouse - Black Root Rot in Pansies

It is fall pansy production time and black root rot can be a problem disease in production areas, especially where produced on the ground. The following is information on this disease and its control.

Black root rot, caused by the soilborne fungus, Thielaviopsis basicola, can be very serious on pansy. This fungus attacks the fine feeder roots. Infected roots are black due to the presence of the fungus. Thielaviopsis basicola also causes a root rot on Helleri holly and vinca. This fungus is common in soils across Delaware and it is active over a very wide temperature range. The fungus infects the feeder roots and gradually kills the entire root system. Black root rot has been a serious problem in pansy production in the Southeast for the past five to seven years. It appears to be related to production in August and September when it is too hot for pansy plants and they are "stressed."Control measures for black root rot during production include:

>Grow pansies off the ground
>Avoid excessive heat stress, especially on young seedlings.
>Avoid other stresses, such as high substrate pH that can lead to micronutrient deficiencies (mainly boron and iron), excessive soil moisture, or excessive salts.

Preventative drenches with labeled fungicides such as 1-[1-[[4-chloro-2-(trifluoromethyl) phyenyl]imino]-2-ropoxyethyl]-1H-Imidazole (Terraguard 50 WP) and thiophanate methyl products such as Cleary's 3336 may help.

Information extracted from "Commercial Pansy Production" by Douglas A. Bailey, Professor, Department of Horticultural Science, North Carolina State University

Wednesday, August 13, 2008

Landscape - Peachtree Borers in Ornamental Trees

The peachtree borer is native to North America. It is an importance pest around most peach-growing areas, and in the landscape will attack, cherry, plum, laurel, and other Prunus species of ornamental trees and shrubs. You will want to apply late summer controls in August. The following is more information.

Borer infestations can be detected by the presence of gum and frass around the base of a tree. The exudate around new feeding damage is soft, sticky, and light brown in color, while older damage is marked by hard sap and dark brown frass. Symptoms are often first noticed in the spring.


Adults are day-flying moths which resemble wasps in appearance and behavior. The female is bluish black with a bright orange band around the fourth or fifth abdominal segment. Her body may be up to 3/4" in length. The male moth is smaller with transparent areas in both front and hind wings. The hind edges of the second through sixth abdominal segments may be marked with yellow scales giving it several thin yellow bands.

Larvae are creamy in color with a brown head and three tiny pairs of legs on the thorax. Fully grown larvae may reach 1.5 inches in length.

Female moths lay eggs in crevices or under rough bark on the tree trunk around the lower portion of the trunk or near the crown. Larvae hatch in 8-9 days and attack the main trunk and larger roots near the soil surface. They feed on cambium tissue and may eventualy weaken or kill the tree. Borers overwinter as larvae in the tunnels and resume feeding the following spring. Most individuals complete development during the summer. Part of the population may require two years to complete the life cycle. Pupation occurs within a silken cocoon covered with chewed wood and frass.

About 99% of the cocoons are formed on the base of the trunk or in the soil within 3 or 4 inches of the tree. In Delaware, adults may emerge from early May to November, but the peak emergence usually occurs about September 1. Females mate about one hour after emerging from the cocoon and start laying eggs soon after mating is completed. They may lay over 1200 eggs with near 100% fertility.


In the landscape, literature sometimes suggests attempting to stab larvae in tunnels with a wire. This is laborious and difficult to accomplish. There are no effective chemicals for larvae already tunneling within the trunk or roots. Suggestions of paradichlorobenzene (PDB) or moth crystals in the soil are also not recommended. Management is aimed at chemical protective barriers to either discourage egg laying, or kill the tiny larvae upon hatching.

Suitable chemicals usually contain the ingredient permethrin. They need to be applied to the bark at the base and lower part of the trunk several times during the season, but especially before and after the peak moth emergence about the first of September. Commercial operations may use sex pheromone traps to monitor the population. The first few days of adult emergence are usually comprised of males. Chlorantraniliprole (Acelepryn) is a systemic labeled for clearwing borers.

Home owners may use multi-purpose landscape sprays labeled for borers containing active ingredients such as permethrin, esfenvalerate or cyfluthrin.

Information from "Peachtree Borer in the Landscape" by Stephen Bambara, Extension Entomologist, North Carolina State University.

Turf and Landscape - Green June Beetles

Green June Beetles can be a pest of turf and landscape areas. The green June beetle is in the Scarabaieidae family and also referred to as white grubs. Unlike many of the other white grub pest of turfgrass this species is unique in that it will come to the soil surface and crawl on the turfgrass at night. Their larval tunneling activity can damage turfgrass stands. The following is more information.


The adult green June beetle (Cotinis nitida L.) is usually 3/4" to 1" long, and 1/2" wide. The top side is forest green, with or without lengthwise tan stripes on the wings. The underside is metallic bright green or gold, bearing legs with stout spines to aid in digging. In the Mid-Atlantic region the names "June bug" and "June beetle" are commonly used for this insect. They're called "fig eater" in the southern part of their range. Do not confuse the green June beetle, however, with the familiar brown May or June beetles that are seen flying to lights on summer nights. The green June beetle adult flies only during the day.

The larvae are white grubs often called "Richworms" because they prefer "high" levels of organic matter for food. With three growth stages they develop and are similar to the other annual scarab species. Their body lengths reach 1/4", 3/4", and 2" respectively. The larvae have stiff abdominal bristles, short stubby legs, and wide body. One unique characteristic of this grub is that it crawls on its back by undulating and utilizing its abdominal bristles to gain traction. Other typical white grubs, like the Japanese beetle grub, are narrower, have longer legs, crawl right side up and when at rest assume a "C" shaped posture.


The adults generally don't feed but occasionally become a pest of fruit. Any thin skin fruit such as fig, peach, plum, blackberry, grape and apricot can be eaten. The principal attraction is probably the moisture and the fermenting sugars of ripening fruit. They occasionally feed on plant sap. In turf situations egg laying females are attracted to moist sandy soils with high levels of organic matter. Turf areas treated repeatedly with organic fertilizers, composts or composted sewage sludge become more attractive to the female.

The grub feeds on dead, decaying organic matter as well as plant roots. This species is commonly associated with both agricultural crop and livestock production areas as well as urban landscapes. Field stored hay bales, manure piles, grass clipping piles, bark mulches and other sources of plant material that come in contact with moist soil are prime microhabitats preferred by both the female for egg laying and the migrating 3rd instar grubs

Life Cycle

The green June beetle completes one generation each year. Adults begin flying in June and may continue sporadically into September. The peak occurrence of adults is during a two week period in mid-July in Maryland and Virginia. On warm sunny days, adults may swarm over open grassy areas. Their flight behavior and sounds resembles that of a bumble bee. At night they rest in trees or beneath the thatch.

The adult females shortly after emerging may fly to the lower limbs of trees and shrubs and release a pheromone that attracts large numbers of males. Frequently, males repeatedly fly low and erratic over the turf trying to locate emerging females. After mating, females burrow 2" to 8" into the soil to lay about twenty eggs at a time. The spherical eggs are white and almost 1/16" in diameter.

Most eggs hatch in late July and August. The first two instar stages feed at the soil thatch interface. By the end of September, most are third instar larvae and these large grubs tunnel into the thatch layer and construct a deep vertical burrow. The grubs may remain active into November in the Mid-Atlantic region. In the more southern states grubs may become active on warm nights throughout the winter. In colder areas they overwinter in burrows 8"-30" deep. The grubs resume feeding once the ground warms in the spring and pupate in late May or early June. The adults begin emerging about three weeks later.


The green June beetle grub differs from other white grubs in their feeding behavior. Damage to turf occurs as a result of their unusual habit of tunneling as well as root feeding. Smaller stage grubs tunnel horizontally in the top 4" of the ground, loosening the soil, eating roots, and thinning the thatch. This activity begins in early to mid-August when the disturbed grass may wilt or die if conditions are dry. Damage is minimal when grub density is low or if the grass receives plenty of moisture. As the grubs grow, tunnels become vertical and deeper with turf damage becoming more severe. Tunnels to the surface are kept open by grubs pushing little mounds of loose soil to the surface. The resulting mounds appear similar to earthworm castings. To determine that a mound was made by a green June beetle grub, wipe the mound away and feel for a hole in the ground about as wide as your finger. Earthworm holes rarely exceed the diameter of a pencil. The soil mound will reappear the next day. Fecal pellets about as big as mouse droppings may also be present on the soil surface near the holes. Fresh mounding activity is especially visible after a heavy rain. The mounds and holes are visible by mid-August, but the damage becomes more pronounced in the following months as the grubs continue to grow. The grubs do feed on some roots, but the major damage to the turf is due to the upheaval of the soil, dislodging of roots from the soil and subsequent weed problems.

The large green June beetle grubs come to the surface at night to feed or "graze" on the turf and individuals may migrate long distances (20-30 ft per night). Grubs may also be found in the twilight hours and on overcast days. Their trails through the dew can frequently be seen on golf course greens.

Besides the direct damage, these grubs cause some indirect problems. The mounds and holes disfigure turf while the tunneling kills the grass. Drought stressed turf mowed very short succumbs easily to this damage. As a consequence, spaces open up as the grass dies and allows for weed encroachment. The tunneling and excavation of subsoil brings acidic soil to the surface and this changes the microhabitat that favors grass and broadleaf weed species. Turf managers using reel mowers have complained that the loose soil and grit from the mounds accumulates on the machinery and dulls the cutter blades, especially when the dew is still on the grass. Additionally, predators such as small mammals and birds damage turf as they dig for the grubs.
To date no thresholds are available for landscape turf or lawns. Treatments are recommended on perennial ryegrass/bentgrass golf course fairways when grub counts exceed five per sq ft. Damage thresholds for Kentucky bluegrass and tall fescue based on field observation are slightly higher at 6-7 grubs per sq ft. Kentucky bluegrass will quickly recover with new growth from rhizomes.

To prevent damage to turf, apply controls to grub stages before many mounds become evident. We recommend an action threshold of five 3rd instar larvae per sq ft. Damage cycles historically run for 3-6 years than subside. During these outbreaks, damage may be expected if high populations of grubs were present the previous year and insecticide control was inadequate. An increase in the number of adults over the previous years observations is also a reason to expect damaging populations of grubs.

Biological-Biorational Control

To date there are no effective commercial biological agents available to control this grub. The most common parasite is a type of digger wasp, Scolia dubia (Say). This beneficial wasp enters the grub tunnel, stings the grub then lays an egg on the paralyzed grub. The resulting larva feeds in the grub, eventually killing it. Increased flight activity in late September by the wasps was noticed after green June beetle emergence. Unfortunately, even though these wasps help reduce the grub population, many people are afraid of being stung and consider them a nuisance or threat to life. These wasps are not aggressive and rarely sting humans. Milky disease products effective against Japanese beetle do not control green June beetle grubs nor do any Bacillus thuringiensis (B.t.) products.

Cultural Control

Some turfgrasses recover from damage once stress factors are removed. For example, species having stolons and rhizomes may repair the damage once the grub population is controlled. Also, the damage resulting from the grub tunneling is less severe when the turf receives sufficient moisture, fertilizer and lime. Overseeding in the fall is critical in preventing weed encroachment the following season. It's helpful to remember that tufgrass cut at a higher height (2 1/2" to 3") is less stressed, and therefore the damage is less visible. Also, turfgrass species such as tall fescue with the wider leaf blades also hides damage better than the fine-leaf grasses such as perennial ryegrass, bentgrass or fine fescue.

Chemical Control

Insecticides are effective on all grub stages and applications may be warranted anytime between August and November, as long as damaging numbers remain active. Spring applications of chemicals are not generally recommended since the grubs are active only for a few weeks and many may have pupated by the time damage becomes obvious. Once the grubs reach the third instar in August or September, they migrate freely and can easily move from an infested area to an adjacent area. To protect golf course greens, treat the greens, collars, and a few yards beyond the collars. The insecticides normally used to control sod webworms, cutworms, and armyworms on the greens will generally suppress migrating grubs. Sevin and Turcam insecticides have been effective in controlling the larval stage. If fairways are treated, the rough areas should be spot treated where there are high grub populations. The risk of high grub populations is generally correlated with areas where the adult beetle populations were most concentrated.

Chemical control of the larvae can be achieved preventatively by applications of imidacloprid (Merit), halofenozide (Mach2), thiamethoxam (Meridian), or clothianidin (Arena) in July or August or by curative applications of carbaryl (Sevin). To control the early instars before the migration phase, application of insecticides must be followed immediately by irrigation with 1/2" of water, or timed with rainfall. A word of caution is appropriate when an curative insecticide treatment is applied. After treatment the grubs come to the surface within 12 hours and die causing a foul order as they decay. Finally, monitor treatment areas carefully because migrating grubs may reinfest an area once the insecticide has broken down. It may be necessary to retreat.

Information by Dr. Lee Hellman, Department of Entomology and Dr. J. Kevin Mathias, Institute of Applied Agriculture, University of Maryland. Some control information from the University of Arkansas Turf Tips.

Tuesday, August 12, 2008

Greenhouse - Poinsettia Leaf Distortion

Poinsettias will be planted in greenhouses in August throughout Delaware. The following is information on leaf distortion in Poinsettia.

Various types of leaf deformation may occur on poinsettia. Often, the damage begins when the leaves are very small. As plants grow, the mature leaves cover the damaged young leaves, so plants are still marketable.

Branches that develop after pinching may develop a few distorted and misshapen leaves. Environmental stresses, overhead fertilization with phosphorus fertilizers, or abrasion may lead to distorted leaves. Very warm temperatures in August, may contribute to this phenomenon. For growers rooting their own cuttings, changes in temperature and humidity as plants are moved from propagation to finishing houses lead to leaf distortion. It is thought that rapid changes in humidity, result in an accumulation of salts along the leaf margins and veins, resulting in leaf injury. This distortion becomes apparent as the injured leaves grow and expand.

Often, thrips feeding is blamed for distorted leaves. However, with thrips feeding you will see white scarring. Poinsettias are not a favored host of thrips, however, they may migrate from spring bedding plants, garden mums or weeds unto the poinsettias. Fortunately, this feeding damage is often not visible by the time the plants are ready for sale.

Information from the New England Greenhouse Update.

Landscape - Grade Changes Can Affect Trees

The following is a short article on how soil grade changes can affect trees.

Adding or removing even a small amount of soil at the surface of the tree’s root zone will damage the tree. Excess soil on top of the roots reduces the oxygen available. Since most of a tree’s roots are in the top 6 inches, removal of soil also means removal of roots. Avoid grade changes greater than 2 inches. Be aware that the root system may spread far beyond the furthest branches (drip line) of the tree, typically two to three times or more.

Information from Dr. Susan Barton, Extension Ornamental Horticulture Specialist, UD.

Monday, August 11, 2008

Greenhouse - Watch Out for Phytophthora in New Poinsettia Plantings

Phytophthora root and crown rot caused by P. nicotianae is a problem you may encounter with recently transplanted poinsettia cuttings. The following is more information on this disease.

The optimum conditions for this disease are saturated soil and high temperatures. The Phytophthora pathogen does not travel easily through the air for long distances. It is possible that contaminated irrigation water can introduce the fungus to new sites but it is very difficult to detect Phytophthora in irrigation water.

Prevention is the key to managing Phytophthora because the disease is difficult to suppress with fungicides once it develops. Phytophthora like Pythium is a lower fungus favored by excess moisture and excess nitrogen fertility. Unlike Pythium, species of Phytophthora are more aggressive, more likely to be host specific.

The most likely source of origin is plant material. Start with soil-less growing media and avoid contaminating growth medium with soiled hands, tools, or flats. Promptly remove diseased plants, avoid splashing water when irrigating, and keep hose ends off the floor.

The best means for controlling Phytophthora crown rot and stem canker is with drenches of systemic fungicides which will move up into crown area such as mefenoxam (Subdue Maxx), foestyl-Al (Aliette) azoxystrobin (Heritage), zoxamide plus mancozeb (Gavel), mancozeb plus copper (ManKocide), and dimethomorph (Acrobat), Check labels for crop appropriateness. These fungicides should be rotated by chemical class to prevent resistance development.

The most effective way to halt an epidemic is to remove all affected plants. Even healthy appearing plants may be infected, so strict sanitation following an outbreak is advised.

Information from the August 8, 2008 posting of the New England Greenhouse Update.

Plants to Consider for Delaware Landscapes - Offered in the Fall UDBG Plant Sale: More Asters

The following is a continuation of the series on plants for Delaware Landscapes featuring those being offered at the Fall UDBG plant sale. The following are some more asters recommended.

Aster turbinellus, prairie aster, native plant, sun, moist soils, 3-5', airy graceful overall effect with pale violet flowers in late Sep-Oct

Aster laevis 'Blue Bird', smooth aster, native plant, sun to part shade, moist soils, violet blue flowers late summer, no staking needed, Mt Cuba introduction. Photo from North Creek Nursery who provided the plugs.

Sunday, August 10, 2008

Landscape, Greenhouse, and Nursery - Harlequin Bugs

Harlequin bugs are active now and can be very destructive, expecially on ornamental Kale and Cabbage. The following is some information.

Harlequin Bug Active in August

The harlequin bug, Margantia histrionica, is actively damaging cleome, snapdragon, and ornamental cabbage and kale in nurseries and landscapes. They cause white spotting of the foliage that turns brown.

Control: Insecticidal soap, neem products, Orthene (acephate), synthetic pyrethroids

Information from the Greenhouse TPM/IPM Weekly Report from the University of Maryland Cooperative Extension.

Landscape - Phragmites Control

Landscape maintenance personnel may have to deal with Phragmites in properties near marshes or water bodies, expecially along the coast and bays. The following is some information on Phragmites and its control.

•Phragmites spreads by rhizomes only (no viable seed) but encroaches onto the landscape from wetland sites.
•One cultural control is to improve drainage where possible (remember you cannot legally drain wetlands). Drying out a site is very effective.
•If Phragmites is encroaching into turf area, maintain regular mowing.
•In problem areas, apply glyhposate in the late summer/early fall. The Rodeo formulation is labeled if the site is considered aquatic.
•Use at least 3-4 qt/A or 3-4oz/gallon use rate. Activity will be slow to develop.
•Landscape barriers used for tree roots and ornamental bamboo containment show potential to contain phragmites.

The State of Delaware has a cost share program for Phragmites control where it has infested large areas (over 5 acres). The following is information on this program:

What is the Delaware Phragmites Control Cost-Share Program?

The Delaware cost-sharing phragmites spraying program being offered by the Delaware Division of Fish and Wildlife is intended to improve wildlife habitat in wetlands that have been degraded by the pest plant phragmites.The Division’s research has shown that effective phragmites control is possible in many areas with consecutive late summer (August through mid-October) applications of glyphosate-based aquatic herbicides. The DE Division of Fish and Wildlife and the U.S. Department of Agriculture’s Natural Resources Conservation Service (NRCS) recently decided to partner to utilize the federal Wildlife Habitat Incentive Program (WHIP) money. This partnership will enable the financial assistance to be increased so that state and federal money will cover 87.5% of the cost, with the landowner contributing the remaining 12.5% (about $5 per acre treated). The Division will be responsible for purchasing the herbicide, determining the herbicide application timing and rates, coordinating the aerial spraying and providing technical assistance.

How do I qualify?
  • Must have a minimum of 5 acres of phragmites and a maximum of 200 acres to be spray treated with herbicide.
  • Must agree to have the property treated for three years.
  • Drainage-ditches are Not eligible.
  • Must inform the Division of property boundaries and agree that the Division and its agents are not held liable for any damage that might accidentally occur on their property due to spraying.

Assistance is on a first come first serve basis and a mid-summer application deadline

How do I Apply?

The State portion of the application is available by clicking here. The federal portion of the application can be obtained at the appropriate County USDA Service Center based on where the property is located.

Thank you for interest in this Program any questions please contact: Bill Jones 284-4795.

Information on Phragmites control is from Dr. Steve Hart, Ornamental and Turf Weed Specialist, Rutgers University. Information on the cost share program in DE is from the DNREC website