Greenhouse - Spider Mite Damage, Spider Mite Closeup With Predatory Mite

Two spotted spider mite closeup. A predatory mite (reddish orange) is also shown. This mite, Phtyoseiulus persimilis, feeds on all stages of two spotted mite and is a very effective biological control in greenhouses. Photo by Jack Kelly Clark http://www.ipm.ucdavis.edu/PMG/NE/phytoseiulus_persimilis.html

Two-Spotted Spider Mite Damage on Pot Rose. Photo from Iowa State University. http://www.ipm.iastate.edu/ipm/hortnews/files/images/spider-mites-rose.jpg

Greenhouse - Spider Mites and Biological Controls

Spider mites can be a problem pest in greenhouses and can explode quickly under the right conditions. Miticides can be effective; however, mites can build up resistance to these chemicals with overuse. Biological controls are available for mite control and can be quite effective. The following is an article from the University of Connecticut on spider mites and their control in greenhouses.

The two-spotted spider mite (TSSM), Tetranychus urticae, is a common pest in greenhouses. This mite has a wide host range including many different annuals, herbaceous perennials, greenhouse vegetables and herbs. Its short generation time, and potential for rapid increase has lead to many populations developing resistance to some commonly used miticides.

Adult female two-spotted spider mites can live for about one month. During this time, they may lay from 100 to 200 eggs. Mite eggs are small, spherical in shape and are laid on the underside of leaves. Eggs hatch in about three days and develop into pale green to light-yellow 6-legged larvae. The larvae develop into eight-legged nymphal stages with a feeding and resting stage. Optimum temperatures for mite development are between 85 to 95oF; with a lower threshold for development of 54°F and an upper threshold of 104° F. The life cycle from egg to adult varies depending upon greenhouse temperatures, relative humidity levels, and age and quality of the host plant. For example, on roses at temperatures of 77/95° F (Day/Night), spider mites developed from egg to adult at 8 days, and 50/68°F (Day/Night), mites developed at 28 days.
Female mites are three times more abundant than males. Fertilized adult females produce both males and females. Unfertilized adult females only produce males. Males have only one set of genes, so mutations such as pesticide resistance, are immediately expressed. Incorporating biological control strategies into your pest management program, can help slow down the development of resistance.

Biological control agents are best used preventatively, when pest populations are low. A regular monitoring program is needed for early detection of spider mites, and to insure the success of a biological control program. Weekly scouting and random plant inspections are needed to detect populations early before feeding damage occurs. Carefully inspect plants in hot, dry areas of a greenhouse or where there is no overhead irrigation that wets the foliage that may wash some of the mites off the leaves. Regularly inspect the most susceptible cultivars or species, and look for signs of plant damage. As spider mites insert their stylet-like mouthparts into plant tissue, they suck out plant juices removing the chlorophyll. At first, you see a slight flecking or stippling (chlorotic spot) on the leaves. Thin-leaved plants such as garden impatiens may show injury more quickly than thick-leaved plants such as ivy geraniums. Mite feeding damage on ivy geraniums is also often mistaken for oedema. As spider mite feeding continues, leaves turn yellow, bronzed and drop from the plant. When high mite populations develop, the fine webbing is extensive. Tag pest-infested plants as indicator plants to determine the effectiveness of biological control measures. A 10x to 16x hand lens is helpful to detect all stages of the mites. Because mites are easily carried on workers or their clothing, do routine greenhouse tasks and scout in mite-infested areas at the end of the day.

There are a number of biological control agents that may be incorporated into your pest management program for two-spotted spider mites. These include different species of predatory mites (Phytoseiulus persimilis, a specialist predator and Neoseilus californicus, a more generalist predator), and predatory midges (Feltiella acarisuga). No parasitoids are commercially available. Outdoors, natural enemies such as predatory mites, predatory thrips, predatory ladybeetles (Stethorus punctum), predatory midges, lacewings and pathogenic fungi may help to keep the spider mite populations low.

Reprinted from "Biological Control of Two-Spotted Spider Mites" by Leanne Pundt, Extension Educator, University of Connecticut. For the full article go to http://www.hort.uconn.edu/IPM/greenhs/htms/biocontrol_2spotmites.htm

Turf and Landscape Weed: Allium Species - Wild Garlic and Wild Onion

Two Allium species, wild garlic and wild onion, are common weeds in Delaware turfgrass and landscapes. The following is information on these weeds.

Wild garlic (Allium vineale) is a perennial weed that has a strong garlic or onionlike odor when cut. It is one of the first weeds to emerge in early spring. Wild garlic produces long, slender, mostly hollow leaves that are dark green and covered by a waxy substance. Leaves emerge from underground bulblets that are covered by thin, papery scales. Flowers may be present on uncut stems and can be white, pink, or purple.

A closely related species, wild onion (Allium canadense), looks very much like wild garlic. Wild garlic is more common in Delaware and has hollow leaves. Wild onion has flat (not hollow) leaves. Depending on the growth stage and time of year, it may be difficult to distinguish between these two species.

Turf - Topdressing Compost to Improve Turf Performance

Compost is an excellent amendment to improve turf performance. The following is a short article on the subject.

Surface applications of compost on established turf

Composts are frequently used as surface applications (topdressings) on established turf. This practice provides a means of gradually incorporating organic matter into the soil without causing extensive disruption of the surface. The two most limiting factors associated with this practice are finding suitable application equipment and working the material into the soil.

Since compost is light and bulky, a spreader with a large hopper is preferred. Modified manure spreaders with conveyor belts and brushes mounted on the back are ideal for spreading compost over large areas. Conventional tractor-mounted fertilizer spreaders have been used successfully, but may require many refills. If spreaders are not available, compost can be applied to the surface by spreading piles into a thin layer with a York rake or a grading blade. For applications over small areas, the compost can be spread with a shovel and worked into the turf with a leaf rake.

When applying compost as a topdressing, it is important to apply a thin layer (about ¼ inch) and work it into the soil. Successive applications of thick layers without soil incorporation will result in a build-up of organic matter at the soil surface that may cause rapid drying of turf roots and form a layer that restricts rooting into the soil. The best way to incorporate compost into the soil is through aeration. A good method of incorporation is to apply the compost first, followed by several passes with an aerator equipped with hollow-tines and a heavy drag mat attached. The drag mat will break-up the cores and mix the compost with the soil, dragging some of the mix back into the holes. This operation is best performed during cool/moist seasons when grass is actively growing. Aeration and dragging can be stressful to the turf during hot, dry weather.

Extracted from "Using Composts to Improve Turf Performance" by Peter Landschoot, Associate Professor of Turfgrass Science, Penn State University.

Landscape and Turf - Choosing a Compost

I just finished a class where we went over soil amendments and fertilizers. One of the best ways to improve a turfgrass or landscape area is with additions of compost. The following is a table from Penn State University on general guidelines in choosing a compost.

Appearance, size, and odor

Color: Brown to black
Size (surface applications): ¼ to 3/8 inch
Size (incorporated): ¼ to ½
Odor: “Earthy”

Physical appearance

Moisture content: 30 to 50 percent
Organic matter: Greater than 30 percent
Ash content: Less than 70 percent

Chemical properties

Carbon : nitrogen ratio: Below or equal to 30:1
Nitrogen: 0.5 to 3.0 percent
Phosphorus: Greater than 0.2 percent
pH: 6.0 to 8.0
Metals: Determined by state and federal agencies
Soluble salts: Depends on species, type of salt, concentration, and application method. Consult test lab or other expert to determine how this will affect the turf or landscape plants.

Use this information only as a general guide. Some composts have properties that do not fall within these guidelines yet are acceptable in certain situations. Others, though they may fit these criteria, may have serious drawbacks.

Reprinted from Using Composts to Improve Turf Performance by Peter Landschoot, Associate Professor of Turfgrass Science, Department of Crop and Soil Sciences, and Cooperative Extension. For the full article go to http://turfgrassmanagement.psu.edu/composts.cfm.

Greenhouse and Nursery - Testing Media for Nutrients

There is often confusion on nutrient tests and pour through leachate tests for greenhouse and nursery media. The following is an article on the subject with a good link to a fact sheet on testing methods from the University of Connecticut and University of Massachusetts.

Many growers are performing their own soil tests for pH and soluble salts on-site. Others are sending samples to different labs for their soil tests and some do a little of both. Often growers end up with a confusing collection of tests done different ways with widely different “numbers”.

There are three commonly used methods of testing soilless media based on the use of water as an extracting solution. They are: saturated media extract, 1:2 dilution method, and leachate pourthru. The number representing the level of soluble salts from a soil test using a 1:2 dilution method are going to mean something different than results from saturated media extract (SME) or leachate pourthru. For example, 2.6 would be “extreme” (too high) for the 1:2 method, “normal” for SME, and “low” for leachate pourthru. Always use the interpretative data for the specific soil testing method used or otherwise you could make an incorrect interpretation of the results. The differences in pH results between the tests is much smaller.

The major difference between the current methods of greenhouse media testing is the way plant-available nutrients and soluble salts are “extracted” from the media samples for analysis. Differences between the actual methods of pH, soluble salts, and nutrient analysis and the laboratory equipment used to do the analyses are not as important as how the plant-available nutrients are extracted from the sample.

When people think of “soil testing”, they might imagine some procedure which analyses the solids in a mix for pH, nutrients, and soluble salts. However soil samples themselves are not actually analyzed during a soil test, but rather plant-available nutrients are pulled out or “extracted” from the sample using an “extracting solution”.

For more information on the three different methods for testing soil , proper sampling and a comparison table with soluable salt levels for each of the methods, see the fact sheet:
Current Methods of Greenhouse Media Soil Testing and How They Differ

From the New England Greenhouse Update Site http://www.negreenhouseupdate.info/index.php

Turf - Controlling Zoysiagrass in Cool Season Turf

I was recently asked about controlling Zoysiagrass in cool season turf. Here are some thoughts.

Zoysiagrass is a warm season grass that goes dormant from mid-fall through mid-spring. Although some homeowners like the grass because of its fine texture and ability to stay green in the middle of summer heat, others hate having the brown look for more than half the year.

Zoysiagrass spreads mainly by underground rhizomes and above ground stolons. This means it produces stems that run on the surface and just below the surface. As such, it can easily invade flower beds, landscape beds, and neighboring lawns. Although zoysiagrass can produce seed, many of the varieties that were planted in the past do not seed much, if at all. Seed should not be the major way that it invades but can be a secondary mechanism in some cases.

Keeping zoysiagrass from invading an area is difficult. Barriers to the underground rhizomes could help. Bury a 12" barrier such as thick plastic, fibergrass, or metal, slanting the barrier toward the area being invaded with another 6" out of the ground. This will keep the underground rhizomes from invading and you will be able to see the above ground stolons as they try to grow over the barrier so you can control them. To control any growing over the barrier, routinely use a sprayer or wick applicator and apply glyphosate herbicide (Roundup and many other brands) on the zoysiagrass growing over the barrier. Mowing will break up the zoysiagrass into smaller pieces that could potentially root and spread the grass even more. If you mow, you need to collect the clippings.

If an area has already been invaded, bite the bullet and use glyphosate (Roundup or equivalent) herbicide and spray the area once the zoysia has greened up in the late spring. This will kill everything but does not leave a residual. Do this every 3 weeks until you see no more zoysiagrass coming back up. You can then reseed or sod in the late summer with the desired turfgrass. You will have a dead area all summer but it is the only way to effectively eradicate it. Digging does not do a very good job, close mowing will not kill it, and there are no good selective herbicides that will kill Zoysiagrass and not the desired grass. There are some reports in the literature that higher rates of MSMA, fenoxaprop, or fluazifop may cause some suppression of Zoysia. Note that MSMA has been routinely used in zoysia in the past as a herbicide so don't expect much control. Of the three, fenoxaprop (Acclaim) will have the most effect on zoysiagrass.

Gordon Johnson, Extension Agriculture Agent, UD, Kent County

Turf and Landscape - Know Your Weeds, Lamium Species

The Lamium genus is in the mint family and includes some very good perennial ornamentals. Two of our most common winter annual weeds, Henbit, and Purple Deadnettle also are in this genus. Pictures of these weeds of turf and landscapes are show below (Images from Turfweeds at Virginia Tech).

Henbit, Lamium amplexicaule, in flower

Henbit, Lamium amplexicaule, in bud stage

Purple deadnettle, Lamium purpureum, in flower.

Purple deadnettle, Lamium purpureum, before flowering

Landscape and Nursery - Black Knot of Prunus

The following are images of Black Knot disease on Prunus.

Joseph O'Brien, USDA Forest Service, Bugwood.org

Robert L. Anderson, USDA Forest Service, Bugwood.org

Tim Tigner, Virginia Department of Forestry, Bugwood.org

Landscape and Nursery - Black Knot of Prunus

The following is an article on the Black Knot disease of Prunus species from University of Maryland Extension.

Black knot of Prunus is a disease caused by the fungus Apiosporina morbosa and is common on many Prunus species in Maryland (and Delaware). Examples include plums, cherries, and flowering almond. Black knot is very easily identified and often can be seen along on the roadside on native black cherry.

Symptoms: Wart-like galls form along the twigs and stems of susceptible plants. Galls may be large (greater than a foot long) and are often easily visible. Early symptoms of black knot may be overlooked because they appear as small light brown swellings on current season’s growth. As the galls age, they darken to olive green (2nd year infection) and eventually become black. Mature galls can be very large and may compromise the structure of the tree on larger stems.

Disease Cycle: In the spring, fungal fruiting bodies form ascospores on the surface of mature black) knots. Wet, rainy weather causes the asci to rupture and eject spores. The spores are splashed and wind blown to newly emerging stems and germination occurs. The first signs of infection appear in autumn as swellings on current season’s growth. Galls are perennial and enlarge every year.

Monitoring: Scouting for this disease should be done in autumn or winter after leaf drop because older knots are easily visible.

Cultural: Remove unwanted volunteer black cherry trees and any severely infected ornamental trees to reduce inoculum. Desired trees with light infections of black knot should also be pruned during the winter. Pruning should be done prior to budbreak and knots should be pruned 6-8 inches below visible symptoms. All resulting debris should be removed from site or burned. Resistant varieties should be used for ornamental plantings, especially if black cherries are nearby.

Chemical Management: Fungicides are only recommended at sites when numerous trees need to be managed (as in a nursery) or if susceptible varieties are located near heavily infested trees that may act as sources of inoculum. Efforts made to correct the situation may take 2-3 years. For most landscapes, cultural practices are usually an adequate control strategy. Spray programs consist of several treatments beginning just prior to budbreak (delayed dormant); applications are repeated as growth emerges. Fungicides may be applied preventively prior to rain when temperatures are above 60 F (conditions favoring the pathogen). Products labeled for control of black knot include chlorothalonil (various trade names), copper hydroxide (various trade names), copper hydroxide + mancozeb (Junction®), and thiophanate-methyl (Topsin®). Remember to rotate modes of action; always read and follow fungicide labels.

Extracted from the March 23, 2007 edition of the TPM/IPM Weekly Report for Arborists, Landscape Managers & Nursery Managers from University of Maryland Cooperative Extension. Go to http://ipmnet.umd.edu/07Mar23L.pdf for the full newsletter.

Landscape - New Landscape Plants to Consider

The following are some new landscape plants to consider. Information is from Andrew Bunting, Scott Arboretum, Swarthmore College.

Parthenocissus tricuspidata ‘Fenway Park’. Fenway Park Boston Ivy. Discovered by an Arnold Arboretum employee near the famous Boston ballpark, this plant has leaves that emerge yellow, gradually turn green and flame red in fall. This is a climbing deciduous vine.

Leycesteria formosa Golden Lanterns ™. Golden Lanterns Himalayan Honeysuckle. This plant has bright yellow-green heart shaped leaves with new growth having a red color. It produces clusters of white flowers with red bracts in the summer and dark purple berries in the fall.

Hydrangea quercifolia ‘Little Honey’. Little Honey Golden Oakleaf Hydrangea. The species is an eight-foot tall plant with bold, oak-like leaves and large, white, pyramidal flower clusters borne in July. ‘Little Honey’, a sport from ‘Pee Wee’, is a compact selection growing only to 3’ in height and width with smaller leaves and flowers. The leaves open a bright golden-yellow and mature to a pleasing chartreuse. Fall color is brilliant red. Performs best in moderate shade and well-drained soil.

Deutzia gracilis Chardonnay Pearls. Chardonnay Pearls Slender Deutzia. This slender Deutzia has lime yellow foliage all summer and is covered with white star-shaped flowers in the spring. It's a compact shrub only 20"-36" tall and 18"-24" wide. This easy to grow, deciduous shrub performs best in a site with partial shade and medium moisture.

Information from Andrew Bunting, Scott Arboretum, Swarthmore College, www.scottarboretum.org

Landscape - Some New Landscape Plants

The following are some new landscape plants to consider. Information is from Andrew Bunting, Scott Arboretum, Swarthmore College.

Broussonetia papyrifera ‘Golden Shadow’, Golden Paper Mulberry. This plant can be grown in shrub or tree form. It is very tolerant of dry conditions and poor soils but may need some part shade due to its light color. It is gold-yellow in spring but will turn more green in summer.

Cercis canadensis ‘Hearts of Gold’, Eastern Redbud. This is a Redbud variety with bright golden foliage. It also produces flowers on young plants allowing for good show from the time of planting.

Cedrus deodara ‘Well’s Golden’. Golden Horizon Deodar Cedar. New foliage is yellow then turns to green-yellow in summer.

Cotinus coggygria Golden Spirit ™. Golden Spirit Smoketree. This smoketree is grown for its unusual golden color. It is a multi-stemmed shrub that will grow 8-15' tall. Older plants may flower and have the characteristic smoketree look in the summer.

Information from Andrew Bunting, Scott Arboretum, Swarthmore College, www.scottarboretum.org

Turfgrass - Spring Seedings

The following is an article on weed control in new spring turfgrass seedings.

Crabgrass and other summer annual weeds are the major limiting factor when establishing cool-season turfgrass in spring. In most areas of the transition zone and north, grasses like fescue, Kentucky bluegrass, and perennial ryegrass can be seeded and established in spring granted you start early and can avoid summer annual weed problems.

Three herbicides are currently registered for crabgrass control during establishment of cool-season grasses. These herbicides include siduron (Tupersan), quinclorac (Drive), and mesotrione (Tenacity). All of these chemicals can be applied at seeding of tall fescue, Kentucky bluegrass, and perennial ryegrass with the exception that quinclorac must be applied seven days before Kentucky bluegrass seeding. Mesotrione is safe on tall fescue but can injure fine fescues (such as creeping red fescue) and low rates should be used on ryegrass establishment. Siduron controls crabgrass, foxtails and some other summer annual grasses but does not control broadleaf weeds or sedges. Quinclorac controls crabgrass, foxtails, and some other summer annual grasses and suppresses many broadleaf and sedge weeds. Mesotrione controls crabgrass and foxtails and will suppress other grasses. It also has activity on may broadleaf weeds and sedges.

In most cases, siduron will need a follow-up treatment with an herbicide that controls broadleaf weeds later in the season. Quinclorac is best applied at planting and approximately five weeks after planting. Mesotrione can be applied at planting and then again at 4 weeks after planting. These three herbicides can make the difference between a stand of turfgrass and a stand of crabgrass when seeding in the spring. Always read and follow instructions on the label before using any pesticide.

Modified with the addition of information on mesotrione from the Frequently Asked Questions section of Turf Weeds from Virginia Tech http://www.ppws.vt.edu/~saskew/turfweeds/?referrer=http%3A%2F%2Fturfweeds.contentsrvr.net%2F

Landscape - Precautions in Using Guy Wires and Stakes

Staking and use of guy wires may be necessary in sites exposed to heavy winds. However, they should be used with caution so you don't harm the tree. The following are some points to consider on the subject from the University of Massachusetts.

Staking is a technique used to protect, anchor, and support recently transplanted trees. The following are some questions and answers on staking.

Do I need to stake trees?

Not usually. Most young trees can stand unsupported, and will be stronger without stakes. Staking actually delays the creation of a strong tree. Trunk movement signals the lower trunk and roots to produce increased growth. A better trunk taper and root system results. Research shows that bare-root trees can stand unstaked as well as B&B or containerized ones.

When is staking recommended?

There are certain situations where staking can be advisable:

>very large tree size
>fall-planted evergreens
>high wind conditions
>very weak trunk
>high population pressure

What are the potential drawbacks of staking?

>Poor trunk development at the base of the tree.
>Increased trunk caliper near the support ties, which produces a negative trunk taper and restricts the vascular tissue conducting water, nutrients, and sugars.
>Wounding or girdling from ties too tight against the trunk, especially when they are left on too long. Concentrated pressure from narrow ties (e.g. elastic webbing, wire, or even wire through a hose) will crush or cut through the bark.
>More wind throw and wind damage later, particularly when the tree is staked rigidly. Most susceptible are shallow-rooted evergreens and trees with a large "sail."

What are the current recommendations?

>Don’t stake if you don’t have to.
>Consider alternative methods of staking.
>Remove stakes and ties within 1 year, or use degradable materials.
>Use flexible ties with a broad, smooth surface.
>If vandalism is a consideration: instead of staking, try planting larger caliper trees, or encircling the tree with heavy posts, wire, or metal grill work.
>If protecting from mowers and foot traffic: sink three 4' stakes halfway into the ground, 15" or so from the tree, and run a line between them to make a triangle.
>If follow-up maintenance within 1 year is unlikely: use 2" x 2" pine stakes, and UV degradable ties. The stakes and ties will fall off by themselves.
>If staking because the trunk is too weak: place the ties 6" above the lowest point where, when you hold the trunk, the top will still return upright after being bent to the side.

Reprinted from Staking Trees, a University of Massachusetts Cooperative Extension Factsheet.

Landscape - Remove Those Stakes and Wires

It may be necessary to use guy wires and stakes to keep trees and large shrubs from leaning with prevailing winds on exposed sites. However, many times wires and stakes are left on too long. The following are some pictures illustrating the problems when stakes and wires are not removed in time.

Picture from UMass Extension

Picture from Tracy Wootten, Extension Horticulture Agent, UD, Sussex County

Landscape - Understanding Pruning Series

The following is the first in a series on understanding pruning. Types of pruning are covered.

Types of pruning

Five basis techniques are used for pruning shrubs: pinching, heading back, thinning, renewal pruning, and shearing. Some plants require more of one method than another, but good pruning is usually a combination of several methods.

Pinching - is the removal of the terminal portion of a succulent, green shoot before it becomes woody and firm. Pinching can greatly reduce the need for more dramatic pruning later on. Whenever (except late summer) you see a shoot becoming excessively long simply pinch or cut the shoot to reduce its length and to promote side branching. Long, vigorous shoots should be cut back into the canopy instead of cut at the outer limits of the existing foliage.

Heading back - involves removing the terminal portion of a woody branch by cutting it back to a healthy bud or branch. Heading back will stimulate shoot growth below the cut thus making the plant more dense. The shape of the plant can be influenced by cutting to inward or outward growing buds. The top bud should be located on the side of the branch that faces the direction new growth is desired. Some plants will have two buds opposite each other on the stem. When such stems are cut, remove one of the buds if you need to control the direction of new growth. If both are allowed to grow, a forked and often weak stem may develop. Repeated heading back with no thinning cuts results in a top heavy plant. Dense top growth reduces sunlight and results in the loss of foliage inside the plant canopy.

Thinning - is the least conspicuous method of pruning and results in a more open plant without stimulating excessive new growth. Considerable growth can be cut without changing the plant’s natural appearance or growth habit. With thinning cuts a branch is cut off at its point of origin from the parent stem, to a lateral side branch, to the “Y” of a branch junction, or at ground level. A good rule-of-thumb is to prune to a lateral that is one-third the diameter of the branch being removed. Thin out the oldest and tallest stems first, allowing vigorous side branch development. This method of pruning is best done with pruning shears, loppers, or a saw --- not hedge shears. Plants pruned by thinning include crapemyrtle, magnolia, viburnums, spireas, smoketree, and lilac. Repeated thinning with no heading back results in plants with long spindly branches. The entire plant may take on a straggly look.

Renewal pruning (rejuvenation) - involves removing the oldest branches of a shrub by prunig them near the ground, leaving only the younger, more vigorous branches which may also be cut back. Small stems (less than pencil size) should be removed. Plants pruned by renewal include abelia, deutzia, forsythia, mockorange, spirea, and weigela.

A variation of renewal pruning involves cutting all branches back to a predetermined height each year. Butterfly bush is often pruned back to woody framework. With time the framework becomes congested and will require some slight thinning. Yellow and red twig dogwood and beautyberry are severely pruned almost to the ground each year to promote the growth of more colorful twigs or berries.

Shearing - involves cutting the terminal of most shoots with shearing or hedge clippers. This method should not be used on foundation plants but should be restricted to creating formal hedges. Shearing destroys the natural shape of the plant. It causes a thick profusion of growth on the exterior of the plant that excludes light form entering the center of the plant (Figure 15-30). Foliage on the interior of the plant dies. The natural renewal growth from within the plant in prevented.

Extracted from "Pruning Shrubs" from North Carolina State University Cooperative Extension.
http://www.ces.ncsu.edu/depts/hort/consumer/factsheets/shrubs/text/pruning.html#broadleaf

Landscape - Mulch and Mulching of Trees

Landscape maintenance firms will be applying and renewing mulch throughout the late winter and spring in the landscape. The following is an article on mulch and mulching of trees in the landscape.

Trees in the forest annually benefit from a natural protective layer over the soil of fallen leaves, needles, and other tree parts that cover and protect both soil and roots. This same protection can be given to the trees that we plant in our landscapes by mulching.

Benefits of Mulch

• Helps to conserve soil moisture; evaporation and the need for watering is reduced;
• Insulates the soil surface, keeping it warmer in winter and cooler in summer;
• Helps control weeds and grass;
• Protects the trunk and surface roots from mechanical injury from lawn mowers and string trimmers;
• Improves soil structure, aeration and drainage;
• Increases soil fertility as organic matter decomposes;
• Reduces soil erosion;
  Prevents soil compaction by reducing traffic;
• Makes lawn maintenance easier; and
• Presents a well cared for appearance.
  

Types of Mulch

There are two distinctly different types of mulch to choose from: organic and inorganic. While both will conserve moisture and reduce damage from mechanical injury, organic mulches, as they decompose, also provide the additional benefit of adding organic matter to your soil. This helps the soil to better retain water and nutrients, giving you healthier trees.

Organic mulches are made from plant material and include composted wood chips, shredded bark, shredded roots, pine needles, compost mixes and leaves. Bark or root mulch is the preferred mulching material for use in the landscape due to its slow rate of decomposition and thus longevity. The material should be weed-free, non-matting, easy to apply, and readily available. Organic mulches decompose at different rates depending on the material and must periodically be replenished.

Inorganic mulches include decorative stone, lava rock, pulverized tires and geotextile fabrics. They are useful for soil protection in high traffic areas but are not recommended for mulching around trees. As inorganic do not contribute to soil and tree health as organic mulches do.

The ideal mulch does not compact readily, retard water and air movement into the soil and breaks down slowly. In addition, the ideal mulch is uniform in color, attractive and does not blow away. Cost and appearance also need to be considered when choosing a mulch.

How to Apply Mulch

Check soil drainage in the area to be mulched. Determine if there are trees or plants that may be affected by the type of mulch. Most organic mulches work well in most landscape situations. However, some plants may benefit from specific mulches such as pine needles or bark that acidify the soil.

Apply a 2 to 3 inch layer of mulch over well-drained soils. Use a thinner layer on poorly-drained soils. While the proper depth is important, the area covered is more important. Since the purpose of mulching is to benefit the roots, the wider the mulch ring, the greater the benefit. Mulch out to the tree’s drip line if possible. Drip line is a line on the ground defined by the outer edge of a tree’s branches.

Do not pile mulch against the tree trunk. Pull mulch back several inches from the trunk so the base of the trunk and root crown are exposed. The mulch ring should resemble a “doughnut,” not a “volcano.”

If mulch is already present, check the depth. Do not add more if a sufficient layer is already in place. Rake old mulch to break up matted layers and restore its appearance.

A properly mulched tree will have a 2 to 3 inch layer of mulch in a doughnut shaped ring. The ring should extend out to the tree’s drip line if possible.

Effects of Poor Mulching

Mulching provides multiple benefits toward improving tree health and longevity. However, these benefits can only be obtained by the tree if the mulch is applied properly and maintained consistently over the live of the tree. When mulch is applied inappropriately by over mulching or piling up against the trunk, it can:

• Cause inner bark tissue to die;
• Lead to insect and disease problems;
• Promote excessive soil moisture and promote root rots;
• Create habitat for rodents that chew the bark and girdle the stem;
• Lead to anaerobic conditions that produce alcohols and organic acids toxic to young plants;
• Cause imbalances in soil pH; and
• Become a matted barrier that prevents the penetration of water and air.

Information from ‘Mulch: Your Tree’s Best Friend.’ Courtesy of the Missouri Department of Conservation.

Greenhouse - Manage to Reduce Botrytis

Botrytis is a major disease problem in greenhouse plants and can be seen infecting flower parts commonly. The following is a report from the University of Maryland on Botrytis.

We are seeing Botrytis on pansy, cyclamen, and primrose this week. Botrytis can invade the plant directly through unwounded plant parts, especially flowers or through wounds such as the stubs left when plants are pinched. Any areas of damaged tissue can be easily invaded by Botrytis.

The Botrytis fungus requires a film of water on plant surfaces to germinate and infect the plant. This film of water must remain on the plant surface for several hours. Any cultural practice that prevents continuous periods of leaf wetness will help prevent Botrytis infection. Proper spacing and sanitation, removal of spent flowers, periodic venting, horizontal airflow fans, and watering early in the day are recommended.

Some fungicide controls include: Decree (fenhexamid), Zerotol (hydrogen peroxide), Spectro (chlorothalonil), and Protect T/O (mancozeb).

Adapted from an article in the February 15, 2008 issue of the Greenhouse TPM/IPM Weekly Report from University of Maryland Cooperative Extension.

Landscape - White Pine Blister Rust

I had an email recently on why Currants and Gooseberries are regulated for planting in Delaware. The issue is White Pine Blister Rust. Contact the Delaware Department of Agriculture Plant Industries Section for more information on the restrictions. The following is an article from Cornell on White Pine Blister Rust.

White Pine Blister Rust (WPBR), caused by the fungus Cronartium ribicola, is one of the most important diseases of white pine in the northeastern United States. White pines, especially young trees, and plants belonging to the genus Ribes (currants and gooseberries) are susceptible to the disease. Although WPBR is occasionally a severe foliar disease on Ribes plants, on white pines it is lethal if allowed to spread from an infected branch into the trunk.Symptoms

On white pine, the initial symptoms appear in late summer or autumn as small, yellow spots on needles. The infection spreads down the needle and into the twig, where slight swelling and yellowing develops during the next growing season. Numerous pale yellow blisters (called aecia) may be as large as 3 mm (1/4 inch) across and break through the infected bark in mid-April to mid-May a year or more after the bark first becomes infected. These blisters rupture and release large numbers of dry, yellow-orange spores. Blisters disappear after spore discharge and form again the next year. As the bark dries out it appears roughened. The sporulation pattern continues over years until the stem is girdled.

Rodents frequently feed on rust-infected bark because of its high sugar content. Bark injured by the rodents yields copious amounts of resin, often obscuring the typical symptoms of rust infection.

On Ribes, the symptoms develop throughout the growing season and are comparatively mild. The lower leaf surface, when infected, becomes pale. This is followed within a few days by the development of tiny orange pimple-like fruiting bodies (uredinia) in which yellow-orange rust spores are produced. These spores cause repeated new infections on Ribes leaves from May through late summer, when another spore-bearing structure of the rust fungus appears. This structure, called a telium, is a short, yellow-brown, hair-like filament. Large numbers of these filaments give the lower leaf surface a fuzzy brown appearance.

Disease cycle

During moist weather in August and early September, after seasonally cool weather has prevailed for about 2 weeks, telia on leaves of Ribes plants produce spores that cause new infections on pine needles. The rust fungus grows slowly within the pine needle and twig; aecia (blisters) first rupture the bark in April-May of the second or third growing season after a pine needle becomes infected. The spores from these blisters (aeciospores) cause new infections on the growing leaves of Ribes plants but are not capable of causing infections on pine. This alternation of host plants is essential for the perpetuation of the fungus; it cannot complete its life cycle on the pine or Ribes alone.The pimple-like uredinia that develop on infected Ribes leaves produce orange spores (urediniospores) that cause new infections on Ribes leaves throughout the growing season. These spores, however, are not capable of causing infections on pines. The telia that develop on infected Ribes leaves in late summer produce spores (called basidiospores) that cause new infections on pines. The infected pine trees provides a place where the rust fungus may safely overwinter; it cannot survive in the Ribes leaves or outside a living host plant.

Control Strategies

Branches with cankers should be cut off where they join the next healthy branch. This cut should be made at least 15 cm or 6 inches beyond the yellowish margin of the canker. This margin can be easily detected by rubbing the area with a wet cloth. Lower branches are most commonly infected. If lower branches are removed, the probability of infection is greatly reduced.Infections on trunks can be eliminated by removed all bark 5 cm or 2 inches on each side and 10 cm or 4 inches above and below the canker margin. After excision of the infected bark or removal of a branch, the area may be treated with a tree wound dressing for cosmetic purposes.Within the blister rust hazard areas, all susceptible Ribes should be removed from the vicinity of valuable white pines.

Ribes are regulated in Delaware. If you wish to plant Ribes in Delaware, contact the Plant Idustries Section of the Delaware Department of Agriculture 302-698-4500 before purchasing or planting to determine if you can plant in your area, and what cultivars you may be able to plant. While reducing Ribes populations will help, it will not completely prevent possible infection since the infectious spores may be carried by air for up to several miles. Cultivated currants and gooseberries may be planted in areas where infection probability is low.The currant cultivars Cornet, Consort, and Crusader are resistant to white pine blister rust. In one study the cultivars Red Lake, Jumbo, Cherry, and White Current were less susceptible and the cultivars Welcome, Redjacket, Green Hansa, Poorman and Pixwell were the most susceptible.

Adapted from "WHITE PINE RUST, Cronartium ribicola" a Cornell University Plant Disease Diagnostic Clinic Factsheet with added information for Delaware.

Landscape - Seiridium Canker on Leyland Cypress

The following is an article on Seiridium canker disease of Leyland Cypress from North Carolina State University.

Seiridium canker, caused by Seiridium unicorne, is probably the most damaging disease on Leyland cypress. Plants of all sizes and ages are affected. Cankers may form on stems, branches and in branch axils causing twig, branch or, at least on smaller plants, stem dieback. Cankers appear as sunken, dark brown or purplish patches on the bark, often accompanied by extensive resin flow. It should be noted that resin exudation often occurs from the branches and stems of otherwise healthy plants of Leyland cypress thus resin flow by itself is not a diagnostic characteristic for Seiridium canker. Scattered twigs or branches killed by the fungus turn bright reddish brown, and are in striking contrast to the dark green healthy foliage. Fruiting bodies of the fungus appear on the bark surface of the cankers as small circular black dots barely visible to the naked eye. Spores of the fungus are spread to other parts of an infected tree, or from tree to tree by water splash from rain or irrigation. The fungus also can be spread from tree to tree on pruning tools. Long distance spread appears to be through the transport of infected cuttings or plants.

Currently there are no chemical control measures recommended for the disease in the landscape or nursery. Avoiding water stress and tree wounding may reduce infection. Infected branches or twigs should be pruned and destroyed as soon as symptoms are noted. Prune at least one inch below the canker, and sterilize the pruning tools between cuts by dipping them in rubbing alcohol or in a solution of 1 part chlorine bleach to 9 parts water. Tools should be cleaned and oiled after using bleach to prevent rusting. Severely affected plants should be removed and destroyed.

Reprinted in part from "Diseases of Leyland Cypress" by Mike Benson, Plant Pathologist; Larry F. Grand, Plant Pathologist; and Ronald K. Jones, Professor Emeritus, North Carolina State University.

Landscape - Dead Leyland Cypress

The drought affected our Leyland Cypress trees last year with many showing sypmptoms ranging from branch dieback to whole tree death. The following is information on this problem.

There are many dead leyland cypress trees in the landscape, especially downstate. Most of the deaths appear to be drought related, but we are also seeing a combination of drought and a fungus disease called Seiridium canker. Seiridium canker is favored by drought stress and causes branch infections that lead to scattered dead branches. If undetected and not pruned the fungus can move into the trunks and cause tree death particularly in small trees. Evergreens should be planted in the spring or in the early fall to give them time to get established before cold weather sets in. Deaths of recently planted trees may be due to late fall planting and the fluctuations in temperature this winter.

Landscape - Clover Mites Can Migrate to Houses

The following is a short article on clover mites that can be an nuisance invader of houses in the early spring.

Clover mites are accidental invaders that can be a temporary nuisance during the early spring. These very small, reddish brown creatures appear only as moving dark spots to the naked eye. Sheer numbers, plus the resulting red-brown stain left behind if they are crushed, make them unwelcome visitors. Clover mites are not blood feeders and will not harm people or pets, nor will they infest household products. Once inside a home or building they will soon die. Clover mites feed on clover and grasses. They can be especially abundant in the heavy, succulent growth of well-fertilized lawns. They usually enter a home around windows or doors so they are usually seen crawling along sills or thresholds. A soapy rag or wet sponge can be used to clean mites off of surfaces. Wipe carefully to avoid crushing the mites and causing stains. The crevice tool of a vacuum cleaner may also be used to pick up mites. Rely on non-chemical control indoors. Do not apply insecticides to kitchen counters or other interior surfaces. There is an increased potential for invading structures when grass extends up to the foundation. A plant bed or open area will provide a barrier that will stop many mites and provide a long term solution to persistent problems. Avoid overfertilizing lawns. This creates situations that are ideal for mites to increase to tremendous numbers. A barrier spray of a pyrethroid insecticide may reduce movement of the mites from grasses to patios, decks, or house walls. Use a sprayer to treat at the base of all exterior doors, garage and crawl space entrances, around foundation vents and utility openings, and up underneath siding. It may also be useful to treat around the outside perimeter of the foundation in a 2 to 6- foot-wide band along the ground, and 2-3 feet up the foundation wall. Follow label directions.

Reprinted and modified from CLOVER MITES CRAWLING By Lee Townsend in the March 12, 2007 edition of the Kentucky Pest News from the University of Kentucky College of Agriculture.

Landscape - Bleeding Cankers on Deciduous Trees

The following is an article by John Hartman, University of Kentucky plant pathologist on bleeding cankers caused by the Phytophthora fungus in deciduous trees.

In recent years there has been much discussion about Phytophthora ramorum, cause of bleeding cankers and sudden oak death disease. Other Phytophthora-caused bleeding cankers on landscape trees have recently been described by Dr. George Hudler of Cornell University in an article in the 2007 volume of Arboriculture and Urban Forestry. In addition to journal articles, I have had the opportunity to hear Dr. Hudler speak on this topic.

Bleeding canker diseases are characterized by trunk lesions that leak fluid through the bark or leave fluid stains on the bark. Bleeding cankers can be caused not only by fungus-like organisms such as Phytophthora, but also by fungi, bacteria, pruning, other tree wounds, or insects. Field diagnosis of a Phytophthora canker requires a specialized kit (e.g., Alert LF Strip; neogen.com) containing a five-minute test that detects only Phytophthora. For laboratory samples of bleeding cankers, the Plant Disease Diagnostic Laboratory uses a Phytophthora-specific ELISA (agdia.com) test.

Bleeding cankers of landscape trees may be caused by a number of Phytophthora species including P. cactorum, P. cambivora, P. cinnamomi, P. citricola, P. nemorosa, P. palmivora, and P. ramorum. Some, like P. ramorum, are not known to be present in Kentucky. To determine the which species of Phytophthora is in a sample, laboratory cultures or PCR tests would also be needed.

The following landscape trees which grow in Kentucky (and Delaware) are known hosts of bleeding cankers caused by species of Phytophthora. Although some bleeding cankers lead to tree decline or death, many of the Phytophthora bleeding cankers are not lethal and trees may be able to compartmentalize the lesions before they spread and girdle the tree.

-Beech can often be seen with Phytophthora-caused bleeding cankers.
-Birch bleeding cankers associated with P. cactorum can cause tree decline.
-Chestnuts are susceptible to ink disease, caused by P. cambivora or P. cinnamomi, and results in bleeding cankers on the roots and lower trunk. This disease was a serious disease of American chestnut before the arrival of Chestnut blight.
-Dogwood crown rot sometimes breaks out into bleeding cankers caused by P. cactorum.
-Elm infected with P. cactorum shows bleeding canker symptoms.
-Horsechestnut bleeding cankers have been attributed to P. cactorum and P. citricola.
-Linden is listed as a host of P. cactorum and producer of bleeding cankers.
-Maple bleeding cankers are often observed in Kentucky. At least five species of Phytophthora have been implicated as causes. Fusarium solani, a completely unrelated fungus, has also been implicated in maple bleeding cankers.
-Oak, in addition to being susceptible to P. ramorum, cause of sudden oak death (not present in Kentucky or Delaware) is also susceptible to P. cactorum, P. cinnamomi, and P. citricola, which cause bleeding cankers.
-Willow bleeding cankers have been attributed to P. cactorum.
-Other trees with bleeding cankers, but not caused by Phytophthora include: Crabapple (Botryosphaeria dothidea), Poplar (Cryptosphaeria populina and Ceratocystis fimbriata), Prunus species (a bacterium, Pseudomonas syringae), Sweetgum (Botryosphaeria ribis), Walnut (two species of the bacterium Brenneria).

Management of Phytophthora bleeding cankers of landscape trees is difficult. Recent development and approval of formulations of phosphorous acid such as Agri-Fos®, Alude®, Arborfos®, and Whippet® provide tools that may be helpful in combating Phytophthora cankers. Such treatments can either be injected or applied with the aid of an adjuvant/penetrant such as Pentra-Bark® that assists in the movement of chemicals directly through the bark into trees. Although much research needs to be done, preliminary results suggest that these treatments will gradually slow the growth of cankers and after a year or two, reduce their size.

Reprinted from PHYTOPHTHORA CAUSES BLEEDING CANKERS ON DECIDUOUS TREES By John Hartman in the February 11, 2008 edition of the Kentucky Pest News from the University of Kentucky College of Agriculture.

University of Delaware Botanic Gardens - Guided Plant Walk

Don't miss the opportunity to go on a guided plant walk of the UDBG in March with Dr. John Frett. You will have an opportunity to see plants being offered in the Spring plant sale growing in the landscape.

UDBG Guided Plant Walk

Date: Thursday, March 27
Time: 4- 5:30 p.m.
Place: Walk will depart from the Fischer Greenhouse.

This plant walk is free with a reservation (302-831-2531). Dr. John Frett will lead this tour of plant sale items so buyers can see plants established in the landscape in larger or mature sizes.

University of Delaware Botanic Garden Events - Plant Sale and Sale Preview Talk

The University of Delaware Botanic Gardens sponsors events for gardeners and commercial landscapers. The UDBG is a wonderful resource for the nursery and landscape industry. The following is information on the Spring Plant Sale and Plant Sale Preview Talk.

The Spring UDBG plant sale is a great place to buy unusual plants with limited availability in the nursery and landscape trade. The sale benefits student internships as well as the growth and development of the UDBG.

Plant Sale Preview Talk

Tuesday, March 18 from 7-9 p.m. in the Girl Scout Building on the College of Agriculture and Natural Resources campus in Newark. UDBG Friends generously sponsor a lecture highlighting plants featured in the spring plant sale. UDBG Director John Frett will show many of the plants offered in the catalog and sale. Refreshments served. The event will include a small, silent auction of select plant gems not found in the catalog or at the plant sale. Plants to be auctioned will be placed on the UDBG website the week before the preview. This talk is free and open to the public.

UDBG Plant Sale

Saturday, April 26 from 9:30 a.m. to 4 p.m.

The UDBG spring plant sale is held on Ag Day each year. Plants include perennials, tender perennials, shrubs, small flowering trees, evergreens and shade trees. Plant sizes range from quarts to 20 gallons.

Turf - Winter Kill

Turf winter kill can be a problem, especially in seasons with fluctuating temperatures or with winter droughts. The following is an article on the subject.

Winter kill is a general term used to describe the loss of turfgrass plants during winter months. Loss of turfgrass plants during winter months can be caused by factors such as: low temperature kill (freeze damage of warm season grasses such as zoysia or bermudagrass), desiccation (drying out of plant material), heaving (freeze thaw cycle forcing roots out of the ground), disease activity (such as cool season brown patch) and insect damage such as fall feeding by grubs.

In most years, heaving and desiccation is the number one reason for winter loss of turfgrass in home lawns, commercial properties, sports fields and golf courses. With the extensive drought conditions throughout 2007, and the freeze thaw cycles we have had in the winter months, loss of turfgrass from desiccation is potentially going to be a continued problem throughout the remainder of the winter. This is especially the case in new seedings (seeded in the fall) and thinner turf stands.

After a winter of periods of alternating mild and cold temperatures; snow, ice, and rain; and frequent day/night thaw freeze cycles, turf areas may be showing symptoms ranging from dead or dying plants to yellow, stunted plants. Winters characterized by a number of freeze-thaw cycles can lead to heaving that can force the grass crown out of the soil where desiccating winds can kill small susceptible seedlings and even larger established plants. The crown region of grass is a growing point region that produces new leaf buds; tiller buds; and, in the spring, new adventitious roots that form the spring root system. Until the new root system develops enough for the new roots to become active, little nutrition and possibly too little water is taken up by the plant. Injured plants may not show stress until the temperatures warm and they begin to grow. By about mid March, you will begin to see these plants turn color and report that the grass is 'going backwards'. It is during the time when the plants begin to re-grow and new roots become functional that turf will look the worst.

Cool season brown patch or yellow patch may also appear on on home lawns, greens and tees. Unlike brown patch, which occurs in the summer, yellow patch (Rhizoctonia cerealis) thrives during cool, wet weather between October and May. Patches are chlorotic (yellow) and typically range from several inches to three feet in diameter. Patch centers are frequently green, resulting in a “frog-eye” or yellowish ring effect. There are a number of fungicides that are effective on cool season brown patch. Even without the use of fungicides, symptoms generally disappear when warm weather returns.

Article adapted from a number of extension sources including writings from Bob Mulrooney, Extension Plant Pathologist, UD and Richard Taylor, UD Extension Agronomist.

Landscape - Dormant Oil Use

Dormant oils should be applied in late winter or early spring for control of cool season insect and mite pests. The following is an article on using dormant oil.

DORMANT OIL. Late February and March is a normal time to apply dormant oils to trees and shrubs before bud break. In this mild winter, we may see great benefit and for past problem areas it is good IPM. The rate is usually 3-4 gallons of oil to 100 gallons of dilute spray. Soak the bark of twigs, branches and the trunk to run off; you will be more effective and economical if the vegetation is pruned first. Consider pruning out the eggs of tent caterpillar or moth pupae before you spray. They are easier to spot before vegetation appears. The dormant oil will help kill overwintering eggs, mites, some scales and other overwintering stages it might contact. For example, adult and nymphal populations of white pine sheath mite might be impacted. Contact is the key as there is no residual with oils.

Late February and March always is a tough month to plan oil coverage. You need wait until the weather warms and it is not likely to freeze overnight. We usually say it should be 45 degrees F or more. Spray on a day when plant material is dry and the wind is not strong, so the oil has a chance to dry slowly, allowing for penetration of the chemical into the insects/insect eggs you are targeting. Do not spray if leaves are just opening, as they often are most vulnerable to chemical damage at this early stage. Do not include a fungicide or sulfur compound with your spray. Avoid brambles and most maples and evergreens with bluish color such as blue spruce. Check the label for plants such as black walnut, beech, holly, evergreen magnolias and redbud since they often exhibit some sensitivity to dormant oils.

Reprinted from an article by Dr. Dewey Caron, Extension Entomologist, University of Delaware in the Ornamentals Hotline from UD Cooperative Extension.

Landscape - Ambrosia Beetle

Ambrosia beetles are a major cause of decline and death of woody landscape plants. The following is an article on the subject adapted from University of Maryland Extension information.

Ambrosia Beetles

Ambrosia beetles are one of the major killers of nursery and landscape plants from Georgia to Delaware. The adult females overwinter and adult activity starts with the first warm weather of spring. You can place traps baited with ethyl alcohol to attract beetles. As most ambrosia beetles overwinter as adults, degree days have little value for predicting emergence time because there is no temperature dependent larval period prior to the first spring flight. With our warm winter it is likely to see emergence in March this year and with the first extended warm period we can expect lots of activity from ambrosia beetles.

Ambroisa beetles commonly attack trees including styrax, Kwanzan cherry, golden raintree, dogwood, holly, weeping willow and sugar maples.

Control: It is important to treat trees before beetles close the galleries with frass. If trees are found with large amounts of frass being pushed out then it is usually too late to apply an insecticide. In the landscape trees can be treated with permethrin (Astro). In the nursery, treat with bifenthrin (Onyx).

Adapted from an article in the March 23, 2007 edition of the TPM/IPM Weekly Report for Arborists, Landscape Managers & Nursery Managers from University of Maryland Cooperative Extension

Greenhouse - Geraniums, Soil pH, and Fertility

The following is an article on the effect of soil pH and fertility on geraniums in the greenhouse reprinted from the Greenhouse TPM/IPM Weekly Report by University of Maryland Cooperative Extension.

Geraniums- soil, pH and fertility

Growers should be using a medium to high drainage soil mix and feeding with 300 ppm nitrogen. A pH of 6.0- 6.3 for zonal geraniums and 5.5- 5.8 for ivy geraniums is recommended using the pour-thru method. If the pH drops below 5.5 - 6.0 on zonal geraniums, you can get iron and manganese toxicity which causes a bronze speckled necrosis on the lower leaf margins. You can raise the pH with liquid lime or calcium nitrate fertilizer if the pH is not extremely low. If the pH gets up to about 6.5 on ivy geraniums, you will start to see an iron deficiency (yellowing of the new leaves). You can lower the pH with sulfuric acid or ammonium nitrate fertilizer. Sprint 330 or 138 can be added to correct an iron deficiency- don’t forget to rinse off the leaves.

Reprinted from the February 8, 2008 edition of the Greenhouse TPM/IPM Weekly Report from University of Maryland Cooperative Extension.

Landscape - More Pine Wilt Pictures, Blue Stain Fungus

Tracy Wootten, UD Extension Horticulture Agent for Sussex County sent me these pictures of a longhorned beetle, beetle damage, blue stain fungus often found with pine wilt, and pine wilt from the pine wilt nematode that is transmitted by the longhorned beetle.

Maryland Cut Flower Short Course

Maryland has an active cut flower growers association. They sponsor great educational events during the year with Maryland Cooperative Extension. The following is an announcement for the upcoming Cut Flower Shortcourse.

Cut Flower Short Course
February 26—29, 2008 at Brookside Gardens, Wheaton, Maryland

Sponsored by Maryland Cooperative Extension, University of Maryland

Co-sponsored by Maryland Greenhouse Growers’ Association, Maryland Cut Flower Growers, and Association of Specialty Cut Flower Growers

2008 Cut Flower Short Course

Brookside Gardens is a 50-acre public display garden situated in Wheaton, Maryland. Included in the gardens are several distinct areas; azalea garden, rose garden, children's garden, formal garden, fragrance garden, Japanese style garden and trial garden. The garden also features two conservatories for year-round enjoyment.

Registration/Check-in on February 26th begins at 8:00 a.m.; the conference starts at 8:30 a.m. Depending on the day’s schedule, sessions end between 3:15 and 4:30 p.m.

February 26, 2008

Growers’ Experiences and Success Stories

Dave Dowling, Farmhouse Flowers & Plants
Maria Price-Nowakowski, Willow Oak Herb and Flower Farm
Bill Preston, Bill Preston’s Cut Flowers
Don Biggar, Galena Blooms Farm
Bert Klotz, Maison des Fleurs

February 27, 2008

>Financial Planning, Regulations, Sales Tax, Recordkeeping, Proper Business Structure
>Building a List of Cut Flowers to Grow: Woody Cut Flowers, Annuals and Perennials
>Making Connections with Wholesalers
>Setting up and Using Trickle Irrigation
>Once You’ve Cut Them: Then what? Postharvest handling, coolers and preservatives
>Fundamentals of Field Growing
>It Starts with N, P and K: Nutrients for cut flowers
>Weed Control Options

February 28, 2008

>Marketing 101
>Selling Cut Flowers at Local Markets
>Growing Toward a Destination Farm: How a grower is getting started with farm tours and floral workshops
>Should you grow organic and how to meet the requirements
>Working With Florists
>Edible Flowers

February 29, 2008

>Forcing Tulips and Lily Production
>Selling Herbs in Cut Flower Bouquets
>Heritage Roses for Superior Cuts and Fragrance
>Cut Flowers to Grow in High Tunnels

Come learn from growers and extension personnel as they cover a variety of topics on how to grow, harvest, store and market cut flowers!

For more information: Contact Suzanne Klick, 301-596-9413 or sklick@umd.edu

Registration form can be downloaded at http://www.ipmnet.umd.edu/08CutflrC.pdf

Greenhouse - Fungus Gnat

The following are images of the fungus gnat adult and larvae. This is one of the most common pests of greenhouses.

Fungus Gnat Adult

Photo by Johnny N. Dell, , Bugwood.org

Fungus Gnat Larvae

Photo by Whitney Cranshaw, Colorado State University, Bugwood.org

Greenhouse - Fungus Gnats

Fungus gnats can ge a problem in the greenhouse when plants are kept too moist. The following is an article on the subject reprinted from the University of Maryland Greenhouse TPM/IPM Weekly Report

We are experiencing warmer than normal temperatures that heat up the greenhouse for several days, followed by cloud cover and rainy weather. This weather is ideal for fungus gnats which can feed on the roots of pansies. We have also had samples from growers where the larvae have bored into the stems, usually when the plants have been held too wet during cloud cover periods.

Many of you have pansies in the greenhouse at this time of the year and are getting ready to move them out into the market in the next 3 - 4 weeks (hopefully). Take care with your watering practices, applying the water when it is predicted to be sunny and warm. Try to water in the morning so that the plants can dry down during the day, and keep the plants on the dry side during the cloudy and wet weather.

We suggest monitoring for fungus gnat larvae in the soil by placing a potato wedge on the soil. Inspect it every couple of days using a 10 -16 X magnifier to examine the side that you had on the soil surface. The fungus gnat larvae are clear (early instar) to slightly whitish as they go into the later instars. They will have a black head capsule.

Controls:

Bti sold under the name Gnatrol can be applied. It is recommended that you make three applications at 7 - 14 day intervals if using Gnatrol. The label recommends that the first application be made at a higher rate followed by two additional applications at lower rates.

Distance applied as a soil drench gives excellent long term control of fungus gnats. Distance is an insect growth regulator that prevents larvae from maturing. The kill is not quick, but it is very effective.

Entomopathogenic nematodes- we have had excellent success using the beneficial nematode, Steinernma feltiae, applied as soil drenches to control fungus gnats.

Reprinted from the February 8 edition of the 2008 Greenhouse TPM/IPM Weekly Report from the University of Maryland Cooperative Extension. Go to http://www.ipmnet.umd.edu/08Feb08G.pdf for the whole newsletter.

Landscape - Pine Wilt Caused by Pine Wilt or Pinewood Nematodes

Pine wilt caused by pine wilt nematode

Photo by USDA Forest Service - North Central Research Station Archive, USDA Forest Service, Bugwood.org

Dead pine tree that was infected with the pine wilt nematode

Photo from the USDA Forest Service - North Central Research Station Archive, USDA Forest Service, Bugwood.org

Longhorned beetle that transmits the pine wilt nematode.

Photo by L.D. Dwinell, USDA Forest Service, Bugwood.org

Landscape - Pinewood or Pine Wilt Nematode

Pinewood or pine wilt nematode is a problem with the black pine group and causes premature death of these trees. The following is a short article on the subject.

Over the winter, I would expect to see some Japanese Black Pines, Pinus thunbergii, die from pine wilt caused by the pinewood or pine wilt nematode, Bursaphelencus xylophilus. This is another disease that is favored by drought stress. It is common to see infected trees in the coastal area of Sussex county. However, we also see the problem in Kent. Remove dead trees now to eliminate the nematodes that are transmitted to healthy trees in the spring by long-horned beetles. For more information on sampling follow this link: http://ag.udel.edu/extension/horticulture/pdf/pp/pp-15.pdf

Adapted from an article from Bob Mulrooney, Extension Plant Pathologist, UD

Turf and Landscape - Star of Bethlehem Control

Star of Bethlehem control has been difficult in the past. We now have some new herbicide tools for this problem weed. The following is an article on the subject.

STAR-OF-BETHLEHEM is a major perennial weed in turfgrass and landscapes. It is a bulbous perennial with fleshy grass-like leaves that grow up to a foot long with a whitish grooved midrib. From April to June, the plant produces bright white flowers with 6 oblong petals that have a distinctive green stripe underneath.

Star-of-Bethlehem generally dies back to underground bulbs during summer following seed dispersal. Ovate bulbs of Star-of-Bethlehem grow in clumps in the soil. Reproduction by seed is minimal but plants may germinate from dormant seed during spring months.

Controlling Star-of-Bethlehem is difficult since the plant can regenerate shoot tissue from vegetative structures following herbicide injury. Most pre- and post-emergence herbicides, including some non-selective materials, do not effectively control Star-of-Bethlehem. Glyphosate-containing products (such as Roundup®) often provide inconsistent and erratic levels of control and are not recommended. Multiple applications of diquat (Reward®) at 3 week intervals may effectively control Star-of-Bethlehem but may severely injure surrounding grasses and plants.

Recently, Research conducted at Virginia Tech University demonstrated that carfentrazone (Quicksilver T&O®) has substantial herbicidal activity on Star-of-Bethlehem and is safe on all cool-season turfgrasses. Applying Quicksilver T&O at 4 oz/acre once or 2 oz/acre twice at 3 week intervals gave 88 to 95% Star-of-Bethlehem control in tall fescue. Unfortunately, single applications of Quicksilver T&O® can not currently exceed 2.1 oz/A. In addition, Quicksilver T&O® is not systemic and Star-of-Bethlehem may continue to be problematic in successive growing seasons.

Reprinted from an article by Dr Steve Hart, Extension Ornamental and Turf Weed Specialist, Rutgers University.

Landscape - Watch for Winter Damage

Years with winters such as this one can lead to more winter damage as plants are subjected to abnormally warm periods followed by brief cold snaps. The following is an article on this subject.

The winter has been pretty mild, but the fluctuating temperature can result in winter damage to broadleaved evergreens. There has been less of this damage this year because the ground has not been frozen for long periods of time but expect to see symptoms in scattered locations. A number of conifers, most notably spruce and Leyland cypress may show evidence of winter injury. With a large amount of plants suffering from the drought and heat of last summer, expect to see continued problems, especially in Sussex and parts of Kent where the soils are very sandy. This trend will continue due to the warm winter. Many plants do not acclimatize properly during warmer winters and subsequently suffer during the brief, but bitter cold periods. Trees damaged during the cold snaps will exhibit discoloration and dieback in spring and summer.

Adapted from an article by Bob Mulrooney, Extension Plant Pathologist, UD.

Landscape - Diagnostic Tools and Resources

The following is a continuation on our series on diagnosing landscape problems with information on tools and resources available.

Basic diagnostic tools:

>Scissors, pruning shears, or a sharp knife to collect samples and observe internal symptoms.
>A hand lens for observing pathogen structures.
>A small, clear glass of water to check for signs of bacteria.
>Clean sandwich bags, ziplock bags, paper towels and rubber bands or twist ties for collecting and incubating samples.
>Some reference books. Several reference books are available for home use, but for detailed pathogen diagnosis, the most complete references are the disease Compendia published by the American Phytopathological Society (APS) Press. Individual compendia are available for specific crops or types of crops (e.g., stone fruits, cucurbits, turf grass, etc.). These compendia provide detailed descriptions of disease symptoms as well as descriptions of the pathogens causing the disease. The APS bookstore can be accessed at http://www.shopapspress.org/

Step-by-step procedures:

>Identify the plant(s) involved.
>Inquire into site history of plant disease or other problems.
>Look for patterns of symptoms on plant parts or whole plants.
>Assess spatial distribution of disease symptoms in the landscape.
>Examine disease symptoms and disease signs using a hand lens when necessary.
>Compare disease symptoms and signs to the images in reference books and those posted on the Internet.
>Perform simple examinations for potential bacterial and nematode diseases with the aid of basic tools listed above.
>Consult with a local Extension agent, then a professional diagnostician, if necessary, or send a sample to a public or private diagnostic lab, depending on the nature of the diseases to be examined.

Resources for Diagnostic Help

Land grant university-based disease diagnostic clinics, along with state agricultural (Cooperative) extension offices, usually provide timely and quality diagnostic service at no charge or for a small fee. However, these public labs are restricted in capacity due to limited financial support. They are often overloaded with disease samples, particularly in the summer. Diagnoses of some samples, such as viral diseases, may fall outside the scope of an individual lab. As a result, private diagnostic services are emerging.

The University of Delaware has a plant diagnostic clinic. Horticultural agents are available in each county extension office for initial consultation. Samples should be brought to the county offices in Georgetown, Dover, or Newark. If necessary, samples will be sent to our diagnostic lab. For routine testing there is no fee. The website for the plant diagnostic clinic at UD is http://ag.udel.edu/extension/pdc/index.htm

There are two types of private services. Some companies provide both diagnostic kits and direct diagnostic services; others provide only direct diagnostic services. These services are particularly valuable for virus testing. These private services are important alternative resources to help meet your plant disease diagnostic needs. For assistance in choosing a diagnostic lab, contact your county horticultural agent.

Extracted and modified from "A Guide to Diagnosing Diseases of Landscape Plants" by Chuan Hong, Extension Specialist; Tom Banko, Associate Professor; and Marcia Stefani, Research Specialist; Virginia Tech. For the full factsheet go to http://www.ext.vt.edu/pubs/plantdiseasefs/450-800/450-800.html

Landscape - More on Diagnosing Landscape Problems

This is a continuation of the series on diagnosing landscape plant problems.

Can you diagnose plant failure by yourself? The answer is 'Yes' for most situations. The do-it-yourself guidelines below provide a list of what to look for, basic tools, and step-by-step procedures. These procedures will guide you in examining a sample, and in narrowing down the possible causes of the problem as closely as necessary to make decisions for disease management.

What to look for. Plant pathologists usually group causes of plant failure into two categories: infectious (that is caused by a pathogen(s)), and noninfectious (caused by environmental stress or improper cultural practices). Identifying whether a problem is infectious or noninfectious is the first thing to determine when we diagnose a plant disease sample.

Environmental stresses and improper cultural practices that can lead to plant failure are numerous. They include too much or too little water, soil or water that is too salty, pH that is too high or low, use of excess fertilizers or nutrient deficiencies, or chemical injuries (from herbicides, pesticides, runoff or other pollutants). As a general rule, noninfectious disease symptoms are distributed evenly over a large area or over several different plant species. They may also be associated with some specific location(s) or cultural practice, such as where herbicide applications were prepared, or with some environmental events, such as frost or a hail storm.

In contrast, infectious disease symptoms develop sporadically, are distributed unevenly, and usually are restricted to a particular plant species, or even cultivar. Therefore, field distribution of diseased plants and symptoms is an important initial observation for disease diagnosis. It is not possible for professional diagnosticians to examine spatial distribution of every disease sample received. Thus, you are in a better position to make these observations than diagnosticians are.

If a disease IS involved, the next question is, "What pathogen(s) is causing the problem?" There are at least ten thousand fungi, and hundreds of bacteria, viruses and nematodes that could cause plant disease. To narrow this down requires some basic knowledge of morphology and biology of the individual groups of plant pathogens. At this stage, plant pathologists usually look for two things: disease symptoms and disease signs.

Disease symptoms are the changes in the plant from its normal appearance in response to the pathogen. Individual (groups of) pathogens may cause specific symptoms. For example, mosaic symptoms are usually associated with viral diseases. Spots and lesions are usually associated with fungal and bacterial diseases. Viruses rarely cause root rots or cankers (stem lesions). Thus, learning symptoms that tend to be associated with the different groups of pathogens is an important step toward correct diagnosis of plant disease problems.

Detecting disease signs may also be helpful at this stage. Disease signs are vegetative and/or reproductive structures of plant pathogens left on the plants or plant parts. Some fungi and bacteria grow on the surface of leaves, stems, petals, etc., where they may be seen. The most obvious examples are rusts and powdery mildews, which can often be identified with the naked eye from the massive amounts of spores or white fungal threads on the plant surface.

Sometimes signs of fungal pathogens may be observed on diseased plant parts after placing them in a humid chamber for a day or two. A plastic bag with a moist paper towel works well for this. Some bacteria may be released from infected plant tissue where they may ooze visibly from wounds under wet conditions. Pathologists sometimes use this trait to test for bacterial disease in the lab by cutting a small piece of infected tissue and placing it in a beaker with tap-water. Bacteria in the plant tissue may ooze into the water, making it cloudy.

A similar procedure may be used to examine certain nematode diseases. Nematodes are large enough to be seen with a hand lens after they are released into water. Thus, disease symptoms and signs along with some preliminary observations can help narrow down the causal agent of many disease samples to specific pathogen groups.

Substantial additional examinations are needed to determine exactly what species causes a disease problem. Justification for this extra effort depends on disease management options. Further identification is justified only for fungal diseases in situations in which a fungicide(s) must be applied to keep the disease under control. There are several fungicides labeled for control of fungal diseases, but some are only effective in controlling a specific group of fungi.
There are two types of fungi: true fungi, and oomycetes (water molds), that cause plant diseases. These different groups of fungal pathogens have different physiologies, so fungicides that can effectively control diseases caused by true fungi may have no impact on those caused by oomycetes. Major oomycete pathogens include Phytophthora and Pythium species, which are primarily responsible for root rot of numerous plants. Also included are the species that cause downy mildews of many crops.

Consulting a professional diagnostician or sending a sample to a diagnostic lab is recommended when you are uncertain about which group of fungal pathogen is responsible for the plant problem. Detailed examinations may be useful for helping with cultural recommendations, or for fungicide recommendations if the services of a licensed pesticide applicator are utilized. However, there are few options for control of bacterial, nematode and viral diseases in the landscape. Thus, diagnosing which group of pathogen is causing the problem is most likely all you need.

Extracted from "A Guide to Diagnosing Diseases of Landscape Plants" by Chuan Hong, Extension Specialist; Tom Banko, Associate Professor; and Marcia Stefani, Research Specialist; Virginia Tech. For the full fact sheet with pictures go to http://www.ext.vt.edu/pubs/plantdiseasefs/450-800/450-800.html