Saturday, February 28, 2009

Ornamentals Hotline Resubscription 2009

It is time to subscribe or resubscribe to Ornamentals Hotline. This one-page newsletter will tell you what you need to know about pests, diseases, weeds and cultural problems in the landscape. It is published weekly during the growing season. Contributors scout the landscape and monitor Cooperative Extension calls. Reading Ornamentals Hotline will keep you in tune with your customers and their landscape problems. Learn when to scout for pests and diseases.

Subscription form. Click on image for larger version to print.

Nursery, Greenhouse, and Landscape - Late Winter Notes

The following are some late winter notes for nurseries, greenhouses, and landscape companies.

CANKER - Early spring is a good time to look around your yard for signs of winter damage, breakage of limbs, and cankers that may not be noticeable once trees and shrubs leaf out. Cankers caused by Botryosphaeria or other fungal opportunists will often appear as sunken, target-shaped or oval areas on branches. Trim back behind the canker before new growth begins.

Botryosphaeria canker. Photo by Theodor D. Leininger, USDA Forest Service,

ROOT ROT - The Diagnostic Clinic has received samples of pansies with poor growth and blackened roots. These plants are infected with the black root rot fungus, Thielaviopsis. Once established in your garden soil, this fungus can persist and cause problems on other annuals such as petunia and vinca. Check your new plants before planting to be sure root systems look light in color and healthy.
Black root rot causing pansy decline.

INSECTS and TEMPERATURE. Spring is quickly approaching and some arthropod pests we may find active in early spring are eastern tent caterpillars, white pine sheath mites, spruce spider mites, and juniper webworms. Did our colder winter have an impact on insect populations? Insect species are affected by cold temperatures differently, so some arthropod populations may decrease while others are unaffected. When your customers ask you to predict pest problems based on the type of winter we’ve had, there really is no simple answer.
Spruce spider mites. Photo by Petr Kapitola, State Phytosanitary Administration,

Information from the resubscription notice of the 2009 Ornamentals Hotline newsletter from the University of Delaware Cooperative Extension.

Friday, February 27, 2009

Turf - Crabgrass Germination and Temperatures

The following is information on soil temperatures and crabgrass germination.

Once the first warm days arrive, the topic of discussion becomes crabgrass. Crabgrass emergence is well correlated with soil temperatures and degree day accumulations. Mike Fidanza and Peter Dernoeden at the University of Maryland proposed the following from their research (Fidanza, M.A., P.H. Dernoeden, and M. Zhang. 1996. Degree-days for predicting smooth crabgrass emergence in cool-season turfgrasses. Crop Science 36:990-996.)

Ave. Min. soil temp. at which initial appearance is observed =54 F
Ave. mean soil temp. at wich initial appearance is observed = 60 to 64F
Ave. Min. soil temp. at which major emergence occurs = 60 to 70F
Ave. mean soil temp. at which major emergence occurs = 73 to 75 F

Soil temperature at a 1 inch depth is used for these measurements. Measuring soil temperatures first thing every morning is the best way to get this number.

Now regarding crabgrass germination and preemergent herbicide applications, in Southern Delaware the window is generally March 1 to April 1, northern Delaware, March 15 to April 15,

Regarding soil temperatures, a rule of thumb is 3 consecutive night soil temperatures above 50 F. When soil temperatures consistantly stay above 50 F, pre-emergent herbercides, if they are to be applied, should be down or going down.

Degree days can also be used. Degree days for crabgrass germination using a base of 53.6 F are as follows:

Thursday, February 26, 2009

Turf - Great Weed ID Site

The following is a link to a great interactive weed identification site from Michigan State University. Most of the weeds on this site are also found in Delaware.

MSU Turf

This site is intended to help you learn the key identification characteristics of common and not-so-common turfgrass weeds found in Michigan and the midwest (most also are found in Delaware). Correct identification is the first step to proper management.

They have created biography pages for each weed to help you better understand why weeds invade. The biography pages include information on habitat, alternative common names (AKA), look-a-likes, management practices and chemical controls.

Give the site a try at

Greebouse and Nursery - Alternatives for Plastic Pots 5

The following is information from a Chinese company that produces biodegradable pots from bamboo fiber.

EnviroArc biodegradable pot's material is totally derived from natural sources which are biodegradable by nature. They were the first company in the world to perfect bamboo pulp for the use in the manufacturing of biodegradable pots. Because bamboo pulp is the main raw material it is 100% organic with no contaminants and they have an uninterrupted supply of raw material to allow high volume production. Bamboo grows naturally easily and quickly (without the need of fertilisers). The bamboo uses is sourced from their own bamboo farms ensuring that none of China's natural bamboo forests (that the panda's rely on for a food source) are destroyed.

With their technology, the materials used are easily moulded into a variety of shapes and forms, with a large range of textures, colors and shapes to choose from. As with all biodegradable products, their pot's organic biodegradable composite means that in nature it will naturally break down safely, relatively quickly and biologically.

If stored as stated, EnviroArc pots have a shelf life of 18-24 months and once disposed of into the earth will be fully biodegradable in under 6 months.

Example of one of their pots.

See their website at

Wednesday, February 25, 2009

Landscape and Nursery - Plants for Delaware Landscapes Featured at the 2009 UDBG Spring Plant Sale V

This year, the University of Delaware Botanic Garden spring benefit plant sale features those plants that add to the biodiversity of the landscape and offer food and habitat for wildlife, especially insects and the birds that eat them. Many native plants are featured. This is the fifth in a series on plants being offered at the UDBG spring plant sale that are recommended for Delaware landscapes.

Amelanchier × grandiflora ‘Robin Hill’, Apple Serviceberry, 20-30', full sun to shade, moist soil conditions. What’s not to love about this small tree: Deep pink buds opening to white flowers in April; sweet edible fruit in June; and yellow to red fall color. Add to this the smooth grey stems in the winter and you have four seasons of outstanding display! Native plant. Photo by Burncoose Nurseries, UK.

Amelanchier laevis, Allegheny Serviceberry, 15-25', full sun to shade, moist soil conditions. Allegheny serviceberry is more tree-like in habit with fewer suckering stems. The new foliage emerges bronze before changing to green in summer and orange-red in fall. The leaves and 4-6 inch long clusters of white flowers in April are covered with soft hairs, separating it from other serviceberries. The sweet black fruits are delicious to humans and wildlife. Native plant. Photo from the Dow Gardens Archive, Dow Gardens,

Arctostaphylos uva-ursi, Bearberry, 1', full sun to shade, dry to moist soil conditions. Evergreen groundcovers are so valuable to the landscape and this is one of the best. The white flowers tinged with pink appear in late April to May, followed by showy red fruit in fall. Plants thrive in poor sandy soils and show good salt tolerance. Native plant. Photo by Dave Powell, USDA Forest Service,

For more information on the 2009 UDBG Spring Plant Sale go to

Greebouse and Nursery - Alternatives for Plastic Pots 4

There are many alternatives to plastic pots being offered for the greenhouse and nursery trade. The following is the fourth in a series of posts on this subject (information from the University of Maryland).

Plastic pots benefited the horticulture business for many years, enabling growers to sell product at just about anytime of the year in an attractive and inexpensive package. Plastic pots are not gone just yet but consumers are interested in products that are environmentally friendly. Plastic is not conceived as environmentally friendly or sustainable material. Limited oil reserves and concern about using anything that is not renewable has changed many of our notions about plastic pots and trays.

This is an important enough topic that we decided to have it as subject matter and discussion point at the 2009 Chesapeake Green Conference in February. Greg Trabka of Ball Horticulture Company laid out several interesting alternatives to plastic pots at the Chesapeake Green Conference. The alternatives vary from pots made from Coir (coconut fiber) and peat moss, wheat based compostable pots, potato flour pots that are biodegradable, and rice hull pots that are biodegradable.

One thing to keep in mind is that the largest pot that can be made so far that has the stiffness or integrity to stand up is a 1 gallon container. None of the alternative pots presently on the market hold up well when growing crops outdoors for several moths or longer. It would be great to have mum pots that held up outdoors and pots that perennial growers could use in their multi-month production of plants in outdoor growing conditions. Alternative pots are still evolving and there are some problems to work out before growers adopt them widely for use in greenhouse floriculture.

Grower concerns include how to make these alternative pots last through the production stage and still be an attractive package for the consumer. Another thing to consider is how well the pots will hold up at the garden centers and how the consumer will get the plants home without making a mess. How to keep the rootballs from imploding before making it to the planting site is the main concern.

Several growers pointed out that many consumers take plants home and let them sit around for a couple of days before they are planted. They are concerned that customers will let roots growing through pots dry out before getting them into the ground. This last problem can be solved with educational literature to let customers know to get plants into the ground quickly.

What is a little confusing for the public is that there are home compostable pots and industrial compostable pots. Home compostable pots can be thrown on the home compost pile and will bread down with little effort. Industrial compostable pots have to be placed in windrow compost piles and turned regularly to get them to break down. The compostable pots appear to be better suited to mechanical planting systems and can be handled in a lot of ways like the familiar plastic pot. Bio-degradable pots break down when planted in the landscape or garden. These biodegradable pots are probably the best system but the trick is have the pots hold up in the production greenhouses with varying length of growing times and growing conditions.

Information from the February 20, 2009 edition of the Greenhouse TPM/IPM Bi-Weekly Report from the University of Maryland Cooperative Extension Central Maryland Research and Education Center

Tuesday, February 24, 2009

Landscape and Nursery - Plants for Delaware Landscapes Featured at the 2009 UDBG Spring Plant Sale IV

This year, the University of Delaware Botanic Garden spring benefit plant sale features those plants that add to the biodiversity of the landscape and offer food and habitat for wildlife, especially insects and the birds that eat them. Many native plants are featured. This is the fourth in a series on plants being offered at the UDBG spring plant sale that are recommended for Delaware landscapes.

Aesculus parviflora, Bottlebrush Buckeye, 8-12', Full sun to shade, moist conditions, Multi-stemmed and wide spreading, this shrub is well suited for massing, and does best in shade conditions. A handsome specimen, pollinators will be lured to the candelabra-like white flowers in June, and then in the fall, the nuts will be coveted by wildlife. Native plant. Photo by David Stephens,

Aesculus paviaHumilis’, Red Buckeye, 15', Full sun to part shade, moist soil conditions. This adaptable plant can be grown as a large shrub. The pure red flowers appear in late spring and contrast well against the deep green foliage. While leaves do not have any significant fall color, they are free from disease. The nuts, produced in the fall, are a good food source for many animals. Native plant. Photo by Dan Tenaglia,,

Amelanchier canadensis, Shadblow Serviceberry, 6-20', full sun to shade, moist to wet soil conditions. The suckering stems produce dense shrubs that often occur in wetlands in their native habitat. Numerous white flowers in early April entice early pollinators. Sweet, edible black fruit mature in June. Fall color typically golden yellow with red or orange tints. Native plant. Photo by the Dow Gardens Archive, Dow Gardens,

For more information on the 2009 UDBG Spring Plant Sale go to

Greenhouse and Nursery - Alternatives for Plastic Pots 4

There are many alternatives to plastic pots being offered for the greenhouse and nursery trade. The following is the third in a series of posts on this subject (information from the University of Maryland).

ITML has coir fiber plantable pots which are biodegradable and sustainable. The coir pots are not stiff by any measurement but they are reported to hold up in greenhouse growing conditions. The coir, a waste product from coconut production, is considered a sustainable product. Once it is planted roots will penetrate through the walls easily. There is also a pot made from potato flour by Dillon Company and this pot is considered biodegradable.

Coir Pot

Information from the February 20, 2009 edition of the Greenhouse TPM/IPM Bi-Weekly Report from the University of Maryland Cooperative Extension Central Maryland Research and Education Center

Monday, February 23, 2009

Greenhouse and Nursery - Alternatives for Plastic Pots 3

There are many alternatives to plastic pots being offered for the greenhouse and nursery trade. The following is the third in a series of posts on this subject (information from the University of Maryland).

Ball has a pot called the OP-47 which is thermoformed and looks like a lot like a standard thin plastic pot (green colored). This OP-47 pot is made from wheat and is rated for industrial composting. This pot is being tried out by a couple of Maryland operations in 2009. It will be interesting to see the public reaction to these compostable pots. Ball has printed compostable on the side of the rim of the pot so the public is aware this pot is different. The tray to hold the pots is yellow and is called PLA and is made from corn based plastic. These trays are industrial compostable.

Information from the February 20, 2009 edition of the Greenhouse TPM/IPM Bi-Weekly Report from the University of Maryland Cooperative Extension Central Maryland Research and Education Center

Sunday, February 22, 2009

Landscape and Nursery - Plants for Delaware Landscapes Featured at the 2009 UDBG Spring Plant Sale III

This year, the Univeristy of Delaware Botanic Garden spring benefit plant sale features those plants that add to the biodiversity of the landscape and offer food and habitat for wildlife, especially insects and the birds that eat them. Many native plants are featured. This is the third in a series on plants being offered at the UDBG spring plant sale that are recommended for Delaware landscapes.

Morus alba, ‘Chaparral’ Weeping Mulberry, 10-20', full sun to part shade, dry to moist soils. The distinctive architecture of the twisted, weeping branches is best appreciated during the winter months but this weeping form, covered with glossy green leaves, makes a striking specimen throughout the year. Fall foliage is bright yellow. Don’t worry, this is a fruitless form. Photo from Garden State Nursery.

Nyssa sylvatica, ‘Wildfire’ Black Tupelo, 30-50', full sun to part shade, dry to moist soils. The brilliant red fall color is vivid and consistent on this selection of black tupelo. Containerized plants establish reliably, since the root system is completely intact. Native plant. Photo by Richard Webb, Self-employed horticulurist,

Oxydendrum arboreum, Sourwood, 25-30', full sun to part shade, moist soils. An elegant understory tree, sourwood produces clusters of pendulous white flowers in the early summer that attract numerous pollinators. The developing fruits turn upright and contrast with the brilliant red autumn foliage to make it seem as though the plant is still in flower in the fall. Native plant. Photo by Wendy VanDyk Evans,

Persea palustris, Swamp Redbay, 15-20', full sun to part shade, moist to wet soils. The broadleaf evergreen foliage offers a real treat during the bleak winter months and can serve as a screen or a backdrop for heavily fruited shrubs. Photo by Chris Evans, River to River CWMA,

For more information on the 2009 UDBG Spring Plant Sale go to

Greenhouse and Nursery - Alternatives for Plastic Pots 2

There are many alternatives to plastic pots being offered for the greenhouse and nursery trade. The following is the second in a series of posts on this subject (information from the University of Maryland).

Fertilpots are a biodegradable wood fiber pot composed primarily of spruce fibers. Fertilpots are biodegradable and are intended to be planted directly in the ground. Water, air, and roots penetrate the walls of the fertilpot so there is supposedly no need for drainage holes. Fertilpots do not require a composting situation to degrade and are planted directly into the ground by the consumer. Fertilpots has come up with a tray for handling of biodegradable containers. Developed jointly by Fertil International and Desch Plantpak, the Dioni tray encourages airflow around the pots for better root formation. The design of the Dioni tray provides an air space which promotes air pruning of the root tips emerging from the porous walls of fetilpots.


Dioni tray.

Information from the February 20, 2009 edition of the Greenhouse TPM/IPM Bi-Weekly Report from the University of Maryland Cooperative Extension Central Maryland Research and Education Center

Saturday, February 21, 2009

Greenhouse and Nursery - Alternatives for Plastic Pots 1

There are many alternatives to plastic pots being offered for the greenhouse and nursery trade. The following is the first in a series of posts on this subject (information from the University of Maryland).

Ball Horticultural Company and Summit Plastic Company are partnering to make biodegradable, compostable pots for the Ball Circle of Life sustainable horticulture program. Circle of Life pots, made of rice hulls, are available in six sizes: 3.5 in. (9 cm), 4 in. (10 cm), 4.5in. (11 cm), 5 in. (13 cm), 6 in. (15 cm) and trade gallon. The pots are made from waste rice hulls from China. It would be nice if the pots were made from rice hulls from America but evidently the Chinese are the ones with the patent on this process. The rice hulls are mixed with glue to stiffen them. The pots look a lot like plastic but some are compostable and others can be planted right into the ground and bio-degrade. Ball has come out with an interesting biodegradable pot with slits in the slide of the pot. The whole pot is planted into the ground and the roots grow into the surrounding ground. The pot is supposed to breakdown during the growing season – at least the part of the pot that is placed in the soil.

Rice Hull Pots.

Information from the February 20, 2009 edition of the Greenhouse TPM/IPM Bi-Weekly Report from the University of Maryland Cooperative Extension Central Maryland Research and Education Center

Greenhouse - Iron Deficiency and Rot Rot on Pansy

Pansies have been a profitable crop for greenhouse growers over the years and are one of the first sales items to offer in the spring planting season. The following are some notes on growing problems you may see in pansies.

Pansies are fairly easy to grow but are susceptible to iron deficiencies in the media pH goes higher than 5.8. When checking pansies showing yellowing, also look for healthy roots. Yellowing may be due to Thielaviopsis root rot (also known as black root rot). Black root rot can also be kept in check by keeping the media pH below 5.6.

Thielaviopsis Root Rot on pansy. Plants are stunted due to black root rot. Photo by Jay W. Pscheidt, 2002, Oregon State University Extension.

Intervienal chlorosis on pansy with a pH level of 6.3. Photo from the University of Maryland

Gordon Johnson, Extension Horticulture Agent, UD, Kent County

Friday, February 20, 2009

Turf - Avoid Foot Traffic on Frost or Ice Covered Turf

The following is information on the effects of foot traffic on frost or ice covered turf.

Trafficking frost or ice-covered turf usually results in extensive physical “breaking” of the leaves. The xylem and phloem tissues that are involved in moving water, nutrients, and carbohydrates around in the plant are usually severed when traffic is applied to ice-covered foliage. The damaged turf leaves don’t fall away completely from the stem, but instead slowly turn brown and die. You will likely see visible damage from the traffic (in the form of footprints, paw prints from pets or wild animals, etc.) within a few days and the evidence of the trafficked turf will remain for several weeks until new leaves form later in the spring. For cool-season grasses that can mean living with the damage well into April or May. The good news is that the damage is primarily cosmetic and does not impact the overall survival of a lawn.

Information extracted from "My Turf’s On Ice" by Mike Goatley, Extension Turf Specialist & Associate Professor, Crop & Soil Environmental Sciences, Virginia Tech.

Greenhouse - Edema

Edema is a common winter and early spring problem on Ivy Leaf geranium. It can also occur on other greenhouse crops. The following is more information on this disorder.

Edema (oedema) is not a disease like a bacterium, or a virus and it is not transmittable from one plant to another. Edema is a physiological problem occurring mainly on ivy geraniums but is also found on sweet potato vine (ipomoea), begonias, cacti, ferns, palms, pansy, cleome and cole crop vegetables like broccoli, cabbage and cauliflower. Some fleshy ­leaved plants such as jade and peperomia are particularly sensitive to conditions which lead to the development of edema although almost any broadleaved plant may be affected.

Edema on leaf. Photo by Joseph LaForest, University of Georgia,

Edema, is a bursting of the cell walls on the underside of the leaf. Symptoms of edema appear as bumps or blisters initially on the undersides of lower or older leaves on a plant. They may then turn brownish or tan and become corky. Severely affected leaves will often turn yellow and fall off the plant. The corky spots sometimes resemble spider mite or thrips damage. To rule out pest damage, use a handlens and check carefully on the undersides of leaves along midveins for spider mites and in growing points for thrips. Mildly affected plants often recover from edema, putting out symptomless new growth, with the arrival of more favorable growing conditions in late spring and early summer. Some plants however are severely affected, have dropped significant numbers of leaves and have badly distorted remaining leaves. These plants are probably not worth saving as they will not recover in time.

Edema is caused by maintaining a greenhouse environment that is not ideal for growing susceptible plants such as ivy geraniums, often combined with over watering. Edema occurs when the growing media remains moist and the greenhouse air is cool and moist. The plant roots absorb water at a faster rate than is transpired through leaf cells causing the leaf cells to rupture. This rupturing of the leaf epidermis and the inner cells causes the raised, crusty appearance on the underside of the leaf.

There are several cultural practices that contribute to edema. First, most growers grow their ivy geraniums in baskets hung above the benches where the air is most humid and with poor air circulation that reduces the transpiration rate. Secondly, many growers are now using saucerless hanging baskets for their ivy geraniums. This type of container retains water after each irrigation including periods of cloudy and overcast weather which results in overwatering. Third, hanging baskets are often on automatic watering systems, all watered at the same time. However, not all hanging baskets dry out at the same rate and therefore, some plants are overwatered. Lastly, during cool, cloudy weather, humidity is high in the greenhouse and plant transpiration rates are low. These factors combine to create the perfect conditions for edema to occur.

What can growers do to prevent edema on susceptible plants? The main method is to carefully manage the greenhouse environment. Begin by using a well drained growing media. Increase light intensity by spacing plants farther apart. Avoid over-fertilizing plants, especially when the plants are growing slowly and avoid growing cultivars that are highly susceptible. Do not over water, and keep plants on the "dry side" during extended periods of low light and cool temperature. Water when air temperature is rising or humidity is low.

Anything a grower can do to improve drainage and air circulation around plants will help prevent edema. Reduce humidity by venting the greenhouse first thing in the morning, even if that means turning up the heat. Make sure there is adequate air flow, whether from fan jets or horizontal air flow fans. Air movement is important 24 hours a day. Do not use saucerless hanging baskets. Instead, use containers that have snap-on saucers, but do not put the saucer on until the crop is nearly finished, or if possible, until point of sale. This will ensure maximum drainage of each basket. When using an automatic watering system, place varieties with similar growth vigor on each line or section, again to eliminate over watering. Lastly, properly manage media pH and soil fertility. Make sure media pH for ivy geraniums is 5.5. Fertilize once every three feedings with calcium and potassium nitrate. Calcium will thicken up the cell walls, making ivy geraniums more resistant to edema.

Reprinted from "Tips for Managing Edema on Spring Crops" by Tina Smith, University of Massachusetts, Extension Floriculture Program

Wednesday, February 18, 2009

Greenhouse - Monitor Your Media pH

The following is a short article on pH issues with greenhouse media and plant deficiencies.

Media pH

Most plants have an optimal pH range in which they perform best. Some plants may prefer slightly acidic media while other plants can tolerate a much lower or higher pH. The pH of the media influences the uptake and availability of all nutrients. Growing greenhouse plants in media with a pH lower than the optimal range can result in poor uptake of macronutrients (in particular Calcium, Magnesium, and Phosphorus) and increased uptake of some micronutrients (e.g. iron toxicity). On the flipside, micronutrient deficiencies generally occur on plants growing in media with a pH higher than the optimal range (e.g., iron or manganese deficiencies).

Iron Toxicity in Marigold probably due to low media pH. Photo by Tina Smith, UMass.

Iron deficiency in petunia probably due to a high media pH. Photo by Tina Smith, UMass.

Written information from the Michigan State University Greenhouse Alert Newsletter March 4, 2008.

Tuesday, February 17, 2009

Greenhouse - High Soluble Salts

High soluble salt levels in greenhouse media can cause plant performance problems or if severe, plant failure. High salt levels usually occur from over fertilization in liquid feeds or excessive release of fertilizer salts from slow release fertilizers. The following is a short article on the subject.

The soluble salt content of the media and irrigation water should be tested frequently throughout the growing process. All soluble nutrients, such as nitrate, ammonium, potassium, calcium, magnesium, chloride, sodium and sulfate, contribute to the soluble salt content of the media. A soluble salts test will alert growers if the salt level starts to creep upward and can also provide an indication of the nutrient status available for plant uptake.

Greenhouse plants vary in their tolerance to salt levels and this tolerance is often dependent upon the growth stage of the plant. Excessive soluble salts can result in reduced growth and loss of vigor, root death, chlorosis and necrosis of leaves, wilting and marginal leaf burn. Excessive soluble salts are generally a result of too much fertilizer present in the soil solution in relation to the plant’s needs. High salts may occur from miscalculation of fertilizer dilutions, poorly calibrated or malfunctioning fertilizer injectors or over-application of fertilizers. Other causes of excessive salt buildup may be inadequate leaching and poor drainage. Excessive soluble salts may be reduced in the media by leaching several times with clear water.

Total soluble salt content is determined with a solu-bridge conductivity meter and is expressed as millisiemen (mS) or millimho (mmho). Millisiemen is the preferred unit for expressing soluble salt measurements. Regardless of the unit, the value is the same. Growers often determine soluble salt content by using one part media to two parts distilled water, allowing the solution to sit idle for up to one hour before taking a reading. Many testing labs determine soluble salt content on the saturation extract.

Soluble salt levels by various test and plant reactions.

Information from "Diagnosing plant problems – don’t forget about pH and soluble salt content" by Steven Gower and Jan Byrne, MSU Diagnostic Services, in the Michigan State University Greenhouse Alert Newsletter, March 4, 2008.

Sunday, February 15, 2009

Landscape and Nursery - Plants for Delaware Landscapes Featured at the 2009 UDBG Spring Plant Sale II

This year, the Univeristy of Delaware Botanic Garden spring benefit plant sale features those plants that add to the biodiversity of the landscape and offer food and habitat for wildlife, especially insects and the birds that eat them. Many native plants are featured. This is the second in a series on plants being offered at the UDBG spring plant sale that are recommended for Delaware landscapes.

Cladrastis kentukea, American Yellowwood, 30-50', full sun to part shade, moist soil conditions. A true star in the garden with a heavenly fragrance. The nearly 12-inch long terminal white clusters provide quite a display in mid May. A great small to medium sized tree for residential landscapes with clear yellow fall foliage. Native plant. Photo from The Dow Gardens Archive, Dow Gardens,

Crataegus crus-galli, Cockspur Hawthorn 20-30', full sun, dry to moist soil conditions. How can you resist — white spring flowers loved by pollinators, deep red fruits eaten by birds, and bronze red to purple red fall foliage. These large shrubs also offer great cover for birds due to their long 2-3 inch spines. Native plant. Photo by Richard Webb, Self-employed horticulurist,

Diospyros virginiana, Common Persimmon, 35-60', full sun, dry to moist soil conditions. The small white flowers in early summer are prized by pollinators and produce 1-2 inch apricot colored fruit. The fall foliage often turns purplish-red about the time the fruit is being savored by wildlife. Native plant. Photo by John D. Byrd, Mississippi State University,

Magnolia virginiana, ‘Henry Hicks’, Sweetbay Magnolia, 25', sun to part shade, moist to wet soil conditions. Difficulty propagating this outstanding magnolia has greatly limited its availability in the nursery trade. This cultivar retains its foliage as well as or better than all other sweetbays. The upright habit, white flowers, and stunning fragrance make this an ideal choice for nearly all gardens. Native plant. Photo by The Dow Gardens Archive, Dow Gardens,

For more information on the 2009 UDBG Spring Plant Sale go to

Greenhouse and Nursery - Disinfestants

The following are some common disinfestants to use to sanitize benches, tools, and equipment in greenhouses and nurseries.


Treatment: Steam or Dry heat
How: Heat materials to 180-200 F for 30 min. under a cover to retain the heat
Target: Bacteria, Fungi, Nematodes, Insects and Weeds.

Treatment: Bleach--Sodium hypochlorite (Clorox®)
How: 1 gal/9 gal water. Dip, spray or brush on and keep the material wet for 10
min. Let drain and rinse metal objects.
Target: Bacteria, Fungi and Nematodes

Treatment: Hydrogen peroxide, Hydrogen dioxide (ZeroTol®)
How: 2.5 oz/gal water. Dip, spray or brush on. Let drain
Target: Bacteria and Fungi

Treatment: 70% Alcohol
How: Dip or swab object and let dry
Target: Bacteria, Fungi, Nematodes and Insects

Treatment: Quaternary Ammonium Compounds (GreenShield®, Triathlon®)
How: Dip, spray or brush on and keep the material wet for 10 min.
Target: Bacteria and Fungi

Information from "Plant Pathology and the Greenhouse" By Janna Beckerman, Assistant Professor, Department of Botany and Plant Pathology, Purdue University

Saturday, February 14, 2009

Landscape and Nursery - Plants for Delaware Landscapes Featured at the 2009 UDBG Spring Plant Sale I

This year, the Univeristy of Delaware Botanic Garden spring benefit plant sale features those plants that add to the biodiversity of the landscape and offer food and habitat for wildlife, especially insects and the birds that eat them. Many native plants are featured. This is the first in a series on plants being offered at the UDBG spring plant sale that are recommended for Delaware landscapes.

Acer rubrum, ‘Sun Valley’ Red Maple, 40-60', full sun to part shade, moist to wet soil conditions. Sun Valley was selected at the U.S. National Arboretum for its brilliant red fall foliage and leaf hopper resistance. Like all red maples, it thrives in wet and compacted soils frequently found in home landscapes. Native plant.

Alnus serrulata, Hazel Alder, 10-20', full sun to part shade, moist to wet soil conditions. Alders rarely occur outside of wetlands in the wild although show much broader adaptability in the landscape. Additionally, they add nitrogen to the soil and support over 160 species of Lepidoptera. Native plant. Photo by Chris Evans, River to River CWMA,

Betula lenta, Sweet Birch, 40-55', full sun to part shade, moist soil conditions. Known for its resistance to many of the damaging insects that plague other birches, sweet birch also supports nearly 230 different Lepidoptera. Plants also have a smooth cherry-like bark and clear yellow fall color. Native plant. Photo by Richard Webb, Self-employed horticulurist,

Carpinus caroliniana, American Hornbeam, 20-30', full sun to full shade, moist soil conditions. A common understory tree in our local woodlands which often turns bright red and orange in the fall. The handsome smooth grey bark reminds you of a beech and like beech its fruits serve as a source of food for wildlife. Native plant. Photo by Richard Webb, Self-employed horticulurist,

For more information on the 2009 UDBG Spring Plant Sale go to

Friday, February 13, 2009

Business - Analyzing your Costs

Cost control or cost reduction in a down economy is essential for business survival. The following is a series of questions to ask as you look at direct costs in your horticultural business enterprises.

The first step is to list your enterprises. For each enterprise list all your direct expense categories and the actual dollars expended for each category in the past year. Try to assign additional costs to that enterprise that would otherwise end up in indirect costs or overhead. For example, vehicle or equipment maintenance costs can be assigned to an enterprise if they are only used in that enterprise or if you know what percent of the time that they are used in the enterprise (cost of maintenance* percent of time used in that enterprise during the year)

For the expense categories that you listed for your enterprise, note whether they increased or decreased last year. Ask why they increased or decreased. Ask is the reason for an increased cost justified or do you need to focus more time on controlling the cost?

Look closely at each enterprise expense category in relation to the coming year and ask the following questions:
1) Is there a potential to reduce costs?
2) If so, how will it be achieved? and
3) What will the potential savings be in dollars.

The next step is to take a closer look at each of your expense categories for the enterprises. This is a drill-down analysis. Take that enterprise and list all actions associated with it where expenses are incurred (labor is used, materials are used). List all specific costs related to each job action.

For each job cost ask the following questions:
1) Is it possible to buy/obtain/hire at a lower cost? How? What will be the savings?
2) Is it possible to reduce use or be more efficient? How? What will be the savings?
3) Is it possible to eliminate the cost entirely? Why? Will it affect the quality of the product or service? What will be the savings?

Gordon Johnson, Extension Horticulture Agent, UD, Kent County

Thursday, February 12, 2009

Greenhouse - Insect Control

The following is a review of insect control for greenhouses including insecticide products registered for different insect pests in greenhouses.

Greenhouse Insect Control

Starting clean

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 ziplock 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 marigolds (mites) and pepper s(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.

Control Products:

Thrips: Avid, Mesurol, Orthene 97, Pylon, 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.

New products

Sucrashield isfrom Natural Forces for controlling aphids, mites, thrips, whiteflies and caterpillars on vegetables, herbs and spices in the greenhouse and outdoors. It is also for use on ornamentals, flowers and bedding plants.

This new product is based on a tobacco plant extract and is available now. The active ingredients, sucrose octanoate esters , have an LD50 of 750 to 1500 ppm for whiteflies, and the label rate is 104 oz per 100 gallons (compared with 4 to 8 oz per 100 gallons for most products). This product is similar to some soap or oil products because it is classified by EPA as non-toxic to people, but requires an application rate of 0.8 to 1.0 percent every 7 to 10 days. Sucrashield bears a WARNING on the label because of eye sensitivity. There is no information on the label about phytotoxicity, so caution is recommended until you have tested it yourself, or until phytotoxicity test data is available.

This product will give herb growers another tool to add to the short list of products labeled for use on herbs.

Kontos is from OHP for controlling mites, whiteflies, aphids, and mealybugs. Kontos can be used in the greenhouse, nursery, and interiorscapes on ornamentals and vegetables.

The active ingredient in Kontos is spirotetramat, a tetramic acid derivative similar to Judo. This is a relatively safe product for humans and pets with a CAUTION on the label. Kontos has good activity on spider mites and whiteflies, including highly resistant whiteflies, like the “Q” biotype. Kontos is expected to be available in spring 2009.

Reprinted from "Greenhouse insect management" by David Smitley, Michigan State University Entomology in the MSU Greenhouse Alert Newsletter (1/09)

Landscape and Nursery - Winter Annual Weeds

The following is some information on winter annual weeds that will be resuming growth as the weather warms up. Some control recommendations are also given.

Over the past several years we have noticed that winter annual weeds have become increasingly widespread and problematic in turfgrass and landscape beds. Winter annuals and some perennial weeds germinate in the late summer/fall, produce vegetative growth, and then will go dormant in winter. As temperatures warm in March and April these weeds will undergo explosive vegetative growth followed by a reproductive phase in late April/May. The increasing pervasiveness of these weeds has been due to moderate fall seasons followed by high amounts of soil moisture as these weeds break dormancy in March/April.

Although these weeds will generally mow out by late May/early June, in many turfgrass sites weed infestations may be so heavy that an application of broadleaf weed herbicide may be warranted to reduce competition with desired turfgrass. If a decision is made to apply a broadleaf weed herbicide, keep in mind that many winter annuals such as chickweed and henbit are tolerant to 2,4-D so be sure the herbicide mixture you choose contains herbicides other than 2,4-D such as dicamba, triclopyr, 2,4- DP (dichloroprop), MCPA/MCPP, or fluroxypyr. For optimum weed control with broadleaf weed herbicides daytime highs should at least be in the 60’s. In addition, there is a greater risk of injury to desired turfgrass if these herbicides are applied under current cool weather conditions. We recommend that broadleaf weed herbicide applications be delayed until sustained warmer temperatures occur.

Wild garlic can be especially problematic. For wild garlic control 2,4-D is a good choice but the ester formulation should be used in place of the amine formulation. Due to the orientation of the leaves of wild garlic, the addition of a surfactant, preferably a high quality non-ionic surfactant with 80 or 90% active ingredients, may increase the retention of the spray solution on the leaves and improve control.

One winter annual weed that has become increasing problematic over the past through years in turfgrass and landscape beds is hairy bittercress. This weed grows in a rosette and is generally not noticed in turfgrass sites until it produces a flower stalk in April/May. Fall or Spring applications of 2.4-D will control emerged bittercress but will not prevent subsequent germination from the soil seed bank. Although an expensive proposition, September applications of Gallery will provide residual control of this weed as well as other winter annuals but not wild Garlic. In landscape beds an early spring application (prior to bittercress flowering) of organic mulch applied at 3 to 4 inches will smother and provide suppression of this weed. More effective control can be obtained with September applications of herbicides such as Snapshot, OH2, or Rout. Always consult the herbicide label to see if all desired plants within the bed are tolerant to these herbicides.

All winter annuals can be effectively controlled with non-selective herbicides such as Roundup, but make sure the spray does not contact desired plants.

Modified from "Get Ready! The Weeds Are Coming" by Stephen E. Hart, Ph.D., Specialist in Weed Science and Patrick McCullough, Program Associate in Weed Science, Rutgers University in the Plant and Pest Advisory Newsletter

Wednesday, February 11, 2009

Greenhouse - Check Your Incoming Plants for Insects and Mites

Greenhouse growers should check all incoming plugs, cuttings, and prefinished plants for insects and mites. The following is an article on the subject from Michigan State University.

Greenhouse growers are already reporting insect activity. We have already seen warm weather insects like two-spotted spider mites on ivy geranium and Lamium cuttings. Inspect all incoming plant products for hitchhikers that you did not pay for but may be getting when your cuttings come in. Look on the underside of leaves with a 16-20x hand lens for mites, or tap cuttings as you open the box over a white sheet of paper and look for the tiny, yellowish-red specks moving on the paper. Check incoming ivy geraniums and spikes also for thrips as low numbers have been seen both on leaves and on sticky cards. Are cards up in your houses that have product in them? Do not ignore the spikes as they are a magnet for thrips and even spider mites this time of the year.

If you have any tropicals or herbs that you are bringing in like Lantana, lavender and rosemary, pay attention for white flies as we have seen some come along with cuttings from southern growing areas. There is a good chance that they are Q-biotype silver leaf whiteflies which are resistant to some insecticides. Click here for management strategies for Q-biotype if it has been confirmed in your greenhouse. Be sure to isolate your pest problems now and control them before moving them to other houses as the season goes on.If you’re not sure of the insect or plant problem, be sure to get it identified correctly before applying a pesticide. I still see growers putting on products that do not work for the pest they are dealing with. Especially in today’s economic times, indentify first then treat. If you’re not sure of the problem, contact your local Extension educator and we will be happy to come out and help you.

Adapted from "Check incoming cuttings for bugs" in the most recent issue of the Michigan State Greenhouse Alert Newsletter by Thomas Dudek, District Extension Horticulture and Marketing Educator, Michigan State University

Landscape, Nursery, and Greenhouse - Labor Verification

The following is information on the status of the E-Verify internet based program to help employers verify legal status (immigration status) of their workers.

E-Verify: Internet-based program to verify employment eligibility

E-Verify is an Internet-based program allowing employers to verify new hires’ employment eligibility by accessing information in the Social Security Administration’s (SSA) database, as well as, the U.S. Citizenship and Immigration Services’ (USCIS) database. Basically, participating employers can compare information taken from a new hire’s I-9 form against the SSA and Department of Homeland Security (DHS) immigration databases. To participate, an employer must accept a Memorandum of Understanding (9 pages) and should consider the users’ manual describing the details of the E-Verify program (79 pages).

An employer who participates in E-Verify is required to verify the employment eligibility of all new employees, independent of their citizenship status. However, participation in E-Verify does not provide a safe harbor from worksite enforcement. A notice of participation and an antidiscrimination notice must be posted clearly visible to prospective employees. According to Scharfen, Acting Director of USCIS, over 69,000 employers representing 269,000 worksites were signed up to use E-Verify by June 2008. According to DHS, more than 10 percent of all new hires were checked through the E-Verify program earlier this year. Several states do require or encourage the use of E-Verify under certain circumstances and one state is trying to limit its use.

The E-Verify program was scheduled to sunset November 29, 2008. However, on July 31, 2008 the House of Representatives voted to reauthorize the voluntary E-Verify program for an additional five years. The Senate was not able to agree on a similar bill, but voted on September 27, 2008 to approve a continuing resolution extending the E-Verify program to March 6, 2009. President Bush signed this bill September 30, 2008. The extension opens up the possibility of a broader immigration debate or an increase in available visas, shortly after the election. On December 23, 2008 the U.S. Chamber of Commerce, in conjunction with other plaintiffs, filed suit against the Department of Homeland Security for making E-Verify compulsory for federal contractors. The Obama administration is currently reviewing this and other programs.

Reprinted from an article by Vera Bitsch, Department of Agricultural, Food, and Resource Economics, Michigan State University

Tuesday, February 10, 2009

Greenhouse and Nursery - Cultural Practices to Prevent Disease

The following are some cultural practices to consider to prevent disease in greenhouse or nursery production.
  • Checking Planting Depth: Follow the planting depth recommended for each species--Planting plants too deeply predisposes them to crown rot, and can result prevent flowering; Planting too shallowly can cause them to topple during watering and can lead to root drying and added stress.
  • Adequately Spacing Plants: Crowded plants prevent good air movement, which promotes foliar diseases. Close spacing also causes plants to compete with each other for sunlight and nutrients. With vigorous plants, the canopy that is created around the plant favors downy mildews, Rhizoctonia, Botrytis, and Phytophthora aerial blights.
  • The right media: There are dozens of greenhouse and nursery media mixes available. A simple rule of thumb to picking out the right media is that larger rooted plants require a larger size mix (larger sized media components). This facilitates drainage and reduces root rot.
  • Appropriate Watering: With the tremendous diversity of greenhouse and nursery plants available, it is difficult to generalize about watering needs. However, it is important to remember that water is for the roots. Avoid overhead irrigation if possible, and when overhead watering, water plants in the morning so foliage can dry before nighttime. Monitor media moisture and do not overwater plants. This is important for media types that hold higher quantities of water. For root rot susceptible plants, choose a media that drains freely.
  • Proper Fertilizing: Fertilizer should only be applied to achieve desired growth or when nutrient deficiencies are noted, such as yellowing (chlorosis). Too much fertilizer, especially nitrogen, predisposes plants to disease.
  • Soil Contact: If at all possible, grow plants so that they are off the ground and not in contact with the soil to avoid potential infection from soil borne diseases.

Adapted in part from Plant Pathology and the Greenhouse by Janna Beckerman, Assistant Professor, Department of Botany and Pant Pathology, Purdue University

Greenhouse and Interiorscape - Know Your Mealybugs

The following is information on identifying mealybugs in greenhouses, conservatories, and interiorscapes.

Citrus mealybug is recognized by a thin purple stripe tha t runs down the middle of the back. These mealybugs are densely covered with white wax and have very short tails.

Citrus mealybug. Photo from the United States National Collection of Scale Insects Photographs Archive, USDA Agricultural Research Service,

Longtailed mealybug have seventeen pairs of white waxy filaments, if you care to count them, around the periphery of the body. In mature females there are two long tail-like projections on the rear of the insect that are longer than the length of the body of the insect.

Long tailed mealybug. Photo by David Cappaert, Michigan State University,

Madeira mealybug looks a lot like citrus mealybug. They are generally a dull gray color under the white wax and lack the single purple stripe on their back that citrus mealybug posses. Their egg sacs are longer and denser than citrus mealybug and male pupal cases may be found in equal numbers to the females. This is a very hard to control mealybug.

Madeira mealybug. Photo by Sally Tucker,

Descriptions from the February 6, 2009 edition of the Greenhouse TPM/IPM Bi-Weekly Report University of Maryland Cooperative Extension Central Maryland Research and Education Center.

Monday, February 9, 2009

Public Service - Plant a Row for the Hungry

All Delaware horticultural businesses and individuals involved in horticulture are encouraged to plant some extra vegetables or fruits in their gardens or in the case of produce growers to send some surplus to help feed the hungry in Delaware in 2009. The Plant-A-Row for the Hungry program supports the Delaware Food Bank and other efforts to serve the homeless, hungry, and families without enough food. The following is more information.

Plant-A-Row for the Hungry
PEOPLE HELPING PEOPLE—One pound at a time...One row at a time.

What Is Plant-A-Row For The Hungry (PAR)?
  • Plant-A-Row for the Hungry (PAR) is a peoplehelping- people program.
  • This innovative public service campaign encourages farmers and gardeners to grow a little extra and donate the produce to local soup kitchens and food banks that serve the homeless and hungry.
  • PAR ’s mission is to provide an avenue through which the more than 70 million farmers and gardeners in this country can help the 31 million men, women and children who go to bed hungry daily.
Produce Farmers and Gardeners You Can Make a Difference!

You can:
  • Plant extra.
  • Deliver the harvest to a food collection site.
  • Give a brochure to someone you know.
  • Help the Food Bank.
Imagine What You Can Do
  • A large planting or bumper crop will mean a great deal to your local soup kitchen, shelter or food pantry.
  • Even one additional row of vegetables can make a difference in your community.
  • Flowers to help brighten the shelter meals.
  • Herbs add both flavor and nutrients to food.
  • If you have no garden space or green thumb there are other ways to help, such as harvest, weighing and delivering produce, and providing storage space for vegetables.

Planting a Row

  • It doesn ’t take a lot to make a real contribution and the time to plan is now! A typical packet of snap bean seeds produces about 20 pounds of fresh, tasty produce. A packet of carrot seeds produces about 100 pounds. The average large, solid tomato weighs about a pound.

Food Bank of Delaware
New Castle: 302-292-1305
Kent/Sussex: 302-424-3301

“Putting Knowledge to Work With the People of Delaware”
For Information on Plant-A-Row


Delaware Cooperative Extension
New Castle County
461 Wyoming Road, Rm. 131
Newark, DE 19716

Kent County
69 Transportation Circle
Dover, DE 19904
302/730-4000 (UD)
302/857-6426 (DSU)

Sussex County
16483 County Seat Highway
Georgetown, DE 19947

The whole brochure for the program can be found at:

Turf and Nursery - 2,4-D at Risk

2,4-D has been an extremely useful and cost effective broad leaf herbicide for decades. It was one of the first herbicides developed and is important for the horticulture industry. There is a possibility of losing 2,4-D. The following is more information and how you can get involved.

EPA is seeking public comments on a petition to revoke all tolerances and cancel all registrations for the pesticide 2,4-D. The petition was submitted by the environmental group Natural Resources Defense Council (NRDC). The NRDC claims in their petition that EPA cannot make a finding that there is a reasonable certainty of no harm from dietary residues of 2,4-D. The petition also states that EPA also did not consider the full spectrum of potential human health effects associated with the pesticide. The public comment process allows anyone with an opinion of the value of 2,4-D in the horticulture industry to provide input, which should then be considered in the EPA’s decision-making process. Public comments must be submitted by February 23, 2009. Information on submitting comments is available at: The docket information is available at:

Sunday, February 8, 2009

Greenhouse - Aphid Banker Plants 1

The following is general information about aphid banker plants that are used to increase numbers of natural aphid enemies in the greenhouse as a biological control strategy.

Aphid banker plants are containers with winter barley or common rye or oats on which colonies of grass-feeding aphid species such as the corn-leaf aphid (Rhopalosiphum maidis), greenbug (Schizaphis graminum), and/or bird-cherry aphid (Rhopalosiphum padi) are established. Banker plants are primarily used to rear prey or hosts, in order to attempt to have a sufficient population of continually reproducing natural enemies.

Banker plants need to be placed along walkways and at the end of benches. It is essential to evenly distribute them throughout a greenhouse. General recommendations suggest that banker plants should be placed approximately 131 feet apart, using 4-5 banker plants per 10,000 ft2, in order to increase parasitization. Some growers will place the banker plants both at the hanging basket and bench or floor level. The drip irrigation also insures that the banker plants will remain irrigated without inadvertently washing the aphid natural enemies off of the plant.

It has also been recommended to distribute containers of rye or barley, with the grass-feeding aphid, among the main crop at a rate of one banker plant per 1,000 ft2 even before aphids are detected. It should be noted that existing recommended rates may vary since limited research has been conducted; start with these rates and adjust in succeeding years based on your experience.

Banker plants may have to be placed closer together or placed in greater frequency within a given area in order to allow parasitoids such as Aphidius colemani to find prey on plants, since research has found that this parasitoid migrates just 3.2 - 6.5 feet from the point of release.

Keep in mind that the bird-cherry aphid is too small for the parasitoid, A. ervi, to develop. A. ervi parasitizes larger aphids such as the foxglove or potato aphid. Although some suppliers sell banker plants with A. ervi, these banker plants are not compatible with A. colemanii banker plants.

If this aphid is your predominant species, one option is to use the predatory midge, Aphidoletes aphidimyza for release onto your banker plants. If using predatory midges, placing the pots in trays with moist sand will help provide pupation sites for the predatory midges. (The predatory midges pupates in the soil).

Reprinted from a January 29, 2009 posting on the New England Greenhouse Update website:

Greenhouse - Aphid Banker Plants 2

The following are guidelines for using aphid banker plants in greenhouses to build up natural aphid controls.
  • Starter aphid banker plants are available from several biological control suppliers.
  • Place orders for banker plants up to 6 weeks before aphids are expected in your greenhouse.
  • Transplant the plugs into larger sized pots (10 inch) so that the grass plants have plenty of room to grow.
  • Wait one or two weeks for grass feeding aphid populations to grow.
  • Lightly release the “aphid mummies” or Aphidius colemani adults onto the starter banker plants. For example, 100 hundred Aphidius per banker plant before it is divided and repotted. Aphidius colemani attacks the grass-feeding aphid, which is not an aphid pest of most greenhouse-grown crops
  • Check banker plants weekly and look for newly parasitized aphids (”aphid mummies”), which indicate that the parasitoids are establishing on the banker plants.
  • Start new banker plants on a regular basis because they will decline and die within a few weeks.
  • Inoculate new banker plants by physically transferring aphids from old banker plants onto new ones every 2-3 weeks.
  • It may be necessary to “protect” or isolate your replacement banker plants from natural enemies (either established in your greenhouse or naturally occurring natural enemies that may enter the greenhouse from outdoors during warmer weather). If so, place banker plants in “starter cages” so you can build up your population of grass feeding aphids before releasing A. colemanii.

Reprinted from a January 29, 2009 posting on the New England Greenhouse Update website:

Saturday, February 7, 2009

Greenhouse and Nursery - Foliar Nematodes

It is important to check overwintering plants in greenhouses and nurseries for signs of diseases. The following is a good article on foliar nematodes in overwintering perennials from the University of Maryland.

Your herbaceous perennials are tucked into overwintering houses in February and you may not be giving much thought to pests on your plants. We thought so also until last week when the UMD Plant Diagnostic Lab received samples of heuchera with leaf spots on the foliage. These symptoms could easily be mistaken for a fungal leaf spot disease. Turns out it was not – it was foliar nematode. These microscopic roundworms move in films of water on plant surfaces and enter leaf tissues through stomates. Like root-attacking nematodes, foliar nematodes have a needle-like structure called a stylet that they use to pierce plant cells and feed on cell contents, resulting in cell death.

Lesions caused by foliar nematodes are first chlorotic, then necrotic. Early symptoms can appear as small speckles or spots, which look very similar to fungal leaf spot diseases or chemical injury. Movement of the nematodes within leaves is restricted by larger leaf veins, resulting in necrotic lesions with an angular shape.

Foliar nematodes overwinter in plant debris, or on infected perennial plants. They survive for long periods of time in leaf tissues, and are spread by propagating infected plants and by splashing water (rainfall, overhead irrigation). The list of plants susceptible to foliar nematodes is quite large, and includes woody plants like azaleas as well as numerous herbaceous perennials (such as hosta, heuchera, hellebores, ferns, begonias, salvia, and anemone).

The easiest way to manage foliar nematode problems is to avoid bringing them into your facility. Carefully inspect new plants for foliar nematode symptoms. If symptoms develop, remove and destroy affected plants. Pylon is registered for controlling foliar nematodes, but this treatment will only knock down populations, not completely eradicate them. Sanitation is key to keeping this pest in check.

Heuchera with small lesions on foliage caused by foliar nematodes. Photo by Selin Balci.

Article reprinted from the February 6, 2009 issue of the Greenhouse TPM/IPM Bi-Weekly Report from the University of Maryland Cooperative Extension Central Maryland Research and Education Center.

Thursday, February 5, 2009

Nursery and Greenhouse - Census of Agriculture Now Gives Numbers on Floriculture Production

The most recent census of agriculture (2007) is now available for access via the internet. This is the first time that information on nursery and greenhouse production has been included. The following is a map from the census showing production in our region.

Number of Farms with Floriculture Crops Grown for Sale: 2007

1 Dot = 10 Farms

You can access the 2007 census of agriculture at

Landscape - New Publication on Tree and Shrub Troubleshooting

The following is information on a new NRAES publication on troubleshooting problems on woody broadleaf trees and shrubs.

Broadleaved Shrubs and Shade Trees
Problems, Picture Clues, and Management Options

Why didn’t my azaleas flower this year? … Why is my maple tree showing its fall colors in July? … What’s been chewing little round holes in the leaves of my roses? … What’s causing those unsightly brown spots on the flowers of my prized dogwood? The answers to these questions and more can be found in NRAES-183, Broadleaved Shrubs and Shade Trees: Problems, Picture Clues, and Management Options, a guide soon to be published by NRAES. The guide was written by Mary Kay Malinoski and David L. Clement, seasoned experts who have 20 years experience fielding such questions at the University of Maryland’s Home and Garden Information Center. The guide will be an invaluable resource for home and master gardeners, students, extension and college educators, landscape professionals, and horticultural consultants. It will also be a useful addition to garden-center bookshelves and landscape-oriented mail-order catalogs.

Brimming with over 400 photos, the guide clearly illustrates over 125 problems that affect broadleaved shrubs and shade trees. Because it is focused around picture clues, it will be useful to those who have little or no prior knowledge of landscape issues. Users simply observe the problem in the landscape and then follow the guide’s easy-to-use, photo-based problem key to zero in on the cause. Management strategies are suggested for most problems.

  • Descriptions of 30 abiotic problems, 30+ diseases, 55+ insect pests, 7 wildlife pests, and 4 miscellaneous organisms (like algae, moss, and mushrooms)
  • 430+ color photos
  • 200+ pages
  • Introductory chapter on diagnostics and nonchemical management strategies
  • Photo-based key to symptoms and possible causes
  • Compact, spiral-bound design with laminated cover
  • Glossary
For ordering information go to
Click on order form for a larger version to print.

Wednesday, February 4, 2009

Greenhouse - New England Floriculture Guide

The New England Floriculture guide is a great resource for greenhouse growers. The following is more information.

New England Greenhouse Floriculture Guide The New England Greenhouse Floriculture Guide is the reference of choice for commercial greenhouse growers throughout New England. This comprehensive manual provides detailed biological, cultural and chemical pest management information for greenhouse floriculture crops. In addition to sections on managing insects, diseases and weeds, one section covers plant growth regulation, and one section addresses greenhouse integrated pest management. An appendix provides additional useful links: published references, websites, state diagnostic clinic contact information, and more. The second appendix addresses pesticide safety.

Single copies of the Guide are available for $25, and bulk rates are available. For ordering information, go to: or call 802-865-5202.

Tuesday, February 3, 2009

Business - Reminder: Surviving and Thriving in Tight Times Workshop Series Coming Up

The following is information on a series of workshops to be held in Dover on horticultural business survival in tight times. This is a part of the Ornamental Short Course series from Delaware Cooperative Extension.

Business Survival in Tight Times

February, 5, 12, 19, 26
Time: 12 noon—3 p.m.
Location: Kent County Extension Office, Dover, DE (Paradee Center next to DelDOT)
Cost: $35 (Fee will be remitted for new businesses or businesses under economic hardship)
Lunch: Light lunch included.
Registration: Register by calling (302) 730-4000

Horticultural business owners and managers should mark your calendars for a series on surviving and thriving in these tough economic times. Landscapers, landscape maintenance firms, lawn care companies, nurseries, greenhouses, garden centers and other horticultural businesses will benefit from these workshops.

Come join us for lunch, learn about approaches to help your businesses in tough economic conditions, and participate in discussions on topics that are important to your business.

This series is designed to help small businesses evaluate their bottom line, determine portions of their enterprise that are profitable, implement cost cutting procedures, manage employees under difficult conditions and prioritize how to deliver products and services successfully to your customers.


February 5 = Business analysis
February 12 = Cost control
February 19 = Labor management and customer service
February 26 = Business opportunities and entrepreneurship

Instructors: Gordon Johnson and Susan Barton

Gordon Johnson, Extension Horticulture Agent, UD, Kent County

Turf - Turf Establishment or Complete Renovation With Compost

The following is information on turf establishment or complete renovation with compost. Compost additions at establishment or renovation can have dramatic effects of the long term health of turf. It is especially useful in disturbed sites, building sites with heavy traffic during construction, and poor soils.


• Application Rate: Apply a 1 to 2 inch layer prior to land preparation. Use the higher rate on sites with exposed subsoil, compaction problems, or that are very sandy.
• Application: Apply using a topdresser or by hand
• Incorporation: Till compost to a 5 to 7 inch depth so you have a 20 to 30% inclusion rate. Add any additional lime or fertilizer needed at this time.
• Prepare Seed Bed: After incorporation, finish preparing area to seed or sod. Smooth the area. Make sure compost is well incorporated. Coarse compost remnants can interfere with weed/soil contact.
• Seed or sod: Use a turf seeder or lay sod. Avoid excessive compaction during seeding or sodding.
• Watering: Water to germinate grass or to establish the sod roots.

Gordon Johnson, Extension Horticulture Agent, UD, Kent County

Monday, February 2, 2009

Lansdscape - Compost Use Recommendations for Landscape Planting Beds

Compost is a very good soil amendment and mineral nutrient source for landscape planting beds - especially where annual displays or perennials are being grown. The following are some recommendations for use:


• Application Rate: Apply a 1 to 3 inch layer of compost (1 to 2 inches is common) prior to planting.
• Application: You can apply the compost by hand or in larger beds using mechanical equipment such as a compost topdresser. You may also use a blower system.
• Incorporation: It is important to till or spade in the compost to a 6-8 inch depth to incorporate into the planting bed. You can add any additional fertilizer at this time, but most commonly with compost you will need no additional nutrients, at least for the first year. You should add lime if needed during the incorporation. Remember that many composts have a near neutral pH so you may need to reduce lime amounts accordingly. Some composts have higher mineral nutrient salt content so full incorporation is necessary to dilute out these salts.
• Finishing the Planting Bed: Smooth the area with rake or or drag.
• Planting: you may plant immediately and then water plants in.

Gordon Johnson, Extension Horticulture Agent, UD, Kent County

Landscape and Turf - What is Compost?

Compost is being recommended for use in turf and landscapes. However, many people do not really know what compost is. The following are some definitions and information on compost and composting.

  • Compost is the natural humus like material that remains when you decompose organic materials such as plants and animal manures.
  • Compost is the product resulting from the controlled biological decomposition of organic material that has been sanitized through the generation of heat and stabilized to the point that it is beneficial to plant growth.
  • Composting is a controlled biologic process in which microorganisms convert organic materials into humus-like material called compost.
  • Active composting is typically characterized by a high temperature phase, that sanitizes the organic materials and allows a high rate of decomposition.
  • This is followed by a lower temperature phase that allows for the product to stabilize, while still decomposing at a lower rate.
  • Compost bears little physical resemblance to the raw material from which it originated.
  • Compost is an organic matter resource that has the unique ability to improve the chemical, physical, and biological characteristics of soils or growing media.
  • Compost contains plant nutrients but is typically not characterized as a fertilizer.
  • Compost is not:
    –Topsoil is Excavated surface soil, 1-4 % organic matter (compost is ~50 % organic matter)
    •‘Black dirt’
    –There are high organic matter soils, usually from drained marshes or swamps but these still are different from compost.
    –Peat is moss from natural bogs or bogs that have been drained
    –Peat is less biologically active, less renewable than compost
    –Fertilizers are more concentrated sources of mineral nutrients. Compost does contain nutrients but at lower levels than fertilizers.

Leaf Compost