Saturday, October 31, 2009

Landscape - Bilingual Bulletins

The University of Georgia Center for Urban Agriculture has a number of english/spanish combination bulletins on its website. These would be very useful tools for training hispanic workers. The following are some links.

Bilingual Bulletins/Boletines bilingüe

Fireblight: Symptoms, Causes and Treatment / Quemazón de las Rosáceas: Síntomas, Causas y Tratamiento

Identifying and controlling most common Spring Plant Diseases in the Landscape / Identificando y controlando las enfermedades de plantas más comunes en la primavera en el paisaje

Nematodes in the Landscape: the Silent Threat to Plant Health / Los Nematodos en el Jardín Residencial: La Amenaza Silenciosaa la Sanidad de las Plantas

Powdery Mildew on Ornamental Plants: Facts and Controls / Cenicillas Polvorientas en Plantas Ornamentales:Hechos y Control

Promoting and Active Plant Disease Scouting in the Landscape / Promoviendo un Monitoreo Activo

Reminders for Improved Drop Spreader Performance / Recordatorios para Mejorar el Funcionamiento de las Aspersoras de productos químicos que funcionan por gravedad

Six Easy Steps for Success with Pre-emergence Herbicides / Seis Pasos Fáciles para tener éxito con Herbicidas Pre-emergentes

Sudden Oak Death / Muerte Repentina del Roble

Top Diseases and Plant Problems on Turf / Enfermedades y Problemas de Cespedes y Ornamentales mas Importantes

Greenhouse - Watch for Whitefly

Watch for whitefly in fall greenhouse crops. The following is a short article on the subject.

Monitor poinsettia and other greenhouse crops closely for the different stages of whitefly. Avoid letting weeds grow under the benches which serve as epicenters for whitefly populations. If you treated poinsettias with imidacloprid (Marathon) or dinotefuran (Safari) as soil drenches after pinching then you should have pretty good control of whitefly on the foliage that expanded after the application. Be sure to continue closely monitoring lower leaves which would have expanded before the systemic was applied. Check pesticides labels to see whether they note “do not apply when bracts are in color”. In past years we have observed that Abamectin (Avid), pyridaben (Sanmite), chlorfenapyr (Pylon), acetamiprid (TriStar) and dinotefuran (Safari) applied as foliar sprays in bract stage without causing any noticeable damage on poinsettia varieties such as ‘Freedom’, ‘Prestige’ and ‘Monet’. When applying pesticides late in the season to poinsettias, it is best to try out a spray on a few plants before treating the whole crop. Other materials that work well include Azatin, Aria, Endeavor, Enstar, Flagship, Judo, Marathon, Pedestal, and Talus.

Reprinted from the October 30, 2009 edition of the Greenhouse TPM/IPM Bi-Weekly Report University of Maryland Cooperative Extension Central Maryland Research and Education Center

Friday, October 30, 2009

Greenhouse - Whitefly Insectide Resistance

Whiteflies can develop resistance to insecticides used for their control in the greenhouse. The following is more information.

Resistance Problems

Unquestionably, chemical controls such as Marathon, Safari, Distance and Avid are presently some of the premiere whitefly management materials with poinsettias. Typically they have shown to be outstanding insecticides and have enabled growers to reduce the number of treatments previously required when managing a poinsettia crop. Unfortunately, these control materials have become regional wide management approaches with their use commonly applied during all phases of the crop’s development stages.

It needs to be remembered that insecticide resistance is a reality in our industry. For example, during the past few years Marathon has experienced widespread resistance problems against silverleaf whiteflies (Q-Biotype strain). When the same insecticide is used extensively over an extended period of time, then resistance will inevitably begin to occur. There are at least 3-dozen insecticides which whiteflies in the Bemisia genus (silverleaf whitefly) are resistant to. Consequently, it is important to try to break the cycle of continual applications of insecticides that presently work best. For example, for the past 2-3 years Safari has become the material of choice for many poinsettia growers. Simply loading up on the latest and greatest insecticide presently available will produce problems. Hoping the pest control industry will continue to be able to produce new materials after others become resistant is an approach that will eventually lead to failures.

Information from "Some Thoughts on the Biointensive IPM Approach for the Management of Whitefly on Poinsettias" by Steven K. Rettke, Ornamental IPM Program Associate, Rutgers University in the October 15, 2009 edition of the Plant & Pest Advisory, Landscape, Nursery & Turf Edition, A Rutgers Cooperative Extension Publication.

Landscape - Smaller Trees for Delaware Landscapes

The following are some smaller trees to consider for Delaware Landscapes

Amur maple (Acer tataricum ssp. ginnala). Hardy; multi-stemmed tree; 15-20’ tall; fragrant, inconspicuous, creamy-white flowers in spring; red fruit in summer that turns brown; bright orange to red fall color; can reseed in wild; tolerant to a wide range of soils and pH.

Japanese tree lilac (Syringa reticulata). Hardy; compact; upright; 15-25’ tall; reddish-brown, shiny bark; large, creamy-white, slightly fragrant, terminal flowers in June; yellow fall color; tolerant to a wide range of soils and pH; urban and salt tolerant.

American hornbeam, musclewood (Carpinus caroliniana). Hardy; wide-spreading; multi-stemmed tree with low branches; 20-30’ tall; fluted, muscle-like bark and branches; yellow to orange-red fall color; slow grower; prefers rich, moist, slightly-acid soil; salt intolerant; shade tolerant. Native tree.

Eastern redbud (Cercis canadensis). Hardy; spreading; vase-shaped tree; 20-30’ tall; reddish-purple new leaves that change to green; brownish-black bark with orange inner bark; reddish-purple flowers that fade to pink in early spring; yellow fall color; prefers a moist; welldrained soil; pH adaptable; partial shade tolerant; native tree.

Apple serviceberry (Amelanchier x grandiflora). Hardy; upright; multi-stemmed tree; 15-25’ tall; smooth gray bark; reddish-bronze new growth; white flowers in early spring; reddish-purple edible fruit in early summer; attracts birds; yellow-orange to red fall color; full sun to partial shade; prefers a moist, welldrained, slightly acid soil.

Thursday, October 29, 2009

Landscape - Tree Planting Tips

Early November is a good time to plant many deciduous tree species. The following are some tips on tree planting.

LOCATE LOGICALLY - Trees need room to develop root systems underground and branches above ground. Don't plant trees that will grow too large in small areas. Also avoid planting under power or telephone lines or too close to buildings. Site suitability will determine which, if any trees to plant. The designated site may be in the lawn, near a patio, along a street or sidewalk, in a garden, in sun or in a shaded spot. Soils may be clay, sandy, saline, compacted, wet or dry, gravelly or even full of old building rubble. Whatever the situation, you will need to determine if the site is suitable for growing a healthy tree. Consider planting for energy conservation. Deciduous trees will shade the west, south and east sides of the home in summer, and evergreen trees along the west and north edges of the lot will provide winter windbreaks.

CHOOSE CAREFULLY - For what reasons are you planting the tree? You may want privacy, increased property values, a windbreak, shade, fall color, flowers, fruit or a bird habitat. Perhaps you want to create a sound barrier. Combine this information with knowledge about the site.
This is a good time to visit your local Cooperative Extension agent. You'll want to consider that fast-growing trees often are weak and subject to storm damage. Think about the mature size and shape of trees and learn whether their roots might invade sewer lines, lift and crack sidewalks or make bumpy lawns. Learn which trees are likely to harbor insects or diseases.

DIG DILIGENTLY BUT CAUTIOUSLY - Before digging, contact your utility company to mark the location of any underground lines. You could be liable for damage done to such lines.
To prepare the site, mark a circle at least 3 times the diameter of the tree's rootball. Excavate the area with a pick and spade. In clay soil, dig to a depth 2-4 inches shallower than the height of the rootball. In sandy soil, dig to a depth equal to the rootball. Leave the bottom of the hole firm and undisturbed. Holes should be saucer shaped.

PLANT PROPERLY - Try to plant trees when the weather is cool, cloudy and humid, but not windy. If you can't plant right away, keep the tree in a cool, shady, protected spot and keep the roots moist. It helps to soak bare root trees and shrubs in a bucket of water overnight before planting. Remove any plastic or metal containers from the rootball. Place the tree upright in the center of the planting hole. If the tree is in a fiber pot, tear off the sides. If the roots of a containerized tree are potbound, "tease out" some of the roots. For balled and burlapped trees, cut any rope tied around the trunk and pull the burlap away. Cut any reinforcement wire, removing as much as possible, but be sure the rootball stays intact. Shovel backfill into the hole; continue until roots are covered and most of the backfill is used. Don't tamp the soil with your feet.

FERTILIZE FRUGALLY! - Don't put fertilizer into the planting hole; it may cause root injury. Next spring, fertilize young trees lightly. Root stimulator solutions have negligible value. You can use them, but they aren't necessary for transplant success.

WATER WELL - Water the soil at relatively low pressure, using the hose or a "bubbler." Let the water, not your foot, settle the soil. If the soil settles below grade, add more backfill. When done, the planting area should be well-soaked and moist backfill should barely cover the top of the rootball. Watering frequency depends on the soil, not the calendar. Dig with a trowel on the edge of the planting area. Soil that feels moist and holds together when squeezed doesn't need water. Overwatering drives air from the soil, causing root suffocation.

PRUNE PRUDENTLY - A newly planted tree needs only minimal pruning. Prune out only dead, diseased or injured branches. Research shows that transplanted trees establish quicker when as much foliage as possible remains. If you do prune, don't use pruning compounds on pruning cuts.

STAKE SENSIBLY - Trees can be staked too tightly or for too long. Don't stake small trees or those not in the wind's path. Large evergreen trees, planted in a windy site, will need staking. To stake,do not use garden hose and wire. Instead run wire through grommeted staking straps or use wide strips of carpeting. This way, the straps, not the wire, passes around the trunk. A year of staking usually is sufficient. Rigid staking of a tree is counterproductive; research shows trees don't develop normally if they're not allowed any sway.

MULCH MEANINGFULLY - A forest tree provides its own mulch with several inches of leaves on the ground. We can imitate this by mulching the planting area with 3 to 4 inches of wood chips, chunk bark, straw, pine needles or shredded leaves. Don't use plastic beneath the mulch; water or air can't penetrate it. Fabric-type weed-barriers are preferable. One thing you won't see in the forest is manicured lawns around a tree. Research shows that newly planted trees are at a disadvantage when they must compete with grass for water, air and nutrients. Keep grass from the planting area for at least one year. If you mulch around trees, instead of planting grass, you also prevent possible trunk damage by lawn mowers or string trimmers.

Adapted from "Ten Commandments of Tree Planting" By Robert Cox, Colorado State University Cooperative Extension agent, horticulture

Landscape - Highly Rated Trees for Delaware

The following are some highly rated trees for planting in Delaware.

Paperbark Maple
Japanese Maple
Blue Atlas Cedar
Hinoki Falsecypress
Dawn Redwood
White Oak
Scarlet Oak
Shingle Oak
Bur Oak
Red oak
Japanese Stewartia
Hedge Maple
Red Maple
Briotti Red Horsechestnut
Shadblow Serviceberry
Heritage River Birch
American Hornbeam
Shagbark Hickory
White Fringetree
American Yellowwood
Kentucky Coffeetree
Common Witchhazel
American Holly
Golden Raintree
Cucumbertree Magnolia
Saucer Magnolia
Star Magnolia
Sweetbay Magnolia
Norway Spruce
Sawtooth Oak
Willow Oak
Japanese Pagodatree
Japanese Snowball
Japanese Tree Lilac
Littleleaf Linden
Chinese Elm

Information from Pennsylvania and Delaware: Tree Species Rating and Valuation Guide; Penn-Del Chapter ISA

Wednesday, October 28, 2009

Landscape and Nursery - Black Root Rot of Holly

The following is a good article on black root rot of Holly from the University of Kentucky.

Black root rot, caused by the fungus Thielaviopsis basicola can do significant damage to hollies in landscape beds. Black root rot is most frequently observed on Japanese holly, blue holly, and inkberry. Susceptible blue holly cultivars include: Blue Angel, Blue Maid, Blue Prince, Blue Princess, Blue Stallion, China Boy, China Girl and Dragon Lady. While English and Chinese hollies are reportedly resistant, American and Yaupon hollies are considered to be only moderately resistant. Other ornamentals known to be susceptible include begonia, cyclamen, geranium, gloxinia, oxalis, petunia, phlox, poinsettia, sweet pea, verbena, and viola (pansy). Black root rot may also affect alfalfa, cotton, cowpea, eggplant, peanut, snapbean, soybean, tobacco, and tomato.

Symptoms. The first symptoms of black root rot include yellowing and marginal scorch of the foliage and shoot dieback. Later, twigs or stems may die back and eventually the entire plant may die. The root system of the declining plant is stunted and decayed. These symptoms could be confused with Phytophthora root rot which was also widespread in landscapes this year. Unlike Phytophthora, black root rot causes black lesions on the infected roots which, in the early stages of disease, contrast sharply with the adjacent healthy white portions. Lesions may appear on the tips of feeder roots or elsewhere along the root. Diagnosis can be confirmed by microscopic analysis which reveals the characteristic chlamydospores of the fungus embedded in the root tissues.

Disease Management.

Landscapers and nursery growers need to be aware that the black root rot fungus can persist indefinitely in the soil or it can survive as a saprophyte on plant debris, so once a landscape or nursery bed is contaminated with the fungus, it is difficult to remove.

Plant only disease-free plants in the landscape. Sometimes diseased, but well-watered and fertilized, nursery-grown hollies or bedding plants will appear to be healthy but, after they are placed in the landscape, they may decline due to more stressful growing conditions. This means it is very important to examine root systems prior to planting. If blackened roots are evident, plants should be rejected.

Avoid planting susceptible plants in soils known to be infested with the fungus. While the fungus is widespread, it may be present in higher levels in soils where black root rot was previously a problem on other plants such as petunia or pansy. Occasionally, when old agricultural lands are developed for housing, homeowners may find they have also purchased a black root rot problem from a former tobacco or alfalfa field as well.

In the landscape, badly infected plants should be removed and the site replanted with a non-susceptible host.

There are no effective fungicide drenches available for controlling black root rot in the landscape. Steam pasteurization or chemical fumigation will eradicate the fungus from propagation and growing media in nurseries. The fungicide Medallion is registered for managing this disease in greenhouses.

Information from "Holly Black Root Rot is Active" By John Hartman in the current edition of the Kentucky Pest News

Landscape - Rose Mosaic Virus

I recently was sent some rose pictures that looked like the plant had rose yellow mosaic virus. The following is more information.

Several viruses are associated with the range of symptoms of rose mosaic, including Prunus necrotic ringspot virus (PNRSV) and Apple mosaic virus (ApMV). The disease does not spread naturally, has no known insect vector, but grafting transfers it to healthy plants. Viruses can be in the rootstock or scion or both and may not show symptoms. 'Madame Butterfly', 'Ophelia', and 'Rapture' are highly susceptible. Some report the disease does not spread; others indicate it may spread very slowly over many years.

Symptoms may range widely depending on time of year, temperature, and type of virus(es) infecting the plant. Characteristic symptoms include chlorotic line patterns (zigzag pattern), ringspots, and mottles in leaves sometime in the growing season. There may also be yellow net and yellow mosaic symptoms. Symptoms often are evident in spring and early summer but may not be on leaves produced in summer. Vein-banding may be on leaves in long hot periods. Flower distortion, reduction in flower production, flower size, stem caliper at the graft union, winter survival, and early leaf drop, and increase susceptibility to cold injury have all been reported. Some infected cultivars may not show any symptoms at all.

Note the irregular pattern of yellow lines on leaves.

Sometimes the leaf veins are yellow in plants infected with this virus.

Cultural control:

Purchase clean and/or certified virus-tested (and found to be free of all known viruses) stock. Remove and destroy infected plants. However, the disease will not spread unless you propagate from or onto an infected bush. Heat-treat scion stock plants 4 weeks at 100oF before grafting.

Information and photos from the Online Guide to Plant Disease Control from Oregon State University

Tuesday, October 27, 2009

Landscape and Nursery - Some Cypress and Falsecypress Species for Delaware

The following are some cypress and falsecypress species that are adapted to Delaware landscapes. Note that the genus Cupressus has been changed for some species to Callitropis. One particularly interesting species is Arizona cypress which deserves wider planting in Delaware as a substitute for Leyland cypress.

Nootka falsecypress (Callitropis nootkatensis) ‘Pendula’, ‘Green Arrow’, ‘Van der Acker’
Arizona cypress (Callitropis glabra) ‘Silver Smoke’
Arizona cypress (Callitropis glabra) ‘Blue Ice’
Japanese falsecypress (Chamaecyparis pisifera) ‘Boulevard’
Japanese falssecypress (Chamaecyparis pisifera) ‘Curly Tops’
Hinoki falsecypress (Chamaecyparis obtusa)

A high priority is to identify alternatives to the overused and problem-susceptible leyland cypress (X Cupressocyparis leylandii). One good example of an alternative to this screen plant is the Arizona cypress (Cupressus arizonica).

There is a debate on the proper nomenclature for this group of plants. This is a botanical lumper-splitter type of project. Some experts separate C. arizonica from C. glabra. Other experts lump them and place glabra as a variety of C. arizonica. The distinction is not as important, however, as the potential this group offers for Delaware gardens.

There are several reasons why this needle evergreen deserves more attention. First of all, the various cultivars all have an eye-catching silver-blue/powder blue color. The blue hue is even better than what you get with the blue atlas cedar (Cedrus atlantica ‘Glauca’). I love the cultivar names: ‘Blue Ice,’ ‘Blue Pyramid,’ ‘Carolina Sapphire,’ and ‘Silver Smoke.’

The second reason to admire this plant is for its rapid growth. For this reason it is grown frequently as a Christmas tree in the Southeast. So far the plant is also quite free of insect and disease problems. I have not observed bagworms, rust, or cankers like some other evergreen options.

The growth habit on young plants is very similar to our native Eastern red cedar (Juniperus virginiana). Because needles are not born in flat sprays like leyland cypress, the overall texture is very soft. Plants are pyramidal in shape and clearly taller than they are wide. As the plant matures it will open up. Very old specimens almost have a weeping, graceful appearance. ‘Blue Ice’ and ‘Blue Pyramid’ may have a much tighter pyramidal habit than ‘Carolina Sapphire.’

Arizona cypress thrives on full sun exposure. The fabulous blue needle color will probably be diminished in more shade. While constant moisture might promote growth, an established plant should tolerate fairly dry conditions.

Need a cute fact for the next garden party? Arizona cypress is closely related to the artistic and beautiful Monterey cypress (C. macrocarpa) found along the California coast. Unlike its cousin, the Monterey cypress does not seem to like the heat and humidity this area of the U.S. Another garden party trivia note: Monterey cypress is one of the parents of the intergeneric hybrid leyland cypress.

Common Name: Arizona Cypress
Varieties to look for: ‘Blue Ice,’ ‘Blue Pyramid,’ ‘Carolina Sapphire,’ ‘Silver Smoke’
Flower Color: none
Blooming period:
Perennial or annual: needle evergreen
Size: 45’ tall by 20’ wide
Exposure: sun to partial shade
Soil: tolerant
Watering: moist best
When to prune: not required
Suggested use: screen/hedge, specimen

Information on Arizona Cypress adapted for Delaware from "Arizona Cypress – Cupressus arizonica Shrub Profile" By: James Robbins, University of Arkansas. Photo also from that publication.

Monday, October 26, 2009

Landscape, Nursery, and Greenhouse - Mite Control

The following is a good table on mite control options for horticultural use from North Carolina State University. Click on the table for a larger version in a new window.

Information from the 2007 Nursery Crops Short Course, Mountain Horticultural Crops Research and Extension Center, Fletcher, NC, North Carolina State University.

Landscape - Understanding Slugs

We are certainly hearing about slug troubles this fall. With the cooler temperatures, slugs seem to be feeding incessantly. Slugs of course are most often problematic in mulched areas and thrive in high moisture parts of the landscape. The following is more information.

Most slugs have a single generation per year with overwintering eggs hatching in spring and slugs developing through spring, summer, and fall. As winter approaches, slugs lay eggs, which overwinter and hatch the next spring. Some adults can also survive over winter until next spring and resume feeding.

If slug problems are particularly bad, you might consider fall applications of metaldehyde baits. Such applications can be effective, but are not the most efficient use of these baits because some adult slugs may have already laid eggs and the chemical treatment might not contribute too much to reducing spring populations.

A final point worth mentioning in the struggle against slugs is that natural enemies have a lot of potential to contribute to slug suppression. Some ground beetle and harvestman (aka daddy long legs) species are voracious slug predators. Reduce insecticide use in landscapes to preserve these predators of slugs.

Adapted from an article in the Penn State Field Crop News.

Sunday, October 25, 2009

Landscape and Nursery - Plants for Delaware Landscapes: Gaura lindheimeri

The following is information on Gaura lindheimeri, a good herbaceous perennial for Delaware landscapes.

Gaura lindheimeri, whirling butterflies, is an herbaceous perennial native to Texas and Lousiana that comes into its own in the late summer and throughout the fall. It is very drought and heat tolerant and can stand up against high humidity without diseases slaying it. It grows in an upright bushy form to a height of 2 - 3 feet and will flower continuously from spring till the first hard frost. G. lindheimeri prefers a moist rich soil with a neutral to alkaline pH, but it grows very well in most soils regardless of moisture or pH. Despite its heat tolerance, G. lindheimeri can thrive from zone 5 - 10 as long as the roots are well mulched for the winter. The flowers are small and white or pink depending on the cultivar, but as the white flower matures it becomes a pale pink. They are arranged on the stem like a gladiola, with a few flowers blooming at a time and are held above the foliage. After flowering, the spent flowers fall cleanly without dead heading. The flower stalks are thin and wiry, often tinged with red or pink depending on the coolness of the night temperatures. G. lindheimeri can be used as a background plant or as a wild flower planting; it doesn’t conform to a formal planting. Some of the newer cultivars are more compact like ‘Swirling Butterflies’ or a darker pink like ‘Siskiyou Pink’, Pretty in Pink’ and ‘Crimson Butterflies’. Pests include aphids, leaf galls, leaf spots, root rot and rust.

Gaura lindheimeri

Information from Ginny Rosenkranz, University of Maryland in the October 23, 2009 edition of the TPM/IPM Weekly Report for Arborists, Landscape Managers & Nursery Managers, University of Maryland Cooperative Extension

Landscape - Salt Tolerance of Landscape Plants

Winter is not far around the corner and deicing salts will be used by road and parking lot maintenance personnel. Excess salts can damage landscape plants. The following are lists of salt tolerant and salt sensitive landscape plants. For areas that receive excess salts from deicing (such as parking lot islands), you should consider salt tolerant species.

Salt Tolerant Shrubs

California privet
Pfitzer juniper
rugosa rose

Salt Sensitive Shrubs


Salt Tolerant Deciduous Trees

black cherry
black locust
bur oak
English oak
green ash
red oak
Russian olive
Siberian elm
weeping willow
white oak
white poplar

Salt Sensitive Deciduous Trees

American linden
black walnut
flowering dogwood
little-leaf linden
red maple
shagbark hickory
silver maple
sugar maple

Salt Tolerant Evergreens

Austrian pine
Japanese black pine
pitch pine
red cedar
white spruce

Salt Sensitive Evergreens

balsam fir
Canadian hemlock
eastern white pine
red pine

Information from "De-Icing Salts Can Injure Roadside Vegetation" by Ann B. Gould, Ph.D., Specialist in Plant Pathology in the Nov. 6, 2003 edition of the Plant and Pest Advisory, Landscape, Nursery, and Turf Edition from Rutgers University

Saturday, October 24, 2009

Greenhouse - Whiteflies on Poinsettias

The following is information on initial signs of whitefly damage on poinsettias.

Often a sign of a large whitefly population directly feeding on the poinsettia crop is chlorotic and bleached stems, leaves and bracts. In order to prevent this from occurring, growers should maintain good sanitation, install and monitor yellow sticky cards and routinely inspect the underside of leaves for the presence of whitefly eggs, nymph and adults. If whiteflies are found implement integrated pest management (IPM) practices to avoid the above problems and prevent whitefly pesticide resistance.

Chlorotic and bleached stems, leaves and bracts are often signs of heavy whitefly pressure on poinsettias.

Information from the Purdue Plant and Pest Diagnostic Laboratory Website

Landscape - Pear Blister Mite

The following is an article on Pear Blister Mite, a pest to be watching for in the landscape

Over the last couple of years we have been seeing more pear blister mite damage on Asian pears, European pears and ornamental pears. These mites are very small and you will need at least a 15 to 20X hand lens to see them. They are white, long, slender, and striated. They also have a few long hairs. Eggs are spherical and pearly white.

Monitoring: Look under bud scales during winter where these mites feed. This feeding can cause buds to dry and fail to develop in spring. In the spring, pear blister mites feed on emerging leaves, flowers and developing fruit. Feeding results in blistered leaf spots that start red and eventually turn black. The spots on the fruit are usually depressed with a halo of clear tissue that tend to run together. Eggs are laid inside the blister which is where young mites start feeding so they are rarely seen.

Control: In late October the females will begin to seek out places on the branches to overwinter. They like to settle down into the bud scales and bark cracks. At this time of year they are moving about on the twigs and are susceptible to pesticide applications. You have a relatively small window in which to treat for this pest. A 2% rate horticultural oil can e applied in late October. The kill rate can be improved with addition of Abamectin (Avid) to the horticultural oil.

Pear blister mite damage.

Article and photo from the October 23, 2009 edition of the TPM/IPM Weekly Report for Arborists, Landscape Managers & Nursery Managers from the University of Maryland Cooperative Extension

Friday, October 23, 2009

Landscape and Nursery - Azalea Cultivars Resistant to Lace Bug

The following are some azalea cultivars that are resistant to lace bug.

Lace bugs are a frequent pest on azalea, rhododendron, pyracantha and other hosts. These laceywinged insects feed on the undersides of leaves, suck leaf sap and leave a chlorotic dot on the upper leaf surface. They overwinter as eggs inserted into the leaves. Black varnish spots on the underside of leaves is diagnostic for this insect. Management techniques may involve malathion, insecticidal soap, pyrethroids, and resistant varieties.

The following azalea cultivars have resistance to azalea lace bug:

Pink Star
Pink Fancy
Salmon Pink
Elsie Lee
Red Wing

Information from the 2007 Nursery Crops Short Course, Mountain Horticultural Crops Research and Extension Center, Fletcher, NC, North Carolina State University.

Greenhouse and Landscape - Pansy Diseases

Keep your eyes out for two diseases of pansy that have been increasing over the years.

Black root rot shows up just about anytime in the greenhouse and landscape. If plants are not establishing or declining without any obvious leaf spotting or other problems carefully dig the plants and check out the roots. If roots are black to very dark suspect black root rot and send in a sample.

Control: in the greenhouse keep medium pH between 5.5 and 6.0 do not reuse plug flats without sterilizing; control fungus gnats. Chemicals that work best as preventative treatment include thiophanate methyl (3336, Fungo) Medallion and Terraguard.

Cercospora leaf spot. Look for irregular spots with dark red- brown margins. This disease can be found in all stages of crop production as well as in the landscape. In the greenhouse try and keep the foliage dry, check frequently, rogue out badly spotted plants from the greenhouse. Fungicides for outside and inside use to control Cercospora leaf spot include Daconil, Compass, Heritage, Insignia, or SI’s such as Eagle (or Immunox for home use).

Information from Bob Mulrooney, Extension Plant Pathologist, UD

Thursday, October 22, 2009

Landscape - Hardy Banana

The following is information on hardy banana, a perennial plant to try in Delaware gardens for a "tropical" look along side of Cannas and similar plants.

A great tropical looking plant, native to Japan’s Ryukyu Islands and is hardy to zone 6 if mulched heavily with leaves in the autumn. Plants can reach 10’ in height, with foliage up to 6’ in length. Plants will produce new offsets each spring around the original plant, creating a great impact for the annual or mixed border!

Besides adding a tropical look to gardens, the hardy banana, Musa basjoo, is a fascinating plant. It, along with other species in the genus Musa are the world's largest herbaceous plants, mostly originating from tropical climates. Many species of Musa routinely grow more than twenty feet tall! The hardy banana grows to be anywhere from 12 to 18 feet tall, so it will probably attract some attention if planted in your garden.

While sometimes we talk about banana 'trees', in fact all parts of the plant are herbaceous–no parts are woody. What many of us mistake for the 'trunk' of the banana tree is in fact tightly wrapped leaves. Botanically speaking this is a pseudostem, meaning 'false' stem. Unlike a lot of plants, the growing point for a banana plant is not near the outside of the plant. It is deep within the pseudostem near the base, much like how German irises and canna lilies grow.

Each pseudostem on a banana plant has a limited lifespan. It only lives as long as it takes it to flower and produce fruit. For many species, this can take the better part of a year. In our climate it is unlikely that the hardy banana will grow long enough to produce fruit. If it does, unfortunately it is not edible.

Why would anyone grow a banana plant that produces inedible fruit? The answer lies in the other common name for Musa basjoo–Japanese fiber banana. Musa basjoo is actually from the Ryukyu Islands of Japan, and historic records indicate the Japanese have cultivated the banana for fiber since the 13th century.

The fibers are extracted from shoots by boiling the shoots in lye. Then the fibers are spun into yarn and used for garments. The fibers extracted from a shoot will vary in how coarse or soft they are. Those near the outside tend to be coarser, while those in the center are much softer. Other cultures also use banana fibers, but the extraction method differs. The end result is very similar. The softest fibers have been compared to silk in how they feel and look when used in textiles. Banana fiber can also be used to make paper.

Musa basjoo, hardy banana. Photo from the Miami of Ohio cold hardy tropical plant research group web site

Information from Rutgers University and an article by Jennifer Schultz Nelson, Unit Educator, Horticulture Macon County, University of Illinois.

Landscape - A Source Guide for Mid-Atlantic Wetland Plants

The following is a good reference on where landscapers can buy wetland plants in the Mid-Atlantic area for doing wetland plantings.

A Source Guide for Mid-Atlantic Wetland Plants

83 Nursery Sources listed with name, address, phone, email, website

Explanation of Terms
Indicator Categories
Characteristic or Form
Hardiness Zone
Hydrology (Tidal/Non-Tidal)
Planting and Maintenance Information
54 pages – Softcover

Order Your Copy today for $17.95! (Virginia Nursery and Landscape Association Members)
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(Includes Shipping & Sales Tax )
(credit cards accepted)

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Developed for the Virginia Nursery & Landscape Association By Cathy Palmintier, Pam Brown & Dr. Bonnie Lee Appleton, Hampton Roads Agricultural Research & Extension Center, Virginia Tech

Wednesday, October 21, 2009

Landscape - Some Trees to Avoid Fall Planting

Early november is a good time to plant many tree species in Delaware. However, there are some species that are best planted in the spring. The following is more information.

Tree Transplanting (Fall vs. Spring)

Some trees are best planted in the spring, as opposed to the fall. Some tree species fail to adequately regenerate their root systems in the fall. They often have borderline hardiness and are best planted in spring so that they’ll have more time to become established before winter. The following is a list of plants that are not well suited for fall plantings and should be delayed until next spring: fir, birch, hornbeam, hickory, flowering dogwood, common persimmon, beech, ginko, American holly, walnut, golden raintree, golden chaintree, sweetgum, tulip tree, magnolia, blackgum, ironwood, sourwood, popular, Prunus species, golden larch, oak, willow, sassafras, cypress, and hemlock. If these species must be planted in the fall, be sure to allow for adequate water at the time of planting and until the ground freezes.

Adapted from an article by Steven K. Rettke in the October 10, 2002 edition of the Plant and Pest Advisory, Landscape, Nursery, and Turf Edition from Rutgers University

Tuesday, October 20, 2009

Landscape and Nursery - Watch For Root Rots

Watch out for root rots in landscape plants this fall, over winter, and next spring. I have confirmed several instances of trees and shrubs dying from Phytophthora root rot this year already.

One of the potential impacts from the wetter than normal season will be increased chances of root rots or reduction of root systems, especially in areas with high water tables or poor drainage. If trees and shrubs begin to turn brown from the top down during the fall or next spring and no other reason can be found for the decline, check the root systems for rotted roots or lack of a good healthy root mass.

Information from Bob Mulrooney, Extension Plant Pathologist, UD

Landscape - Brown Marmorated Stink Bugs

The brown marmorated stink bug, Halymorpha halys, [BMSB] has vastly expanded its impact as a nuisance pest in our area this year. Fortunately, it hasn't been a problem downstate. The following is more information.

First discovered in Allentown, PA in 1996, this insect has now spread its range to 25 States From the West Coast North to Wyoming, South to Mississippi and along the Eastern seaboard. It has a typical stink bug shape with a mottled brown color and does emit a pungent odor when crushed. Light brown-black nymphs hatch from light-green eggs and progress to the adult stage within several weeks. There was one generation per year reported in PA, but more are likely in areas with warmer weather. The ¾” long adult is generally the most visible life stage and it has been seemingly encountered everywhere this fall. Like other stink bugs, it feeds by inserting its sucking mouthparts into leaves and fruit of desired plants. Fruit distortion from stinkbug feeding can be referred to as “Cat-Facing”. Hundreds of hosts have been identified and there is concern that BMSB will become an agricultural pest of fruit trees and ornamentals where it becomes established. It feeds on Paulownia, apples, cherries, peaches, mulberry, soybeans, persimmons, etc. The good news is that BMSB does not appear to yet have damaging economic impact on ag crops and ornamentals. While abundant, its main impact is as a nuisance pest. Therefore, control methods should be primarily directed at monitoring for desired plants that are heavily damaged and refraining from treating unnecessarily. While an inconvenience, this pest does not yet warrant control in our area. For nuisance infestations indoors, one may choose to simply vacuum them up and or otherwise dispose of them. Restricting BMSB entry by caulking/sealing exterior gaps also helps to keep them out. Pesticide applications to exterior structural surfaces would only be warranted as a last resort in extreme circumstances. Educating others to do the same with this nuisance invader is also an important strategy.

Brown marmorated stink bug adult. Photo by Susan Ellis,

Information from Casey Sclar, IPM Coordinator, Longwood Gardens

Monday, October 19, 2009

Landscape - Mulch and Termites

In the past, it was thought that termite colonies could not establish in mulch. The following is a short article that shows that this might not be the case.

Termites in Mulch?

Termites have underground colonies and feed on wood, and may be found in mulch. In the past, most entomologists agreed that any termites brought into a site via mulch were workers and not reproductives (queens), and therefore there was little risk of a new colony developing. However, new research shows that if the mulch contains enough white worker termites, and they are given access to soil, these termites do have the ability to develop into secondary reproductives and establish a new colony! In light of this, bagged mulch should be stored on pallets off the ground, so termites cannot gain access to the mulch. Termites need ground to wood contact to easily gain access to the wood food source from their underground colony. Likewise, piles of mulch should not be stored directly on the ground. Keep bags of mulch in the sun as well, since termites should not survive high temperatures that build up during the day. Also beware of adding too much mulch to the landscape (2 to 3 inches is plenty).

Information from Steven K. Rettke in the October 10, 2002 edition of the Plant and Pest Advisory, Landscape, Nursery, and Turf Edition from Rutgers University

Sunday, October 18, 2009

Landscape - International Society for Arboriculture Certification Program

The International Society of Arboriculture is a worldwide professional organization dedicated to fostering a greater appreciation for trees and to promoting research, technology, and the professional practice of arboriculture. They have a certification program that landscape professionals working with trees should consider. Below is a snapshot from their certification web page and a link to the page.

The ISA's certification information web page can be found at

Landscape - Penn-Del Chapter of the International Society of Arboriculture

The Pennsylvania-Delaware Chapter of the International Society of Arboriculture was founded in 1960. Their mission is to provide quality educational opportunities for its members. There are currently over eight hundred members in the chapter including commercial, consulting, municipal, and utility arborists, researchers and educators, horticulturists, and individuals interested in the care of trees and landscapes. Landscape professionals working with trees are encourages to become a certified arborist. A snapshot of their home web page is shown below with a link to take you to their page.

To go to their web page for more information the link is

Saturday, October 17, 2009

Landscape - Avoid Tree Wrapping

The following is a short article on why to avoid tree wrapping.

Tree wrapping, or wrapping the trunk of young trees after transplanting, is not recommended. In the past, wrapping was done on fall transplants in order to reduce sunscald and frost cracks. However, replicated studies have shown that wraps are not a deterrent to these problems. Wrapping can actually create problems by reducing photosynthesis (because young stems contain chlorophyll), and increasing potential pest attack from borers and certain diseases. The best benefit from wrapping is protection from chewing rodents. For this purpose, it should be in place only during the dormant season.

Information from Steven K. Rettke in the October 10, 2002 edition of the Plant and Pest Advisory, Landscape, Nursery, and Turf Edition from Rutgers University

Greenhouse - Cercospora Leaf Spot of Pansy

A common disease of pansy is Cercospora leaf spot. The following is more information.

Greenhouse grown pansies may have problems with Cercospora leaf spot. Leaf spots tend to be on the older leaves or leaves that are close to the substrate surface. Initially leaf spots are 1- 3 mm in size with a sunken center. The leaf spots become dark gray or purplish in color, and have a feathery appearance. If left untreated the leaf spots will continue to expand, coalesce, and may cover the whole leaf. These leaves may turn yellow and drop off the affected plant. Sanitation is important in controlling Cercospora leaf spot – plants with severe symptoms should be discarded. Keep the leaves free of moisture as much as possible. Irrigating plants early in the morning will allow the leaves to dry off quickly and remain dry going into the coolness of the evening. There are a variety of fungicides that are labeled for this disease on pansy including mancozeb (Dithane T/O, Protect DF and others), thiophanate methyl (Cleary’s 3336), fludioxonil (Medallion), and chlorothalonil + thiophanate methyl (Spectro 90 WDG).

Note small spots on lower leaves of this pansy plant caused by the Cercospora fungus.

Information and photo from the October 16, 2009 edition of the Greenhouse TPM/IPM Bi-Weekly Report from the University of Maryland Cooperative Extension Central Maryland Research and Education Center

Friday, October 16, 2009

Turf and Landscape - Fall Fertilization

Fall fertilization can be beneficial in the landscape if you follow some simple guidelines. The following is more information.

In turf, a second or third fall fertilizer application is often recommended with moderate amounts of Nitrogen (N), low phosphorus (P), and moderate to high rates of potassium (K), of course depending on soil test results for P and K. Timing of this application can affect turf performance. October applications can promote continued top growth and excess N at this time can reduce winter hardiness. If applying fertilizer in October, use modest N rates. A later fertilizer application at the end of November, can help root systems continue to grow and keep turf greener, longer into December. However, excess N at this time may be subject to leaching losses so limit soluble N fertilizers to modest rates that roots can utilize. Fertilizers with higher percentage of temperature dependent slow release N are very appropriate for fall applications. Potassium is important for improved wintering over and P is important for root growth so added P and K can be beneficial in the fall if soil levels are not high (based on a soil test).

Most other landscape plants require little or no fall fertilization if they are in the middle of fertilized lawns or in well maintained long-term established mulched beds with high organic matter. However, new landscapes, plantings in poor (low organic matter) soils, or landscapes that have been under stress may need additional fertilization. Woody landscape plants and some perennials continue root growth until soils are at freezing temperatures so fertilization using materials with low to moderate N, some P, and higher K levels can be beneficial to winter performance. Root growth will be improved and bud health can also be enhanced. However, excess N in the fall can promote bud break and new growth, or continued shoot growth in some plants, leading to increased winter damage.

Gordon Johnson, Extension Agriculture Agent, UD, Kent County

Tuesday, October 13, 2009

Landscape - Pruning Deciduous Trees Workshop at the Morris Arboretum

The following is information on an upcoming workshop at the Morris Arboretum of the University of Pennsylvania near Philadelphia.

Pruning Deciduous Trees

Date: Tuesday, October 20, 9 a.m. – 3 p.m. Rain date: Thursday, October 22
Fee: All day: $110 (including lunch) Fee: Morning only (9 a.m. – 12 noon) $60
Instructor: Iana Turner , Horticulturist, Morris Arboretum
Credits: This course carries 5.5 CEUs for ISA arborists and 1.0 PCH credit for the full day class.
Registration: To register call the Morris Arboretum at 215-247-5777, ext. 125 or 156.

Pruning young trees for healthy structural development is cost-effective care. This class will explain how recent research on pruning has changed both practice and understanding. Age-adjusted pruning strategies will be stressed to maximize tree longevity and structural health. In addition, techniques will be discussed to help tree managers evaluate the arboricultural work of others under their supervision. The morning session will consist of a lecture and a demonstration. The afternoon session will feature supervised, hands-on pruning. Participants may sign up to take the morning part only, or the entire daylong class. Please bring a hand pruner and a small orchard saw for the afternoon session.

Landscape - Sustainable Site Initiative

The following is information on the sustainable sites initiative. This initiative seeks to increase sustainable landscaping throughout the US.


Three years of research and work culminates this November 5th, as the Sustainable Sites Initiative will release the first full national rating system for sustainable landscapes as part of the Guidelines and Performance Benchmarks 2009 report . This latest report takes into account feedback from hundreds of individuals and organizations across the country and around the world. In addition, the report release will include a supplemental educational report, titled Making the Case for Sustainable Landscapes , that provides scientific and economic arguments underlying the guidelines, and will highlight several case studies for sustainable practices.

Upon the release of the Guidelines and Performance Benchmarks 2009 , the Sustainable Sites Initiative will also formally open the Call for Pilot Projects. Projects selected for the Pilot Program will be the first to test the rating system and will be included in the Reference Guide, to be released in 2012. The Initiative will accept applications online starting November 5 through February 15, 2010. Any type of designed landscape is eligible to participate, ranging from academic and corporate campuses, parks and recreation areas, transportation corridors to single residences, with a minimum project size of 2,000 square feet. Fees for participating in the pilot project process will run between $500 to $5,000 depending on project budget (there may be limited scholarships available based on need).

For more information on the pilot projects, visit can learn more about the Sustainable Sites Initiative at these upcoming conferences. Check the Sustainable Sites website for the most current listings.

Sunday, October 11, 2009

Greenhouse - Planning for Biological Controls

The following is a good article from the New England Greenhouse Update website on preparing for using biological controls in greenhouses before the spring season.

If you are planning to use biocontrol for pest management in your greenhouse for spring crops, then it is time to prepare now. Management, growers and staff all need to be on-board and involved. A biological control program should never be started in the middle of a growing season. Begin a biocontrol program that will be at the start of a new crop cycle. Biocontrol prevents problems, it does not fix problems, which is why planning needs to be done now.

Begin by reviewing pest problems from this past year and VERY IMPORTANT, avoid pesticide use 3-4 months prior to using biological control. When crops are in the greenhouse, develop and start a consistent monitoring procedure. Set a start date for using biological control. Develop a strategy based on your production planning, that is right for your particular situation. Start using biological control agents in your propagation area, right from the start. If you are buy in rooted or unrooted cuttings ask your supplier/broker to supply specific information on what pesticides may have been using on the cuttings. Toxic pesticide residues either on in or around the greenhouse or on plant material is one of the main reasons for failure using biocontrol control agents. It is important to phase out the use of pest control materials in the organophosphate, carbamate, and pyrethroid chemical classes prior to releasing natural enemies since many materials in these chemical classes can persist for four months or longer in the greenhouse.

For more information on the compatibility of pest control materials with natural enemies refer to on-line databases under side effects, such as Koppert, Inc., or Biobest . Talk with your supplier of natural enemies, too. Research is continuing on the compatibility of pest control materials with natural enemies.

During the transition period, before using biocontrol, growers might use products that are not necessarily compatible with natural enemies, but have a short residual effect of less than 2 weeks. Examples of these pesticides are abamectin (Avid), imidacloprid (Marathon, Tristar), dinotefuran (Safari) and pyriproxyfen (Sanmite). Products that are compatible and have short residual include bifenazate(Floramite) and pymetrozine (Endeavor).

Article by Tina Smith, UMass Extension and Leanne Pundt, UConn in the New England Greenhouse Update

Landscape - Using Mulches in the Landscape

The following is a good article from Rutgers University on how to use mulches in the landscape.

Although the mulching of trees and shrubs is an important plant health care practice, their effects can sometimes produce unexpected consequences. Different mulching materials should influence supplemental fertilizer practices. Nitrogen fertilizers can be applied to help reduce nitrogen immobilization where wood pallet or hardwood bark is found. Alternatively, where plants are growing in composted mulches, nitrogen application rates need to be adjusted to avoid over-stimulation. Over fertilization, especially with high nitrogen, may decrease mycorrhizae. It is most important to use these products when trees are first planted.

If raw or fresh mulches are used, they are best applied in the late fall or winter in order to reduce their initial negative effects on plant growth and health. As soon as the organic matter is partially decomposed and the competition for nutrients begins among soil microorganisms, then the beneficial effects can begin. Composted leaf and twig litter are best because they will support the growth of mycorrhizae. In natural forests where there is decaying leaf litter, the non-woody roots, and especially mycorrhizae, will be abundant in the highly organic top layer of soil. In cities, more composted wood and leaves should be added in correct quantities to soil about the base of trees.

Information from Steven K. Rettke, Ornamental IPM Program Associate in the September 17, 2009 edtion of the Plant & Pest Advisory, Landscape, Nursery & Turf Edition, from Rutgers University

Saturday, October 10, 2009

Landscape and Nursery - Fall Fertilization Pros and Cons

The following is a good article on the pros and cons of fall fertilization from Andrew Ristvey from the University of Maryland.

Fall fertilization of landscape plants is truly a beneficial practice as long as certain guidelines are followed. This has been a contentious issue with experience on both sides challenging fall fertility. Physiologically speaking, even though the tops of plants have gone dormant or have slowed down, fall is an active period for roots. They are still growing and absorbing nutrients for next year’s spring flush until soil temperatures inhibit biological activity. All of next year’s spring buds will grow from stored nutrients attained this year. So the most effective application of fertilizers for next year’s growth is during late summer and fall of this year. However, because of dry and hot weather often experienced in Maryland towards the end of summer, optimal fertility times are towards the fall period.

Certainly, the most important growth factor for plants is water, and that was made evident this past mid-summer, when plant water stress was high. In the landscape, especially where plants do not have the luxury of irrigation, hot summer weather will inhibit plant growth. Fertilization should be minimized or stopped until better climactic conditions promote growth.

It is true that an over-application of nitrogen in fall can potentially awaken near dormant buds and expose plants to damage from frost which is just around the corner in our region. One relatively new study in the Journal of Arboriculture reviewed past research and looked at the effect of fall nitrogen fertility on cold hardiness of 5 landscape trees including Leyland cypress, crape myrtle and red maple in North Carolina. In most cases the researchers found no significant differences in hardiness of spring bud tissue with different nitrogen treatments for all the species. So there exists some evidence that fall fertilization does not reduce winter hardiness. But I have seen a heavy application of nitrogen in container grown plants increase vegetative growth in fall resulting in frost damage. However, those plants had not become completely dormant.

Most fall-based fertilizers are low in nitrogen and have higher ratios of phosphorus and potassium. Obviously, a serious fertilization program should rely upon a soil fertility test so that adequate amounts of nutrients are applied without risking toxicities or antagonisms (one nutrient overapplied can affect the availability of other nutrients). However, in general, a half rate of a low nitrogen or a 50% WIN combination in October should be considered as long as there is no longer any shoot activity. In container culture, a very low soluble nitrogen application (with excellent irrigation management to prevent nutrient runoff) may be acceptable periodically until temperatures fall below 55 °F, especially if your controlled release fertilizer prills no longer contain nutrients. Remember that fruit tree nutrition is based on leaf samples which should have been taken before the harvest. Fertilize according to those samples.

Information and photo from the October 9, 2009 edition of the TPM/IPM Weekly Report for Arborists, Landscape Managers & Nursery Managers from the University of Maryland Cooperative Extension

Landscape - Woolly Aphids

You may see woolly aphids on many trees and shrubs in the landscape. The following is more information.

Woolly aphids (family Eriosomatidae) are found in the fall on many hardwood trees and shrub species including elm, silver maple, ash, alnus, alder, apple, pear, pine, spruce, hawthorn, and juneberry (Amelanchier). They are small (2-4 mm in length), pear shaped insects, and are often covered with white waxy strands. Woolly aphids generally have a primary host on which they overwinter, and a secondary host on which they spend much of the summer. They usually overwinter as eggs laid in bark of their primary host. The following spring, eggs hatch into females which give birth without mating. Each female can produce hundreds of offspring, so populations can grow rapidly. After one or two generations on the primary host, winged females are produced, and they fly to secondary hosts where they remain for the rest of the summer. Additional generations of aphids are produced until late summer or early fall when winged females fly to a primary host where they give birth to tiny male and female aphids that mate. Gravid females deposit a single large egg (or eggs) into protected locations in the bark and then die. While woolly aphids generally have two hosts, many species can sustain themselves on their secondary host alone. Woolly aphids feed on leaves, buds, twigs, and bark, but can also feed on the roots. Damage symptoms include twisted and curled leaves, yellowed foliage, poor plant growth, low plant vigor, and branch dieback. Natural enemies help keep these aphids from becoming a problem. In addition to the physical damage to the plant, accumulations of wax and shed skins can be very conspicuous on the leaves, twigs, and bark.

Woolly aphids.

Information and photo from the October 9, 2009 edition of the TPM/IPM Weekly Report for Arborists, Landscape Managers & Nursery Managers from the University of Maryland Cooperative Extension

Friday, October 9, 2009

Greenhouse and Nursery - Reusing Pots, Flats, Trays, and Other Containers

The following is a short article on reusing containers in the greenhouse.

While some growers clean and re-use pots, trays and flats and it is important to do it properly. Plant pathogens such as Pythium, Rhizoctonia and Thielaviopsis can survive in root debris or soil particles on greenhouse surfaces. If the previous crop had a disease problem, then avoid re-using those containers. It is also a good idea to avoid planting crops that are prone to Thielaviopsis problems, like pansies, in containers that have been previously used.

All containers should be washed thoroughly to remove soil particles and plant debris before being treated with a greenhouse disinfectant, even if there was no evidence of disease in the crop. Debris and organic matter can protect pathogen spores from coming in contact with the disinfectant solution.

There are several products available for disinfecting surfaces including quaternary ammonium products (Greenshield®, Physan 20™, Triathlon®), and hydrogen dioxide (ZeroTol®, OxiDate®). Follow label directions for these products - labels indicate that pots must be soaked for at least 10 minutes in these products to be fully effective. A 10 percent solution of household chlorine bleach (one part bleach to 9 parts of water) may be used for pots and flats, but the solution has a shorter activity period than other disinfectants, losing half its strength in 2 hours. Chlorine bleach is also phytotoxic to some plants, and must be used in a well-ventilated area to protect workers

Information from the New England Greenhouse Update Website

Landscape - Adelgids

The following is information on control of common adelgid insects in Delaware landscapes.

The Eastern Spruce Gall, Cooley Spruce Gall and Hemlock Woolly Adelgids all over-winter as immature females and are vulnerable to control treatments during the late months of the year. The product of choice with smaller plants is the use of horticultural oils or soaps when good coverage can be achieved. Remember to target sprays onto only the most recent growth or terminal twigs and buds where the adelgids are located. Heavy populations of HWA on large hemlocks are best controlled with an imidachloprid (Merit) treatment.

Hemlock woolly adelgid & treatment limitations:

The autumn season is an excellent time to control this hemlock pest, if no controls have been applied to date. The adelgid nymph is exposed on the underside of new growth, at the base of individual needles from May through early November. By November, it begins to cover itself with the white, wooly wax. Information from the US Forest Service indicates that hemlocks that have experienced over 50% needle loss from the adelgid will not recover in subsequent years (even if treated). Therefore, it is important that treatments be made when the needle loss is below 50% if hemlocks are to recover or survive. Fall treatments of insecticidal soaps, horticultural oils, or Merit are very effective. Excellent spray coverage is required with soaps or oils. When using Merit drenches, be certain adequate soil moisture exists.

Hemlock woolly adelgids. Photo by John A. Weidhass, Virginia Polytechnic Institute and State University,

Information from Steven K. Rettke, Ornamental IPM Program Associate in the September 17, 2009 edtion of the Plant & Pest Advisory, Landscape, Nursery & Turf Edition, from Rutgers University

Thursday, October 8, 2009

Greenhouse - Cleaning The Greenhouse

The following is a good article on cleaning the greenhouse prior to major production time. Information is from the New England Greenhouse Update

It is best to clean greenhouses as they become empty rather than to wait until just prior to the spring growing season. Cleaning early will eliminate over-wintering sites for pests and reduce populations for the next crop cycle. Greenhouse pests will overwinter in weeds and protected areas in unheated greenhouse, especially if the winter is unseasonably warm.

Remove leftover plants and debris and clean the floor of soil, organic matter and weeds. Clean areas around furnaces and along side walls where small weeds are usually found. Use weed barriers, repair tears in worn weed barriers and do not use stone on top. Stone will trap soil and moisture and create an ideal environment for weeds, diseases, insects and algae. It is also a good time to correct any drainage problems and low spots in greenhouses.

Next, disinfect the growing and plant handling areas, and irrigation system. There are several different types of disinfectants that are currently used in the greenhouse for plant pathogen and algae control including quaternary ammonium compounds (Green-Shield®, Physan 20®, and Triathlon®), hydrogen dioxide (ZeroTol®, Oxidate®), chlorine dioxide (Selectrocide), hydrogen peroxide plus peroxyacetic acid (ScaniDate) and sodium carbonate peroxydrate (Green Clean Pro®, TerraCyte®). All these products have different properties, so read and follow label directions. Chlorine bleach may be used for pots or flats, but is not approved for application to walls, benches or flooring. Alcohol is flammable and therefore not used as a general disinfectant. However, it is useful as a dip or swipe treatment to disinfect propagation tools. If possible, disinfectants should be used on a routine basis both as part of a pre-crop clean-up program and during the cropping cycle.

Organic growers have limited options for disinfectants. Oxidate® is the only material mentioned above that is currently listed by the Organic Material Review Institutes (OMRI), see Ethyl or isopropyl alcohol is also allowed under the organic standards. Organic growers should always check with their certifying organization before using any material new in their farming practices.

Landscape - Leafminer Overwintering

The following is information on leafminer overwintering in the landscape.

Arborvitae, Boxwood and Holly leafminers all over-winter as live larvae within foliage tissue. Pale colored lines or blotches indicate the leafminer presence in evergreen leaves. Inspect mines for live larvae and physically remove infested leaves when populations are small. Heavily infested plants can be noted in your records and scheduled for treatment next season. If soil moisture is adequate, then a soil systemic (e.g. Merit) can be applied during the fall months.

Holly leafminer mines on leaf. Photo by Daniel Herms, The Ohio State University,

Information from Steven K. Rettke, Ornamental IPM Program Associate in the September 17, 2009 edtion of the Plant & Pest Advisory, Landscape, Nursery & Turf Edition, from Rutgers University

Wednesday, October 7, 2009

Landscape - Bagworms in Fall

The following is information on bagworms in the fall. They are now inside the bags and the only control is hand picking or waiting until they come out next year.

Obviously any type of spray applied in the fall or winter for bagworm control would be a waste of time and material. Over-wintering eggs are contained within the dead female bags. Most of the bags containing eggs are located on the upper portions of infested trees or shrubs. With this higher elevation, it is theorized that a certain percentage of a recently hatched population in late spring can more effectively be transported by the wind to new hosts. Remove individual bags by hand when populations are low and the upper portions of the plant can be reached. Otherwise, indicate in your records that sprays may be required during the late spring or early summer when the young larvae hatch and begin feeding.

Bagworms on conifers have pupated. During the fall mating and egg lying will occur within the female sack. Bagworms hatch out in mid-June from the over-wintering eggs within the dead female bag. Researchers in Kentucky have determined that most newly hatched bagworms disperse away from the ‘parental’ host plant. This may be because the offspring from only a few bags have the potential to defoliate a small plant. About 75% of immature bagworms disperse by ‘ballooning’ into the wind, and were observed traveling hundreds of feet. Failure to control populations upwind from a susceptible host may leave a potential reservoir of the pest in the future. (Reference: Cox and Potter, J. Arbor. 9/90) .

Information from Steven K. Rettke, Ornamental IPM Program Associate in the September 17, 2009 edtion of the Plant & Pest Advisory, Landscape, Nursery & Turf Edition, from Rutgers University

Tuesday, October 6, 2009

Turf - Mulching Leaves in Lawns

Mulching leaves in lawns has been shown to have no negative effects and is a practice you should consider for your clients because it will improve the soil and eliminate leaves going to landfills. However, this should be done several times during the fall to prevent leaf buildup that damages turfgrass. The following is more information.

Trees will be dropping their leaves soon and it is important to prevent a heavy layer of leaves from building-up on your turf before winter. Heavy layers of tree leaves will shade the grass can smother and kill grass yet this fall. Plus tree leaf cover favors a damaging winter turf disease called snow mold. The easiest way to dispose of leaves is to simply mow them into the turf. Regular mowing during the fall will chop the leaves into small pieces and allow them to filter into the turf. Research at many universities shows that tree leaves can be mulched without any detrimental effects on the soil or turf regardless of turf or tree species. Actually, just the opposite may be true where tree leaf mulching may help improve the soil. Mulching leaves with a mower is much easier than raking, blowing, and/or vacuuming the leaves like we have done in the past. Plus it disposes of the leaves without filling up our landfills and saves our cities thousands of dollars in disposal costs. Regular mowing over dry leaves is most effective for this, but deep layers of leaves or wet leaves may require raking. Heavily wooded lots may also require leaf disposal because of the sheer volume of tree leaves.

Information adapted from the 10/25/2007 edition of the Turf Tips newsletter from Purdue University.

Landscape - Fall Leaf Color 6

The following is a continuation of the series on fall leaf color in deciduous plants. This post is a continuation on Anthocyanins that cause pink, red, and purple colors in fall leaves.

Anthocyanins (continued)

Kevin Gould of the University of Auckland in New Zealand is at the forefront of research on leaf anthocyanins. Senescing leaves seem to need special protection against bright light exposure because the metabolic pathways for the initial capture of energy don’t lose their efficiency as rapidly as the subsequent processes for processing that energy do. Bright light that reaches senescing tree leaves overloads light-gathering chlorophyll and slows it down (photoinhibition). Anthocyanins can offload some of that excess energy, decreasing photoinhibition, sustaining photosynthesis rates necessary to provide energy for nutrient resorption and other critical processes during senescence.

Anthocyanidins, formed from anthocyanins, are flavanoids: antioxidants that are beneficial to human health and possibly able to help prevent such diseases as cancer, Alzheimer’s disease, and cardiovascular disease. While reading an article on the human health benefits of consuming anthocyanin-rich blueberries, Gould decided to investigate the possibility that the antioxidizing powers of the leaf anthocyanins he was investigating also benefited their source plants. In test tube experiments he found anthocyanins purified from tree leaves were four times more effective at soaking up damaging free radicals than vitamins C and E. He and his colleagues devised a method to induce and observe an oxidative burst of hydrogen peroxide by using a needle to pierce the upper layers of a New Zealand shrub that produced red pimples when pierced by aphids. Gould and his coworkers were able to observe bursts of the powerful oxidant hydrogen peroxide one minute after stabbing leaves with a needle. In red leaf tissues the burst faded quickly, while in green tissues the hydrogen peroxide concentrations soared for at least ten minutes. These results suggest that anthocyanins function as protective antioxidants in plant leaves.

Anthocyanins may protect physiological processes in leaves from cold temperatures. Gould notes that a birch species he encountered in Finland held on to its red leaves year round, despite temperatures that plunged to -40 degrees C. William Hoch of the University of Wisconsin-Madison ranked the intensity of red coloration in autumn of species in nine genera of woody plants either from a cold zone in Canada and the northern U.S. or from a milder maritime climate in Europe. The species that produced the most intense red coloration came exclusively from the North American cold zone.

Linda Chalker-Scott of the University of Washington proposes that anthocyanins help leaves retain water. Anthocyanins dissolve in water, whereas chlorophyll and many other cell pigments do not. Water loaded with any dissolved substance has lower osmotic potential: a decreased tendency for water to flow away. Many plants produce soluble anthocyanins that may help leaves retain water when subjected to osmotic stresses from drought, salt buildup on leaf surfaces, and heat. Loading water with solutes also lowers its freezing point, possibly affording added frost protection to senescing leaves.

The evolutionary theorist W.D. Hamilton and Samuel P. Brown of the University of Montpelier speculated in a recent paper that the healthiest trees might put on the flashiest fall displays of (anthocyanin) red leaves. They further speculated that this leaf signal might give fall-feeding insects, such as aphids, a warning to avoid trees that are healthy and have the best defenses. This is an intriguing possibility for yet another role of anthocyanin in tree protection.

Information from "Why Tree Leaves Turn Color in Autumn" by Jeffrey O. Dawson, Professor of Tree Physiology, Department of Natural Resources and Environmental Sciences, University of Illinois at Urbana-Champaign. Go to for the full article.

Monday, October 5, 2009

Turf - Rust in the Fall

Rust is a common problem on ryegrass and Kentucky blugrass in the fall. The following is more information.

Rust on perennial ryegrass and other turfgrasses is favored by the cool, moist weather of fall. Look for yellowing of turf. Close examination of the individual grass blades will reveal the reddishorange pustules of the rust fungus. It can cause some thinning of turf but the best treatment at this time of year is fertilizing the lawn. Lawns will outgrow the fungus in most cases. Rust is usually a low fertility, low vigor problem on turf.

A variety of related fungi cause rust. Ccommon names include leaf rust, crown rust, and stem rust, and the disease occurs almost exclusively on Kentucky bluegrass and perennial ryegrass. Rust is largely cosmetic, but the orange spores that dislodge easily from leaf surfaces can be a greater nuisance, covering shoes, pets, and lawnmowers with a rusty residue. Rust can severely damage new spring-seeded lawns that lose vigor during heat and drought conditions.

From a distance, rust-infected turf appears chlorotic. Symptoms occur in a diffuse pattern around the initial site of infection as disease increases. Outbreaks often first occur in shaded or protected areas, such as around the bases of evergreens or next to a structure’s foundation. Close inspection of rusted leaves reveals numerous yellow-orange pustules on leaf blades. Walking through grass with significant amounts of infection will disturb and release the spores within these pustules and leave a distinct orange color on shoes and pets. These spores, carried by the wind, spread the disease to other areas during the growing season. Rust outbreaks are most common in late summer and early fall, although sometimes the disease is active in the early spring, especially on poorly nourished turf. Rust is a disease of slow growing turf, so factors such as summer heat and drought stress, low nitrogen fertility, compaction, and shade contribute to poor growth tend to favor rust development. Rust outbreaks require moderate temperatures (50°-60°F) and long evening dew periods (more than 10 hours). The pathogen survives as resilient spores over the winter or as inactive mycelium in dormant turf.

Rust Control

Maintaining a healthy and vigorous turf stand is the most effective and efficient method of rust control. Since slow growing turf in late summer is most vulnerable to outbreaks, small amounts of nitrogen fertilizer (0.25-0.5 pound of N per 1,000 square feet) in chronic trouble spots—shaded and possibly compacted areas—will help control the disease. The nitrogen will promote leaf growth and allow for regular mowing, which helps the turf outgrow rust’s relatively slow infection cycle. Avoiding irrigation during the early evening also will help limit disease spread by lessening the chance of extended dew periods.

DMI and QoI (strobilurin) fungicides are very effective against rust, but on well-established turf, should be considered only as a remedial treatment when cultural practices fail to prevent an outbreak. On newly seeded stands, fungicides should be appliedat the first sign of disease. In most cases, a single application of an effective fungicide, combined with efforts to encourage turf growth, will quell outbreaks.

Rust on perennial ryegrass. Photo from the August 10, 2009 edition of Turf Tips from Purdue University

Information from Bob Mulrooney, Extension Plant Pathologist, UD in the Current Ornamentals Hotline from UD Extension and Rick Latin, Turfgrass pathologist in the August 10, 2009 edition of Turf Tips from Purdue University

Landscape and Nursery - White Prunicola Scale

The following is information on white prunicola scale. This scale pest has active crawlers this time of year.

White prunicola scale crawlers are active. This armored scale feeds on a number of hosts including: Acer, Alunus, Aucuba, Buxus, Forsythia, Ilex, Ligustrum, Malus, Prunus, Rhododendron, Syringa, and others. Crawlers of the second generation are active at 2314 - 3586 [3010 peak] GDD. Male scales are elongate, felted, white and light yellow at one end; whereas females are round with light yellow covers slightly off center. Male scales are inconspicuous white masses on the undersides of branches. Chemical control includes horticultural oil, insecticidal soap, dinotefuran (Safari), pyriproxyfen (Distance) or one of the pyrethroids.

White prunicola scale. Photo from the June 3, 2005 edition of the Branching Out newsletter from Cornell Cooperative Extension

Information from Brian Kunkel, Ornamental IPM Specialist, UD

Saturday, October 3, 2009

Greenhouse - Alert on Salvia Divinorum

Greenhouse growers should be aware that there is concern about the use of Salvia divinorum as a drug by young people. The following is more information.

Salvia - A Hallucinogenic?

An article in The Washington Post mentioned that Salvia divinorum has attracted the attention of young people across the United States. Salvia divinorum is not the same as the salvia that greenhouse growers have been selling as a flowering bedding plant or herb. S. divinorum is creating a stir because the foliage contains salvinorin that can be dried and smoked to provide a short-lived hallucinogenic trip. The U.S. Drug Enforcement Administration has labeled salvia a drug of concern. You may find that young customers are suddenly interested in salvia this spring, even though the salvia that greenhouses are growing is the not the salvia that they are really interested in.

Photo from / CC BY-NC-ND 2.0

Information from October 2, 2009 edition of the Greenhouse TPM/IPM Bi-Weekly Report from the University of Maryland Cooperative Extension Central Maryland Research and Education Center.

Friday, October 2, 2009

Landscape - Fall Leaf Color 5

The following is a continuation of the series on fall leaf color in deciduous plants. This post is on Anthocyanins that cause pink, red, and purple colors in fall leaves.


Anthocyanin pigments are responsible for the pink, red, and purple leaves of sugar and red maple, sassafras, sumac, white and scarlet oak, and many other woody plants. They are formed in sap inside the vacuole, a storage compartment within plant cells, when sugars accumulate and combine with complex compounds called anthocyanidins. Anthocyanidins are a subclass of flavanoids, a group of antioxidant compounds found in plants including fruits and vegetables. The variety of pink to purple colors in leaves is due to many, slightly different compounds that can be formed. Their color is also influenced by cell pH. These pigments usually are red in tree species with acidic sap, and are purplish to blue in alkaline cell solution. Anthocyanins are not commonly present in leaves until they are produced during autumn coloration. A few trees, however, such as 'Crimson King' Norway maple produce reddish leaves throughout the growing season due to anthocyanins. Trees lacking the genes for production of anthocyanin develop yellow and brown shades of autumn color.

With the formation of the abscission layer and with higher viscosity of cell sap under cold conditions, the phloem tissues of a tree’s vascular system, the pathway for conduction of sugars out of leaves, become less efficient and are eventually severed where the leaf petiole joins the tree branch. However, the nonliving xylem vessels that transport water and nutrients from the roots upward, remain intact. This allows them to continue to carry water to the senescing leaves while sugars derived from continued photosynthesis and the conversion of stored starch to soluble sugars are trapped by the impaired phloem of the abscission layer and are available for anthocyanin production. Trees of the same species growing together often differ in color because of differences in amounts of soluble sugars in the leaves for anthocyanin production. These differences are caused by genetic and environmental factors. Leaves exposed to the sun, such as those on the outside branches of the tree crown, may continue photosynthesis and turn red while others in the shade may be yellow. A single tree may even have branches with different colored leaves due to differences in leaf shading. It is common to see sugar maples with reddish leaves only on exposed outer branches of the upper crown.

Fall weather conditions favoring formation of bright red autumn leaf color are warm sunny days followed by cool, but not freezing, nights. Rainy or cloudy days with their reduced sunlight near the time of peak coloration decrease the intensity of reddish autumn colors by limiting photosynthesis and the sugars available for anthocyanin production. There is an old wives' tale that claims rain washes the color out of leaves. It is not true, but the overcast conditions do reduce light intensity, and heavy rains and high winds can sweep the leaves off trees prematurely.

Information from "Why Tree Leaves Turn Color in Autumn" by Jeffrey O. Dawson, Professor of Tree Physiology, Department of Natural Resources and Environmental Sciences, University of Illinois at Urbana-Champaign. Go to for the full article.

Thursday, October 1, 2009

Landscape - Fall Leaf Color 4

The following is a continuation of the series on fall leaf color in deciduous plants. This post is on tannins that cause brown and bronze colors in fall leaves.

Tannins cause the brown hues in leaves of some oaks and other trees in the autumn. The golden yellow or copper colors produced in some leaves, such as those of beech, result from the presence of tannins along with the yellow carotenoid pigments. Like the carotenoids, these compounds are always present, but only become visible as chlorophyll and carotenoids both disappear from leaves. They are common products of metabolism in trees, deposited in the cell sap inside the vacuole as well as in cell walls, and often accumulate in dead tissue. Considered waste products, tannins actually act as a defense mechanism in plants against pathogens, herbivores and hostile environmental conditions. Consumed in sufficient quantities, bitter-tasting tannins are toxic to susceptible herbivores. Oaks defoliated by gypsy moths often produce a secondary flush of leaves higher in protective tannins than the first set of leaves. Tannins discourage insect feeding on leaves and bark, and, in the case of the lip-puckering, unripe persimmon fruits, discourage fruit and seed consumption by animals until both the fruit and seed are ripe. Once ripened, fruits are sweet, attracting seed dispersing animals, and seeds have a fully developed seed coat to prevent seed destruction in passage through the digestive tracts of animals.

The leaves of green tea, a woody plant, are a source of beneficial human dietary tannins. Monomeric flavanols, the major components in green tea, are precursors of condensed tannins. Tannins from grapes and oak barrels used for aging play an important role in preventing oxidation in wine. Tannins in fruit juices, such as those found in pomegranate juice, provide antioxidant and other health benefits to humans. Perhaps research will also find evidence for a similar function in senescing leaves.

Information from "Why Tree Leaves Turn Color in Autumn" by Jeffrey O. Dawson, Professor of Tree Physiology, Department of Natural Resources and Environmental Sciences, University of Illinois at Urbana-Champaign. Go to for the full article.