Monday, August 31, 2009

Landscape - Azalea Caterpillars

Azalea caterpillars can be active this time of year. The following is more information.

The female Azalea caterpillar moth lays clusters of eggs on the underside of leaves, and caterpillars feed gregariously. Early instars appear red with four white to yellowish longitudinal lines down each side. Older larvae have read heads, red legs, and black bodies with white to yellowish 'broken' longitudinal lines down each side. This gives older larvae a spotted appearance. Young caterpillars skeletonize leaves, and as larvae age, they consume entire leaves. Caterpillars will raise both ends off of leaves when disturbed, thus displaying a C shape. Control options when larvae are small include Bacillus thuringiensis (kurstaki), Conserve SC, Sevin, or pyrethroid insecticides.

Azalea caterpillars in mass. Photo by Arnold T. Drooz, USDA Forest Service,

Information from a past issue of the UD Ornamentals Hotline Newsletter.

Landscape - European Hornets Out Now

European hornets are now active in Delaware landscapes feeding on ripe fruits. The following is more information on this insect.

The European hornet is a large wasp resembling a yellow jacketsbut much larger. The European hornet is about 35 mm (1.5 inches) long and is brown with yellow markings. Nests are rarely constructed in open areas and are more likely to be found in protected areas such as tree cavities, bird houses, barns, or sheds. During the summer, these hornets feed on large insects such as caterpillars, grasshoppers, flies, and bees. European hornets damage a number of ornamental trees and shrubs including, lilacs, rhododendrons, birch, ash, and dogwood. The hornet gains nourishment from the plant sap and the bark may be used as nesting material. Workers expand the nest throughout the summer, and in the fall the next season's queens mate with newly emerged male hornets. European hornets feed on substances high in carbohydrates in the fall. These food sources include overripe fruits, tree sap, soft drinks, juices, and possibly honeydew produced by insects such as aphids or scales. This hornet is also known to attack small fruits such as grapes and consume the sugars. European hornets do not reuse nests and populations die off with the onset of cold weather. The only effective method of control is nest removal. A pressurized wasp and hornet spray with a range of 10 15 feet is desirable. Treatments should be made at dusk or after dark to ensure most of the hornets are in the nest. Caution should be used when treating hornet nests since hornets guard the nest, can sting repeatedly, and can fly at night.

European Hornet. Photo by Jessica Lawrence, NC State Entomology Department,

Information from Brian Kunkel, Ornamental IPM Specialist, UD

Sunday, August 30, 2009

Greenhouse and Nursery - Pythium Rot on Mums

We often see Pythium problems on mums in Delaware. The following is an article on this disease that is a problem this year in many areas of the Northeast due to the wet weather.

The 2009 growing season for fall mums has presented real challenges for the growers. The cool and wet weather of June and early July were less than ideal conditions for growing fall mums. As the summer progressed many growers pushed the mums with fertilizer trying to keep the mums in a vegetative state. Now in late August the varied weather has brought on diseases common to fall mums. A Pythium species, most likely Pythium aphanidermatum, was observed in roots and stems of the specimens from several growers. Symptoms of Pythium attack vary with temperature, moisture, and the species of Pythium involved. The first symptom is often a wet, black basal rot which extends several inches from soil surface. Affected plants wilt and collapse rapidly. Often the fungus invades leaves touching the soil and progresses into the stem at the node, causing a black lesion. In such cases, plants may not exhibit root and basal stem rot. Root rots are also common in Delaware.

Pythium is favored by high fertility and high moisture; avoid overwatering and overfertilizing. Pythium is a natural inhabitant of the soil and can survive there indefinitely as well as in dirt and debris in the greenhouse. Use soilless growing media media. Keep hose ends off the floor and avoid contaminating growth medium with soiled hands, tools, or flats. Fungicides for controlling Pythium include Aliette, Alude, Banol, Banrot 40 WP, Subdue Maxx, Stature DM (drench) Terrazole 35 WP, and Truban 30 WP. Many greenhouse isolates of Pythium are resistant to Subdue. Recommend a drench with a systemic chemical, followed by a sprench to target lesions above soil line. Avoid consecutive applications of fungicides within the same chemical class: rotate among different active ingredients' mode of action for best results.

Stem rot on mum caused by Pythium. We also see root rots caused by Pythium in Delaware. Photo by P. Lopes, University of Massachusetts.

Information from M.Bess Dicklow, Extension Plant Diagnostic Clinic and Paul Lopes, Floriculture and Greenhouse Crops Program in the New England Greenhouse Update

Landscape - Orangestriped oakworms

The following is information on Orangestriped Oakworms from North Carolina State University. This is an occasional pest in Delaware.

Orangestriped oakworms are sometimes very abundant on oaks in summer. They occasionally feed on other hardwoods as well. The moth is brown in color with a white spot and a dark stripe on each forewing. The moths emerge in June and July and deposit their eggs in clusters of several hundred on the underside of oak leaves. The eggs hatch in about a week. The tiny, green caterpillars eventually grow into attractive black caterpillars with yellow or orange stripes running lengthwise along their bodies. Young caterpillars feed in groups whereas older caterpillars tend to be solitary, although there may be thousands of caterpillars on a single tree. Small trees are sometimes defoliated completely by midsummer.

As the caterpillars mature, they are often seen crawling along sidewalks, driveways and yards. These caterpillars may wander for a considerable distance while searching for a place to pupate. You can step on these without fear, as long as you have on shoes. They dig into the soil three or four inches and pupate there. There is usually one generation per year, and the caterpillars overwinter as pupae in the soil. Control is complicated by the size of many of the infested trees. Most people do not have sprayers that can reach very high into shade trees, and by the time the caterpillars descend and crawl about on the soil they are extremely resistant to pesticides. Fortunately, late summer defoliations are much less damaging to the health of trees than early spring defoliations. In most cases it is probably better to rely on birds, diseases and parasites to lower the population next year.

For more information, see If you would like to consider boosting the paper wasp predator population with nest boxes in the spring, see

Orangedstriped oakworm. Photo by David Cappaert, Michigan State University,

Information from Steve Bambara, Extension Entomologist in the August 28, 2009 edition of North Carolina Pest News

Saturday, August 29, 2009

Landscape - Powdery Mildew Showing Up on Crape Myrtles This Year

Powdery mildew has been showing up on crape mrytles this year, even in resistant varieties. The following is more information.

Powdery mildew on crape myrtle has not been a problem for many years since the introduction of new cold tolerant varieties (devl. at the National Arboretum and other places) that also happen to have powdery mildew resistance. But, this season has been so favorable for powdery mildew (especially the last several weeks) that we have seen powdery mildew on flower trusses of some of these cultivars. Remember resistance is not immunity. While levels have been low, homeowners have probably never seen powdery mildew on their crape myrtles before. While infection doesn't affect overall plant health, it may be severe enough to prevent flower buds from opening.

Information from Bob Mulrooney, Extension Plant Pathologist, UD

Landscape - Leopard Moth Caterpillar Damage

The following is information on damage from Leopard moth caterpillars, a pest you may see in Delaware.

At 2-3” long, the leopard moth (Zeuzera pyrina) is a large moth, introduced from Europe/N. Africa and found May-September in Delaware. Adults have black and white spots on their wings. Early symptoms of damage from Leopard mothe caterpillars are girdled or broken twigs and branches with wilted/yellow foliage. Monitor trees for branch and limb dieback, which may be mistaken for squirrel activity. Scout dead limbs for exit holes (possibly with silk coverings and resin flow) at the end of broken stems. Fine white frass pellets and possibly pupal skins may be left in bark crevices and inside these galleries.

Larvae damage over 125 tree species incl. oaks, maples, lilacs and apples. They have an unusual life cycle (2 years or longer). Several yellow eggs are laid in small clusters usually in bark crevices. After 10 days, newly hatched larvae crawl some distance before burrowing into a young branch and tunneling into the heartwood to begin feeding. When a branch is too small, the caterpillar exits the branch, migrates along the outside, and tunnels into a larger branch to complete its next caterpillar stage. At the end of the first year, caterpillars are 1” long, yellow with dark spots. At maturity (2”), tree branches up to 3.5 inches and tree trunks may have been fed upon. Pupation occurs in its final gallery.

Leopard moth seems to strike only individual trees and does not spread rapidly. Female moths are not strong fliers. Spread may be through infested nursery stock. Control by pruning out affected limbs/branches. Woodpeckers, other birds and squirrels are important biological controls. As with all borers, growing a healthy tree is the best defense against injury. Chemical control is not practical because of the lengthy flight time. Note that this species shouldn't be confused with the Great/Giant Leopard Moth (Hypercompe scribonia) a native woolly bear caterpillar.

Leopard moth. Photo by James Solomon, USDA Forest Service,

Leopard moth caterpillar tunnelling in wood. Photo by James Solomon, USDA Forest Service,

Information from Casey Sclar, IPM Coordinator, Longwood Gardens and Emma Seniuk, Professional Gardener Student, Longwood Gardens

Friday, August 28, 2009

Landscape - Diplodia Tip Blight in Pines

This time of year, tip blight in some pines is very evident. The following is more information:

Austrian and Mugo pines growing in landscapes are showing the effects of infections by the Diplodia tip blight fungus, Diplodia pinea. The disease is noticeable in landscape pines now. Austrian, Mugo, and Scots pines are often planted in landscapes because of their dense, green foliage and symmetrical shape. When healthy, a grouping of Austrian pines can form an attractive year-round screen. Diplodia tip blight, also known as pine tip blight, or Sphaeropsis tip blight, is a devastating disease worldwide, but especially here on exotic two-needle pines such as Austrian pine (Pinus nigra), Mugo pine (P. mugo) and Scots pine (P. sylvestris) in landscape settings and Christmas tree plantations.

Tip blight symptoms on Austrian pines first appear on the newly elongating candles (shoots) in late April to early May. As its name indicates, the shoot tips are killed very quickly and by late May, the diseased tips are noticeably necrotic and stunted. Needles, even before they are out of the needle sheaths, start to turn a straw brown color and droplets of resin can be seen exuding from these dead needles. Some of the diseased needles may begin to break out of their sheaths, but often their growth is halted resulting in stunted, dead needles. Symptoms on Austrian pines are most characterized as progressing from the shoot tip inward. Over a few days to a week all of the needles on infected candles will turn brown and die and shoots will appear brown through late summer. The candle as a whole will be stunted, necrotic, and eventually brittle from resin exudation. The necrotic shoot and needles can sometimes give these dead tips a gray color.

As the fungus progresses from the tip back towards the trunk, older needles will turn straw color and die. This generally happens later in the year or the following year. Progression of the fungus can lead to branch dieback and eventually death of the tree. These symptoms typically start in lower branches of the tree and progress toward higher branches year after year until the tree dies or is so damaged it needs to be removed. On landscape Austrian pines disease symptoms generally begin to appear after trees reach cone-bearing age, typically 12-13 years old. Close examination of infected shoots will often reveal the presence of tiny black dots (pycnidia) on the base of infected needles. Pycnidia are black fungal structures embedded in and protruding through the host tissue, and in D. pinea are only produced on dead host tissue, such as cone scales and dead needles. Pycnidia are tiny but can be seen with the naked eye, resembling black pepper sprinkled on the dead cones and needles. It is not uncommon to see dead cones and needles from infected trees covered with pycnidia. The pycnidia release spores in warm, rainy spring and summer weather which we have had in abundance this year. These spores are dispersed by rain splash and windblown rain.

Pines are most susceptible to D. pinea infection in spring when shoots are just elongating and not yet lignified. As the fungus colonizes the host, it kills the host cells resulting in necrotic symptoms and sometimes resin production. An additional field symptom, canker disease, also is often accompanied by excess resin. After the fungus has killed the host tissue, it can produce pycnidia which can overwinter and be a source of inoculum the following spring.

Information from "Diplodia Tip Blight Is Causing Dead Shoots on Pines" By John Hartman in the current edition of the Kentucky Pest News. For the full article with pictures go to

Landscape - Current Pests

The following are pests you should be on the watch for now in Delaware landscapes.

Clearwing borer populations (Lilac/Ash, Dogwood, and others) are prevalent. Protect trees as needed with pyrethroids like permethrin or bifenthrin.

Watch for building whitefly populations on annuals and select perennials. Parasites may move in and turn the normally yellowish nymphs black or other management strategies may be required.

The USDA has initiated a citizen survey for the Asian longhorned beetle (not yet ID’d in DE). Interested persons may receive a letter and identification sheet, along with a card to return to report findings. Call the PLSC office (302-831-2534) for materials.

Japanese maple scales have been found in egg & crawler stage in Kent County.

Puss caterpillars were found feeding on Ilex & Acer. This caterpillar has a nasty sting associated with its hairs, so be careful moving plant material. Feeding damage is not severe on plants so treatment is not often warranted.

Tuliptree & magnolia scale crawlers are approaching peak crawler activity. Horticultural oil, Insecticidal soap, Distance are good products for crawler control.

Information from the "What's Hot" section of the Ornamentals Hotline Newsletter from the UD Cooperative Extension Ornamentals Group.

Thursday, August 27, 2009

Turf and Landscape - Weed Seed Bank

With the ample moisture provided by recent rains, I see many turf areas and landscapes with weeds going to seed at this time. This will add to the weed seed bank and make weed management more challenging in the future. The following is more information.

Weed Seed Bank is a term used to describe the reservoir of viable weed seeds on the surface or in the soil profile. One major weed management goal in turf and landscapes should be to reduce the weed seed bank. Late summer is a major challenge because many weeds such as crabgrass are going to seed, especially in low maintenance areas. This adds to the weed seed bank and will make future weed control more challenging. It takes several years with no additions to the seed bank to reduce weed pressure. This is because of dormancy mechanisms allowing some weed seeds to remain viable for years.

The key to managing the weed seed bank is to not let weeds go to seed. For crabgrass, to get a 75% reduction in the seed bank, it will take 3 years of active control measures making sure there is little seed head production. To reduce weed seed head production in turf, mow more frequently using very sharp blades. This is especially critical in late summer. One challenge is low growing weeds that produce seed heads below the height of mowing. Herbicides will be your best option in that case (for large multi-tillered crabgrass use quinclorac – Drive herbicide). There are also some growth regulators registered for seed head suppression in specific weeds such as annual bluegrass.

Gordon Johnson, Extension Agriculture Agent, UD, Kent County

Wednesday, August 26, 2009

Landscape - Dog Day Cicada

You often will see dead or dying cicadas at this time of the year in the landscape. This is the dog-day cicada. The following is more information.

Annual Cicadas Are Very Active in August

In August you will often hear pockets of male annual cicadas drumming on their abdomens to attract female mates. The dog day cicada was given this common name because they are active during the celestial occurrence of the dog star formation in the sky. These large, greenish cicadas are an annual event and really do not cause the extensive damage that the 17-year female cicada does to tree branches. In late August your customers will find the annual cicada on the ground dying after mating and egg laying. Control is not necessary for the dog day cicada.

Dog Day Cicada. Photo by David Cappaert, Michigan State University,

Information from the August 21, 2009 edition of the TPM/IPM Weekly Report for Arborists, Landscape Managers & Nursery Managers from the University of Maryland Cooperative Extension

Greenhouse and Nursery - Early Flowering in Mums

We are seeing earlier flowering in mums this year. The following is more information.

Chrysanthemums Flowering Early

Many greenhouse growers put out their mums this year withput pinching or without Florel applications. The cool nights of late July and August have made many of these mums set flower buds early. The result is that many mums are shorter than normal and the flowers will be opening at the end of August to early September. A couple of growers made multiple applications of Florel this season and their plants are still vegetative and appear to be larger in size. It is a tough call each season whether you should apply Florel or not. This season it would have been a good idea. Hopefully, early mum sales will be good.

Information from the August 21, 2009 edition of the Greenhouse TPM/IPM Bi-Weekly Report from the University of Maryland Cooperative Extension, Central Maryland Research and Education Center

Tuesday, August 25, 2009

Landscape - Foliar Nematodes on Perennials

The following is information on foliar nematodes in perennials. Be on the look for this pest in the last weeks of summer.

Foliar nematode injury will increase as perennial foliage ages and we get more leaf wetness from dew and rain. Be on the lookout for symptoms of this nematode pest causing premature dying of foliage in the garden. It is easily overlooked or misidentified. The main symptoms are the angular spots on the leaves limited by the vein pattern of the leaf. The wet weather will be getting aids in movement of the nematodes over the leaf surfaces since they swim in a film of water then enter the leaves through stomata. The host range is very large including popular plants such as hosta, peony, anemonies, ferns, bugbane, plumbago, and many others. Remove infected leaves and destroy them. We still do not have any effective chemical controls for the home or commercial landscape.

Information from Bob Mulrooney, Extension Plant Pathologist, UD

Turf - Recommended Turfgrass Varieties

With late summer or fall planting coming up for turfgrasses, I thought I would reprint the current recommended varieties from the Maryland/Virginia turfgrass variety working group. We would recommend these varieties for mid-state and lower Delaware.

2009-2010 Virginia-Maryland Turfgrass Variety Recommendations

Authors as Published: Mike Goatley, Turfgrass Specialist, Virginia Tech; Whitnee Askew, Research Associate, Virginia Tech

The Maryland-Virginia Turfgrass Variety Recommendation Work Group meets each Spring to consider the previous year’s data from Virginia and Maryland National Turfgrass Evaluation Program (NTEP) trials and to formulate these recommendations. Virginia and Maryland variety recommendations are essentially identical except for specialized grasses and research situations that differ due to adaptation and state regulation. To qualify for this recommended list turfgrass varieties: 1) must be available as certified seed or, in the case of vegetative varieties, as certified sprigs or sod; 2) must be tested at sites in both Virginia and Maryland; 3) must perform well, relative to other varieties, for a minimum of two years to make the list as a “promising” variety and for three years to make the recommended category. All test locations in Virginia and Maryland are considered in making these recommendations. Seed availability may vary between turf seed suppliers. Some species and varieties may have limited adaptation.

Kentucky Bluegrass – Individual varieties selected must make up not less than 10%, nor more than 35% of the total mixture on a weight basis. All varieties must be certified. Selections can be made from Category I alone or various combinations of Categories I, II, and III as noted. Kentucky bluegrasses listed as “Promising” (Category III below) can account for no more than 35% of the blend by weight).

Category I – Recommended Kentucky Bluegrass Varieties (65–100% of blend by weight).
Award, Awesome(3), Beyond, Bordeaux(3), Brilliant, Cabernet(3), Courtyard, Diva, Everest(3), Everglade, Excursion, Glenmont(1), Impact, Juliet, Liberator, Midnight, Moonlight(3), NuDestiny, NuGlade, Princeton 105, Quantum Leap, Raven, Skye, Sudden Impact, Total Eclipse(3), and Touche.

Category II – Promising Kentucky Bluegrasses (10–35% on a weight basis) – These grasses have performed in the top statistical quality category for a minimum of 2 consecutive years in Virginia and Maryland trials. Seed may be difficult to locate for some cultivars. Note: Durablue, ThermalBlue, and ThermalBlue Blaze are commonly referred to as Hybrid Bluegrasses, but they are classified by USDA as Kentucky bluegrasses. To date they have had better performance in traditionally warmer areas of Virginia.
Alexa II, Aries, Aura, Barrister, Belissimo, Bewitched, Bluestone, Durablue, Emblem, Everglade, Ginney II, Granite, Mystere, NuChicago, NuDestiny, Rhapsody, Rhythm, Solar Eclipse, ThermalBlue, ThermalBlue Blaze, Wild Horse, Yankee, Zinfandel

Tall Fescue – For tall fescues, both recommended and promising varieties can be used in the VCIA Sod Certification Program.

Category I – Recommended Tall Fescue Varieties (90–100% on a weight basis)
2nd Millennium, Avenger, Biltmore, Bingo, Blackwatch, Bravo, Cochise II(3), Cochise III, Constitution, Coyote II, Crossfire II(3,4), Davinci(3), Daytona(3), Endeavor(3), Falcon IV, Fidelity, Forte, Good-En(3,4), Grande(4), Grande II, Greenkeeper WAF, Guardian 21, Houndog 5, Hunter, Inferno, Justice, Magellan, Masterpiece, Matador(3), Matador GT(3), Onyx(3,4), Padre, Picasso(3), Penn 1901, Raptor, Rebel Exeda, Regiment II, Rembrandt(3), Southern Choice II(3), SR 8250(3), Taos, Tarheel, Tarheel II, Tempest, Titanium, Tombstone, Turbo, Ultimate(3), Watchdog, and Wolfpack.

Category II – Promising tall fescue varieties (may be 90–100% of the mixture on a weight basis)
3rd Millenium SRP, Aggressor, Aristotle, AST 7002, AST 7003, AST 9003, Braveheart, Bullseye, Cannavaro, Catelyst, Cezanne RZ, Cochise IV, Compete, Escalade, Einstein, Essential, Faith, Falcon V, Falcon NG, Fat Cat, Finelawn Xpress, Firecracker LS, Firenza, Gazelle II, Greenbrooks, Guardian 21, Hemi, Hudson, Jamboree, Lindbergh, Monet, Mustang 4, Ninja 3, Raptor 2, Rebel IV, Renovate, Reunion, Rhambler SRP, Rocket, Shenandoah, Shenandoah Elite, Sidewinder, Speedway, Spyder LS, SR 8550, SR 8600, SR 8650, Stetson II, Tahoe II, Talladega, Terrier, Titanium, Toccoa, Traverse, Trio, Tulsa Time, Umbrella, Van Gogh, Wolfpack II

Kentucky bluegrass varieties recommended for mixing with tall fescue sod to enhance sod strength (up to 10% of the seed mixture by weight): All cultivars in Categories I and II above.

Bermudagrass – Varietal differences in texture and winter hardiness are important considerations. If no notation follows the variety name this indicates it has performed in the top statistical category at both Blacksburg and Hampton Roads Research Stations. Varieties with the notation # are only recommended in the warmer regions of Virginia due to concerns regarding their cold tolerance. Note that there are no guarantees regarding winter survival for any recommended or promising variety, and one not noted for cold tolerance might perform well indefinitely in colder regions of the state depending on climate patterns.

Category I – Recommended vegetatively propagated bermudagrass varieties: Aussie Green#, Celebration# , GN-1#, Midfield, Midiron, Midlawn, MS-Choice#, Patriot, Premier, Quickstand, Shanghai, Tifton 10, Tifgreen#, TifSport, Tifway#, Tifway II#, Tufcote, and Vamont.

Category II -Recommended seeded bermudagrass varieties: Blackjack#, Contessa, Transcontinental#, Princess-77#, Pyramid 2#, Riviera, Savannah#, Sovereign, Southern Star#1, Sundevil II#, Veracruz#, and Yukon.

Zoysiagrass – (Varietal differences in texture and winter hardiness are important considerations.)

Category I – Recommended vegetatively propagated zoysiagrass varieties: Meyer. Category II – Recommended seeded zoysiagrass varieties: Zenith, Compadre Category III – Promising vegetatively propagated (V) and seeded (S) zoysiagrass varieties: Cavalier (V), Companion (S), Himeno (V), J-14 (S), J-36 (S), J-37 (S), Marquis (V), Sunburst (V), Zorro (V), ZEN­400 (S), and ZEN-500 (S). Promising for Eastern VA only: DeAnza (V), El Toro (V), Emerald (V), Jamur (V), Miyako (V), Victoria (V), and Zeon (V).

Perennial Ryegrass – (not for use in sod production) Use certified seed.

Category I – Recommended perennial ryegrass varieties:
Affirmed, Applaud, Apple GL, Brightstar SLT, Brightstar II, Buena Vista, Calypso 3, Catalina II, Divine, Exacta, Gator 3, Grand Slam(3), Inspire, Jet, Line Drive GLS, Manhattan 4, Paragon GLR, and Stellar.

Category II – Promising perennial ryegrass varieties (limited data/availability of seed): 1G Squared, Accent II, AllStar 3, Amazing GS, ASP6004, Attribute, Barlennium, Charismatic II, Citation Fore, Dart, Dasher 3, Defender, Derby Xtreme, Exacta II GLSR, Fiesta 4, Fusion, Grand Slam 2, Gray Fox, Harrier, Homerun, Keystone 2, Kokomo II, LS 2300, Manhattan 5 GLR, Notable, Palace, Palmer IV, Phenom, Plateau, Pleasure Supreme, Palmer 5, Primary, Protégé GLR, Prototype, Regal 5, Repell GLS, Revenge GLX, Secretariat II GLSR, Silver Dollar, Soprano, SR 4600, Stellar GL, Transformer, Uno, Zoom.

Fine Fescues – For general use in low maintenance areas or in partial to full shade. Promising varieties have limited performance data or availability as certified seed. Neither blending varieties nor mixing species have been studied extensively in MD or VA. Limited research does not indicate any advantage to blending or mixing varieties from the different fine fescues (e.g.; creeping red, chewings, hard, or sheep fescue). Use only certified seed.

Creeping red fescue – Recommended varieties: None. Promising: Cardinal, Class One, Epic, Fortitude, Garnet, Pathfinder, and Wendy Jean.

Chewings fescue – Recommended: 7 Seas, Longfellow II, SR 5130,. Promising: Ambassador, Compass, Lacrosse, and Zodiac.

Hard fescue – Recommended: Berkshire, Chariot, Discovery(4), Gotham, and Predator. Promising: Firefly, Oxford, Reliant IV, Spartan II, and SR 3000.

Sheep fescue – Recommended or promising: None at this time.

Kentucky bluegrass varieties recommended for mixing with fine fescue sod to enhance sod strength (up to 10% of the seed mixture by weight): All cultivars from Kentucky bluegrass Categories I, II and III

Varieties marked with superscript notations denote the following:
(1) to be considered for removal in 2010 due to declining performance relative to other varieties.(2) to be considered for removal in 2010 due to declining seed quality.(3) to be considered for removal in 2010 due to the absence of recent testing of certified seed lots in MD and VA.(4) to be considered for removal in 2010 due to lack of recent testing in MD and VA.

Sunday, August 23, 2009

Landscape and Nursery - Deep Planting Problems

I recently was called to look at a christmas tree farm with failing plants. The problem was related to planting too deep. The following is more information on this problem.

Many trees and shrubs are set too deeply from the time of planting, or they settle too deeply over time. A planting depth of only one-inch too deep can cause trouble. It is not uncommon to see trees planted as much as three or more inches too deep. Deep planting causes bark deterioration at the soil line, which will eventually kill the plant. It usually takes a few seasons for a newly planted tree or shrub to die from this. Various symptoms point to excessively deep planting. Some new growth may develop each spring, only to die-off during the stress of summer. Advanced symptoms of depth-related stress are cankers and deep cracking of the bark. A canker is an area of dead tissue on a woody stem. Some shallow cracking of bark is normal for many trees as the trunk grows. A tree may survive until fall but may not survive the winter because of an insufficient storage of food reserves caused by the damaged bark.

Information from "Common Abiotic Plant Problems", Home & Garden Mimeo # HG 86, University of Maryland.

Saturday, August 22, 2009

Nursery and Landscape - Deal with Circling Roots in Trees and Shrubs in the Nursery and Before Planting

The following is information on dealing with circling roots in trees and shrubs in the nursery and prior to planting in the landscape.

Dr. Ed Gilman, tree researcher and professor at Univ. of Florida, suggests we need to take drastic steps to correct tree root defects in container grown trees and shrubs. Rather than just slicing, he advises removing the outer inch of the rootball from container-grown trees. To see photos on how to do this, go to Any large diameter surface roots should also be cut with pruners just before the points where they kink or bend. New roots should branch from those cuts and grow outwards as nature intended (unless planted too deep, but that is another topic), establishing a good root system for the long run.

These practices can certainly add stress to the tree during establishment, making frequent watering during the first season more critical than ever. Root defects are most common in container production because hitting the container wall disrupts the natural outward direction of root growth, instead causing the roots to circle and/or dive downwards. However, even B&B trees may have hidden root defects from container growing early in the production cycle, or from roots bent when planting bare-root liners into the production field. Once the roots become woody, their kinked shapes are permanent defects.

Good nursery practice includes root pruning each time the plant is stepped up, but that is not always done. If not corrected when planted into the landscape, the circling roots near the trunk continue to enlarge and may end up girdling the stem. Even if stem girdling does not result, few branch roots develop to the outside of circling roots, which can cause the tree to be unstable and have a reduced feeder root system. Most people don’t realize that tree decline and death in 10-20 year old trees may have been predetermined by the root architecture present when planted.

Root defects are less severe on shrubs because they typically have more fibrous and branched root systems than trees. Most shrub root problems can be prevented by purchasing plants that are not root bound and properly planting them in decent soil. Slicing exterior circling roots and removing any matted root layer at the bottom of the pot should give a shrub a good chance of living a long and productive life.

So, to slice or not to slice? I say “yes”, do slice but don’t stop there. The green industry as a whole needs to address root defect problems from propagation to landscape establishment, to help stem the epidemic of tree failures in the landscape. As a landscaper, retailer or producer, you can help by inspecting roots and refusing to buy (or sell) trees and shrubs which are rootbound or have visible root defects. Growers should consider using containers which have been designed for air-root pruning and step up unsold trees and shrubs into larger containers rather than holding them in the same pots once roots begin to circle. Teach your workers how to prune roots when transplanting, whether the plant is going into a larger container or into the landscape.

Information from Cathy Neal, Ph.D., Specialist in Ornamentals, University of New Hampshire Cooperative Extension Adapted from her article in News & Views for New Hampshire’s Green Industry, University of New Hampshire Cooperative Extension, July 2009.

Landscape - Oak Skelelatonizer

The following is information on the oak skeletonizer, an insect pest of oaks in DE.

The oak skeletonizer is a native insect that has two generations per year in our area and is active from 547--2846 GDD base 50. The second generation is usually sometime during late July to August. The larvae are yellowish green and prefer to eat red oaks, but also feed on chestnuts and other oak trees. Early instars feed as leaf miners, but older larvae feed externally and skeletonize the leaf. Mature larvae drop from leaves on silken threads when disturbed. Populations vary by year, thus some years damage may not be noticed. Severe infestations or repeated attacks by this insect can result in crown thinning, die back, and possibly increase the trees susceptibility to other pests such as borers. Larvae form white ribbed cocoons on the leaves, twigs, or other nearby structures. Control options include B.t., bifenthrin, deltamethrin, cyfluthrin, or cyhalothrin.

Oak skelatonizer larvae, cocoons and defoliation on underside of leaf. Photo from James Solomon, USDA Forest Service,

Information from Brian Kunkel, Ornamental IPM Specialist, UD

Friday, August 21, 2009

Landscape - More on Bacterial Leaf Scorch on Oaks

The following is more information on bacterial leaf scorch of oaks which can be seen in Delaware landscapes at this time.

Bacterial leaf scorch on oaks in the red oak group can be found now. Infected trees have leaves with brown leaf margins (like drought damage). Since we have not been in a drought, lack of water is an unlikely cause of the symptoms, but since the bacterial infection restricts water flow, drought symptoms appear. This is a debilitating disease that can take several years to a decade to kill the tree and there is no cure. Symptoms can be reduced or masked with oxytetracycline injections, but trees cannot be cured. Plant hoppers vector the bacteria from symptomless weed hosts and transmit it to oaks during feeding. If you have suspect trees, tests will confirm the presence of the bacteria in leaf petioles. Contact the Plant Diagnostic Clinic at 320-831-1390 or on the web for more information on testing. The web has many articles on BLS-- here is a good one

Leaf scorch symptoms on red oak. Photo from the Minnesota Department of Natural Resources Archive, Minnesota Department of Natural Resources,

Information from Bob Mulrooney, Extension Plant Pathologist, UD.

Landscape - Yellownecked Caterpillars

You may see yellownecked caterpillars feeding in trees this time of year. The following is more infomation.

Yellownecked caterpillars have a jet black head, yellow and black stripes and some white hairs. Directly behind the head is a bright yellow-orange segment. Oaks are often attacked along with basswood, maples, elms, walnut, fruit and nut trees. Adults emerge during June-July, mate, and females lay eggs on the undersides of leaves. This caterpillar feeds gregariously, skeletonizing leaves as early instars and consuming most of the leaf when they are older. When disturbed, larvae assume a “Ushaped” defensive posture to reduce the likelihood of attack by predators and parasitoids. Larvae actively feed between July through September depending on location and when eggs were laid, but there is only one generation per year. Birds, predatory insects, and parasitoids attack this pest. This pest seldom causes serious harm to trees and treatments are not often warranted. Chemicals available for control include B.t., spinosad, azadirachtin, or one of the pyrethroids.

Yellownecked caterpillars. Photo by Gerald J. Lenhard, Louisiana State Univ,

Information from Brian Kunkel, Ornamental IPM Specialist, UD

Thursday, August 20, 2009

Turf - Seeding Turf

With turf seeding period coming up, the following are some general guidelines to follow.

Late summer or early fall is the ideal time to seed turf grasses. The following are some points to consider for these seedings. Before seeding, address any problems that would affect turf growth (weeds, fertility, compaction). Purchase high quality seed with a recent germination test. Use improved turf varieties, with good disease resistance, adapted to our transition area (turf-type tall fescue for most general applications). Go to for recommended varieties from the MD-VA turfgrass working group. Single varieties or mixtures of several varieties of the same species with similar appearance and growth habit are recommended for uniform sites. Mixtures of 2 or more species (such as turf-type tall fescue with creeping red fescue) are often used where multiple environments exist in the same property such as mixture of partially shaded and open areas. However, in a multi-species mixture, the best adapted species will be dominant. Seed into moist soil conditions or provide irrigation to achieve good germination. Soil-seed contact is critical for germination – use a packer type seeder for new seedings or complete renovations; use a slit seeder for partial renovations into existing turf. The ideal seeding period in Delaware is from the last week in August through the month of September. Grass seedling survival is greatly improved if there is 4- 6 weeks of growth before a hard frost.

Gordon Johnson, Extension Horticulture Agent, UD, Kent County

Landscape - Bacterial Leaf Scorch

Hot weather in mid-summer is the time that you often see bacterial leaf scorch on infected trees. The following is more information.

Bacterial leaf scorch (BLS) is a disease with a name that definitely understates the impact on infected trees. It causes far more than leaf scorching. The bacterial pathogen can slowly kill mature trees in 8-10 years.

Here's what you may see. About mid-summer, infected trees appear to have environmental leaf scorch. The same trees appear healthy again the next spring, but scorching returns each summer, becoming progressively worse over 5 or 6 years, thinning the canopy and eventually killing the tree. I have seen the problem on Illinois oak trees, but other trees may also host this disease.

Bacterial leaf scorch is an infectious plant disease caused by a bacterium called Xylella fastidiosa. The pathogen is systemic, living only in the xylem. The most frequent hosts of this disease in the U.S. include elm, oak, sycamore, mulberry, sweetgum, sugar maple, and red maple. At the University of Illinois Plant Clinic we have confirmed BLS on pin, red, shingle, bur, and white oaks. Kentucky pathologists report BLS on pin, red, scarlet, bur, white, willow, and shingle oaks; silver, sugar, and red maples; sweetgum, sycamore, planetree, hackberry, American elm, and red mulberry. Look for scorch symptoms that occur in early summer to midsummer and then intensify in late summer. The scorched leaf edges or tissue between veins may be bordered by a yellow or reddish-brown color, but not in all cases. The symptoms may occur first on one branch or section of branches and slowly spread in the tree from year to year. The pin oaks we have seen infected have general thinning. It is one of those situations that you hope will be better next year but only gets worse.

There is no cure for this disease. Some have tried injections with oxytetracycline, but none have shown more than disease suppression with this antibiotic. Since the pathogen is in the xylem, cleaning pruning tools before moving to another tree is important to reducing spread of the disease. Xylem-feeding leafhoppers and spittlebugs are thought to spread the bacterium in landscape trees. Transmission between trees through root grafts has been reported.

Unlike most other bacteria, Xylella fastidiosa cannot be isolated in the lab. However, it may be confirmed using serological techniques. ELISA (enzyme linked serological assay) testing can be done and is used to help identify the Xylella pathogen. The most reliable test results occur in August and September, possibly because the bacterial population in trees is higher late in the season.

Bacterial leaf scorch on oak. Photo by Randy Cyr, Greentree,

Information reprinted from an article by Nancy Pataky in the current edition of the Home, Yard, and Garden newsletter from the University of Illinois

Wednesday, August 19, 2009

Turf - Core Aeration for Thatch Management

Core aeration is a good way to manage excess thatch buildup in turf. The following is more information.

Core cultivation (aeration) can be used to reduce thatch accumulation, modify the physical characteristics of thatch, and remove thatch from the soil-turf interface. A single treatment may not be as effective as dethatching in removing thatch debris, but it is less injurious and disruptive to the turf. The soil cores removed with core cultivation should be redistributed throughout the turf and thatch layer. This can be done by allowing the soil cores to dry and then dragging the cores with a steel mat or chain link fence. A dethatcher can also be used to break up soil cores. The redistribution of the soil cores into the turf modifies the physical and chemical qualities of the thatch, making it a better growing medium. Soil incorporation will also enhance thatch breakdown by improving conditions for microbial activity.

Information from "Thatch Management in Turf" Rutgers University Extension Factsheet FS740 by James A. Murphy, Ph.D., Extension Specialist in Turfgrass Mamagement

Turf - Fall Liming

Late summer and fall are good times to apply lime to turf areas. The following are some considerations in liming lawns and turf areas.

Fall is a great time to address soil fertility issues, including liming. Recent soil tests from a reputable lab will give you some guidance on how much (if any) lime would be needed. Two pH figures are reported on a soil test report: pH and buffer pH. The pH figure tells you whether or not you need lime and the buffer pH value tells you how much is needed to reach the target pH for turf (6.0-6.5 for most turf in Delaware).

Raising soil pH is the goal of liming. If magnesium is deficient or low in the soils, those soils may benefit from the application of dolomitic limestone (Hi Mag), though magnesium availability increases with increases in pH; otherwise use calcitic lime (Hi Cal).

A few other things to keep in mind:

1. Tillage is the best way to incorporate lime when doing a new planting or complete renovation. In existing turf, core aeration is a way to move some lime into the root zone of turf and get better response to liming.

2. If surface applying lime, do not apply urea based fertilizers soon after application of the lime. Urea volatilizes much more quickly on an alkaline surface, and nitrogen is lost to the atmosphere.

3. Calcium deficiencies are extremely unlikely in Delaware and most states in the Mid-Atlantic; apply liming materials to adjust pH up, not to supply calcium (which becomes abundant at optimum pH levels). Most of our soils contain abundant amounts of available calcium, and turf uses only a small amount of calcium.

4. Gypsum does not raise soil pH. This includes waste products like ground wallboard.

Adapted from "Liming Considerations for Late Summer and Fall" Keith Diedrick and Robert Mullen in the current edition of the Crop Observation and Recommendation Network Newsletter from the Ohio State University.

Tuesday, August 18, 2009

Turf - Thatch

Thatch buildup can be a problem in some turf, especially bluegrass. The following is more information.

Excessive thatch accumulation is a problem on many turfgrass sites. Thatch is a layer of organic material consisting of tightly intermingled, living and dead plant tissues derived from crowns, stems, and roots. These parts of a turfgrass plant have a relatively high lignin content. Lignin is an organic compound that is highly resistant to microbial breakdown. Accumulation of a thatch layer occurs when the production of organic material (such as lignin) exceeds the rate of decomposition within the zone between green leaf tissue and the soil surface.

To assess thatch accumulation, remove a section of grass and soil from the turf using a knife, soil probe or shovel, and measure the depth of accumulated thatch. Depths greater than 1/2 inch indicate that corrective measures may be needed to reduce the thatch layer. Measurements from several locations through the turf area are needed because of the variable nature of thatch.

A thatch depth less than 1/2 inch can be beneficial because it improves turf resiliency and wear tolerance, and insulates the soil from extremes in air temperature. However, as thatch accumulates beyond 1/2 inch, the disadvantages begin to outweigh the benefits. Excessive accumulation tends to increase the susceptibility of a turf to heat, cold, and drought stress. Localized dry spots, scalping, disease, and insects may also be enhanced by excessive thatch. Such difficulties may develop as excessive thatch accumulates because the turfgrass plants will tend to have a greater portion of their crowns, rhizomes, and roots growing within the thatch rather than the soil. A weakened, poorly rooted turf is also more prone to injury and requires increased management.

Turfgrass species differ in their tendency to accumulate thatch because they have different growth rates, growth habits, and percentage of various cell wall components (Table 1). Lignin is one cell wall component that resists microbial breakdown. Vigorous species and cultivars with high lignin content accumulate thatch more readily than those with slower growth rates and lower lignin content.

Information from "Thatch Management in Turf" Rutgers University Extension Factsheet FS740 by James A. Murphy, Ph.D., Extension Specialist in Turfgrass Mamagement

Turf - Fairy Rings

You may see circular areas of diseased turf during late summer. These are called fairy rings. The following is more information.

Fairy Rings in Turf

This disease, caused by a group of fungi known as basidiomycetes, is visible on many golf greens and home lawns in late summer. Symptoms typically appear as continuous or interrupted rings of dark-green turf. Mushrooms, which are often associated with fairy ring, usually develop in the spring and fall. Although fungicides are not effective against all species of the fungi that cause fairy ring, Bayleton, Headway, Heritage, Insignia and Prostar have provided good control in many university tests. For best results, maintain adequate soil moisture and fertility to mask symptom expression. Spike affected turf prior to irrigation and the application of fungicides to enhance water movement into the soil profile. The use of surfactants may enhance fungicide efficacy and aid in symptom suppression.

Fairy rings. Photo by Lester E. Dickens,

Information taken from the August 21, 2008 edition of the Plant & Pest Advisory, Landscape, Nursery & Turf Edition, from Rutgers University.

Monday, August 17, 2009

Landscape - White Mold in Perennials and Annuals

In beds that are over-irrigated or in cool, wet periods, you can have problems with white mold in perennial and annual beds, especially in very lush plantings. The following is more information.

White mold, a disease caused by the fungus Sclerotinia, is a common problem on many vegetable crops. However, this fungus infects more than 370 species of plants, including many common landscape annuals and perennials. Ornamentals known to be susceptible are aster, begonia, daisy, delphinium, hydrangea, marigold, pansy, peony, petunia, salvia, snapdragon, and zinnia. Often, the first symptom noticed on infected plants is wilting. Upon closer inspection, a white, fluffy mycelium can be seen on infected plants. This white growth soon (in 7 to 10 days) develops into sclerotia, fungal resting structures specialized to withstand harsh environments such as winter. The sclerotia initially are white but mature as hardened, black structures ranging in size from 1/16 to 1/2 inch.

The sclerotia can be found both on external plant parts and also inside the stem. It is these structures that germinate and cause new infections in future years, so diseased plants should be immediately removed from the garden.

Other characteristic symptoms caused by this disease are water-soaked, brown lesions on stems. The characteristic white mold develops only during wet weather and often disappears as the plant dries down, leaving tan (bleached-looking) lesions and stems.

Initial infections need moisture and relatively cool temperatures to occur. However, the microclimate in irrigated flowerbeds can be ideal for disease development even in dry seasons, especially if planting densities are high. There is no control once infections have occurred; however, protective fungicide sprays of materials such as thiophanate-methyl can be effective if timed correctly. Remove diseased plants to reduce chances of infections in future years. The sclerotia can survive for 3 to 5 years in the soil, so consider planting nonhost species if an area was heavily infested.

The presence of a white, fluffy mold and dark sclerotia are diagnostic for this disease. This growth is very white and wispy, compared to the dense gray mold of Botrytis. Southern blight, a disease caused by the fungus Sclerotium rolfsii, also produces a white mold, usually present on the base of the stem. However, the sclerotia produced by this fungus are small and tan to brown in color, greatly resembling mustard seeds.

White mold in zinnia bed. Photo from the University of Minnesota Yard and Garden News.

Information taken in part from the University of Illinois, Home, Yard, and Garden Newsletter (July 17, 2007).

Landscape - Getting Hydrangeas to Turn Blue

The following is a good article on getting some Hydrangeas to turn blue in the landscape.

With so few true blue flowering shrubs for our landscape, it is no wonder so many of us are drawn to the beauty of blue hydrangeas! Only one species of hydrangea we commonly see for sale and in our northern landscapes include cultivars that can be coaxed to bloom a true blue or, if desired, a pure pink. It is Hydrangea macroplylla which is also known as the bigleafed hydrangea. Endless Summer® is the most common cultivar of this hydrangea we see for sale in the north as it is able to bloom off of both old and new wood. This is unlike most other H. macrophylla cultivars which bloom on only old wood.

So, what makes bigleaf hydrangea turn blue , pink, or a shade in between? The primary contributor is soil pH. Soil pH ultimately influences the pH within the plant cells. The critical part of the plant cells for pH and color are the large watery vacuoles within the bract cells (colorful portion around the small true flowers that look like petals). The pH in the vacuoles influences the configuration and how light reflects to our eyes from the pigment anthocyanin. Anthocyanin is a plant pigment that ranges in color typically between blue and pink and can appear cream or colorless in the transition between blue and pink. The color the tissue appears depends on the pH of the cellular fluid and also other factors including presence and association of metal ions such as aluminum. There are multiple anthocyanins and they all share a common core chemical structure and are distinquished by placement of side chains and sugars connected to the core structure. Different anthocyanins have slightly different properties and color ranges. Different plant species and even cultivars within a species can have a different types of anthocyanins and different relative concentrations. Anthocyanins generally appear more towards the blue end of their range when the cellular pH is more alkaline (or higher in number) and more pink when the cellular pH is more acidic or lower.

What??? Doesn't this seem counterintuitive and contradictory? We have been told to lower the pH of the soil we have our hydrangeas planted in with elemental sulfur or aluminum sulfate to make the bracts turn blue and the opposite with lime or gypsum to make them turn pink. Interestingly, the pH within the vacuoles of petal cells moves the opposite direction as the pH of the soil. So, in order to raise the pH within the vacuoles of bract cells and make our hydrangeas turn blue, we actually lower the pH of the soil around our plants and visa versa for pink.

Bailey Nurseries, the introducers of Endless Summer® produces tens of thousands each year and most of them are grown and sold with blue flowers. There are actually three different cultivars in the series now and they all share the ability to bloom on both old and new wood. There is Endless Summer® original, Endless Summer® Blushing Bride, and now the latest addition, Endless Summer® Twist and Shout. For the Endless Summer® original being coaxed to turn blue, the flowers first appear white and then turn blue from the outside of the large colorful bract inward towards their middle until the whole bract is blue. A question arose if it would be possible to make the petals color up and turn blue sooner (being white for less time). Doing so would reduce production time. In order to work towards answering this important question, we started by doing a series of bract pH tests to understand if bract pH is consistent during expansion and coloration or if it changes and is the trigger or somehow associated with when the bract can turn blue.

We collected mature and immature heads of Endless Summer ® original from plants grown to be pink and other plants being grown to turn blue. We also collected heads of Endless Summer® Blushing Bride (it is a cultivar that has a little bit of blush to it and is stays primarily white). Throughout our bract pH tests, we took a uniform amount of bract tissue and put it in distilled, deionized water. We spun it at 14,000 rpm in a centrifuge. This very fast motion broke the cells and allowed the liquid content within cells to mix with the purified water. After spinning in the centrifuge it was amazing to see the bracts holding their form, but appearing clear or white no matter what color they started as. The solution then appeared the color of the bract before we spun it. We tested the pH of the solution with a standard pH meter.

We sampled fully expanded pink and blue bracts of Endless Summer® original. The solution from the blue bracts had a pH of 6.10 and the pink bracts 5.94. We also took immature florets of Endless Summer® original that were white at the base and their tips were starting to turn blue. We cut a number of small florets separating the white bases from the blue tips and measured the pH of bract tissue of these different colors separately. The white bases were a pH of 5.59 and the blue tips were 5.84. Therefore, for the Endless Summer® original grown to be blue with low soil pH, we saw a clear transition in pH from 5.59 for the white base of an immature bract to 6.1 when the bract was fully blue and mature. We didn't explore all the same stages and color transitions for Endless Summer® original grown to be pink. This is something worth pursuing in the future. It is interesting the pH of a mature pink floret was 5.94. This strangely happens to be a higher pH than that of the blue portion of a bract as it first began to turn blue (5.84).

We also decided to look at the pH in Endless Summer® Blushing Bride. This hydrangea does not turn blue or pink even when pH is altered. It likely produces very little anthocyanin in general and therefore basically remains cream to white regardless of pH. The sample taken from young expanding bracts of Endless Summer® Blushing Bride were a pH of 5.82 and the fully expanded florets were 5.96. A trend of an increase in bract pH was also observed in Endless Summer® Blushing Bride as it matured. The pH of a mature bract of Endless Summer® Blushing Bride was intermediate of that of mature bracts of pink (5.96) and blue (6.1) Endless Summer® original.

In the end this initial experiment helped us learn that there is a strong and clear association with blue bract color and bract pH in Endless Summer® original. The blue color seems to go hand in hand with an elevated pH as it starts out white, begins to turn blue, and then matures as a stronger blue. A subsequent question we would like to answer is if anthocyanin is already present in the white bract tissue and cannot turn from white to blue until the petal pH is further elevated, or if anthocyanin is just not present in the white tissue yet and is synthesized at the point in bract development when we typically begin seeing blue coloration. If the latter is true, it is likely that we cannot speed up blue coloration of bract tissue in Endless Summer® original. The limiting factor in that case won't be the pH, but when anthocyanins are synthesized.

The next steps in this study would be to directly test for anthocyanin pigment in different aged bracts to learn when it is synthesized as well as to possibly do some simultaneous tests growing Endless Summer® original hydrangeas in a range of different low soil pH's. Growing plants in a range of different low soil pH's would be the most direct way to see the effect on coloring rate of florets based on soil pH and also to learn the effect of such pH levels on overall plant growth.

Reprinted from "Getting Hydrangeas to Turn Blue" by David C. Zlesak and Gail Soens, University of Minnesota Extension Educator and Bailey Nurseries New Variety Coordinator / Section Grower Bud and Bloom Hydrangeas & Roses in the University of Minnesota Yard and Garden News

Sunday, August 16, 2009

Landscape - Cercospora Leaf Spot of Hydrangea

The following is information on Cercospora leaf spot of Hydrangea which is now present in the landscape.

Cercospora leaf spot on hydrangea is appearing in the landscape again. The irregular purple to purple- rimmed spots with gray centers infect both Hydrangea macrophylla and Hydrangea quercifolia. With lots of rain or overhead irrigation, this fungus disease can cause spotting that detracts from the overall appearance of the plants. If defoliation occurs, which does not happen often, plant health can be compromised. Most of the time fungicides are not warranted.

Fallen diseased leaves are the primary source of spores of the causal fungus Cercospora hydrangeae. These spores are spread to the healthy lower leaves by splashing water. Once C. hydrangeae is introduced into a planting of hydrangea, yearly outbreaks of this disease are likely to occur. Frequent late summer rain showers will not only greatly increase the rate of disease spread, but also intensify the level of leaf spotting and defoliation. Extended periods of drought will usually suppress disease development and spread.

In the landscape and container nursery, removing dead diseased leaves, applying enough nitrogen to maintain a moderate growth rate, and surface watering will help slow the development and spread of Cercospora leaf spot. Since the appearance of symptoms is usually delayed until late summer to early fall, protective fungicide sprays are rarely needed for the control of this disease on hydrangea in the landscape or nursery. For effective control of Cercospora leaf spot with a fungicide, begin applications when spotting of the leaves is first seen and continue applying that treatment as needed. Typically, protective fungicide treatments are suggested only on highly valued plants that suffer noticeable damage every year. Fungicides registered for the control of Cercospora leaf spot include azoxystrobin, chlorothalonil, myclobutanil, and thiophanate-methyl.

Cercospora on Hydrangea. Photo from the University of Arkansas.

Information from Bob Mulrooney, Extension Plant Pathologist, UD and "Diseases of Hydrangea" by Austin K. Hagan, Extension Plant Pathologist and Professor, and Jackie M. Mullen, Extension Plant Pathologist and Diagnostician, both in Entomology and Plant Pathology at Auburn University.

Saturday, August 15, 2009

Landscape, Nursery, and Greenhouse - Neem Based Products

The following is information on products from the neem tree that are used for insect and disease control.

Neem pesticides are derived from seeds of the neem tree (Azadirachta indica syn. Melia azedarachta a relative of the mahogany tree), a subtropical shade tree growing or cultivated in many developing nations. Many different forms are available commercially and knowing what's out there can really help. Seed extracts (oils) are common and may contain certain insecticidal ingredients. Soaps or just the general seed oil are also available.

Neem pesticides containing azadirachtin (AZA) kill insects by disrupting their growth and development. They are also strong insect repellents. Neem products with AZA control a broad range of pests, providing superior control of chewing insect pests such as caterpillars, leaf beetles, and sawflies. The amount of AZA present in a formulation varies and may reflect whether the product is a Ready-to-Use (RTU) formulation or a concentrate. Commercial applicators can buy AZA containing brands such as Azatin, Azatrol, Azamax, etc. Home Garden trade names include Safer BioNeem, Neem-Away Insect Spray, and others.

Clarified hydrophobic extracts of neem oil are products that do not contain any AZA and are similar in use pattern to insecticidal horticultural oils and powdery mildew fungicides. Trade names include Green Light Neem Concentrate, Trilogy, and many others. This is the type most often found on retail store shelves.

Fatty acids from neem seed are insecticidal soap (potassium salt fatty acid)/neem blends that vary in their concentration of AZA and should be used with the same care as any insecticidal soap. Trade names include Bon-Neem and Organica K+ Neem.

Many neem products carry OMRI listings that also allow them to be useful tools in organic production. Formulations (particularly those with AZA) provide a level of pest management equal to that of many synthetic counterparts from a botanical source.

Information from Casey Sclar, IPM Coordinator, Longwood Gardens

Friday, August 14, 2009

Landscape - Daylily Leaf Streak

The following is information on daylily leaf streak, a disease of daylilies now present in the landscape.

Daylily leaf streak has made a real resurgence during this hot, humid, rainy period the last couple of weeks. The foliage will get diffuse brown spots and develops into long steaks of dead tissue bordered by yellow tissue. The old dead leaves will make the plants look unsightly until the weather changes and new healthy leaves replace them later in the month. This is a fungus disease caused by Aureobasidium microstictum. Avoid damage to the leaves, which is one of the ways it enters the plant. Avoid highly susceptible varieties and limit overhead irrigation. Fungicides can be helpful if applied preventatively (before symptoms appear). I have had success with some of the triazole fungicides such as myclobutanil (Systane, Eagle, Immunox) and Banner MAXX.

Daylily leaf streak. Photo by Tom Creswell, Purdue University.

Information from Bob Mulrooney, Extension Plant Pathologist, UD

Turf and Landscape - pH Management

Managing pH is one of the most important aspects of soil fertility and soil health in turf and landscapes. As fall planting season approaches, take measures to assess soil pH and ammend soils as needed.

Late summer/fall planting season for turfgrasses, perennials, and cool season annual beds is coming up. It is important to not to forget pH management as you prepare soils for planting. If you have not done so already, take soil samples from areas to be planted and send to an accredited lab (such as the UD Soil Testing Lab) for pH and mineral nutrient testing. The test results will provide information on lime requirements – both rate and type of lime to use for standard plantings (or soil acidifying requirements for acid loving plants).

Most woody plants can tolerate a wide range of pH’s; however, perennials, annuals, and turfgrasses are more sensitive to pH. For the majority of these plants the ideal pH range is 6.0-6.5. If pH values are below 5.3 root growth will be impacted, toxic levels of Aluminum and Manganese may be present, and you may see deficiencies of Magnesium and Calcium. If an area has been over-limed in the past and the pH is above 6.8 you may see micronutrient deficiencies such as Manganese or Iron (especially in turf). For acid loving plants (blueberries, Azaleas, Rhododendrons) that thrive in pH’s below 5.4, elevated pH can result in poor growth and micronutrient deficiencies.

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

Thursday, August 13, 2009

Weather - August Rainfall

We have had considerable rainfall over the first 2 weeks of August across mid-state. The following are some August rainfall totals:

Blackbird = 2.20 inches
Bridgeville = 1.56 inches
Dover = 1.01 inches
Ellendale = 1.49 inches
Georgetown = 1.14 inches
Harrington = 2.17 inches
Kitts Hummock = 1.45 inches
Milford = 3.19 inches
Sandtown = 1.11 inches
Smyrna = 7.06 inches
Townsend = 0.31 inches
Viola = 2.21 inches

As you can see, rainfall still is extremely variable. Smyrna continues to receive significant rainfall. However, not far away in the Townsend area there has been little rain. Milford also has had considerable rainfall this month.

The humid, wet weather along with heavy dews have set up conditions for many diseases in ornamental plants and turf. For example, we are seeing more downy mildews this year and Pythium in turf.

Gordon Johnson, Extension Horticulture Agent, UD, Kent County

Wednesday, August 12, 2009

Greenhouse and Nursery - Fascination Growth Regulator and Mums

In cases where mums are too short or compact late in the season is there any remedy? You might try the growth regulator Fascination. The following is more information.

Some growers have asked about using Fascination [a cocktail of two plant hormones, gibberellic acid (GA4+7) and benzyladenine (BA) in equalproportions] to increase plant height. Fascination increases height by stretching the distance between the leaves. Trials using Fascination on poinsettias have shown that it will stretch soft tissue about an inch per application. Response is quick, within one week of application you will know how much additional growth the treatment produced. Application can be repeated as needed but results are best when shoot growth is still soft and several of the upper internodes have not yet expanded. Once stems harden they will be less responsive to treatment and late treatments may just cause the flower buds to stretch above the foliage. Trials using Fascination on garden mums has been minimal at this time but preliminary results show increased stem length with a 10ppm spray application.

For more information (and photo) of Fascination on mums: GroLink July Newsletter

Information from the current New England Greenhouse Update posting

Landscape - Saddleback Stinging Caterpillars

One common stinging caterpillar you may encounter this time of year is the saddleback caterpillar. I have been "stung" many times by these critters when working in corn research plots in Maryland in the past. They are also found in the landscape. The following is an article on the subject from the University of Kentucky.

Caterpillars are tasty morsels for predators so many species rely on camouflage to stay off the menu. Those that can protect themselves, stinging caterpillars for example, stay in plain sight and advertise with bright or distinctive markings. They are covered with sharp, brittle bristles that break off and stick in the skin like so many cactus spines. Unfortunately, that’s not all, the bristles are hollow and contain an irritating substance that produces a very unpleasant skin reaction.

Saddlebacks are relatively common and are among the most venomous species in North America. A full grown caterpillar is brownish red, about 1.25 inches long, and has several distinctive characteristics which include two fleshy horns studded with spines on each end, shorter armed bumps along both sides. The back carries a bright green "blanket" trimmed in white, with brown-to-purple central spot or "saddle", also trimmed in white. Saddlebacks occur on many plants including apple, basswood, cherry, chestnut, dogwood, elm, maple, oak, plum, and even corn. They are most abundant at this time of year.

A brush with a saddleback results in immediate pain followed by swelling and blistering if the spines are not removed. The irritation should be gone in 8 hours or less if the spines are removed. They can be stripped cellophane or adhesive duct tape. Wash the area with soap and water and apply an ice pack to relieve the irritation. Contact a physician immediately if the irritation does not subside of if other symptoms appear.

More information on stinging caterpillars is available in

Saddleback caterpillar. Photo by Herbert A. "Joe" Pase III, Texas Forest Service,

Reprinted from "Caterpillars That Pack a Punch" By Lee Townsend in the current edition of the Kentucky Pest News from the University of Kentucky

Tuesday, August 11, 2009

Greenhouse and Nursery - Mum Premature Budding and Short Plants

The following is information on premature budding in mums and why plants may be shorter than normal from the New England Greenhouse Update.

Premature budding.

Chrysanthemum flower buds initiate easily and develop rapidly, especially if plants are stressed in any way. Lack of adequate fertilizer and cool nights are causes for premature budding. When grown outdoors, we are relying on natural daylength and temperature to control the timing of the crop. Chrysanthemums are short-day plants. Both flower initiation and development of the flower buds occur more rapidly under short days than in long days. However, temperature has a greater influence than daylength on flowering of garden mums. With several cool nights in a row, garden mums can initiate many buds prematurely which results in early flowering of plants.

Short plants.

Again, short plants are a result of plants setting bud too early. In chrysanthemums, flower bud initiation marks the end of vegetative growth. Garden mums initiate leaves rapidly. Cool weather early in the growing season will reduce the number of leaves formed on each shoot, thereby, resulting in plants with fewer nodes and shorter plants. Another reason for smaller, harder plants may be due to lack of nutrients. Frequent rain made it difficult to keep plants fertilized. As a result, nutrients were leached and plants stopped growing.

Information from the current post on the New England Greenhouse Update Webpage

Landscape - Diagnostic Technique Mini-Seminar

The following is information on an upcoming program on practical diagnostic techniques for landscape managers in Maryland.

Practical Diagnostic Techniques (and more!) for Landscape Managers

Date: Wednesday, September 16, 2009
Time: 9:00 am - 1:00 pm
Location: Dave & Busters, White Flint Mall, Kensington, MD
Directions: Dave & Busters is located on the top level of White Flint Mall in Kensington
Registration: MDPREPAYMENT IS REQUIRED FOR ADVANCED REGISTRATION. CANCELLATION POLICY- Cancellations received by September 11th will receive a full refund. No refunds will be given after September 11th. No refunds due to inclement weather.
Go to for online registration.

Enhance your skills in disease and insect diagnosis-and low risk control methods. Join other landscape managers and gain practical information and skills you can put to use everyday!

9:00 - 9:45 Practical Diagnostic Techniques for Landscape Managers in Landscape Disease Problem Solving. Karen Rane, Director of the Plant Diagnostic Clinic and Extension Plant Pathologist, University of Maryland

9:45 - 10:15 How to use a dissecting scope to examine scale, tree borer and nematode samples. Karen Rane, Suzanne Klick, Stanton Gill and Jeff Gabric

10:15 - 10:30 Coffee break - chance to visit exhibitors

10:30 - 11:15 Scales and borers are two of the most destructive pests of landscape trees and shrubs. Learn how to identify major armored and soft scales and determine when they are most susceptible to control options. Landscape plant material has suffered from a great deal of tree borer damage in 2009. Learn how to identify and monitor the major tree borers, and discover control options. Stanton Gill, Extension Specialist in IPM and Unit Coordinator, University of Maryland Extension

11:15 - 12 Noon Learn how to mix, apply and evaluate the efficacy of beneficial nematodes, and how to make beneficial nematodes work in an IPM or organic approach to landscape management. Jeff Gabric, Becker Underwood, Nematode Field Development Specialist, Becker Underwood Company of England

12 Noon Lunch, networking and chance to visit exhibitors

Program sponsored by the Landscape Contractors Association of MD-DC-VA

Monday, August 10, 2009

Landscape, Greenhouse, Nursery, and Turf - New Insect Control Products

The following is information on some new insect control products available for use in the horticultural industry.

New Products for Ornamental Greenhouse, Nursery, and Landscape Pests

A new product Kontos is available to manage most sucking pests in greenhouses. It is also labeled for use in nurseries. Kontos from OHP is effective against whiteflies, aphids, mealybugs, thrips, and other insects. Kontos has a unique mode of action (IRAC group 23) that makes it an important tool in resistance management programs. This could be particularly important as a product to rotate with Conserve (spinosad) to kill thrips. It is also soft on beneficial organisms. More information on Kontos can be found at:

In ornamental landscapes we now have Acelepryn by Dupont. This unique chemical has a very low vertebrate toxicity. So low in fact that it does not require a signal word on the label. It is effective on many landscape pests and can be used as a foliar spray or drench to provide translaminar and systemic plant protection. Acelepryn also is soft on beneficial organisms compared to older products. More information about Acelepryn can be found at

As new products become available it is important to begin incorporating them into insecticide programs. These products are less toxic to vertebrates, pollinators, and beneficial insects than products such as organophosphates and pyrethroids. They can also help reduce development of resistance and prolong the effective life of other products.

Reprinted from the current issue of the North Carolina Pest News

Sunday, August 9, 2009

Turf - Pythium Blight

We sometimes see Pythium blight in our turfgrasses in Delaware during hot humid and wet weather. The following is more information.

Pythium Blight

With the recent hot, humid weather, Pythium blight has been reported on golf and landscape turf. Pythium thrives in low or poorly drained areas, especially when the night temperatures are above 68 to 700F. For best results, improve drainage, water in the early morning hours (midnight to 8 am), avoid over-fertilization, and apply Alude, Banol, Chipco Signature, Disarm, Headway, Heritage, Insignia, Koban, Magellan, mancozeb, Prodigy, Quell, Segway, Subdue MAXX, Terraneb SP, or Terrazole, according to the manufacturer’s recommendations. Caution: Koban and Terrazole can be phytotoxic during hot weather, so follow label directions carefully and experiment on a small area before treating large areas if using either product at this time of year.

Lawn infected with Pythium blight. Photo by William M. Brown Jr.,

Information from Bruce B. Clarke, Ph.D., Specialist in Turfgrass Pathology, Rutgers University from the July 23, 2009 edition of Plant & Pest Advisory, Landscape, Nursery & Turf Edition from Rutgers University.

Landscape, Nursery, and Greenhouse - Perfect Year for Downy Mildews

This has been the perfect year for downy mildews in ornamental plants. The following is more information.


Symptoms of downy mildew most often appear on the upper leaf surface as a patchy yellow, purple, or brown discoloration bounded by leaf veins. Affected leaves may defoliate prematurely, and stunting may also occur in some species, such as snapdragon, and in seedlings and bulb crops. To see why the disease is called “downy mildew,” turn the leaf over. Evident on the lower leaf surface are the characteristic downy tufts of white to purple/grey fungal growth. This growth consists of spores (called sporangia or conidia) that are easily dislodged and disseminated by wind and splashing water.

Disease development

Downy mildews develop on susceptible crops during cool (58 to 72ºF), fairly humid (> 95% RH) conditions when spores from previously infected tissue are splashed or blown by air currents to colonize new sites. As infection progresses, symptoms develop, and the downy tufts of spores associated with leaf lesions may appear on the lower leaf surface. Fungal development ceases for most downy mildews when weather becomes dry and warmer than 80ºF for 24 hours. In the absence of susceptible plant tissue, downy mildew pathogens in cold climates survive in plant debris, soil, or weeds. Watch closely for symptoms in susceptible crops during periods of cool, humid weather. When you see foliage that is discolored, turn the leaves over to check for mites or downy mildew sporulation. Symptoms of this disease can be confused with other fungal (such as Botrytis blight and powdery mildew) or bacterial diseases, foliar nematode, or some nutritional deficiencies.

Disease management

To manage downy mildew, first “manage the moisture”: space plants to ensure good air circulation and rapid drying of foliage after irrigation. Avoid overhead irrigation when the weather is generally cool. In greenhouses, reduce relative humidity to less than 85% by, again, properly spacing plants, and use horizontal air flow fans to improve air circulation throughout the house. Fill the house with warmer, drier air by venting and heating two or three times per hour at dawn and at dusk. Practice good sanitation techniques. Discard all diseased plants as well as plant debris that may harbor spores, and control weeds that may be another source of downy mildew inoculum. Protect susceptible crops during cool, wet weather with preventive fungicides. Active ingredients labeled for control of this disease include azoxystrobin, Bacillus subtilis, copper, dimethomorph, fosetyl-Al, kresoxim-methyl, mancozeb, phosphite, trifloxystrobin, and triadimefon + trifloxystrobin (Armada). To reduce the possibility of the development of fungal resistance to some of the newer systemic fungicides with single or few modes of action, rotate these chemicals with protectants such as mancozeb. Avoid the sole use of any fungicide for extended periods of time when other reliable products are available, and refer to label for timing, host plants, and rates.

Information reprinted from "Downy Mildew in Ornamental Plants" by Ann B. Gould, Ph.D., Specialist in Plant Pathology, Rutgers University in the July 23 edition of the Plant and Pest Advisory; Landscape, Nursery, Turf edition. Information Source: Gleason, M. L., M. L. Daughtrey, A. R. Chase, G. W. Moorman, and D. S. Mueller. 2009. Diseases of Herbaceous Perennials. APS Press, St. Paul, MN.

Saturday, August 8, 2009

Landscape - Current Pests

The following are some current pests active in Delaware landscapes.

Pine needle scale 2 crawlers are actively searching for places to settle and feed. They are active around 1622-2745 [2053 peak] GDD Base 50. Some treatment options include: horticultural oil, insecticidal soap, dinotefuran, acetamiprid, and pyriproxyfen.

White prunicola scale crawlers are also starting to become active this week.

Cicada killers are actively flying about defending territories, paralyzing cicadas, and scaring people. Treatments are seldom warranted because these nonsocial non-aggressive wasps seldom sting.

Catalpa caterpillars are feeding in New Castle County. Smaller (younger instars) can be controlled with B.t., but larger caterpillars may need spinosad, chlorantraniliprole, acephate, or synthetic pyrethroid.

Information from the current Ornamentals Hotline Newsletter from the University of Delaware Cooperative Extension.

Landscape - Oystershell Scales

Be on the look for oystershell scales in the landscape. The following is more information.

Oystershell scales feed on ash, cotoneaster, dogwood, maples, willow, popular and many other trees and shrubs found in the landscape. This scale attaches to twigs, branches, and trunks and feeds on surrounding cells sucking out sap and killing them. Heavy infestations may encrust branches and cause stunting, yellow foliage, bark cracking and branch dieback.

Pennsylvania reportedly has one generation a year, but research conducted by the Penn-DEL research group found two generations st present: 1 generation crawlers at 305-799 [445 peak] GDD base 50 and 2 generation crawlers at 2113-2259 GDD Base 50. The scale is light to 50 dark brown or gray and oyster-shaped in appearance. Adult females are white, crawlers are white to light yellow, and eggs (overwintering stage) are white.

Lady beetles, predatory mites, and parasitoids attack crawlers and adult oystershell scales. Prune out heavily encrusted branches to reduce infested plant material and reduce future crawler populations. Some chemical control options include: horticultural oil or insecticidal soap during crawler activity, acetamiprid, dinotefuran, azadirachtin, acephate or a pyrethroid (e.g., deltamethrin) are other products available for effective scale management.

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

Information from Brian Kunkel, Ornamental IPM Specialist, UD.

Friday, August 7, 2009

Compost Use Considerations

The UD IPM program has an extension project looking at the effect of compost on soil health. While this project is focusing on vegetable crops, some initial observations can equally apply to evaluating compost for ornamental and turf usage. The following is more information.

We are evaluating 3 different composts, an agricultural grade compost made specifically for improvement of field soils, a yard waste based compost, and spent mushroom soil compost. These were applied at a ½ inch rate and 2 inch rate and then mixed into the soil. Plant performance and soil quality measurements are being evaluated and compared to fumigated soil and untreated controls

The Ag grade compost was hard to apply due to the high moisture content; whereas the yard waste compost spread easily (well screened and appropriate moisture). Plant performance in the Ag grade compost has been excellent at both rates; the yard waste based compost has shown signs of nitrogen deficiency especially at high rates; and the spent mushroom soil based compost has showed signs of salt injury in the high rate treatment but good growth in the low rate treatment. These observations illustrate the need to evaluate compost sources before application. Some critical factors to consider are compost maturity, C:N ratio, salt content (EC), nutrient composition, pH, partical size and uniformity, moisture content and weight. In these studies the ag grade compost was fully mature, had moderate levels of nutrients, and a low salt content. The yard waste based compost was not mature (thus the N deficiency), had low nutrient content, and low salts. The spent mushroom soil compost was not well screened, had high nutrient content, but also had high salt levels.

Gordon Johnson, Extension Agriculture & Horticulture Agent, UD, Kent County