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, Bugwood.org

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

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.
Rights

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.

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 http://hort.ifas.ufl.edu/woody/circleremoving.shtml. 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, Bugwood.org

Information from Brian Kunkel, Ornamental IPM Specialist, UD

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 http://www.apsnet.org/online/feature/bls/

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

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, Bugwood.org

Information from Brian Kunkel, Ornamental IPM Specialist, UD

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 http://pubs.ext.vt.edu/2907/2907-1397/2907-1397.html 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, Bugwood.org

Information reprinted from an article by Nancy Pataky in the current edition of the Home, Yard, and Garden newsletter from the University of Illinois http://hyg.ipm.illinois.edu/article.php?id=100

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.

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, Bugwood.org

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

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 http://blog.lib.umn.edu/efans/ygnews/2009/08/

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.

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

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.

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

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
http://www.grolink.com/pdf/Belgian%20Mums%20Newsletter%20July%202009.pdf

Information from the current New England Greenhouse Update posting http://www.negreenhouseupdate.info/index.php/updates

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 www.ca.uky.edu/entomology/entfacts/entfactpdf/ef003.pdf

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


Reprinted from "Caterpillars That Pack a Punch" By Lee Townsend in the current edition of the Kentucky Pest News from the University of Kentucky http://www.uky.edu/Ag/kpn/kpn_09/pn_090811.html

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 http://www.negreenhouseupdate.info/index.php/august/445-chrysanthemums-early-flowering-and-short-plants

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 http://www.lcamddcva.org/memform/september09.cfm 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

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: http://www.ohp.com/PIB/PDF/kontos_490_pib.pdf.

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 http://www2.dupont.com/Professional_Products/en_US/assets/downloads/pdfs/H65676.pdf.

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 http://ipm.ncsu.edu/current_ipm/09PestNews/09News17/pestnews.pdf

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., Bugwood.org.

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

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.

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.