Inspector Findings in Kentucky

Pests to Watch for in May

By Win Dunwell, Extension Horticulturist

1250 people attended the Associated Landscape Contractors of America (ALCA) Student Career Days in Lexington. Dr. Bob McNiel received a standing ovation at the awards ceremony in recognition of his organizing this very impressive event. I was told the limiting factor to growth of a landscape contracting company is attracting qualified personnel. That explains the long hours and expense the 80 plus landscape companies expended trying to attract the students to intern or work for their firm. Competitive salaries helped companies succeed in their quest.

By Lee Townsend, Extension Entomologist

Several samples of bark beetle damage have come in recently. The approximately pencil-lead diameter holes mark the emergence holes of small dark beetles whose larvae can tunnel extensively beneath the bark. Stresses during the previous growing season(s) are often major contributing factors to these infestations. Unfortunately, there is no effective solution.

Dendroctonus borers are the most aggressive borers in pines and attack and develop in all species of yellow pine, eastern white pine, and spruces. They initially attack the mid and lower trunk but the infestation spreads up and down the tree over time. Females create S-shaped galleries and deposit eggs along the way. The larvae tunnel at right angles to the main gallery. Eventually, they move into the corky outer bark and eventually produce pupation chambers. They emerge through exit holes in the bark after transforming into the adult stage. Several overlapping generations are produced each year; this complicates the effective timing of preventive bark sprays.

Ips beetles, or engraver beetles, normally attack trees struck by lightning, or recently felled trees. However, when large numbers are present, they can attack and kill young, healthy pines and the tops of older trees. Problems in the home landscape tend to involve weakened or stressed trees that have been recently transplanted into unfavorable sites.

Engraver beetle galleries radiate in all directions but eventually tend to run parallel to the grain. They frequently appear as a "Y" or "I". Females lay eggs along the sides of the galleries and the legless, grub-like larvae tunnel into the phloem. Mature larvae pupate in expanded areas or cells in the inner bark. There can be several generations each year.

Cultural Controls

*Proper watering and fertilization will promote tree health and generally reduce the chances of successful borer attack. Vigorously growing trees tend to be able to fight off borer attack.

*Examine plantings regularly and prune dead or damaged limbs as feasible.

*Protect trees from physical injury as much as possible. Any injury that causes pitch flow can result in attack by borers.

*Plant white pines with hardwoods or under a hardwood canopy to reduce attack by Dendroctonus.

*Plant only on medium soils, there should be no hard pan within three feet of the soil surface. This will allow root growth and promote general tree health.

*Remove and destroy trees killed by borers. Select replacement species carefully to avoid a repeat of the problem.

*Consider site selection and avoid putting replacement trees back into poor sites that will stress trees.

*In many cases, it is best to remove and destroy heavily damaged trees because they are unlikely to recover and will serve as a source of borers to attack other trees.

by Paul Vincelli, Extension Plant Pathologist

This article was written for golf coarse superintendents but should be applicable to those of you who work with turf.

Alert^TM disease detection kits are commercially available diagnostic kits for detecting Brown Patch, Dollar Spot, and Pythium Blight. Each kit contains all the materials necessary to test up to six samples for one disease, at a cost of around $84.00 per kit (plus S&H). Tests can be completed in about ten minutes, making on-site diagnosis possible. Separate test kits are purchased for each of the three diseases. A summary of research and field experience with the kits follows.

PYTHIUM BLIGHT: Based on the work I have conducted or seen, these kits are accurate for diagnosing Pythium blight (=cottony blight) when it is present in the foliage. I see real value in golf course superintendents using the kit for this purpose. Pythium blight is a very aggressive disease under hot, muggy conditions, and it can kill a lot of turf quickly. Also, in perennial ryegrass, it can be difficult to distinguish brown patch from Pythium blight based on symptoms and signs, and it makes a big difference when selecting a fungicide. Given the risk of being wrong about this disease, whether on perennial rye or any other grass, I see a great value in using these kits during the summer to confirm your own visual diagnoses.

PYTHIUM ROOT ROT OR DYSFUNCTION: The kits may have potential for field diagnosis of this complex problem, but it isn't straightforward. First, be sure to carefully wash all soil off roots before testing. Any soil contamination can give a false positive. Pick individual roots with tweezers and wash very well; it really has to be done right. Then even if you get a positive reading, what does that mean? Pythium fungi can colonize roots of perfectly healthy plants, and there are quite of few Pythium fungi found in roots of creeping bentgrass that appear to be harmless, sometimes even stimulatory to the plant. Conducting the test well and interpreting the results correctly is very difficult for Pythium root infections.

BROWN PATCH: The kits work well for detecting Rhizoctonia solani, the common cause of brown patch in grasses. Based on my information, they do not detect some less common pathogens like Rhizoctonia zeae, so there is some possibility of an occasional false negative. However, R. zeae only occurs during sustained very hot weather, so most of the outbreaks of brown patch in Kentucky will be correctly diagnosed.

DOLLAR SPOT: The kits are accurate but perhaps irrelevant for many circumstances. On golf turfs, this disease is readily diagnosed accurately by superintendents, so I'm not sure a kit is needed for this.

DISEASE PREDICTION: Claims have been made are made that diagnostic kits also have value in forecasting when fungicide sprays are needed. Superintendents can collect turf before symptoms develop and test it for disease activity. The intensity of the test's color reaction is supposedly a guide to how much need there is for a fungicide application. My own work here at UK has been consistent with that of others throughout the country. Stated simply, there is too much variation in the test result to use the kits to predict the need for a fungicide spray. For example, in my evaluations, highly diseased tissues collected locally often give a weakly positive reaction. A positive reaction has great value from a diagnostic standpoint. However, the blue color is sometimes not dark enough to call for a fungicide spray based on the kit's instructions, even though the disease is out of control. There are several possible reasons for the discrepancy, but the bottom line is that it happens.

SUMMARY: Reveal kits do reliably detect Dollar Spot, Brown Patch, and Pythium Blight when present. Likewise, they can help a turf manager rule out these diseases when the cause of a particular disorder is unclear. I highly recommend the kits for diagnosis of these diseases, assuming the cost of the kits is not prohibitive. Even given the high cost, golf course superintendents may find value in having the Pythium Blight kit on hand for quick, on-site diagnosis of this explosive disease. There is unfortunately no diagnostic kit for gray leaf spot, an emerging and highly destructive disease of perennial ryegrass. I currently do not recommend their use to schedule fungicide applications on high-maintenance turfs in Kentucky.

By Mike Potter, Extension Entomologist

Most people don't think about spider mites infesting landscape plants until later in the summer. While this is true for twospotted spider mites and European red mites which thrive under hot, dry conditions, the spruce spider mite and southern red mite prefer cooler temperatures and are most active in the spring and fall.

Spruce Spider Mite- (damage shown at left) this mite feeds on more than 40 species of conifers. Most often attacked are spruce, pine, juniper, fir, arborvitae, hemlock, taxus and false cypress. Prolonged feeding causes yellowing, browning, and premature needle drop, often originating from the canopy interior. Heavy attacks can cause branch dieback or death of the entire plant.

Spruce spider mites overwinter in the egg stage attached to the base of needles or on the bark. Eggs hatch in early spring, and mature in 2 to 4 weeks. Damaging populations may be reached in April and May, before warm summer temperatures slow their activity. Populations rebound in the fall with the return of cooler weather, and feeding may continue into December or beyond if winter temperatures remain mild. Damage inflicted by mite infestations present now (during spring) often go unnoticed until the heat and dryness of June and July.

Southern Red Mite- This is the most common and destructive spider mite on broad-leaved evergreens, especially Japanese and American hollies, azaleas, viburnum, roses and rhododendron. Feeding on the undersides of leaves causes stippling, browning, occasional distortion, and premature leaf drop. Southern red mites overwinter in the egg stage on the undersides of leaves. Like the spruce spider mite, its numbers are greatest during cooler periods of the spring and fall.

Diagnosing Infestations- Spider mite populations can increase rapidly and cause extensive damage in a very short time. Therefore timely inspection of susceptible landscape plants is key. An efficient way to sample vegetation for mites is to hold a sheet of white paper under a branch and tap the foliage sharply. If mites are present, they will be dislodged and appear as slow- moving specs on the paper. Spider mites are tiny about the size of the period at the end of this sentence. A 10 – 20 power hand lens is helpful for clearly seeing the mites, which will appear yellow, green, orange, purple, black or nearly transparent.

Mite-infested foliage has a stippled or flecked appearance where the mites have fed. Also visible may be webbing, pale-colored cast "skins" shed by developing mites, and spherical, often translucent eggs. When scouting for spider mites, pay particular attention to plants having a history of mite problems. Spider mites often re-infest the same plants year after year.

Controlling Infestations- Spider mites are one of the more difficult landscape pests to control. When buying new plants, it pays to inspect the lower leaf surfaces for evidence of mites. Spraying plants with a strong stream of water from a garden hose will dislodge some mites off leaf surfaces. The approach is generally more effective on smaller plants with non-dense foliage and low mite populations. If used, water sprays should be directed upward against the lower leaf surfaces and the technique will need to be repeated on regular intervals. Low populations of spider mites will sometimes be held in check by naturally occurring predatory mites, which feed on both eggs and active stages.

Elimination of moderate to heavy infestations usually requires the use of specific pesticides known as miticides. Effective homeowner products are limited to such options as horticultural oils and insecticidal soaps. Nursery and landscape professionals may also want to consider using Hexygon, Joust, Morestan, Pentac, Scimitar or Talstar. Always read and follow the directions accompanying the product. Some miticides (e.g., oils) may harm or discolor certain types of landscape plants.

Good spray coverage is essential. Thoroughly wet the foliage and try to contact as many mites as possible, paying particular attention to leaf under surfaces where most mites are living. In most cases, two or more applications at 5-10 day intervals will be needed for satisfactory control. Spider mite eggs which have not yet hatched are unaffected by most miticides; the same is true of larvae and nymphs that are molting. During molting, spider mites remain inactive beneath the former skin, which serves as a barrier against insecticides. The quiescent mites also do not feed, rendering products that kill by ingestion temporarily ineffective. Consequently, if only one application is made, some of the mites will survive and the infestation will persist.

by Mike Potter, Extension Entomologist

Honeylocust plant bug - Eggs have hatched and the young nymphs are feeding on the expanding leaves of honeylocust. Feeding by the small, pale green insects causes distortion, stunting and discoloration of the foliage. Leaf damage persists throughout the season. Nymphs transform into adults by mid-May, and lay eggs in woody tissues. Winter is passed in the egg stage.

Damage from honeylocust plant bug rarely endangers tree health, but can be a concern in terms of cosmetics. Early activity is often overlooked and infestations are not recognized until symptoms appear. By this time, control efforts are no longer effective. Nurseries who want to avoid cosmetic damage should examine expanding leaflets for the small, green nymphs and treat while the insects are still active. Insecticidal soap, 2% horticultural oil, or conventional insecticides (e.g., Sevin, Dursban, Tempo, Talstar, Scimitar) are effective. Check the foliage 7 to 10 days after the first treatment to determine whether or not another application is needed. There is only one generation each year.

Hawthorn Lace Bug - Egg hatch has begun and nymphs are feeding on the undersides of hawthorn leaves. Lace bugs suck plant sap and cell contents, producing yellowish stippling on the upper leaf surface. In addition, dark, shiny spots of excrement are excreted on the leaf undersurface. The injury, in addition to being unsightly, can reduce plant vigor. Lace bugs may have two or more generations each year, each requiring about 30 days. Insecticides such as Orthene, malathion, Dursban, and synthetic pyrethroids (e.g., Tempo, Talstar, Scimitar) may be used for control. Thorough coverage of leaf under sides is important.

By David G. Nielsen, Professor Emeritus, Dept of Entomology, Ohio State University. Taken from The Buckeye, Educational update, Oct. 1996.

Black vine weevil is a naturalized pest in North America that attacks a wide range of woody plants from azaleas to yews. This parthenogenetic species (all of them are females) was probably introduced from Europe in the mid-18^th century, and was reported as a pest of nursery and landscape plants by the 1800's in eastern North America. Currently, it is one of the most commonly encountered and damaging pest of woody plants in nurseries and landscapes throughout most of the eastern, central and western United States. Although it causes severe economic hardship in small fruit production in Europe, most of its damage in North America is limited to landscape plants in the northern half of the U. S., southern California and parts of Canada: Throughout its range it completes one generation per year.

In most areas, black vine weevil overwinters as rather large larvae. The following spring, the voracious larvae consume small, absorbing roots and girdle larger roots and crowns of plants. Symptoms of larval feeding include late budbreak, chlorosis and plant death. Larvae complete development in May and June and pupate in the soil; adults begin emerging about two weeks later. Soon after adults emerge above ground, they begin chewing semicircular notches in leaves of azalea, rhododendron, Japanese hollies, boxwood, euonymous, taxus and a broad range of other cultivated and wild evergreen and deciduous plants, including conifers. All adult feeding is done at night.

Black vine weevil presence is most easily detected by inspecting leaf margins for evidence of adult feeding. Sometimes, homeowners and nursery producers will plant a favorite, leafy weevil host like hosta near suspected infestations to determine when adults become active. Another way to determine when adults begin to emerge above ground in the spring is to place scraps of wood or burlap on the soil surface beneath plants that are suspected of harboring weevils. These articles can be turned over in the morning to locate beetles that hide there during the day. First beetle activity should be marked on your calendar.

Newly emerged beetles feed for approximately four weeks before they begin ovipositing. Consequently, the first application of insecticide to kill beetles before they can reproduce should be made about three to four weeks after the first beetle is found or the first new leaf notching occurs in the spring. Since beetles will continue to emerge into August, treatment should be repeated at three to four week intervals until then. All applications should be made with a hydraulic sprayer or other device that ensures thorough coverage of all leaf surfaces of plants you wish to protect.

Product choice for adult weevil control is limited, but some of the materials that are available are extremely effective, providing they are applied on a timely basis, using equipment that will allow thorough coverage. High pressure, high volume sprayers are best for controlling vine weevil adults.

The synthetic pyrethroids (e.g., Talstar, Tempo, Scimitar/Topcide), bendiocarb (Turcam, Dycarb) and guthion have proven most effective in out pesticide development studies with black vine weevil adults. Guthion is highly toxic, inexpensive and available for use in the nursery but IPM tactic, that's called inspection or monitoring, is one of the most cost effective exercises a pest manager can perform. If larvae are detected, it's time to retreat. If larvae are found, then there is no reason to spend valuable resources for a control project that is not indicated.

If you wish to try a biological insecticide to control vine weevil larvae in containers, use Exhibit, BioVector, or another product that contains the entomogenous nematode, Steinernema carpocapsae. The juvenile infectives carry a bacterium that causes the insect's gut to rupture and the insides to putrefy. This species of nematode has been effective in our trials, providing the medium temperature is above 60 degrees and below 100 degrees F. We are currently evaluating a different species of parasitic nematode, Heterorhabditis bacteriophora, in three states for vine weevil control. This nematode was somewhat effective against large larvae in the field this spring in well-drained, sandy soil in northern Ohio and is expected to perform well in containers. It is a larger nematode that actively seeks out its host. Preliminary indications are that it is an excellent parasite of weevil larvae. We need to determine if this species can be formulated in a way to provide both efficacy and long enough shelf life to be practical for use in landscapes and nurseries.

Whereas we do not see new adulticide products on the horizon for black vine weevil, we may be nearing the time when growers of container plants will have dependable, preventive and curative products that preclude establishment or provide complete control of larvae when used as drenches. The product used as a preventative has already been labeled for use in nurseries; the experimental, curative material is in only its second year of testing. During 1996, we established container studies to determine if these products and usage patterns provide 2-year protection from vine weevils. Our earlier studies have indicated efficacy.

By Lee Townsend, Extension Entomologist

Slugs and snails are almost universal pests in greenhouses. Their soft, unsegmented bodies, exude a slimy, sticky, mucous-like substance that leaves characteristic shiny trails in their wake. They come from the soil or the surrounding area.

Slugs use their rasping mouthparts to feed on most any kind of plant. Immatures tend to feed on surface tissue while larger individuals eat irregular holes in foliage. They usually feed at night and hide in moist, dark areas during the day. Slugs and snails may eat several times their own body weight each night so damage can be serious within a short time. Their damage is often blamed on cutworms or other insects but the slime trails are key clue in diagnosing the problem.

Although slugs are hidden during the day, they apparently are not repelled by light. Rising temperatures spur them to crawl down to their hiding places to rest and absorb water through their skin. As temperatures start to fall, slugs actively begin foraging, again. Slugs may be active during the day after a cooling shower as long as the temperatures decline or remain steady. Slugs are so sensitive to temperature that they can detect temperature changes as gradual as 2° F per hour! Slugs prefer temperatures in the low 60's but they can lay eggs and develop normally but more slowly when it is cooler. Development stops at 41°F. Slugs can survive slight freezing but they tend to hide in cold weather and are protected. Slugs try to avoid temperatures above 70°.

Slugs are sensitive to air currents. Gentle breezes cause them to turn toward the source and extend their antennae. As the breeze becomes stronger, the slugs turn away from the source, evidently to escape dehydration. Improved ventilation may force slug to move. Slugs can survive a short period of time in the water but they will drown after several hours.

Slug baits containing metaldehyde may be used for control. Best results are usually obtained if the baits are applied in the afternoon watering is delayed until the next day. Slugs feed intermittently so several applications of bait are necessary for control.

Metaldehyde baits may attract slugs from up to 3 feet away. The toxic effects of metaldehyde seem to be primarily due to dehydration as metaldehyde elicits excessive mucus production (mucus is 98 percent water and 2 percent mucoproteins.) Thus in dry weather, metaldehyde is more effective. In wet weather, slugs sometimes can absorb enough moisture to compensate for the water lost in mucus production and therefore recover from the effects of metaldehyde. However, if slugs consume too much metaldehyde, they do not recover.

Control of slugs in the greenhouse consists primarily of placing baits in areas where the slugs will find them. The effectiveness of such baits is greatly increased by placing the bait under a board, pot, or flat. Slugs will not crawl across a barrier of copper metal or wooden surfaces treated with copper sulfate.

Good sanitation with the removal of extraneous vegetation and trash piles or other material which might offer food or shelter to these pests will aid in the effectiveness of the control program. (Adapted in part from Florida Cooperative Extension Service information)