Categories 1, 2a, 3, 4, 10 & 12 (Cat. 2a: 8:30 AM - 12:20 PM, Testing at 1:00 PM; Cat. 3, 10. 12: 8:30 AM - Noon, Testing at 1:00 PM; Cat. 1, 4, 10, 12: 9:45 AM - 2:00 PM, Testing at 2:00 PM)

THE 10th NATIONAL DOGWOOD ANTHRACNOSE WORKSHOP - SEPTEMBER 22-25, 1997

by John Hartman

Plant pathologists from throughout the U.S. are scheduled to meet in Lexington next month to discuss flowering dogwood problems, with emphasis on dogwood anthracnose caused by the fungus Discula destructiva. The 10th National Dogwood Anthracnose Workshop will be held at the Campbell House Inn in Lexington, but also includes field visits to see anthracnose and other dogwood diseases first-hand.

A pre-conference tour to Natural Bridge State Park is set for Monday, Sept. 22. Contributed and invited papers will be presented and displayed during Tuesday and Wednesday sessions. Wednesday afternoon, Sept. 24, a tour of local nurseries and dogwood field plots will be made, and participants will observe first hand, dogwood management in the nursery, dogwood insect problems, dogwood variety reactions, dogwood powdery mildew, and effectiveness of dogwood powdery mildew fungicides. The Wednesday tour ends with a visit to Waveland State Shrine, and the workshop ends with a wrap-up session Thursday, September 25.

Anyone interested in dogwood problems is invited to present their research or survey observations at the meeting, and those only wishing to come and learn are also welcome. A registration fee of $35 includes tour expenses, a meal, admission to Waveland and proceedings. Depending on circumstances, a pro-rated fee may be available for those attending only part of the meeting. For registration information, please contact Jack Doney or John Hartman or the Department of Plant Pathology, University of Kentucky, Lexington, KY 40546 (606/257-5779). For inclusion into the proceedings, reports of presentations must be received by August 31.

CURRENT BLUE MOLD STATUS

by William Nesmith

The BLUE MOLD WARNING issued on August 8 for EASTERN and NORTHERN KENTUCKY TOBACCO GROWERS remains in effect. Most of Kentucky's tobacco crops have been too dry and growing too poorly to experience serious blue mold activity. However, some areas of eastern Kentucky have experienced more timely rains with considerable fog, favoring strong and damaging blue mold activity. Also, growers of crops located in other communities receiving significant rainfall late last week and during the past weekend, should remain watchful of blue mold.

There are now sufficient spore-loads to drive epidemic levels of blue mold in eastern and northern Kentucky, and to also threaten other areas of Kentucky and other states and nearby regions. Therefore, growers with late-planted crops need to remain alert to a changing blue mold situation.

Unfortunately, for drought stressed crops in serious need of rain, the wet weather forecasted for last week was not sufficiently protracted to relieve the stress. Fortunately, it also did not favor widespread blue mold development in Kentucky. However, localized blue mold activity increased sharply in communities where rains and fog developed.

Fungicide applications are not warranted in most areas of Kentucky, but in areas under blue mold warnings or watches, properly applied fungicide sprays will provide the best protection against blue mold. County Extension Agents need to post current advisories for their counties, especially in counties with newly developing activity. Be especially protective of crops developing from layby to near topping. Acrobat MZ continues to provide excellent protection in my plots.

VIRUS COMPLEX COULD DAMAGE LATE CROP

by William Nesmith

The virus complex has been increasing recently in late-set crops of burley tobacco. Because the crop, in general, is growing poorly due to dry weather, the virus activity has gone unnoticed. Should late crops of virus-susceptible varieties begin to grow well, infected plants could be damaged significantly from the viruses, through stunting and blighting due to death of midrib tissues.

The level of virus activity in tobacco was very light until early August, but has recently been increasing rapidly recently following strong winged-aphid activity. Little damage occurred to crops transplanted in May, regardless of the susceptibility of the variety planted. Greatest incidence and damage is expected in crops transplanted after June 25 to virus-susceptible varieties. Particularly hard hit in some fields have been the varieties with black shank resistance but high susceptibility to these viruses, such as 14XL8, R610, and Va 509.

There are no controls available at this stage of the season for these viruses. If strong virus activity is present in highly susceptible varieties, be careful with costly inputs such as fungicide sprays and irrigation.

CUTWORM 1997 WRAP UP

by Ric Bessin

This past spring was very difficult for many corn producers across the state. Conditions were good for early planting, but the weather turned cool then wet. Consequently, many fields suffered from poor stands. The most common causes were cool temperatures, wet soils and cutworms. Cool temperature and slow growth after corn emergence set the stage for serious cutworm losses. This article will address cutworm management in field corn, the options producers have available, and the advantages and disadvantages of each.

What are the goals of corn management early in the season? I see three main objectives, getting the crop in on time, establishing a good, uniform stand, and keeping costs reasonable. This is also the time when soil fertility is adjusted and herbicides are applied. Developing a cutworm strategy is one step to obtaining a good stand. Unfortunately, there is no one solution to managing cutworms in corn in Kentucky. There are several alternatives, each of which has some advantages and disadvantages. Some methods will work better for some, whiles other strategies may be selected in some situations.

The three primary strategies are:

1. Use of a preventive cutworm treatment;
2. Monitor apply rescue treatments according to economic thresholds;
3. Not using a preventive treatment and not monitoring for cutworms or applying rescue treatments.

Each of these strategies has some distinct advantages and disadvantages for producers.

(1) Use of a preventive cutworm treatment. This strategy is the most conservative and anticipates the potential for cutworm stand loss by using an insecticide before, during or after planting. This strategy reduces risk and saves labor because it does not require the return visits to monitor and the time and expense of having to come back with a rescue treatment.

Both liquid and granular preventive treatments can be very effective. Granular treatments for cutworms (Aztec 2.1G, Force 1.5G, Force 3G, and Fortress 2.5G) will provide 50 to 85% control depending on the product and the method of placement. Granular insecticides, when used for cutworm control should be placed as a band or T-band in the row. An infurrow application buries the material and results in very limited control at best. Liquid insecticides may be broadcast, banded, mixed with preemergent herbicides, or impregnated on fertilizer before, during or after planting. Often a particular preventive treatment is selected that may also control other early season insect pests, such as armyworms or corn rootworms. Using a preventive treatment allows the producer to focus on other on farm activities rather than monitor for cutworms. Preventive measures can provide control when adverse weather conditions may delay the application of rescue treatments.

However, there are some disadvantages to the widespread use of preventive cutworm treatments. First, not every field in each year has economic levels of cutworms that need to be controlled. Data collected by the Kentucky IPM Program from 1988 through 1992 indicated that on average about 15% (1 out of 7) of fields have cutworm infestations that approach the economic threshold. In other words, 6 out of seven fields do not require control of cutworms. So in the absence of economic cutworm infestations, preventive controls increase production costs without direct benefit to the producer. The second disadvantage is that heavy infestations of cutworms can overwhelm some preventive treatments. In fields with a history of serious cutworm problems or in years when cutworm activity is high, even fields that have received preventive treatments may need to be scouted and rescue treatments applied.

(2) Monitor apply rescue treatments according to economic thresholds. The first advantage to this strategy is the of control production costs by limiting the unnecessary use of preventive treatments. A cutworm insecticide is only used if cutworms are present at economically damaging levels while the crop is vulnerable. Used properly over time, this strategy can save the most in production costs while effectively managing cutworms. The key to this method is the detection of the damaging levels of cutworms before serious stand loss occurs (before the economic injury level is reached). Fields need to be scouted regularly while the corn is less than 12 to 18 inches in height using standardized scouting methods. The timeliness of monitoring cannot be overstated, because cutworms can cause serious stand loss in a short period of time. The other advantage to monitoring for cutworm activity is that the producer can be alerted to extreme infestations and can adjust insecticide rates accordingly. Through scouting the producer can be alerted to other pest and agronomic problems that may require attention.

However, incomplete or infrequent cutworm monitoring can lead to trouble. If cutworm monitoring is haphazard or incomplete, poor decisions can mean economic loss. Two common mistakes are made when scouting fields for cutworms.

So, which strategy do you select to manage particular fields? This is not an easy question to answer. It will depend on the available resources to the farmer, availability of scouting services, equipment for applying cutworm controls (insecticide boxes and sprayers), history of cutworm activity, and risk factors for the particular field. Monitoring for cutworm and the use of rescue treatments requires a dedicated effort. Many producers choose to do this themselves, while others use one of several scouting services to monitor activity. Others without access to scouting services and other on or off farm commitments may choose not to monitor.

Assessing the Potential for Cutworms Incidence of cutworm activity is not completely random. Fields with certain characteristics have a greater likelihood of cutworm activity. Cutworm infestations are governed in large part by crop rotation, late planting, low-damp areas of the field that drain poorly, excessive fall and early season weed growth, and the tillage or amount of surface residue. Because of these factors, strategies for cutworm control need to be developed on a field by field basis. Corn planted into sod has a greater potential for cutworm and wireworm activity. Corn following soybeans or wheat and using reduced tillage are also at greater risk to cutworms. While reduced tillage is encouraged for soil and energy conservation, fields using these practices tend to have higher levels of weeds and decaying organic matter. The increased crop residue and weediness of reduced tillage fields may place these at a higher risk for infestation than conventional tillage fields by encouraging cutworm egg-laying. However, controlling weeds after a cutworm population has established itself will force the cutworms to feed on the corn seedlings. Ideally, weed control should be initiated 10 to 14 days prior to planting to reduce cutworm levels.

In summary, I recommend that fields with one or more of the risk factors listed above and a history of cutworm problems be managed with either of the first two cutworm management strategies. Ideally, the monitoring and the use of rescue treatments will always be recommended as the primary cutworm management strategy in Kentucky, but in the absence of monitoring in fields that are at risk, producers should not leave cutworm management to chance and the fortunes of nature.

For descriptions of common cutworms and information on cutworm biology, see ENT-59, Cutworm Management in Corn. Cutworm monitoring methods and thresholds are also included in this publication. For a list of recommended insecticides, see ENT-16, Insecticide Recommendations for Field Corn. Enter the titles here

ESTIMATING LOSS FROM GRAY LEAF SPOT AT DENT STAGE

by Paul Vincelli

As corn crops approach the dent stage, some producers may be interested in assessing how much yield loss potential gray leaf spot poses this year. This is of particular concern with the delay in crop development experienced in most corn fields. A later-developing crop potentially can suffer more disease development and yield loss from gray leaf spot than an earlier crop.

The general guidelines provided below may be useful to producers, Extension Agents, and others interested in gray leaf spot. Visually estimate the disease level on the ear leaf of at least 25-30 plants selected at random from the field. Consider any tissue that is not green to be diseased, both yellowish tissue and tan, dead tissues associated with gray leaf spot lesions. Asa reminder, gray leaf spot lesions are gray to tan, narrow, rectangular lesions 1/4 to 2 inches long, sometimes surrounded by a yellow halo. It takes a bit of experience to feel comfortable making ratings of percentage diseased tissue. For what it is worth, the best practice I have found is to look over the ear leaf carefully several times, then imagine how much of the total length of the leaf would be diseased if all of the diseased tissue begun at one end, say the stalk end, of the blade.

You will note that Table 1 simply provides ranges of expected yield loss. This is because corn hybrids respond differently to the same amount of disease. Some hybrids have more disease tolerance than others, and are better at mobilizing carbohydrates out of the stalk to fill grains as the leaves blight away. Table 1 doesn’t take into account losses in test weight or in stalk strength. All fields with serious blighting from gray leaf spot should be scouted for lodging potential as harvest approaches. Scout for lodging potential by pushing stalks 8-12 inches from vertical as you inspect the field. Harvest early if 10-15% show stalk weakening by this test.

Table 1. General Guidelines for Estimating Yield Loss Due to Gray Leaf Spot in Corn at the Dent Stage.

% blighted tissue on the ear leaf at dent	Range of expected yield loss
5% or less	0 to 2% yield loss
6-25%	1 to 10% yield loss
Over 25%	Loss of at least 10% is likely, with more possible depending on severity and timing of symptoms. Yield losses of over 70% are possible in the worst outbreaks, although losses of this level are uncommon in Kentucky.

LOCUST TREES AROUND SOYBEAN FIELDS CAN LEAD TO BEETLE FEEDING

by Lee Townsend

The very same locust leafminers that have been turning black locust foliage brown can feed on soybeans and may be present in spectacular numbers (20+ per soybean plant ). This situation was seen in a Bourbon county field late last week. Fortunately, the beetles were feeding almost exclusively on soybean leaves and did not damage flowers or pods. The activity was concentrated in fields where fence rows contained locust trees, the source of the beetles. The insects and damage were concentrated in the first 4 to 6 rows. Small numbers of beetles and sparse feeding could be seen up to about 20' into the fields.

Adults are 1/4" long flat, orange-yellow beetles with a broad black stripe down the center of their backs. They scrape off and chew leaf tissue from the surface of the leaf, leaving a chain-like feeding site. When many beetles feed on a leaf, the entire surface is skeletonized. This feeding activity can extend over a 45-day period as new adults emerge and feed before moving to overwintering sites. The beetles may feed a little on pod tissue but damage is usually inconsequential.

Treatment thresholds are in the range of 100+ beetles per foot of row but defoliation estimates can be used too. Insecticidal control is rarely justified.

DECISION-MAKING TIME FOR WHITE GRUBS

by Mike and Dan Potter

White grubs are the most important insect pests of turfgrasses in Kentucky. Several different kinds of white grubs, in particular, the larvae of masked chafers and Japanese beetles can cause severe damage. Injury occurs when the grubs feed on the grass roots. The cutting of the roots kills the grass and loosens the turf so that it can be rolled back like a carpet.

This year the Japanese beetle flight was light, whereas masked chafer flight activity was about average. Consequently, grub populations in most areas are likely to be low-moderate. Despite the fact that drought-stressed lawns are more vulnerable to feeding injury, most lawns throughout Kentucky will not need to be treated for white grubs this year. Homeowners or turf managers considering a white grub treatment should first confirm that treatment is justified.

Diagnosis

Drought stressed or diseased turf can easily be mistaken for grub damage. Early symptoms of white grubs include gradual thinning, yellowing, and weakening of the grass stand followed by the appearance of scattered, irregular dead patches. As damage continues, the dead patches may increase in size, and apparently healthy turf areas may suddenly wilt. The turf may feel spongy as you walk over the infested area.

Sod that is heavily grub-damaged is not well anchored and can be pulled loose from the soil like a carpet, exposing the white, C-shaped larvae. (If the brown patches do not pull up easily, the problem is usually related to other causes.) Another indication that white grubs may be present is if moles, skunks or flocks of blackbirds find the turf attractive. White grubs should also be suspected if adult beetles were abundant in the area in June and July, or if you had a serious grub problem last year.

To determine the degree of infestation, sample the lawn in sever-al spots. In each area, cut out a square-foot piece of sod and inspect the roots closely for grubs. (Note: any grubs that are present in mid-August will be small -- about 1/4 to 1/2-inch.) After examining the sample, tamp it back into place and water it well to encourage recovery. An average of 8 or more grubs per sample may indicate a need for treatment. Healthy, vigorous, well-watered turf will often tolerate higher grub densities (10-15 per sq. ft.) without showing damage.

Control

If damaging numbers are present, the ideal time to treat curatively is now, while the grubs are still small. Grubs are still vulnerable to most insecticides in September, but treatment should not be made any later than mid-October. Normally the entire lawn will not need to be treated. Grub "hot spots," which can be confirmed by sampling, are most likely to be in full sun, lawns seeded with Kentucky bluegrass, lawns that were heavily irrigated during June and July, and turf areas that were damaged by grubs in previous years. For best results, mow the lawn and rake out dead grass and thatch before treatment. Water the lawn immediately after application to wash the insecticide down into the root zone where the grubs are feeding. Watering in is especially important for spray applications; once spray residues dry on foliage, they cannot be washed into the root zone by later drenchings. For this reason, granular formulations may be easier to use since timing of irrigation is not so critical. Treated areas should be drenched with 1/2 - 1 inch of water, using a lawn sprinkler. The required amount of water can be determined by placing a disposable pan or rain gauge in the treated area. Several products are labeled for curative control of white grubs on home lawns. Certain formulations containing diazinon, Dylox, Oftanol, or Sevin may be used by homeowners, whereas other products, such as Turcam, may be used only by certified applicators. Several additional products (e.g. Mocap, Crusade) may be used on golf courses, but not home lawns. Dylox 6.2G has worked particularly well for curative control in University of Kentucky tests; Oftanol, Diazinon and Sevin have also given adequate control. Products containing Dursban (chlorpyrifos), however, have performed poorly. Merit (marketed under the brand name GrubX(TM) to homeowners) is highly effective, but must be applied preventively, that is, before the damage appears. Merit works best against very young grubs. Because it is fairly long-lived in soil, it can be applied prior to egg hatch. The optimal application window for Merit is June 1 to late July in Kentucky. Thus, the period for using this product has already passed for this year. Milky disease products (Doom) have performed poorly in research trials in Kentucky. Formulations containing insect-parasitic nematodes also cannot yet be recommended as reliable alterna-tives to conventional grubicides. For more information about the effective and responsible use of these pesticides, consult the product label and ENT-10, Controlling White Grubs In Turfgrass.

CRICKET WARS

by Mike Potter

"Hundreds of black, ½ -inch long bugs are hopping out of my grass, flower beds, and onto my patio . When I open the garage door in the morning, a bunch more jump inside. What are these critters and how do I get rid of them? Many homeowners have called with this complaint in recent days. The culprits are field crickets.

Warm, humid conditions often produce outbreaks of field crickets during late summer in Kentucky. Infestations are especially common around buildings that are heavily mulched, landscaped or overgrown. Crickets lay their eggs in moist soil, and the immatures (nymphs) pass through several instars. There may be 1-3 generations per year.

Management

Field crickets are basically a nuisance pest, i.e., they do not bite, transmit diseases or infest foodstuffs. Since they are dependent upon moisture, they typically do not survive indoors more than a few days. One option, therefore, is to do nothing other than vacuum or sweep up those that manage to get inside. Removing excess amounts of mulch, weeds and debris close to the foundation will make the area less attractive to crickets. Installing tight-fitting door sweeps, sealing cracks, and other forms of exclusion (see Entfact-641 How to Pest-Proof Your Home), will further limit the entry of crickets, spiders, and other miscellaneous outdoor arthropods.

For clients demanding immediate relief, pest proofing can be supplemented by an exterior treatment with an insecticide. Homeowners will get the most for their efforts by applying longer-lasting liquid formulations containing synthetic pyrethriods (e.g., Spectracide Bug Stop(R)) or microencapsulated (slow-release) Dursban, stocked by some hardware/ lawn and garden shops. Apply with a compressed air or hose end sprayer, treating along the base of exterior doors, up underneath siding, and around the outside perimeter of the foundation in a 2 to 6-foot wide band along the ground, and 2-3 feet up the foundation wall. Homeowners or businesses who choose not to tackle these activities may wish to hire a professional pest control firm. Cricket problems ultimately "fix themselves," with the onset of cold weather.

by Julie Beale and Paul Bachi

Tobacco diseases this week have included more of the black shank/soreshin complex, Fusarium wilt and bacterial hollow stalk, in addition to scattered blue mold activity.

Highlights this week on ornamentals include: crown gall on marigold, Phyllosticta leaf spot on magnolia and maple, take-all on bentgrass and summer patch on Poa annua.

FOLIAR FUNGICIDE TEST RESULTS, SPRING 1997, SCHOCHOH, KY

by Don Hershman

A foliar fungicide test was conducted at Walnut Grove Farms in Schochoh, Ky during the spring of 1997. The soft red winter wheat variety, Pioneer 2552, was planted on October 14, 1996 in 7-in. rows. Plots 3.5 ft X 15 ft were established in late March after the second of two nitrogen applications (45 lbs actual N on 2/10 and 65 lbs on 3/3) had been made. Fungicide treatments were applied with a CO2 backpack sprayer delivering 25 gpa at 40 psi. The spray boom was equipped with flat fan nozzles. Fungicides were applied at various stages of wheat development as indicated in the results table. Treatments were replicated four times and were arranged in a randomized complete block design. Tilt fungicide applied at flag leaf extension is the only labeled treatment in this study. Later applications of Tilt and all treatments involving Quadris are experimental.

Growth stage progressed rapidly early in the season, but the period from flag leaf emergence to head emergence was delayed due to an extended period of cool, but dry, conditions. These conditions also limited foliar disease development until relatively late into grain fill. Note that late onset of disease in Kentucky is not uncommon and occurs about once every four or five years. Of course, conditions more conducive to disease development also occur on a regular basis. The primary disease in the test was Stagonospora nodorum leaf blotch (SLB). Leaf rust levels were light to moderate in non-treated plots by the end of the season. Glume blotch (the head phase of SLB) levels were insufficient to justify making disease ratings.

All treatments provided significant disease control relative to the non-treated check. However, because of the late onset of disease, only two treatments yielded more than the check and no treatment provided for increased test weights, which were uniformly high in all plots. This study reinforces what we have always said about foliar fungicide use in Kentucky: fungicides are only of economic value when disease pressure is sufficient to adversely affect crop yield and/or test weight. There is no question that many fields this past spring were adversely affected by disease. However, the majority of wheat fields had limited disease pressure and, thus, were in the same situation as the test location. One only need consider that in 1997 we achieved the second highest ever state yield average to believe that diseases were a minor problem state-wide.

by Patty Lucas

University of Kentucky Research Center

Insect Trap Count for August 8 - 15 1997

	Princeton
European Corn Borer	0
Corn Earworm	30
Southwestern Corn Borer	0
Fall Armyworm	10
Tobacco Budworm	6

Lee Townsend
Extension Entomologist