DOGWOOD BORER and BRONZE BIRCH borer flight begins soon (ENT 43);
HONEY BEES are starting to swarm.
EUROPEAN PINE SAWFLIES feeding on old needles (Entfact 410);
DOGWOOD BORER and BRONZE BIRCH borer flight begins soon (ENT 43);
HONEY BEES are starting to swarm.
A Crop and Pest Management Field School will be held June 30, 2005 at the Agronomy Research Farm (Spindletop) in Lexington. This field school is designed to provide a hands-on learning experience with crop, soil, and pest management issues in grain crops. Topics to be covered include: Herbicide Symptomology on Grain & Horticultural Crops; Weed Identification; Insect Problems, Identification, & Management; Corn Growth and Development Stages; Soybean Production, Soybean Rust, & Other Foliar Diseases; and Phosphorus Losses in Agricultural Soils.
This educational training session has been approved for 6 CEU credits for Certified Crop Advisers (3 hrs Pest Management, 2 hrs Crop Management, and 1 hr Soil & Water) plus Pesticide Applicator Training recertification credits have been requested. Preregistration is requested by June 17 to participate in this educational training program. For more information you can contact Dr. J. D. Green ( jdgreen@uky.edu ) (859) 257-4898 or a registration form can be obtained at the following website: http://www.uky.edu/Ag/Agronomy/Extension/FieldSchool05.pdf .
The UK Agronomy Research Farm (Spindletop) is located at 3250 Ironworks Pike (Hwy 1973) on the north
side of Lexington between Newtown Pike (Hwy 922) and the Kentucky Horse Park.
As of May 13, blue mold had not been reported in the United States. Active blue mold has been found in Cuba and western Mexico; however, weather conditions have not been favorable for movement from these areas to the U.S. We will continue to monitor data from the North American Plant Disease Forecasting Center and provide alerts as necessary.
We are also in the process of updating the Kentucky Blue Mold Warning System web page. I would like to ask those who use the page for any suggestions that would make the page a better resource. Comments can be sent to me at kwseebold@uky.edu.
For the latest blue mold status and other tobacco disease information, check the KY Blue Mold Warning System online.
http://www.uky.edu/Agriculture/kpn/kyblue/kyblue.htm
For more information about tobacco pests, visit "Insect Management Recommendations".
Seedling damage by early season insects is becoming apparent in some areas of the state as the weather warms. White grub, wireworm, cutworm, stink bug, southern corn leaf beetle, and corn flea beetle damage have been reported from various areas in the state. The good news is that weather conditions now are promoting rapid seedling growth that moves these seedlings quickly past the small vulnerable stages.
White grub damage can be characterized by uneven stands, yellowing or purpling of lower leaves, and wilting of the entire seedlings. White grubs are larvae of several species of scarab beetles, including Japanese beetle, masked chafers, and May beetles. Of those that attack corn seedlings, May beetle grubs are the most damaging. They attack just below the crown of the plants severing the first major roots. Once symptoms of damage begin to appear, there are no effective rescue treatments.
Wireworms attack the seed and seedling corn. Damage is characterized by uneven stands, skips in the row, and deadhearting and tillering of seedlings. A deadheart is where the older leaves of the seedling appear healthy, but the youngest leaves emerging from the whorl are dead. Wireworms often bore into the base of the seedling to feed on the growing point, killing the youngest leaves. As with white grubs, there are several species of wireworms that are common. These are the larvae of click beetles. Some of these species may have extended life cycles lasting two or more years. If you suspect wireworm damage to seedlings, dig up suspicious plants and look for a hole in the base of the stem near the growing point or damage to the coleoptile before emergence. This is where the attack usually occurs. Once symptoms occur, there are no effective rescue treatments.
Cutworms damage is recognized by most, but can be confused with damage caused by the southern corn leaf beetle. With cutworms, the whorl or the young seedling is usually completely cut. Cutworms may carry some of the severed leaves or stem to its burrow where it can continue to feed on these during the day. Unlike wireworm and white grubs, there are very effective rescue treatments for cutworms. We recommend that a rescue spray be considered if 3 percent or more of the plants have been cut and 2 or more live cutworms are present per 100 plants. Generally, we are more concerned with small cutworms rather than large ones, as the large ones have already done their damage.
The southern corn leaf beetle feeds on early- planted corn. This insect pest has become more of a problem in the past couple years and may not be properly recognized by many growers. It can reduce stands through feeding on young seedlings. Particularly while conditions are poor for rapid seedling growth, growers need to monitor fields for this insect pest.
Southern corn leaf beetle is a small (<1/4 inch) dark beetle that is camouflaged and easily blends in with the soil. When disturbed it readily drops to the ground. The beetle attacks young seedling by feeding on the leaf margins and chewing into the side of the stem. The damage can easily be mistaken as young cutworm or armyworm feeding. With the southern corn leaf beetle, damaged seedlings were cut with one side of the stem remaining attached, but laying on the soil as would be the case with cutworms. The beetles will lay their eggs at the base of the plants and larvae feed on the roots of corn during the early summer. There are no thresholds for southern corn leaf beetle, but Illinois and Iowa have used 25% infested/damage plants as a guideline for treatment. A few insecticides are specifically labeled for Southern corn leaf beetle, including Capture 2 EC, Lorsban 4 E, and Warrior T (suppression).
Stink bug damage is beginning to appear as distorted, poorly growing plants. Stink bugs feed with piercing-sucking mouthparts and remove plant juices. They also inject enzymes into the plants which dissolves plant tissue around the wound. They feed at the base of the stem just above the soil line. Leaves that emerge often have four holes in a row, but unlike holes caused by boring insects, these holes have margins that have been dissolved by stink bug enzymes and appear faded. Unfortunately, it takes days for the damage to appear, usually long after the stink bug has moved on. Stink bug damage is common around field margins but may extend into the centers of no-till fields.
Corn flea beetles are also common in many fields, but the damage is most minor and plants recover quickly as conditions that promote rapid growth return. Corn flea beetle damage appears as fine scratches on the upper surface of the older leaves. The pin-head size flea beetles are often found near the damage. While flea beetles can vector the bacteria that causes Stewart's Wilt, most field corn hybrids are non susceptible to this disease. Much of the corn in the state was treated with one of several seed treatments (Gaucho, Cruiser, or Poncho) which will protect seedlings from corn flea beetle. Field corn infrequently requires treatment for corn flea beetle.
For information about corn pests, visit
"Insect Management Recommendations".
Codling moth, plum curculio, and rosy apple aphids are active on the developing crop. While codling moth numbers have been low this year, growers still need to maintain traps and carefully watch for adult moths this year. Traps have proven an effective to properly time insecticide sprays to get their maximum benefit and to eliminate unnecessary sprays for codling moth. Trials in the early 90's demonstrated that the use of codling moth traps could reduce insecticide use by as much as 30 percent on apples.
Plum curculio damage has appeared on small apples. The females damage the apples as they create crescent-shaped flaps on the young apples when they lay their eggs. These crescent-shaped injuries increase in size as the apples grow and appear as 1/2-inch callused areas on the side of the fruit by harvest. Several insecticides are labeled for plum curculio and will provide excellent control when applied during the petal-fall to first-cover period.
Rosy apple aphid damage is beginning to show up on some trees. Rosy apple aphid injects a toxin into the tree that causes the leave to improperly unfold. The damage leaves are rolled tight, unrolling the central leaves often reveals the colony of purplish aphids. Fruit around the colonies fail to grow properly and are knobby. Control of rosy apple is best accomplished prior to bloom, when the colonies first begin to develop and before the damage has occurred. For more information on apple insect management, refer to ID-92, 2005 Commercial Tree Fruit Spray Guide.
Fire blight symptoms are appearing statewide. In many trees, the "burned" shoots are not yet visible, but initial wilting of shoots associated with infected clusters is now visible. These shoots will soon die. Infected flower (fruitlet) clusters may show only one fruitlet with a blackened pedicel while the others are still green. Peeling the bark from the woody twig subtending an infected flower/fruit cluster will reveal internal browning and streaking indicating that the bacteria have already moved into the twig. Such twigs will show wilting shoot tips, early symptoms of fire blight. These symptoms have been occurring for over a week in some western Kentucky locations. Rain on April 22, just following a week of warm, mild weather, triggered much of the fire blight statewide. However, if flowers were open, primary infections may have occurred April 7 - 12 during an earlier warm, rainy period.
Orange rust is appearing on shoots of blackberries statewide. Masses of bright orange foliage on wild blackberries may be noticed along the roadsides in many locations. Infected shoots may be stretched and deformed. Bright orange signs of the rust fungus are visible on leaf edges and on leaf undersides. Blackberries in commercial and backyard plantings which show rust symptoms should be removed and destroyed; infected blackberries growing in fencerows and weedy areas nearby should also be removed and destroyed.
Vegetable producers in Kentucky are faced with numerous challenges as they try to bring a successful crop to market: rising cost of inputs, competition from out-of-state growers, and pests. The latter includes plant diseases, which affect all vegetables grown in the Commonwealth. In recent years, Phytophthora blight has become increasingly problematic on pepper, tomato, eggplant, and cucurbits in the United States. The disease has decimated the pickling cucumber industry in Michigan, canning pumpkins in Illinois, and peppers in Florida. In Kentucky, serious outbreaks have been reported on summer and winter squash, cucumbers, watermelons, and peppers.
Phytophthora blight is caused by Phytophthora capsici, a fungus-like organism belonging to a group called the Stramenopiles. Relatives of can be found in Kentucky and cause diseases such as black shank of tobacco, damping-off on many crops, and downy mildew of vegetables (blue mold on tobacco). Symptoms, which vary somewhat between crops, include damping off, root rots, crown rots, stem rots, and lesions on leaves and fruit. Lesions on stems are darkened and water-soaked, often extending a few inches above the soil line - similar to black shank of tobacco. Lesions on leaves tend to be circular and initially water-soaked in appearance. Later, a tan to dark brown color will develop. Circular lesions are common on fruit, and will appear water-soaked and sunken. The surface of the lesion may be covered in a thin, yeasty film, particularly in damp weather, made up of mycelium and sporangia of P. capsici. The plant parts affected by Phythophthora blight differ between hosts, as shown in the following table.
| Host crop | Susceptible tissues |
|---|---|
| Cantaloupe | leaves, fruit* |
| Cucumber | leaves, fruit* |
| Eggplant | crown, leaves, fruit* |
| Pepper | roots, crown*, stem*, leaves, fruit* |
| Pumpkin | crown*, stem*, leaves, fruit* |
| Summer squash | crown*, stem*, leaves, fruit* |
| Tomato | crown, stem, fruit* |
| Watermelon | fruit* |
| Zucchini | crown*, stem*, leaves, fruit* |
Plant mortality is commonly seen in hosts with highly susceptible crowns and stems, while crops such as cantaloupe, cucumber, and watermelon will appear relatively healthy until fruit set.
Phytopthora blight is favored by warm, wet conditions. Initial infections arise primarily from resting spores (oospores) on crop residue that germinate and produce sporangia. Sporangia release zoospores, or swimming spores, that will actively move in water films to plant parts. Numerous sporangia are then produced on infected plants that provide inoculum for secondary cycles. The pathogen is also spread by splashing of water and infested soil onto the host, movement of infested soil by human activity, and on infected transplants. Under favorable conditions, disease spread is rapid and often devastating.
Management of Phytophthora blight can be difficult once the pathogen has become established in a field. Individual tactics are not effective because of the wide host range and persistent nature of P. capsici, whose oospores can survive for 5 years (or longer) in the absence of a host. Planning a management strategy for Phytophthora blight must begin prior to planting a crop. Once started, epidemics of the disease are nearly impossible to stop! Growers should avoid planting crops susceptible to P. capsici in fields where Phytophthora blight has been historically high. Rotations of 3-4 years away from susceptible crops should be implemented to keep P. capsici populations low. Fields should be prepared to minimize areas that promote standing water - install drain tiles if needed and break up hardpans. The pathogen requires free water to develop and spread, and wet spots are usually the first place that Phytophthora blight appears. Plant into raised beds, which will promote drainage; fill in depressions around transplants with soil to eliminate pockets that will collect water. Do not use surface water to set transplants or irrigate the crop. Phytophthora capsici can be found readily in ponds and creeks and can be established in clean fields that are irrigated with surface water. Equipment, vehicles, and feet should be sanitized when moving from infested to clean fields. Host resistance is largely unavailable for most crops; however, a few lines of pepper that are tolerant to P. capsici are available. These include 'Aristotle', 'Paladin', 'Revolution', and 'Emerald Isle'.
Fungicides and fumigants are labeled for many of the crops susceptible to P. capsici. Early applications can reduce the incidence and severity of disease; however, fungicides alone will not provide adequate control of Phytophthora blight and should be used as part of a comprehensive management plan. Pre-plant fumigation with chloropicrin-containing products or metam sodium has been shown to reduce pathogen populations and delay the onset of disease in problem fields. Mefenoxam (Ridomil Gold or Ultra-Flourish) can be applied at 0.5 lb a.i./A (1 pt of Ridomil Gold or 1 qt of Ultra-Flourish) prior to transplanting peppers and eggplant, followed by up to two supplemental applications of 0.5 lb a.i./A. Two fungicides on the market can be used after transplanting or seeding to suppress Phytophthora blight. Acrobat is labeled for suppression of crown rot and fruit blight on peppers and cucurbits, while Tanos, a new material from DuPont, is labeled for use on peppers and cucurbits for suppression of foliar and fruit blight only. To be effective, these materials should be applied before symptoms appear as part of a regular fungicide program. See product labels for rates and application directions and restrictions.
For several years, Chipco Signature® (active ingredient fosetyl aluminum) has been used widely in tank-mixes for disease control on creeping bentgrass putting greens. There also have been periodic research reports (including at UK) showing that certain tank-mixes which included Chipco Signature® sometimes provided improved turfgrass quality independent of the control of known diseases. Reasons for this improved activity are not fully understood, but I suspect that the "inert" components of the formulation may have some beneficial effect on turfgrass physiology, providing some increase in tolerance to environmental stresses under some conditions. It should be noted that the improved stress tolerance sometimes seen with these tank-mixes is not a "magic bullet" against moderate to severe environmental stress under all circumstances.
When absorbed by plants, fosetyl Al is broken down to release phosphite ions (PO3-) in the plant tissue. (The phosphite ion is sometimes referred to as phosphonate). The way in which the phosphite ion controls disease is complex and still somewhat mysterious. To a degree, phosphite can inhibit growth and sporulation of disease-causing organisms, thus acting as a direct fungal toxin like most other fungicides. However, phosphite is also is known somehow trigger increased biochemical plant defenses, which is not typical of most products sold as fungicides.
In February 1995, fosetyl-Al came off patent, and within a short time other phosphite-containing products came to market. Given the growth in the availability of phosphite-containing fungicides, we conducted a field study in 2003 & 2004 to test a selection of these. Our expectation was that they would provide essentially equivalent control, but we were surprised to find some differences in performance.
Key Features of Study Design
The site was a soil-based 'Penncross' creeping bentgrass putting green (mowing height 0.188 in.). The site received nitrogen twice in the autumn and early winter. Preceding and during summertime test periods, nitrogen and irrigation inputs were minimal in order to provide a moderate level of stress on the turf.
Each test included both a "negative control "(plots treated with water only) and a "positive control" (plots treated with a spray program expected to give good control of diseases at this site). In both years of the study, the positive control was a biweekly tank-mix of Chipco Signature® mixed with a full rate of an alternation of Chipco 26GT® or Daconil Ultrex® (see tables for details). All phosphite fungicides tested were used at their full application rate in combination with a half-rate of Chipco 26GT® alternating with Daconil Ultrex® (referred to below as phosphite fungicide programs). We used half-rates of Chipco 26GT® and Daconil Ultrex® in order to put the phosphite fungicides through stringent testing conditions. Because we used the contact fungicides at half-rates, another experimental control was the application of half-rates of Chipco 26GT® alternating with Daconil Ultrex® but without a phosphite fungicide. Finally, in 2004, we added another experimental treatment where we substituted Chipco Aliette® for Chipco Signature® to test the effect of the green dye in the latter, and we added Magellan, another phosphate fungicide.
Summary of Results
o Dollar Spot Control
All of the phosphite fungicide programs tested provided good control of dollar spot in both years of testing. Unexpectedly, however, we did see differences among the phosphite spray programs, especially in the 2003 season when dollar spot was more severe. On most assessment dates, there was no significant difference in dollar spot control achieved by the phosphite fungicide programs, but in later assessment dates, small but statistically significant differences emerged, with all products tested providing less control than the Chipco Signature® program in late July (table 1).
o Turf Quality
Turf quality ratings that did not include damage from dollar spot were made; thus, turf quality results reported here are independent of dollar spot damage. In both years of testing, all phosphite fungicide programs tested provided improved turfgrass quality as compared to the water-treated control. However, statistically significant differences were evident among phosphite fungicide programs in 2003, with all products tested providing some reduction in turf quality compared to the Chipco Signature® program in several assessments (table 2). In 2004, no statistically significant differences in turf quality among phosphite spray programs were evident (data not shown). The generally mild temperatures in 2004 coupled with mild rainfall deficits of short duration resulted in lower levels of stress on the turf than in 2003.
Conclusion
The phosphite fungicide programs tested all provided good control of dollar spot and some improvement in turfgrass quality. However, our data revealed unexpected but statistically significant differences in both disease control and turfgrass quality among the products tested, especially under more stressful growing conditions. The differences among phosphite fungicide programs typically were modest, but small improvements may be meaningful given the high aesthetic expectations and the pronounced agronomic stress that can occur on putting greens.
Although most of these products differ slightly in chemistry of the active ingredient (different cations associated with the phosphite ion, for example), it seems unlikely that this would account for the observed differences in performance. We suspect that the differences in performance we observed are due to differences in formulation (inert ingredients and other aspects of formulation, many aspects of which are proprietary). We currently are participating in an ongoing multi-state study led by Dr. Erik Ervin at Virginia Polytechnic Institute which will hopefully shed some light on this question.
Table 1. Dollar Spot Control, 2003 Test
| Number of dollar spot infection centers/plot² | |||||
|---|---|---|---|---|---|
| Treatment and rate/1000 sq ft¹ | 10 Jun | 17 Jun | 2 Jul | 15 Jul | 30 Jul |
| Experimental Controls | Water | 14.3 a | 37.3 a | 38.3 a | 72.0 a | 57.3 a |
| Signature 80WG 4 oz + Chipco 26GT 2SC 4 fl oz alternate Signature 80WG 4 oz + Daconil Ultrex 82.5WDG 3.2 oz |
2.7 b-e | 0.0 f | 0.0 c | 0.3 cd | 0.0 i |
Chipco 26GT 2SC 2 fl oz alternate Daconil Ultrex 82.5WDG 1.6 oz |
2.0 cde | 1.0 def | 0.0 c | 0.7 cd | 5.7 cde |
| Phosphite Fungicide Programs Signature 80WG 4 oz + Chipco 26GT 2SC 2 fl oz alternate Signature 80WG 4 oz + Daconil Ultrex 82.5WDG 1.6 oz |
0.7 de | 0.3 ef | 0.0 c | 0.0 d | 1.7 ghi |
| Resyst 45.8%SL 5 fl oz + Chipco 26GT 2SC 2 fl oz alternate Resyst 45.8% 5 fl oz + Daconil Ultrex 82.5 WDG 1.6 oz |
3.7 a-d | 1.3 def | 1.0 bc | 1.0 cd | 7.7 b-e |
| Vital 4.2L 6 fl oz + Chipco 26GT 2SC 2 fl oz alternate Vital 4.2L 6 fl oz + Concorde 82.5WDG 1.6 oz |
1.3 cde | 1.0 def | 0.7 bc | 2.0 c | 10.0 be |
| Alude 5.17L 5 fl oz + Chipco 26GT 2SC 2 fl oz alternate Alude 5.17L 5 fl oz + Daconil Ultrex 82.5WDG 1.6 oz |
3.0 b-e | 1.3 def | 0.0 c | 1.0 cd | 9.3 bcd |
¹ One of the two tank-mixes was applied alternately at two week intervals between 28 May and 23 Jul.
² Means within the same column followed by the same letter are not significantly different, Waller-Duncan k-ratio t-test (k=100, P< 0.05). Arithmetic means are presented with statistical groupings based on log10 transformed data.
Table 2. Turf Quality, 2003 Test¹
| Creeping bentgrass³ | Poa annua | Overall turf quality | ||||
|---|---|---|---|---|---|---|
| Treatment and rate/1000 sq ft² | 2 July | 22 July | 25 June | 10 July | 22 July | 5 Aug |
| Experimental Controls | ||||||
| Water ………………………………………………………. | ND(d) | ND | ND | ND | 4.7 e | 3.3 hi |
| Signature 80WG 4 oz + Chipco 26GT 2SC 4 fl oz alternate Signature 80WG 4 oz + Daconil Ultrex 82.5WDG 3.2oz |
ND | ND | ND | ND | 7.7 a | 6.3 abc |
| Chipco 26GT 2SC 2 fl oz alternate Daconil Ultrex 82.5WDG 1.6 oz ……………………… |
ND | ND | ND | ND | 6.8 abc | 4.7 efg |
| Phosphite Fungicide Programs | ||||||
| Signature 80WG 4 oz + Chipco 26 GT + 2SC 2 fl oz alternate Signature 80WG 4 oz + Daconil Ultrex 82.5WDG 1.6 oz |
8.0 a | 8.0 a | 7.3 a | 6.3 a | 7.5 a | 5.3 b-e |
| Resyst 45.8%SL 5 fl oz + Chipco 26GT 2SC 2 fl oz alternate Resyst 45-8%SL 5 fl oz + Daconil Ultrex 82.5WDG 1.6 oz |
7.3 a | 6.3 b | 5.3 b | 4.3 b | 6.3 bc | 5.0 d-g |
| Vital 4.2L 6 fl oz + Chipco 26GT 2SC 2 fl oz alternate Vital 4.2L 6 fl oz + Daconil Ultrex 82.5WDG 1.6 oz |
7.7 a | 6.0 b | 5.3 b | 5.0 ab | 5.7 cde | 4.3fgh |
Alude 5.17L 5 fl oz + Chipco 26GT 2SC 2 fl oz alternateAlude 5.17L 5 fl oz + Daconil Ultrex 82.5WDG 1.6 oz …….. |
7.3 a | 6.0 b | 5.3 b | 3.7 b | 6.0 bcd | 6.7 ab |
¹ Scored on a 1-9 scale, where 9 = excellent turf health. Dollar spot damage was excluded from
turf quality assessments.
² One of two tank-mixes was applied alternately at two week intervals between 28 May and 23 Jul.
³ Means within the same column followed by the same letter are not significantly different,
Waller-Duncan k-ratio t-test (k=100, P< 0.05).
(d)ND=no data.
Sycamore anthracnose. Anthracnose symptoms have become very noticeable on Sycamore in the past week. Out in the countryside, from a distance, it appears that all the leaves on internal and lower branches have suddenly turned brown. A closer look at infected green, expanding leaves reveals irregular dark, necrotic blotching centered along the leaf veins or leaf edges. These dark blotches may turn a tan color as the diseased areas of the leaves dry out. In the same trees, tips of young shoots with newly expanding leaves are wilting and dying because of twig or shoot infection. The nearly continuously wet and cool weather the last week of April very likely provided disease-favorable conditions for anthracnose infection. While symptoms developed, the warm, dry weather the first half of May provided at least a temporary halt to infections. With a resumption of rainy weather, the disease could continue to spread in the foliage. Symptoms on some trees are quite severe.
The incidence and severity of anthracnose diseases of landscape trees varies with the season. When we have cool springs with extended periods of wet weather, antracnose diseases are worse. At least for part of the spring, that kind of weather has occurred. As the weather dries and becomes warmer, sycamores normally put out new, healthy foliage by early summer. However, the legacy of crooked branches (because lateral shoots take over when terminals are killed by anthracnose) and multiple shoots arising from the base of a killed branch may be still visible many years later. Sycamore anthracnose is caused by the fungus Apiognomonia veneta, and the fungus attacks both sycamore and London plane.
Ash anthracnose. Brown blotches along leaflet edges can be seen now on new ash foliage. Many of these infected leaflets will begin to drop soon and carpet the walks and lawns nearby. Ash anthracnose is not normally a threat to ash tree survival, however, and the ash trees will simply put out a new set of leaves. The ash anthracnose fungus is a species of Discula.
Anthracnose management in landscape trees. When trees are forced to refoliate, carbohydrate reserves are depleted, so it is important to maintain good growing conditions for infected trees.
Shade trees and woody ornamentals under stress from previous defoliation, sun scald, drought, soil compaction, incompatible site selection, or mechanical injury are especially vulnerable to borer attack, as are young trees for the first two years after transplanting. Our common borers include the larvae of several species of moths (clearwing borers) and beetles (bark beetles, shothole borers, flatheaded and roundheaded borers). Most borer infestations are discovered when emergence holes are seen in dying branches or trunks or when larvae are found when removing damaged limbs. The adults are rarely seen.
While insecticide applications may help to reduce re-infestation by borers, it is unlikely that they will prevent death of heavily infested trees. Preventive sprays applied to the trunk and/or limbs provide a barrier to kill adults or larvae as they try to chew into the bark. In most cases, treatments will not kill borer larvae that are already present.
The cancellation of Lindane and removal of homeowner uses of Dursban (chlorpyrifos) has changed the options for borer control on trees and shrubs. Homeowners have two alternatives. The first is a trunk or limb spray with an insecticide containing the pyrethroid permethrin and having borer control instructions on the label. These conditions are met by Astro 3.2 EC and Green Light Borer Killer which are labeled for bark beetles, clear wing borers, flatheaded borers and roundheaded borers. There are several other shade tree and ornamental insecticide products for home use that contain permethrin but they are labeled for foliar pests and do not include borer control on the label.
The second homeowner option is Bayer Tree & Shrub Insect Control, which contains the active ingredient imidacloprid. This systemic insecticide is applied as a soil drench with the rate determined by trunk circumference. The label includes flatheaded and roundheaded borers but there are no specific directions on timing of the application.
Certified commercial applicators have a longer list of spray options - bifenthrin (Onyx Insecticide), carbaryl (Sevin 80 WSP or SL), chlorpyrifos (Dursban 50W), in addition to permethrin (Astro 3.2 EC). Several formulations of imidacloprid are labeled for control of flatheaded and roundheaded wood borers. Examples include Discus Nursery Insecticide (cyfluthrin + imidacloprid) and Marathon 60 WP, Marathon II, Merit 2F, and Merit 75 WP (imidacloprid).
Timing of borer control sprays is very important. Borer species that have very short, distinct flight times may be susceptible to a single insecticide application but several treatments may be necessary for species that are active over a period of several weeks. ENT-43, Insect Borers of Trees and Shrubs, and Entfact 437, Borers That Attack Landscape Pines, give specific information on important pests.
Here are short profiles of our common borers:
Clearwing moth borers are day-flying moths that resemble wasps in appearance and behavior. Their larvae (cream-colored caterpillars with distinct heads and segmented thoracic legs) bore into wood and expel coarse brown frass from cracks in the bark. Examples include - ash borer, banded ash borer, dogwood borer, lesser peachtree borer, lilac borer, and oak borer.
Flatheaded borers are beetles with a blunt anterior ends that taper to pointed abdomens. Some species have a distinct metallic sheen. The legless larva is white to cream-colored with a distinct broad, flat area right behind the head. Exit holes through which adults leave trees have a distinct D shape. Examples include the flatheaded appletree borer and the bronze birch borer.
Roundheaded borer adults (longhorned beetles) have long, cylindrical bodies with antennae that often are longer than the body. The white to cream-colored legless larva is cylindrical and does not have a distinct expanded area at the anterior end. Most roundheaded borers develop in weak, dying, or felled trees, or dead limbs. Their exit holes are round.
Bark beetles or shothole borers include many species from a variety of families. The adults are small, usually dark brown to black beetles. The legless larva is C-shaped with a yellow to brown head. The small round exit holes of bark beetles may riddle infested trees.
Samples recently diagnosed have included bacterial blackleg, Pythium root rot, Rhizoctonia damping off, target spot and cold injury on tobacco; Mycosphaerella leaf spot on strawberry; fire blight on apple (as well as on ornamental pear); leaf curl on peach; plum pockets on plum; Pythium root rot, Botrytis stem canker, chemical and cold injury on tomato; scab on potato; nutritional problems on muskmelon; and Pythium damping off on watermelon.
On ornamentals and turf, we have diagnosed Rhizoctonia root rot on foxglove; Botrytis blight, Pythium root rot, and Rhizoctonia root rot on geranium; Alternaria leaf spot on impatiens; Pythium root rot on petunia; anthracnose on ash and sycamore; Pseudonectria canker on boxwood; sawfly on pine; winter injury on various ornamental species; yellow patch and Pythium root rot on bentgrass; and necrotic ringspot on bluegrass.
UKREC-Princeton, KY, May 7 - May 13, 2005 | Black Cutworm
| 11
| True Armyworm
| 1
| Corn Earworm
| 2
| European Corn Borer
| 1
| | |
For information on trap counts in southern Illinois visit the Hines Report at - http://www.ipm.uiuc.edu/pubs/hines_report/comments.html The Hines Report is posted weekly by Ron Hines, Senior Research Specialist, at the University of Illinois Dixon Springs Agricultural Center.
NOTE: Trade names are used to simplify the information presented in this newsletter. No endorsement by the Cooperative Extension Service is intended, nor is criticism implied of similar products that are not named.
Lee Townsend
Extension Entomologist