MAPLE PETIOLE BORERS may cause leaf drop of maples (405)
APHIDS (103) on maples and other shade trees
SPRUCE SPIDER MITES (438) can cause yellowing of spruce, hemlock, arborvitae, and other hosts.
COLORADO POTATO BEETLES will be out soon (Entfact 312)
MAPLE PETIOLE BORERS may cause leaf drop of maples (405)
APHIDS (103) on maples and other shade trees
SPRUCE SPIDER MITES (438) can cause yellowing of spruce, hemlock, arborvitae,
and other hosts.
In last week's article, we reviewed the epidemiology and management of Pythium root rot in the float system. In the final installment of this series, we'll cover diseases of tobacco transplants caused by Rhizoctonia solani and by bacterial plant pathogens.
Soreshin and Damping-off
As you might imagine, the float system creates near-ideal conditions for Rhizoctonia solani to grow and infect tobacco seedlings. Rhizoctonia means "root killer" in Greek, and is an accurate description of what this fungus can do to young tobacco transplants. Damping-off, or soreshin, may occur early in the development of the tobacco seedling and first appears as a water-soaked lesion at the base of the plant (near the junction of plant and growth media). Later, the lesion will take on a sunken, brown appearance and will eventually girdle the plant. Girdled seedlings will fall over and eventually die. Seedlings with mild infections of R. solani that are later transplanted may contribute to large-scale outbreaks of soreshin in the field, and may also be more susceptible to black shank.
Moisture, a readily available commodity in the float system, and temperatures above 70 °F are optimal for growth of R. solani. A common inhabitant of agricultural soils, R. solani can survive on organic matter and will colonize growth media used in tobacco transplant production. Primary infections occur when actively growing hyphae, or fungal threads, come in contact with roots or stems. Hyphae then form infection cushions that produce enzymes that will degrade plant tissues. The fungus derives nutrition from the decomposed portions of the plant and is therefore considered a "necrotroph". Infections can spread from plant to plant, and organic matter (plant debris) can serve as a bridge between infected and healthy seedlings. Survival structures called sclerotia are formed after the food source has been exhausted.
Infested soil or Styrofoam trays are the most common inoculum sources of R. solani. As with Pythium spp., tobacco roots embedded in Styrofoam float trays will serve a source of inoculum of R. solani (in the form of sclerotia or dormant hyphae) if trays are re-used.
Rigorous sanitation is the chief means by which soreshin is managed in the float system. The first step is to limit the amount of fungal inoculum in the transplant system. Growers should consider using new Styrofoam trays for each transplant cycle. This is an extra expense and may not be an economically viable option for some growers. Used trays should be steam-heated to 165-170 °F for 30 minutes (after the heating chamber reaches operating temperature). Methyl bromide, though effective, is expensive, dangerous, and may be difficult to obtain. Dipping used trays in bleach or other disinfectants will not eliminate R. solani from old trays because the chemicals cannot penetrate and reach pathogen-infested roots that have grown into the tray. Do not re-use growth media. Remove as much leaf debris as possible during clipping operations. Avoid prolonged periods of leaf moisture; ensure adequate ventilation of float systems. Complete control of soreshin with fungicides is unlikely; however, some suppression can be achieved with Dithane DF. Dithane DF can be applied at a rate of 0.5 lb/100 gallons of water once plants have reached the size of a dime. Begin applications before symptoms appear and continue on a 5-day schedule.
Target Spot
Target spot is caused by a different strain of R. solani, AG (anastomosis group)-3, than the one that causes soreshin. Target spot begins in localized areas, or foci, and commonly occurs after the plant canopy has fully formed. Small, water-soaked lesions appear on leaves and will expand rapidly under conditions of warm temperatures (> 75 °F) and high humidity. Lesions normally have a transparent-light green appearance and may be surrounded by a chlorotic (yellow) halo. Dead leaves will turn brown and adhere to the float tray. Fungal growth may be present on leaves and stems in the form of web-like strands (mycelia).
Initial infections usually arise from inoculum on R. solani-infested trays, although inoculum may also enter the transplant facility from outside sources. Basidospores, generated by the sexually reproducing phase of this fungus(Thanatephorus cucumeris), are released under favorable conditions and contribute to spread of the disease within the transplant facility.
As with soreshin, sanitation and good growing practices are the best defense against target spot. Fair suppression of target spot can be obtained with Dithane DF applied as directed by the label.
Bacterial Soft Rot (Blackleg)
Warm, wet conditions in the transplant facility provide an optimal environment for Erwinia carotovora subsp. carotovora and other bacterial species that cause soft rot, or blackleg. Seedlings with bacterial soft rot appear rotted or slimy and may exhibit a jelly-like growth along with a foul odor. Systemic infections result in darkened stems that advance on one side of the seedling primarily.
Several factors can lead to severe outbreaks of bacterial soft rot. These include excessive nitrogen (when growers "push" transplants), warm (>75 °F) temperatures, a dense canopy, and wounding of seedlings. The latter occurs routinely during clipping and can lead to rapid spread of bacterial soft rot if carried out when plants are wet. Cultural practices are the most important ways to prevent of bacterial diseases. Avoid excessive nitrogen, provide adequate ventilation, and clip plants after they have been allowed to dry properly. Remove leaf debris after clipping operations. Streptomycin can be used in outdoor plant beds to suppress bacterial diseases, but is not specifically labeled for use in transplant facilities; however, this use is not specifically prohibited either. Three-five gallons applied to 1000 sq. feet of a 100-200 ppm solution of streptomycin has been shown to suppress bacterial diseases. Growers who choose to apply streptomycin in the float system must accept all liability and should be aware that phytotoxicity may occur with higher rates of the material.
Blue Mold Status
Active blue mold has not been reported in the U.S. as of 22 April 2005. A blue mold advisory will be issued when the disease is reported in the U.S.
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".
Neonicotinoid seed treatments (Gaucho, Gaucho Extra, Prescribe, Poncho 250, Poncho 1250, and Cruiser Extreme Pak) for corn have been very popular among corn producers the past two years. These products have to be ordered on the seed when the seed order is placed. While the duration of control and the spectrum of pests controlled varies with the type and amount of the insecticide placed on the seed, the neonicotinoid seed treatments can suppress a wide range of insect pests including black cutworm, wireworms, white grubs, corn flea beetle, seedcorn maggot, corn leaf aphid, and corn rootworms. This class of insecticide is taken up systemically by the seedling and moved throughout the plant.
Hopperbox insecticide treatments for corn have been available for many years and have used Lindane, Lorsban, Diazinon, or, more recently, Permethrin as the chemical to suppress soil insect pests that could attack the seed or seedling. These products have good soil activity, but are not systemic. There are a few new hopperbox seed treatments now available for corn that use imidacloprid as the insecticide, this is the same active ingredient found in Gaucho, Gaucho Extra, and Prescribe. So how will the hopperbox imidacloprid treatments compare with the pre-applied imidacloprid treatments? It is important to look at the chemical per seed when comparing these products, as the greater the amount chemical can provide higher levels of suppression. The two imidacloprid hopperbox treatments will provide a rate of 0.16 mg imidacloprid per kernel, assuming uniform mixing and that all of the product ends up on the seed rather than the equipment. This rate is comparable to the Gaucho rate, but consideralby less than Prescribe (1.34 mg/kernel) and Gaucho Extra (0.6 mg/kernel). The hopperbox imidacloprid labels list the same pests controlled as the Gaucho label, wireworms, white grubs, corn flea beetle (through the first leaf stage), seedcorn maggot, and seedcorn beetle. Both also list fire ants, but those are not an issue for Kentucky.
For information about corn pests, visit
"Insect Management Recommendations".
The potential threat of Asian soybean rust this year is on the minds of soybean producers. In discussions with producers, some are considering a change in their production practices because of the potential threat of this disease.
There are still many uncertainties about soybean rust and its impact including: our lack of experience in dealing with this disease; or, when it may arrive during the growing season (early or late); or, if it will even be present in Kentucky; or, how widespread and severe its distribution will be; or, if the weather will be favorable for the disease. If rust becomes an issue the only certain management strategy is proper fungicide applications (products, timing, coverage, etc.). Some other management strategies may be effective, but without further evidence or experience, a change in production methods is not a recommended strategy.
Most production factors will not affect whether a field does or does not become infected with soybean rust; however, a change in certain production practices could reduce yield potential, even if soybean rust is not present. The best management approach for this disease is to use production practices that maximize yield potential. If rust occurs, the additional costs for fungicides will be a worthwhile investment to protect that high yield potential.
Production practice changes being considered by some producers are: soybean varieties/maturity groups, planting date, row spacing, and plant populations.
Soybean Variety/Maturity Group: Currently, there are no varieties available with resistance to soybean rust and it will be at least 5 to 10 years before resistant varieties are developed. Therefore, select varieties with maximum yield potential, based on performance tests, from maturity groups that are adapted to your area or region. In Kentucky, adapted varieties include those from late MG III, MG IV, and early MG V for various regions of the state.
While there may be some logic for selecting varieties from ultra-early maturity groups to possibly reduce the impact of soybean rust (or to reduce the number of needed spray applications), the yield potential of these unadapted maturity groups is reduced. Even without soybean rust, their yield typically would be less than that of varieties from adapted maturity groups.
Planting Date: Plant during the optimum planting period. Begin planting when soil temperature is at least 60-65° F to promote rapid emergence and uniform stands. This usually occurs from late April to early May in Kentucky. Complete planting by early June to avoid a yield decline.
While there may be some logic for extremely early plantings (before soil temperature reaches 60° F) to reduce the impact of soybean rust, planting date studies show no yield advantage (and often a yield loss) for extremely early plantings over traditional planting dates. With very early plantings, stand uniformity and plant vigor is often reduced.
Spreading out planting dates within the optimum planting period (along with some variation in soybean variety maturity) is a good practice that would result in differential stages of soybean development among your fields. If soybean rust occurred, this would provide a better opportunity (particularly with limited sprayer capacity) to spray soybean acres in the time necessary to protect yield. Based on experiences in Brazil, and unless our experience in the U.S. proves otherwise, significant rust infection usually does not occur until R1 (beginning bloom) or later and fungicide applications prior to R1 are usually not beneficial.
A University of Kentucky publication (AGR-184) predicts when soybeans will first flower (growth stage R1) based on different planting dates and maturity groups. It can also be found at the Grain Crops Extension website: www.uky.edu/Ag/Agronomy/GrainCrops/.
Row Spacing: There was a 12-15% average yield advantage for narrow rows (15 inches or less) in previous row spacing research at the University of Kentucky. This yield advantage was greater in high-yield environments and also greater and more consistent in late (double-crop) plantings. The great majority of soybeans are planted in narrow rows in Kentucky.
Some producers are considering a switch back to 30-inch rows to better facilitate equipment for late-season spray applications. The yield loss of run-over rows from sprayer traffic (which will vary according to sprayer boom width) in narrow row soybeans will be much less than the yield gained for using narrow rows. A good alternative, by coordinating planter and sprayer size, is to establish skip-rows (unplanted rows) in your narrow row system to facilitate wheel tracks for late-season spray applications. The yield loss for unplanted rows would be very minimal (or non-existent) with a slight savings in seed costs.
Even without soybean rust, wide rows would have a 5 to 6 bu/acre yield disadvantage. If soybean rust occurs, the yield advantage for narrow rows should more than compensate the cost of a fungicide application to protect that yield gain.
Plant Populations: It is not certain what effect plant density may have on soybean rust; most likely it will not be significant. However, many soybean fields are planted using excessive seeding rates. Now may be a good time to reduce seeding costs, without sacrificing yield.
Studies have shown that soybean plant populations as low as 100,000 plants per acre, in many cases, yield as well as 200,000 plants per acre. Reducing seeding rates to achieve final plant densities of 110,000 to 130,000 plants per acre would result in a seed cost savings of over $10 per acre, particularly with higher priced seed. If soybean rust occurs, the seed cost savings could be better invested in fungicides.
In summary, without further evidence, or until our experience in the United States proves otherwise, the best management approach for soybean rust is to use production practices that maximize yield potential. To change certain production practices because of the potential threat of soybean rust, would likely result in reduced yield potential. This inherent loss in yield potential would occur, irregardless of whether soybean rust became an issue this year. It would be more justifiable to maintain those production practices that maximize yield potential. If rust occurs, then additional costs for fungicides would be a good investment to protect that maximum yield potential.
For more information about soybean pests, visit
"Insect Management Recommendations".
Fusarium head blight (FHB) of wheat, and deoxynivalenol (DON) accumulation in harvested grain, are periodically very serious problems in Kentucky. The 2004 FHB epidemic was the worst since 1991, and many producers experienced significant yield and grain quality losses.
On April 22, 2005, the Kentucky Department of Agriculture, after consultation with the Environmental Protection Agency (EPA), declared a crisis exemption which allows producers to apply Folicur 3.6F to suppress FHB/DON through May 6, 2005. Kentucky submitted a section 18 application to EPA for this use in mid-January, 2005, but for a variety of reasons a ruling by EPA was delayed. This temporary measure of declaring a crisis exemption was carried out to assist wheat producers whose crops will be flowering before May 7. However, the section 18 application is still "in play" and hopefully will be approved by EPA to assist producers whose crops flower after May 7.
Folicur is manufactured by Bayer CropScience. This new fungicide tool will reduce the risk of FHB and DON when used with other FHB/DON management tactics (see http://www.ca.uky.edu/ukrec/newsltrs/news03-2.pdf).
Let me say up front that Folicur is not a "silver bullet" for managing FHB/DON. A great deal of research suggests that about 30-40% reduction in FHB symptoms and DON accumulation is a reasonable expectation for winter wheat. Sixty percent control or more has been achieved in rare field studies in the U.S., but these are atypical results. In other words, do not expect Folicur to provide the same level of FHB/DON control as you have come to expect when fungicides are used to control other wheat diseases. The key is to think in terms of disease suppression, not control. Nevertheless, a 30-40% reduction in FHB and DON could have a significant economic impact locally, and state-wide, if FHB is moderate to severe in 2005. But be advised that significant losses due to FHB and/or DON may occur even where Folicur has been applied if weather conditions favor severe FHB this spring,
The crisis exemption allows for a single ground or aerial application of 4 fl oz/A of Folicur 3.6 F to wheat through very early flowering (Feeke's stage 10.51). Applications cannot be made within 30 days of harvest. A copy of the crisis exemption label must be in your possession at the time of application.
Excellent fungicide coverage on wheat heads is crucial to achieve the greatest possible FHB/DON suppression. This is no small challenge since most spray systems used in wheat were developed to deliver pesticides to foliage (horizontal structures). In order to maximize coverage on heads (vertical targets), significant changes may need to be made to the sprayer boom system. Also, discipline must be exercised to ensure that proper sprayer pressure and volumes are used.
For ground application, research has shown that best head coverage is achieved with a double-swivel nozzle configuration of XR8001 flat-fan nozzles oriented forward and backward at a 45 degree angle. Acceptable coverage can also be achieved with a single nozzle configuration using TwinJet TJ8002 nozzles. When using either the double-swivel nozzle or the single TwinJet configuration, best head coverage is achieved when the boom is set 8 to10 inches above the heads, spray pressure is 30 to 40 psi OR 80 to 90 psi, fungicides are delivered in 15 or more gallons or water/A, and ground speed does not exceed 8 mph during application.
For aerial application, nozzles should be angled to direct spray 90 degrees to the direction of travel. Spray droplet size should range from 300 to 400 microns and Folicur should be delivered in no less than 5 gallons of water/A. It is best to spray early in the morning or at other times when heavy dew is present. This will facilitate fungicide coverage on heads.
Regardless of the method of application, be sure to tank mix the lowest rate of a spray surfactant with Folicur to enhance coverage and optimize treatment effectiveness.
Folicur must be applied at a specific time, early flowering, in order to be effective. The optimal time for application is 25% of primary heads, scouted at several random sites in a field, showing anthers (pale, yellow-green structures about 1/8-in-long). Much beyond 25%, and it may be too late. The flip side - applying Folicur before full head emergence/early flowering can seriously compromise FHB/DON suppression. This brings up a point of tension that wheat producers may face this spring. Delaying application of Folicur to achieve FHB/DON suppression could allow for excessive build-up of other fungal diseases. Conversely, application of other labeled fungicides before full head emergence will control other diseases, but will have no impact on either FHB or DON. I would advise growers that foliar disease development should take precedence since little is to be gained by suppressing FHB/DON if serious losses are incurred by allowing fungal diseases to develop.
One desire we all have is for fungicides to be used only when needed. Regular field scouting for foliar fungal diseases has been successfully used by growers for many years to determine if and when to spray fungicides. However, this is not possible with FHB since once symptoms are present it is TOO LATE to spray with Folicur. Below are some general guidelines to help you determine if you should spray Folicur for FHB/DON suppression this spring:
If most or all of the above conditions exist when the crop is at 10-15% flower, you should consider spraying Folicur within one or two days.
An exciting new tool that can be used to help determine the FHB risk is a new web-based, disease forecasting model recently made available by Penn State University, Ohio State University, and the U.S. Wheat and Barley Scab Initiative. This forecasting model, which is reported to be 80+% accurate in predicting conditions conducive for FHB epidemics, utilizes realtime weather data from numerous National Weather Service stations within each state. When you enter into the "Risk Map Tool" section of the FHB prediction center home page, you will be asked if you are growing winter or spring wheat and, if winter wheat, whether the field has corn residue that covers 10% or more of the soil surface, regardless of tillage system used. At that point you will come to US map and are asked to click on your state. This will bring you to the main FHB Risk Management Tool page.
The FHB Risk Management Tool page will have a map of Kentucky showing the locations in the state where the weather data are being retrieved. To the upper left corner of the page is a calendar section labeled "Flowering Date". This section needs a bit of explaining. You will note right away that the model will only let you input a "flowering date" as late as the current day. It also covers the preceding 7 days. So, if you estimate your crop will flower on May 7, but it is only May 3, the best you will be able to do is to determine if the weather on May 3 is favorable for FHB, and establish what the FHB risk has been for the preceding 7 days (April 26 to May 2). Of course, since your crop is not flowering, the real FHB risk is zero, no matter what the forecast model says. Nevertheless, that information will tell you if FHB is brewing or not. My advice is to begin determining the FHB risk using this model several days out from crop flowering. Keep checking your wheat and keep checking the model every 1 to 2 days. By the time your crop reaches 10 to 15 % bloom, you will have a good feel for the FHB risk in your area. If the forecast model says the FHB risk is high (medium if you are not a risk taker), and the forecast matches your local weather reality, then you might consider spraying Folicur within 1 to 2 days.
The web address for the FHB Prediction Center is http://www.wheatscab.psu.edu/. Check it out. Once you actually see it and play around with it, what I have said above will make much more sense. The model does have several practical limitations in predicting final FHB levels; these are clearly discussed within the Prediction Center web site. Perhaps the greatest limitation of the model is that it does not account for weather conditions during flowering and grain fill. This is where the model failed us in 2004. Specifically, disease-favorable weather occurred during late flowering and grain fill and greatly impacted final FHB/DON levels. As I said earlier, the forecast model is 80+% accurate, so final FHB/DON conditions will not always be reflected by the model's risk output. The authors of the model discuss this limitation under "Reality Check" in the "Model Details" section of the Prediction Center.
There should be plenty of Folicur in Kentucky at this time since Bayer moved product into the state as a result of the soybean rust section 18 granted a few months back.
We all hope that FHB is non-existent this spring and that growers achieve record yields and grain quality. However, if this is not the case, wheat producers now have an additional tool to consider, and possibly use, to minimize FHB and DON development this spring.
See "Insect Management Recommendations" for more wheat pest information.
Periodic periods of cool, wet weather in spring favor activity of large patch disease of zoysia, a disease that actually begins in the autumn as this warm-season grass goes into dormancy. Large patch affects zoysia and to a lesser extent, bermudagrass. The disease is caused by certain strains of the common soil-borne fungus Rhizoctonia solani. Turf managers may recognize this fungal name as the same as the cause of brown patch of cool-season grasses such as tall fescue and perennial ryegrass. However, the strains that cause large patch of warm-season grasses are typically distinct from those that cause brown patch of cool-season grasses.
Large patch is favored by chronic high soil moisture. Thus, an important cultural management practice is to improve drainage in affected areas by filling low areas or installing tile drainage. Avoid over-irrigation, especially in spring and autumn. Avoid adding nitrogen fertilizer in September or during periods in spring when the disease is visibly active (indicated by a bright orange color at the patch margin). Large patch is less severe at higher mowing heights, so on fairways, raise the mowing height by 0.25 inch in mid-to late-September. Studies suggest that disease development is not influenced by nitrogen rate and source or by pre-emergence herbicides.
On sites with a chronic history of the disease, one or two preventive fungicide applications can be helpful. Most studies indicate that the damage evident through mid-spring is best controlled with one or two applications in the autumn. (However, ongoing studies at Purdue are raising some questions about this, so watch for continuing insights as those studies continue.)
Make the initial fungicide application when thatch temperatures drop below 70EF, usually in mid- to late September. Although autumn applications are the most important, under Kentucky conditions, re-treatment in late spring is often necessary on zoysia, especially if sustained wet weather occurs in mid- to late spring. If applying fungicide to zoysia in the spring, make the application when the first indication of active disease (a bright orange color at the patch margin) is observed. On bermudagrass, late-spring fertilization with nitrogen will help many swards outgrow the damage without the need for springtime application of fungicide.
When using a fungicide, use the highest labeled rate of the product selected, and apply in a minimum of 2.5 gal water/1000 sq. ft. There is no need to irrigate or syringe after application if clippings are not being removed.
Fungicides with the highest efficacy against large patch include azoxystrobin (Heritage), flutolanil (Prostar), PCNB (Cleary's PCNB, Penstar, Terraclor, Turfcide, and possibly others), and triadimefon (Bayleton).
A case of yellow patch (cool-weather brown patch) was diagnosed last week on a mixed perennial ryegrass/Poa annua sward in Central Kentucky. This disease produces circular patches usually no greater than a foot in diameter of turf with yellowing and blighted foliage. This disease is caused by Rhizoctonia cerealis, a cool-weather cousin of the Rhizoctonia solani strains that cause the diseases mentioned in the previous article.
Normally no treatment is recommended for springtime cases of this disease. Typically the turf will outgrow the damage. Putting greens should be watched, of course, but I wouldn't be concerned except for the Poa annua on the green, since that host is particularly susceptible. On creeping bentgrass, springtime infections typically are confined to leaf blades only; symptoms often disappear without fungicide treatment with the onset of warm weather and regular mowing.
Cultural practices that can help are as follows. Improve soil drainage and reduce excessive thatch. Autumn applications of nitrogen may help the turf outgrow symptoms the following spring, particularly when an application is made after the last mowing. For sites with a chronic, recurring problem, a nitrogen application in November is important in preventing late winter turf damage. Mow as needed to avoid tall, dense growth. Based on the reports I have seen, the most effective choices for preventive treatment are fludioxonil (Medallion) and flutolanil (Prostar). I haven't seen enough data on the efficacy of preventive treatments using azoxystrobin (Heritage) to make a judgment, however, limited field experiences suggest that azoxystrobin (Heritage) is an effective fungicide for curative treatments on Poa annua.
Dogwoods (Cornus florida) continue their popularity as Kentucky landscape trees despite the destructive potential of diseases such as Phytophthora crown and root rot, Discula anthracnose and powdery mildew.
Managing dogwood anthracnose, caused by Discula destructiva. Dogwood anthracnose, also called lower branch dieback, is mainly a problem in heavily shaded landscapes and in the forest. Where it occurs, the disease can cause leaf spots, blotches, blights, twig and branch dieback, and eventual death of the tree. The following suggestions will help reduce dogwood anthracnose:
Managing powdery mildew, caused by Erysiphe pulchra. Powdery mildew occurs in open landscapes as well as in heavily shaded areas. Native dogwoods vary in their susceptibility to the disease - severely affected and lightly affected trees may appear in the same landscape. The disease can be troublesome in nurseries, especially on seedling trees, and is less of a problem in the forest environment.
Managing Phytophthora root and collar rot caused by Phytophthora spp. Several species of Phytophthora are thought to be capable of causing root and collar rot of dogwood. This disease mostly occurs in wet and poorly drained landscape and nursery locations.
Warmer temperatures are triggering the emergence of key horticultural pests. If control is warranted, the time for action is now when pest life stages are most vulnerable. These timely recommendations have been made possible by the phenological management schedule developed by the UK Horticultural Entomology Research Lab. A copy of the table can be found in extension publication ENT-66, Timing Control Actions for Landscape Insect Pests.
Lilac borer/lesser peachtree borer- Adults of both species are, or soon, will be laying eggs on the bark of susceptible plants. Principal hosts for lilac borer include lilac, ash and privet; for lesser peachtree borer, peach, plum, and flowering cherry. Woodborers are among the most destructive and difficult to control pests of landscape plants. The larvae tunnel and feed under the bark of trees and shrubs, destroying water and sap-conducting tissues. This causes a loss of vigor and overall weakening that can eventually kill the tree. Infestation sites also provide entry points for disease organisms. Symptoms include dieback, cankers or cracked bark, and accumulations of sawdust-like frass on the bark or at the base of the tree.
Controlling borers is difficult because there is only a narrow window of opportunity for treatment. Eggs are laid on the bark of preferred hosts and within 1 to 2 weeks, the young borer larvae emerge and quickly tunnel inward. Once inside the tree, the larvae are protected from insecticide sprays. Therefore, the key to control is having a lethal residue of insecticide on the bark to intercept newly hatched borers before they burrow into the tree. Lindane and chlorpyrifos, the perennial 'standards' for borer control, are no longer available and have been replaced by pyrethroids such as Onyx (= bifenthrin, the active ingredient in Talstar, with bark-penetrating solvents), Astro, and Permethrin Pro. The trunk and major limbs of susceptible trees should be sprayed to runoff as specified on the label.
Holly Leafminer- Adult holly leafminers are beginning to fly and lay eggs in newly expanding holly leaves. The small, pinprick feeding punctures and oviposition scars of the tiny adult flies do not harm the tree, but subsequent mining by the larvae is cosmetically unappealing. Control of the egg-laying adults can be accomplished by applying insecticides such as Orthene, Sevin, Talstar or Tempo, just as the newly expanding leaves are unfurling. Control of larvae already in the leaves (mid- to late May) can be attempted with one of the systemic materials, e.g., Cygon, Dimethoate, or Di-Syston. Blue holly is relatively resistant to leafminer injury.
Oystershell Scale - The vulnerable "crawler stage" of the oystershell scale has begun to hatch. Susceptible hosts include lilac, willow, maple, ash, apple, dogwood and others. Infested limbs and twigs are encrusted with 1/8-inch long curved scales that resemble miniature oystershells. Crawlers are susceptible to sprays of 2% horticultural oil, insecticidal soap, Tempo, Scimitar, malathion, and a variety of other conventional insecticides.
Samples diagnosed during the past week have included Pythium root rot on wheat and Pythium root rot, temporary phosphorus injury and fertilizer burn on tobacco.
On greenhouse ornamentals, we have diagnosed powdery mildew on begonia and high pH/high alkalinity on petunia. On landscape ornamentals and turf, we have seen iron deficiency on holly; Kabatina twig blight on juniper and arborvitae; black knot on ornamental cherry; white pine decline; winter injury on juniper, holly and spruce; and yellow patch on turf.
UKREC-Princeton, KY, April 15 - 22, 2005| Black Cutworm
| 2
| True Armyworm
| 14
| Corn Earworm
| 0
| European Corn Borer
| 0
| | |
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