Kentucky Pest News mailings would normally switch to First Class mail at this time of the year. In compliance with a recent administrative decision prompted by postage costs, all departmental mailings with numbers of 200 or greater must be sent using Bulk Rate postage. With 1,300 subscribers, this will affect the KPN. Much of the information in this free newsletter is perishable and delays in bulk mail delivery may make recommendations or information in the articles obsolete by the time they are received.
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Most readers who work with perennial ryegrass are aware of the emergence of gray leaf spot in the past decade as one of the most destructive turfgrass diseases known. Those of you with experience against gray leaf spot know how rapid and destructive the disease can be.
Fungicides remain our first line of defense against gray leaf spot, because all commercial varieties are susceptible and cultural practices can provide only limited control under high disease pressure. Because of the high cost of fungicides, many turf managers are interested in ways to use these important products more wisely and economically. My opinion is that at this time, there is no better way to optimize the use of fungicides than to scout your own swards for the disease and to microscopically verify the presence of the causal fungus in diseased tissues. Experienced turfgrass pathologists agree that microscopic verification is important because it is often not possible to positively identify this disease based on symptoms alone.
Proper scouting can help you decide:
The University of Kentucky Cooperative Extension Service will hold a workshop for turf managers and other interested professionals on microscopic identification of gray leaf spot of perennial ryegrass. Details are as follows:
Date & Time: June 20, 2001, from 1:00-5:00
Location: The University of Kentucky campus in Lexington
Cost: $900, Registration must be received by
Monday, May 7
While the cost may seem high at first glance, registrants
will actually be getting a lot for their money. Each
registrant will receive a high-quality compound binocular
light microscope (40-1000X magnifications, with halogen
illumination and high contrast lenses), which you will
learn to use during the workshop. In addition, each
registrant will receive dissecting kits, lense cleaning
supplies and other laboratory materials, a notebook
including color images, a 2X desk magnifier with built-in
illumination, and a field magnifying glass.
Learning Objective: As a result of this workshop, you will be able to detect Pyricularia grisea (the causal fungus of gray leaf spot) in diseased turfgrass tissue. This skill will provide the foundation for a scouting and monitoring program for gray leaf spot.
If interested in attending, please contact Pat Yancey
at
pyancey@pop.uky.edu
pyancey@pop.uky.edu for a registration form.
Registration is limited in order to provide a high-
quality learning experience for those who attend.
Interested Kentuckians should act soon, since out-
of-state registrants will be accepted on April 20.
Registration and payment must be received by
Monday, May 7.
Frankfort, KY If it sounds too good to be true, chances are, it is. That's according to officials in the Kentucky Department of Agriculture who say several vendors usually appear across the Bluegrass State about this time every year, selling ineffective chemicals at cut-rate prices.
"Each spring, we in the Department receive many complaints from home gardeners, farmers, and others who purchase cheap but ineffective chemicals over the telephone or on the Internet," said Billy Ray Smith, Commissioner of Agriculture. "The sellers of these products usually claim they're comparable to well- known national brands, and for some folks, the cheaper prices are hard to resist."
Pressure tactics are frequently used by sellers of such chemicals. "If the seller tells you to buy his product now or the deal will be gone forever, that's a strong indication that his product is no good," said John McCauley, Director of the Division of Pesticide Regulation.
The KDA's Ken Franks works with licensed pesticide retailers throughout Kentucky and says if you are considering buying a chemical product over the phone or on the Internet, you should ask the seller several questions.
--Ask for the products' EPA registration number.
--Call the KDA to ensure the product is registered for
use in Kentucky.
--Ask for the product's active ingredients and record
the percentages of each.
--Ask how many square feet or acres the product will
cover.
--Request complete directions for use of the product.
--Ask for the company's name, address, and
telephone number.
--Compare the product to a similar one offered by
your local retailer.
--Ask if the seller has a license to sell in Kentucky and
ask for his name and license number.
--Keep a record of all of this information.
"You should never buy a product that requires cash upon delivery," Franks said. "Sometimes these vendors will send you the product whether you ordered it or not, so be careful about who you talk with."
For additional information contact Ken Franks at (502) 564-7274 or
ken.franks@kyagr.com.
Most herbicide labels discuss mixing instructions
largely because this process can impact the
effectiveness of the spray mixture. It was
recognized several years ago that the sequence of
mixing herbicides together as tank mix
combinations can be important, particularly when
different formulations are included in the mixture.
The general rule for adding materials to the spray
tank is to start with wettable powders first, followed
by flowables, emulsifiable concentrates, and water
soluble liquids. Surfactants or oil concentrates are
usually added last. The specific sequence may vary
depending on products used.
The 'jar test' method that is described on may product labels may help determine physical signs of compatibility of products but will not indicate the potential for antagonism as it relates to crop injury or weed control.
The use of nitrogen fertilizers such as 28% nitrogen, 10-34-0, or ammonium sulfate as additives can sometimes impact effectiveness of spray mixtures. Ammonium sulfate as well as 28% liquid nitrogen may reduce activity of Accent Gold, whereas, 10-34- 0 is the preferred source of nitrogen as an additive with this herbicide. The sequence in which nitrogen fertilizers are added in the spray mixtures may also impact the activity of certain herbicides. For example, ammonium sulfate should be included first when it is used with Roundup Ultra.
Some products are not very stable in water over time and should be sprayed soon after they are mixed. This is especially true of many of the sulfonylurea herbicides. In order to avoid product degradation, Accent Gold should be applied within 4 hours after mixing compared with 24 hours for Accent.
Consulting the labels of all materials involved in a spray mixture may help avoid problems with mixing, crop injury, or weed control.
The plant activator Actigard 50 WP, marketed by Syngenta, was labeled late last season for blue mold control in tobacco. Actigard contains acibenzolar-S- methyl which has no significant direct activity against the target pathogens. Instead, the active ingredient gives control by inducing (triggering) a series of natural chemical reactions in the treated plant that activate the plant's own resistance mechanisms - called the SAR (systemic activated resistance). Consequently, disease control is normally not obtained until four or five days after the application is made and there may be other desirable and undesirable physiological changes that occur under certain conditions in the treated plant.
I have conducted a large number of laboratory and field trials with Actigard and the SAR mechanism on tobacco. Colleagues in other states have also evaluated Actigard. It is effective in activating this important disease control, and it can be a valuable
tool in blue mold control. However, it is not a panacea and it can have side-effects! I strongly urge growers to follow directions carefully, in order to achieve the desired disease control without causing crop damage. Application rate and timing are critical to achieving control while minimizing the phytotoxicity. The label clearly states these "do nots" and I urge growers to follow label warnings:
Actigard 50 WG is labeled on both burley and dark tobaccos as a foliar application in the field at the rate of 0.5 oz/acre, with a limit of two applications per season.. Application cannot begin until after the plants reach a height of 18" (stalk length from bud to the soil line). A second application can be made 10 days later. Earlier applications can cause significant phytotoxicity and yield reduction. Even with the recommended use pattern, Actigard often causes a yellowing of the leaf, that often declines or disappears, but may not, depending on a number of other facts. This chemical has no rescue effects, so it must be applied in as a preventive.
It is important that blue mold be controlled with another fungicide (Acrobat MZ) until the plants are large enough to tolerate the Actigard. Keep in mind that the earlier blue mold attacks the plant the greater is the damage, so this is an important point. Furthermore, if the plants already have blue mold when the application of Actigard begins, the phytotoxicity can be severe, because blue mold has already triggered the SAR reaction. Under Kentucky conditions, we are often approaching 30 days post transplanting before plants are 18" tall, and large enough to tolerate the chemical. In general, we have found that control lasts for about 10-14 days post treatment, so additional fungicide sprays may be needed late in the season too, especially with the medium-late and late maturing varieties.
For those reading articles from flue cured tobacco, you could become confused. Realize that flue cured tobacco may be less sensitive to the phytotoxicity reaction than is burley.
The preharvest interval is 21 days and the re-entry interval is 12 hours. Actigard is compatible with most insecticides and fungicides used on tobacco at the labeled stages of growth. However, it cannot be mixed with foliar fertilizers or sucker controls due to phytotoxicity problems. I have experienced very serious crop injury in plots when it was applied with foliar fertilizer.
Thorough coverage (using the equipment and methods used for Acrobat MZ) improves control, but we have usually obtained good control with the spray nozzle arrangements used to deliver sucker controls in 20-30 gallons of water per acre. If the tobacco is under heavy fertilization and is in a highly conducive sites for blue mold, thorough coverage is recommended for maximum disease control.
I urge County Extension Agents to work closely
with growers during the evaluation and adjustment
period with this new disease control tool, especially
demonstrating its phytotoxicity problems if applied
incorrectly, and its high potential for disease control
when used correctly. This would make an ideal
topic for field days at the county level - focusing on
how to use and not use this tool. Please contact me
for guidelines in setting up such educational
demonstrations.
For the latest blue mold status, check the KY Blue Mold Warning System.
http://www.uky.edu/Agriculture/kpn/kyblue/kyblue.htm
There are several options for managing tobacco
insect problems in the 2001 crop. The tobacco insect
season begins with the flea beetle, a common visitor
in all fields. These small, brown insects can riddle
newly set transplants and keep them from getting
off to a good start. An average of 3 or more beetles
per plant is the recommended treatment guideline, a
level that is often exceeded during the first 3 to 5
weeks after plants are set in the field.
Preventive flea beetle control can be accomplished
with a transplant water application of either
Orthene (or other acephate products) or a transplant
or float tray drench treatment with Admire. These
insecticides provide excellent protection against flea
beetles during the critical first few weeks of the field
season.
The Admire treatment (1 fl oz per 1,000
plants) should control aphids until topping time, the
point at which these insects are no longer a threat to
yield.
Tobacco aphids, budworms, and hornworms are the
key pests during the remainder of the season.
Preventive applications of Orthene or Admire will
not have any effect on these insects. Regular field
checks, use of treatment guidelines, and
applications of a foliar spray are the backbone of
tobacco insect management.
For more information about tobacco pests, visit "Insect Management Recommendations".
Options that help manage regrowth of Italian
ryegrass plants following burndown herbicide
applications in no-tillage corn include: Roundup
UltraMAX, or a similar glyphosate formulation,
applied only to Roundup Ready corn; Lightning
applied only to Clearfield corn, Liberty applied only
to Liberty Link corn, or Accent applied to regular or
herbicide-resistant corn hybrids.
Last year's research on these options showed a benefit in delaying the postemergence application until sufficient regrowth of ryegrass has occurred following the burndown herbicide treatment. Regardless of herbicide option, Italian ryegrass control ranged from 53 to 63 % for treatments applied at 1 week after planting and 66 to 80 % for treatments sprayed at 2 weeks after planting. Delaying postemergence applications until 4 or 6 weeks after corn planting resulted in 93 to 100% control of Italian ryegrass. It is important to note that in this particular study nitrogen fertilizer was sidedressed approximately 6 weeks after planting; consequently, regrowth of Italian ryegrass was relatively slow in recovering from the burndown application. It is likely that the rate of regrowth would have been faster had the nitrogen been applied at planting.
These postemergence options may also help in limit further increase or spread of this weed from seed produced from escaped plants. The amount of ryegrass that was re-infested with seed produced from plants that escaped postemergence herbicide treatments ranged from 1 to 58%. Re-infestation of Italian ryegrass was relatively low for Roundup and Liberty regardless of timing of application. Accent and Lightning treated plots also had low levels of re-infestation of Italian ryegrass when treatments were applied at 4 or 6 weeks after planting.
There have been several reports of cutworm and flea
beetle activity. However, there have been several
contradictory reports of the level of cutworm
activity in the southwestern portion of the state. But,
regardless of the level of activity in someone else's
fields, you need to be monitoring your fields as soon
as the corn emerges. During periods of fluctuating
cold and warm weather, considerable damage by
flea beetles and cutworms can occur to corn.
While the corn is small, it needs to be monitored for
insect activity at least twice a week, but three times a
week is better. A considerable amount of damage
can occur over a short period of time, so regular
monitoring is necessary. Planting date, seed
treatments, field location, crop and weed residue, as
well as other factors to the likelihood of insect
problems in seedling corn, for this reason it is
important to monitor your fields carefully. Waiting
for your neighbor to spray or not to spray is a poor
management plan.
For more information about corn pests, visit "Insect Management Recommendations".
In recent years herbicide resistance has become an
important issue to consider when making weed
management decisions. The first case of weed
resistance in Kentucky reported in the 1980's was
smooth pigweed to the triazine herbicides (i.e.
Atrazine and Princep). Smooth pigweed resistance
to ALS (Acetolactate Synthase inhibiting) herbicides
such as Pursuit and Classic was confirmed in 1996.
Several producers in 2000 reported lack of adequate
smooth pigweed control in corn fields treated with
both atrazine and an ALS-inhibiting corn herbicide.
These ALS herbicides (Accent, Beacon, Exceed, and
Spirit) are generally considered very effective for
pigweed control.
Smooth pigweed seed was collected from five corn fields in Kentucky to evaluate whether or not these plants were resistant to either atrazine and the ALS type herbicides. In a greenhouse study plants from four of the five seed sources exhibited tolerance for Beacon and Classic up to 10 times the normal application rate. Whereas, three of the five smooth pigweed sources also showed resistance to atrazine equivalent to 10 lb ai/A. These results indicated that smooth pigweed in some crop fields appear to have developed both atrazine and ALS resistance.
Based on these results, corn producers experiencing poor pigweed control may need to reevaluate their herbicide programs. Atrazine and ALS-type herbicides may still be needed to control other weed species. However, herbicide products that have other modes of action will be required to effectively control the pigweed. Listed below are herbicides used in corn and soybean that have specific activity on the ALS enzyme which is the primary mode of action for these herbicides. These herbicide products should be avoided in fields with inadequate pigweed control.
Herbicides with similar ALS mode of activity
CORN herbicides: Accent, Accent Gold, Basis Gold, Beacon, Broadstrike, Exceed, Hornet, Lightning, Permit, Python, and Spirit.
In recent years herbicide resistance has become an
important issue to consider when making weed
management decisions. The first case of weed
resistance in Kentucky reported in the 1980's was
smooth pigweed to the triazine herbicides (i.e.
Atrazine and Princep). Smooth pigweed resistance
to ALS (Acetolactate Synthase inhibiting) herbicides
such as Pursuit and Classic was confirmed in 1996.
Several producers in 2000 reported lack of adequate
smooth pigweed control in corn fields treated with
both atrazine and an ALS-inhibiting corn herbicide.
These ALS herbicides (Accent, Beacon, Exceed, and
Spirit) are generally considered very effective for
pigweed control.
Smooth pigweed seed was collected from five corn fields in Kentucky to evaluate whether or not these plants were resistant to either atrazine and the ALS type herbicides. In a greenhouse study plants from four of the five seed sources exhibited tolerance for Beacon and Classic up to 10 times the normal application rate. Whereas, three of the five smooth pigweed sources also showed resistance to atrazine equivalent to 10 lb ai/A. These results indicated that smooth pigweed in some crop fields appear to have developed both atrazine and ALS resistance.
Based on these results, corn producers experiencing poor pigweed control may need to reevaluate their herbicide programs. Atrazine and ALS-type herbicides may still be needed to control other weed species. However, herbicide products that have other modes of action will be required to effectively control the pigweed. Listed below are herbicides used in corn and soybean that have specific activity on the ALS enzyme which is the primary mode of action for these herbicides. These herbicide products should be avoided in fields with inadequate pigweed control.
Herbicides with similar ALS mode of activity
SOYBEAN herbicides: Canopy, Classic, FirstRate, FrontRow, Harmony GT, Pinnacle, Pursuit, Python, Raptor, Scepter, Squadron, and Synchrony STS.
Codling moths have begun to show up in
pheromone traps this spring. Now is the critical
time to monitor for the moths in commercial
orchards. Be sure that traps have fresh pheromone
lure (less than one month old) and check traps daily
until the biofix is reached. The biofix is the date
when the fifth codling moth is trapped.
After the biofix has occurred, degree days are calculated on a daily basis and a running total is kept (see Predicting Insect Development Using Degree Days in ENTFACT-201 ). The codling moth has a 50 F threshold temperature. These degree day accumulations are summed until they reach 250. At 250 DD an insecticide is applied for control which coincides with egg hatch. If codling moth are abundant (more than 10 per trap per week), a second spray may be necessary 7 to 10 days later.
Codling moth trap catch records need to be maintained throughout the summer to monitor additional generations. However, after the initial biofix it is only necessary to examine the traps twice a week. A threshold of five moths per trap per week is used to determine if there are sufficient levels of moths to warrant an insecticide application.
Cases of spring dead spot on bermudagrass are being observed in the region. Look for patches, usually 2 ft or less in size, of dead grass as the turf breaks dormancy. In Kentucky, the disease is caused by several species of Ophiosphaerella fungi present in the soil. These fungi infect the roots of bermudagrass as it goes into dormancy; they are active in a range of 50-75 F, with greatest activity at 60 F. These autumn infections predispose the plant to low-temperature death during winter. Since only small patches of grass are infected, dead patches appear in spring instead of the large areas normally associated with winter-kill from purely cold temperatures.
At this stage, recovery can be promoted through regular fertilization. The disease cannot be totally prevented on sites where the disease is active, although management practices can greatly reduce the severity of the disease. For starters, minimize late-summer nitrogen fertilization; make the last nitrogen application by mid-July, and allow the nitrogen to run out by early September. Raise mowing height before Labor Day to improve carbohydrate storage for autumn and winter. Minimizing thatch can also help. In fact, disruption of the turf can also help reduce disease pressure. A study by Ned Tisserat at Kansas State University showed that physical disruption of the turf through a combination of verticutting (1/4 inch deep) and aerifying performed twice yearly significantly reduced spring dead spot damage.
Maintain the soil pH around 5.2 to 5.3 (extracted in distilled water). Reducing pH will not eliminate the disease but it can significantly reduce disease pressure. The best way to accomplish this is to use ammonium-based fertilizers rather than urea or nitrate-based fertilizers; wash ammonium fertilizers off leaves if applied when temperatures will exceed 80 F. Use of ammonium-based fertilizers changes the pH just in the rhizosphere (the soil around the root), which is really the only place you need the pH change. Be aware that an ammonium-based fertility program often takes several years to show a benefit, so sticking with the program pays off. Another, more heavy-handed way to reduce soil pH is to apply flowers of sulfur to affected areas. Apply no more than 2 lb/1000 sq ft and then wait a couple of years to see if sufficient pH reduction has taken place. I encourage a "go-slow" approach with sulfur because in some soil types, heavy applications of sulfur can lead to slow spring green- up and temporary turf thinning, particularly in soils with little organic matter.
Maintain adequate potash fertility. On putting greens, avoid using topdressings with a pH above 6.0. Although several fungicides are available, fungicidal control of this disease has been very inconsistent in our research. I haven't seen enough consistent benefit that I would recommended them for any site other than bermudagrass greens. If using fungicides, apply in early September and water in prior to drying.
The winter of 2000-2001 was cold, though not extremely cold (minimum temperatures near zero degrees Fahrenheit in some locations). Nevertheless, significant cold injury to woody plants occurred in Kentucky. Then, last week, while spring flowering trees were in full bloom, spring frost, ranging from 25-31 degrees, caused additional injury. Most of us readily recognized the spring frost injury symptoms, because dead foliage and flowers appeared in the next day or two. Although plants were hurt by winter injury, the cause and effect relationship is less obvious. County Extension agents are seeing many problem trees and shrubs, as we are in the plant disease diagnostic laboratory, this spring. How can a cold, but not extremely cold, winter cause injury to plants?
Winter injury weather. The most likely cause of the winter injury came with the near-zero temperatures which began December 22, 2000. Autumn, with gradually falling temperatures, is a period when woody plants gradually harden-off to withstand the rigors of winter cold. Due to a relatively mild fall (temperatures sometimes in the 70's during November) plants did not become acclimated to cold weather. Thus, the cold December temperatures froze tissues that were not yet ready for cold.
What effect did the winter injury have on woody plants? Winter injury in Kentucky was geographically scattered and sporadic. We have observed xylem browning in apple twigs and twigs and branches of other woody plants. When xylem parenchyma tissues are injured and turn brown, the xylem fails to function and the affected branches suffer from water stress and the newly emerging leaves die. We have also observed symptoms of needle browning of a variety of conifers, including spruce, and pine. (Don't mistake winter roadside salt spray injury with winter injury to pines.) Some spruce buds simply failed to develop into new shoots following initial bud swell. Over-all the winter freeze damage has been pretty mild - but it is a significant problem to those tree owners whose trees are affected.
The spring frost. Much higher than normal temperatures two weeks ago caused plants to lose dormancy rapidly. Thus, the heavy frost of last week injured very tender emerging tissues. Flower petals of crabapples turned brown. New growth of ash trees turned black within a few days. Numerous landscape trees and shrubs showed some damage to tender tissues, but many did not. It is not likely that the spring frost will affect long- term plant survival.
What can we expect? We should continue to see damage from the winter freeze. Look for dead twigs sticking out from green growth developing from buds on more dormant stems. In some cases, damage could involve an entire plant or selected branches. Branch death often appears to be random. In the case of conifers needles may turn brown and fall off green stems. Expect fungi such as Botryosphaeria to appear in cankers. Botryosphaeria cankers often occur in woody tissues that have been injured by cold. Cracking and peeling of bark from the trunk and major branches may still occur. Freezes can result in death of conductive tissues and cambium that had not hardened off. Failure of these layers of cells to thrive can result in the bark sloughing off over the coming weeks. If injured tissues are not repaired, the problem could worsen during hot, dry summer weather. As for spring frost-injured shoot tips - they will die back and, provided the tree or shrub has adequate energy reserves, new growth will emerge from latent buds on the twigs.
What can be done to help injured plants? Plants at greatest risk are those that have been under environmental or other forms of stress over the past few years. There is relatively little that can be done to revive plants suffering the extreme effects of the freezes. Plants which have not been grossly disfigured can be helped in the following ways:
--Provide adequate moisture through the dry periods regardless of the time of year.
--Now that live foliage is appearing, dead wood should be removed. This will improve the visual appearance of the plant as well as reduce the potential for future problems. Dead tissue can act as a good entrance site for insects and wood rotting organisms.
--Do not fertilize woody plants with high nitrogen fertilizers now. If fertilizer is needed it is best applied in late fall after the plants have become dormant.
Lilac borer/Lesser peachtree borer- Adults of both species are, or soon, will be laying eggs on the bark of susceptible plants. (Patti Savage, Woodford Co. Horticulture Agent, reported catching lilac borer adults in pheromone traps on 4/23) Principal hosts for lilac borer include lilac, ash and privet; for lesser peachtree borer, peach, plum, and flowering cherry. Wood borers 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 (Dursban) continue to be the 'standards' for borer control. 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, pin prick 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, Dursban, Sevin or Talstar 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.
Oaks are hosts to a variety of gall-making arthropods. Galls are irregular plant growths which are stimulated by the reaction between plant hormones and powerful growth regulating chemicals produced by some insects or mites. Galls may occur on leaves, bark, flowers, buds, acorns, or roots. Leaf and twig galls are most noticeable. The inhabitant gains its nutrients from the inner gall tissue. Galls also provide some protection from natural enemies and insecticide sprays. Important details of the life cycles of many gall-makers are not known so specific recommendations to time control measures most effectively are not available.
A sample of roly poly galls (also called succulent
oak gall) arrived today. This distinctive gall is
similar in size and appearance to hollow green
grapes. Inside, in a small, loose "seed like" structure,
is the larva of a tiny wasp. These galls seem to
appear in place of leaves or reduce the size of
infested leaves, but they do not affect tree health.
There is no effective control.
European pine sawfly larvae have been found
feeding on Mugho pine. They are gray-green
caterpillar-like insects with black heads. There is an
off-white stripe down the middle of the back and
slightly lighter stripes on either side of the body.
They larvae feed in clusters on Scots, Austrian,
Mugho, and white pine. These larvae feed on old
foliage and seldom kill trees but shoots may die or
be deformed and losses in diameter growth and
height may occur. They can feed on bark of new
shoots. There is one generation of this insect each
year.
Physical removal by shaking the larvae into a
bucket of soapy water is an option in the landscape.
Sawflies look like caterpillars but are the immature
stages of a wasp. Thus, they are not susceptible to
Bt insecticides. Insecticidal soap, Orthene, or Sevin
are among the insecticides that can be used for
control.
Many clients having been calling about the large,
black bees hovering around eaves, decks, and wood
siding of their homes and outbuildings. These are
probably carpenter bees searching for mates and
nesting sites. Carpenter bees cause cosmetic and
structural damage to wood. They can also be quite
intimidating and have the potential to inflict painful
stings.
The Problem- Carpenter bees are similar in appearance to bumble bees, but have different nesting habits. Bumblebees generally nest in the ground, whereas carpenter bees tunnel into wood to lay their eggs. Bare, unpainted, weathered softwoods are preferred, especially redwood, cedar, cypress and pine. Painted or pressure-treated wood is much less susceptible to attack. Common nesting sites include eaves, fascia boards, siding, wooden shake roofs, decks and outdoor furniture.
Carpenter bees overwinter as adults in old nest tunnels. After mating, the fertilized females excavate galleries in wood, laying their eggs within a series of small cells. The cells are provisioned with a ball of pollen on which the larvae feed, emerging as adults in late summer. The entrance hole and tunnels are perfectly round and about the diameter of your finger. Coarse sawdust, the color of fresh cut wood, is often seen beneath the entry hole, and burrowing sounds may be heard within the wood. Female carpenter bees may excavate new tunnels or enlarge and reuse old ones. Serious damage can result when the same piece of wood is worked year after year.
Males are often aggressive, hovering in front of people who are around the nests. The males are harmless, however, since they lack stingers. Female carpenter bees can inflict a painful sting, but seldom will unless handled or molested.
The Solution- The best time to control carpenter bees is before tunnels are fully excavated. For homeowners, liquid sprays of Sevin, Dursban, or synthetic pyrethroids (e.g., Bayer Advanced Home/Lawn & Garden Insect Killer, Spectracide Bug Stop, Ortho Home Defense System) can be applied directly into nest openings, or sprayed as a deterrent onto wood surfaces attracting large numbers of bees. Residual effectiveness of such applications is only about 7-14 days, so the treatment may need to be repeated. Tunnels that have already been excavated can also be treated with an insecticide dust (e.g., Sevin, Drione), 'puffed' into the nest opening. Wasp and hornet aerosol sprays are also effective, and generally more convenient than dusts for treating individual galleries. Although carpenter bees are less aggressive than wasps, female bees provisioning their nests will sting. Treatment is best performed at night or while wearing protective clothing.
Leave the holes open for a few days after treatment to allow the bees to contact and distribute the insecticide throughout the nest galleries. Then plug the entrance hole with a piece of wooden dowel coated with carpenter's glue, wood putty, or other suitable sealant. This will protect against future use of the old tunnels, as well as moisture intrusion and wood decay.
Carpenter bees normally will not tunnel into painted wood. Therefore, a more permanent solution is to paint unfinished wood surfaces, especially those with a history of being attacked. Wood stains and preservatives are less reliable than painting, but may provide some degree of repellence versus bare wood. To further discourage nesting, garages and outbuildings should be kept closed when carpenter bees are actively searching for nesting sites. The annoying flying/nesting habit usually subsides by late May.
In the Diagnostic labs last week, we received samples of tobacco with cold injury, spiral root, Pythium root rot and Rhizoctonia damping-off. On greenhouse ornamentals and vegetables, we saw tuberous begonia with sunscald, geranium with Pythium root rot, New Guinea impatiens with impatiens necrotic spot virus, and tomato and pepper seedlings with Rhizoctonia damping off. From the landscape, we saw samples of freeze injury on apple and yellow patch on bentgrass.
| UKREC-Princeton, KY, April 13 - 20, 2001 | |
| Black Cutworm | 3 |
| True Armyworm | 68 |
Lee Townsend
Extension Entomologist
