Many corn fields experienced long periods of wet soils after planting. When soils are generally wet to saturated early in the season, the corn plant produces a shallower root system than in seasons when periods of drying take place. Compounding this situation is the fact that root rots have been diagnosed in a number of instances in Kentucky corn fields, principally root rot caused by the fungus Fusarium verticillioides (formally known as Fusarium moniliforme, the same fungus that can produce fumonisins in the grain). Root rot caused by F. verticillioides is typically triggered by some stress to the plant, including herbicide injuries. Pythium root rot is favored by soil saturation, so fields with poor drainage (either poor surface drainage or poor internal soil drainage) are prone to this problem.
Fields of corn with root systems that are shallow due to post-planting rains and damaged by root-rotting infections will have a difficult time filling grain should weather conditions turn dry. All one can do at this stage is adopt a wait-and-see attitude. However, for fields that dry down quickly during harvest, it would be valuable to review the overall production system for stresses: the appropriateness of hybrid selection, the weed control program, degree of soil compaction, fertility, etc. The UK Extension publication, A Comprehensive Guide to Corn Management, ID-139, is an excellent resource for such a purpose.
For information about corn pests, visit
"Insect Management Recommendations".
Few scientists I have talked with, or heard speak, believe agricultural commerce will be the means by which soybean rust (SBR) makes its way into the continental United States. Having said this, everyone I have heard speak on the topic also feels it is not an impossible scenario.
The SBR pathogen, Phakopsora pachyrhizi, is not seed-borne, but it could infest trash in seed and bulk grain. This, however, is a remote possibility for a variety of reasons. First, soybean is harvested AFTER plants drop their leaves. Thus, the vast majority of rust-infected leaves will be on the ground when the crop is harvested. Secondly, even if some dead leaves with rust make there way into harvested seed/grain, the chances are very high that the fragile urediniospores of P. pachyrhizi would die soon after harvest. Finally, it is my understanding that seed and bulk grain produced in Brazil are almost always processed through cleaners and dryers following harvest. This further reduces the chances that viable rust spores will contaminate those products. Of course, meal is even further processed, compared to seed and bulk grain.
On the other hand, SBR can be present in all above-ground plant parts, including pods and stems. Thus, if a seed lot or bulk grain shipment is contaminated with SBR in pods or stem pieces, the risk for bringing in P. pachyrhizi with seed and grain may be increased. I say may, because I really do not know. This type of information - specifically, the survival characteristics of urediniospores of P. pachyrhizi - have been studied very little.
At present, there are no published data indicating how long Phakopsora pachyrhizi urediniospores could survive in a shipment of soybean seed, grain or meal. At a conference in St. Louis hosted by the American Soybean Association this past January, I heard that it takes a minimum of 60 days for a bulk grain shipment of soybean to make its way into a U.S. port following harvest. The period for seed could be significantly shorter. Under normal circumstances, the SBR fungus would not be expected to survive in trash for this length of time. A concern was raised at the meeting that urediniospores might remain viable in containment longer than we think because of the higher moisture level and lack of light in the hull of a cargo ship. There is a great need for research to be conducted in this area.
In the meantime, officials with the Animal and Plant Health Inspection Service (APHIS) are on high alert and are closely scrutinizing each shipment of soybean whose port of origin is a county with known infestation of SBR. When I searched the World Wide Web on this topic, it became clear that there is a great deal of unrest and concern by all parties involved that we do everything possible to keep SBR from being imported with moving seed, grain, and meal shipments.
Most scientists at this time are still convinced that SBR will naturally make its way into this country as a result of wind-blown urediniospores from South America, or perhaps in the winds of a hurricane system originating over Africa.
I will conclude with a statement made in a February 23, 2004 USDA-APHIS report entitled "Status of Scientific Evidence on Risks Associated with the Introduction into the Continental United States of Phakopsora pachyrhizi With Imported Soybean Grain, Seed, and Meal":
"Soybean leaf debris associated with "foreign material" found in soybean grain presents a theoretical pathway for the introduction of SBR. However, normal commercial practices minimize the presence of "foreign material" to less than 2%. Moreover, as it is a normal commercial practice to harvest soybeans after the plants have been defoliated, leaf debris should compose only a fraction of the "foreign material"; therefore, making "foreign material" found in grain an unlikely pathway for introduction of SBR."
For more information about soybean pests, visit
"Insect Management Recommendations".
As fruit crops begin to ripen across the state, one insect pest is almost certain to cause problems, the green June beetle. Unlike the Japanese beetle that is primarily a leaf feeder, although it will attack damaged fruit and sound fruit on occasion, the green June beetle almost exclusively feeds on the fruit. It may be easier to list fruit that this pest does not attack as most of the fruit crops are vulnerable. Growers of peaches, apples, grapes, blueberries, and blackberries have regular battles with this pest.
Green June beetle is attracted to ripening fruit often in the last few days before maturity. This is when the sugar content of the fruit begins to peak. Damage by green June beetle often attracts other insect harvest pests including sap beetle, Japanese beetles, fruit flies, wasps and bees.
Control of green June beetle is not easy. Although we have very effective sprays that can eliminate the pest, the difficulty is timing. They typically arrive in the last few days before harvest begins. The required pre-harvest interval (PHI) of the more effective sprays is longer than period before harvest will begin, so they cannot be used when the beetles arrive. Growers often will substitute a less effective material with a short pre-harvest interval in order to comply with the required waiting period.
Sanitation is also very important, not only for green June beetle, but the other pests that are attracted to the damaged fruit and the scent of the fermenting plant juices. To the extent the practical and possible, the damaged fruit needs to be removed from the orchard/vineyard. In intense situations or where organic-certification precludes the use of synthetic insecticides, netting can be used over small plants and vines as a barrier to the beetles.
When I started my professional career with commercial vegetable producers 34 years ago, a long-standing, successful Virginia vegetable grower told me this. "Teach them that water is critical to vegetable production. In dry seasons they need timely irrigation, but when Mother Nature supplies it in wet seasons, they will need timely fungicide sprays ahead of the rains." In my opinion, that advice is as fitting today as it was in 1970.
The protracted periods of rainy weather this spring have led to a number of serious disease outbreaks in commercial vegetable crops. Even growers with much past success are having serious problems in disease management. On most new vegetable farms, the inoculum load has been low previously, allowing some to escape serious disease in recent years and get by with less than good spray programs for a few years. Such, have not learned earlier of the need to incorporate a strong disease management program in their operation. At a recent field day, I reminded the audience that one must always give luck its due credit in assessing management issues - until a disease is critical, the critical value of controlling it is not visible! A poor spray program in situations of low disease pressures can be adequate. Such luck can guide one to decide that recommended spray programs are not as important as others have advised, leading to inadequate equipment, omitted or reduced sprays, and lack of needed products in the supply system. Some experienced sages have even been hurt by relying too heavily on newer products and extending spray intervals rather a using them in a rotational pattern with proven preventive products and closer spray intervals. Long spray intervals look real good to the bottom-line in dry weather, but some are seeing a very different bottom line (in red) from those same programs in this wet season.
Vine crops are especially hard hit on some farms from outbreaks of anthracnose, gummy stem blight, Alternaria leaf spots, and scab even before we enter the season for Phytophthora blight, powdery mildews and downy mildews. By the way, expect an earlier than normal season for all three diseases and at much higher levels than normal.
Although a number of other issues are involved, such as site selection, rotation, and infested transplants, with the operations I have reviewed, fungicide application difficulties seem central to the problems. Some growers just have not used much fungicide. Some were waiting to see if the disease would become serious enough to warrant spraying. Others have not used them often enough, mainly relying on the schedules used in drier seasons then trying to "chase" the outbreak rather than preventing it. Some have been waiting for it to stop raining so they could get into the field; those need to realize that heavy grass- sod spray-strips have a place in our soils. Some have abandoned wet areas of the field and left it unsprayed for the pathogens to use as a staging area; those could have helped themselves with either prompt destruction or some spot spraying with back-pack equipment. Abandoning a portion of the field is leaving it for the pest to colonize. Others that apply a tank mixture of fungicides and insecticides have been afraid to spray during the day time for fear of killing their bees (a major concern) so they have been waiting for dark, yet by late in the day and at dark thunderstorms have moved in, often night after night. Separate the fungicide and insecticide application in such weather, because you need that fungicide on and dried before the rain, with morning applications often being the best options to insure drying for the wet event. Some have selected the wrong fungicides for the problems present.
Fungicides are important tools for controlling infectious diseases in commercial vegetable crops. Chemical fungicides work mainly as preventives but some newer eradicants (curatives) have moved into the system. However, where curatives are available they need to be used in a preventive manner, rather than always relying on that curative potential, by either applying in a tank mixture or a rotation pattern with other effective products. Plan to control by inhibiting subsequent infections of the pathogen rather than by curing the diseased plant, because the pathogens have very short reproductive cycles and build their numbers very rapidly, in a matter of days.
Application timing is very important relative to when the infection and sporulation events are occurring in disease development. For most fungicides, applications should be made before the disease even begins, or no later than when the first few lesions appear. Why? Because these materials stop the pathogens by preventing spore germination and preventing subsequent infections and not by killing/eradication of the pathogen after it is already inside the plant. Most infections occur while the leaf is wet, so the fungicide needs to be on target tissue and dried before the moisture event. Failure to appreciate this concept has been central to most of the decision making in problem fields that I have encountered. Yes, there is a lot to do in a day, and it is difficult to find time to do it, but disease prevention measures must take a higher priority in some seasons than others. Wet seasons are disease seasons!
Good spray coverage is a critical issue with fungicide use. Protective fungicides should be applied to achieve good coverage for the best protection under strong disease pressure. Although some products are formulated to be less sensitive to coverage issues than others, the goal for all should be good coverage put in place and dried before the wet events.
Spray adjuvants or surfactants should be used if the product label recommends them to ensure uniform coverage. Do not use these materials unless the label indicates they are needed.
It is important to maintain proper application intervals with fungicides, especially in wet weather. If it rains before the material is dry on the foliage, most of the fungicide will wash off. Yet infection occurs while the plants are wet-when the protective chemical is most needed! If it seems likely that the fungicide can remain on the foliage for two hours or more before a rain, it is best to go ahead and make an application. This is particularly true if the spray interval has been long and/or a protracted weather event is involved. In addition, regular applications are needed to keep up with new plant growth and loss of the applied material due to weathering. With the fast growth rates experienced this season, it is not uncommon to have one or two feet of new growth that has no fungicide between applications. If inoculum is in the field, that foliage has probably already become infected.
Scots and Austrian pines in Kentucky landscapes and along highways are now showing symptoms of pine wilt disease caused by the pine wood nematode (Bursaphelenchus xylophilus). Although we see the disease mainly on Scots pines, Austrian pines are also susceptible, and on rare occasions white pines show the disease. In some cases, the disease completes the demise of trees already infected with pine tip blight disease.
Symptoms. The first visible symptom is discoloration of needles from green to yellow to brown. These symptoms are accompanied by a marked decrease in resin flow that is apparent when a branch is cut and resin does not seep readily from the wound. Wilt and death of affected trees may occur gradually or very rapidly. Brown trees can be seen now within groups of pines and they contrast markedly with nearby heathy green trees. Trees infected in the spring may wilt and die by late summer.
Spread. Long-horned cerambycid beetles carry the nematodes on and in their bodies as they emerge from infected (usually dead) trees. Beetles then migrate to nearby pines where nematodes enter healthy shoots through feeding wounds left by the beetles. They migrate into resin canals where they rapidly multiply and cause the pines to wilt and die. Dying pines are attractive to the beetles for breeding; the cycle then repeats.
Sampling for diagnosis. Positive diagnosis of this disease requires microscopic identification of the nematode. A recently wilted or killed pine can be sampled by collecting the portion of an affected branch closest to the trunk. A good sample might consist of a branch section 1/2 inch or more in diameter, and about a foot long. Alternatively, samples consisting of sapwood can be taken from the trunk or main branches using a hatchet or an increment borer. It is best to collect several samples from various parts of the tree. Put the wood samples in a plastic bag and submit them to the Plant Disease Diagnostic Lab via the County Extension Office.
Disease management. If pine wilt nematode disease is confirmed in a planting of pines, remove and destroy the affected trees. This measure will help prevent spread of the disease to nearby healthy pines. Control of the insect vector with insecticide treatments has not proven to be a useful tool for managing pine wilt disease. Under unusual experimental conditions, the pinewood nematode was shown to move from fresh infected pine wood chips to young Scots pines. Thus, it is probably a good idea to compost fresh chips from pine wilt-infested trees for at least one month before using them as mulch around susceptible pine species.
Chigger bites, a sure sign of summer, can be the "souvenir" of a blackberry-picking trip, working, or playing in overgrown brushy or grassy areas. Chiggers usually feed where clothing fits tightly against the skin - waistbands, etc. Digestive juices used by the mites to dissolve skin cells cause bite sites to become red and swollen. Later, angry red welts will form that itch intensely for several days. As if that were not enough, bite sites can become infected if they are scratched incessantly.
Here are some ways to protect yourself-
Wear long pants tucked into boots or socks to keep chiggers on the outside of your clothing Wear loose fitting clothing and avoiding sitting or lying directly on the ground.
Avoid walking through overgrown fields and brush, especially from July through early September. Instead, walk in the center of mowed trails to avoid vegetation where chiggers (and ticks) congregate.
Use an insect/ tick repellent. Products containing diethyl toluamide (DEET) or permethrin (clothing only) are most effective. Be sure to read and follow directions for use on the container. A hot, soapy shower immediately after coming indoors will remove chiggers that have not yet attached.
Control of chigger infestations in large yards, parks, camps, picnic sites, and other recreational areas is often impractical. However, chiggers in play and picnic areas and around trails can be reduced by vegetation management. Regular mowing and brush removal creates a less favorable habitat for chiggers and the rodents and other small animals on which they feed. This is the way to a long-term solution. Insecticide sprays may provide some temporary reduction of chiggers. They are most effective when directed into areas where chiggers and their animal hosts are likely to frequent. Options include bifenthrin (Ortho Lawn Insect Killer), carbaryl, (Sevin), cyfluthrin (Bayer Advanced Lawn and Garden Multi-Insect Killer, and any of a number of products containing permethrin. Be sure to read the product label carefully to be sure the site you are planning to treat is on the label. Also, look for specific instructions for applications against chiggers that can increase control.
Recent samples in the Diagnostic lab have included stinkbug injury, zinc deficiency, and Fusarium stalk rot on corn; black shank, blue mold, frogeye leaf spot; soreshin, Fusarium basal stem canker, black root rot, Rhizoctonia leaf blight, Fusarium wilt; tomato spotted wilt virus, manganese toxicity, hollow stalk and weather fleck (ozone) on tobacco.
On fruits and vegetables, we have diagnosed Fusicoccum canker on blueberry; anthracnose, bitter rot, black rot and potash deficiency on grape; bitter rot, cedar-apple rust, fireblight, frogeye, Pythium root rot on apple; brown rot on peach; Entomosporium leaf spot on pear; Blumeriella leaf spot on cherry; anthracnose on walnut; anthracnose and Rhizoctonia stem rot on bean; and Fusarium wilt, early blight, bacterial speck and spot; Septoria leaf spot and Cladosporium leaf mold on tomato.
On ornamentals and turf, we have seen southern blight on hosta; Pythium root rot and manganese deficiency on chrysanthemum; Rhizoctonia stem rot and Pythium root rot on petunia; powdery mildew on dogwood; scab on crabapple; Actinopelte leaf spot on oak; Phomopsis twig blight on juniper; Verticillium wilt on smoketree; Cercospora leaf spot on willow; and summer patch on turf.
|UKREC-Princeton, KY, July 2-9, 2004 ||Black Cutworm
||European Corn Borer
||Southwestern Corn Borer
To view previous trap counts for Fulton County, Kentucky go to - http://ces.ca.uky.edu/fulton/anr/ and click on "Insect Trap Counts".
For information on trap counts in southern Illinois visit the Hines Report at - http://www.ipm.uiuc.edu/pubs/hines_report/index.html. The Hines Report is posted weekly by Ron Hines, Senior Research Specialist, at the University of Illinois Dixon Springs Agricultural Center
Several of Kentucky's largest or most unusual insects will be active over the next few weeks. A few species that are most likely to appear and at least arouse curiosity are:
The female dobsonflies lay their eggs on overhanging branches or structures over streams. The larvae called "hellgrammites" usually occur under stone in streams where they feed on insects that live in the water. The larvae live for several years in the water and are used as bait by fishermen. The adults only live a few days to reproduce, then die.
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.
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