WATCH FOR:
By Lee Townsend

EUROPEAN PINE SAWFLY LARVAE feeding on pines (ENTFACT 410);
MIMOSA WEBWORM damaging mimosa and honeylocust;
BAGWORM egg hatch (440);
HOUSE MOSQUITOES breeding in standing stagnant water.

BLUE MOLD UPDATE
By Kenny Seebold

They say that a watched pot never boils. This old saw is holding true for blue mold in 2005. We've been monitoring the disease for several months - watching it like hawks - and it has yet to spread to the U.S. This is great news for Kentucky farmers, who deserve a break after a couple of tough disease years. No one wants the blue mold "pot" to boil over, but history tells us that an epidemic of some sort is inevitable.

Plant pathologists have the reputation of crying wolf constantly, or being like the fellow on the street corner carrying the sign that reads "THE END OF THE WORLD IS NIGH". Everyone knows that we pathologists are happy only when fields are blighted. In fact, a grower told me once that when a plant pathologist is smiling, it's time to worry.

The reason behind all this rambling is that it's time to start thinking about (and planning for) blue mold, even though we are in no apparent danger at the moment. And it is time for your tobacco pathologist to get out his end-of-the-world sign. Things are calm on the disease front for now, but it is important that we keep an eye on float beds and tobacco fields for signs of disease. Historical data shows that blue mold, on average, begins to show up in Kentucky around the third week of June. I will continue to monitor the status of blue mold outside Kentucky, using the National Blue Mold Forecast, and provide timely warnings if the disease begins to move our way. It should be noted that the National Blue Mold Forecast is a great predictive tool, but it is not infallible. Forecasts are made using data on the known locations of active blue mold in the country, and we all know that it would be very easy for outbreaks to go unreported. We need to keep a close watch on the tobacco crop as we head into June, particularly if cool and rainy weather sets in, and be prepared to act if blue mold appears with or without warning.

Let's hope that blue mold is not a major issue in 2005; however, let's also make sure that growers are on a good disease management program before blue mold hits. That's the best way to keep the disease in check AND the smile off your pathologist's face.

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".

Bt TRAIT CAN REDUCE MYCOTOXIN LEVELS
By Ric Bessin and Paul Vincelli

Mycotoxins are natural toxins produced by fungi. There are two classes mycotoxins of concern that can occasionally develop in corn produced in Kentucky. Fumonisins, the more common in Kentucky, are produced principally by the fungus Fusarium verticillioides (formerly Fusarium moniliforme). Fumonisins can cause fatal diseases of horses and swine, and pose a known risk to other livestock. Fumonisins also have been shown to cause cancer in laboratory rats, and in humans fumonisins have been associated with esophageal cancer and serious birth defects called neural tube defects. Aflatoxins are produced by the fungus Aspergillus flavus. The aflatoxins are highly potent liver carcinogens in animals and may be carcinogenic to humans, as well. Aflatoxin contamination is uncommon in Kentucky corn but can occur when sustained hot, dry weather occurs during grain fill. Both mycotoxins are regulated by the U.S. Food and Drug Administration. More information on aflatoxins and fumonisins is available in the following Extension publications:

Fumonisin, Vomitoxin, and Other Mycotoxins in Corn Produced by Fusarium Fungi. ID-121. http://www.ca.uky.edu/agc/pubs/id/id121/id121.pdf

Aflatoxins in Corn, ID-59. http://www.ca.uky.edu/agc/pubs/id/id59/id59.pdf

Corn hybrids containing the Bt trait have been commercially available for almost a decade. This trait results in the produced of a delta-endotoxin which poisons the European corn borer (ECB) as it feeds. The currently available Bt traits are very effective against ECB but are less effective against corn earworm and fall armyworm. All of these insects can play a role in enhancing contamination of corn with fumonisins or aflatoxins, by creating wounds in kernels that allow fungal infection and by carrying spores on their bodies.

Because the feeding activity of these lepidopterous insects enhances the risk of mycotoxin contamination, a number of studies in the U.S. and elsewhere have tested whether the Bt trait reduces the risk of mycotoxin contamination.

To put it simply, there is strong evidence from several well-conducted studies showing that many Bt hybrids have a substantially reduced risk of fumonisin contamination as compared to non-Bt counterparts. If the field has heavy pressure from ECB and conditions favor fumonisin contamination, reductions in fumonisin contamination of 80-90% are common in these studies.

The most substantial and consistent reductions in fumonisin contamination have been observed with hybrids in which the delta-endotoxin is produced in all plant tissues, including kernels. This makes sense, because insect feeding in the kernels provides A. flavus and F. verticillioides with an easy access into the kernel where it can produce mycotoxins. Occasionally, fumonisin reductions are observed in hybrids where the delta-endotoxin is produced in green tissue and pollen (but not kernels). Although direct protection of kernels more effective in reducing fumonisin contamination, these hybrids probably lower overall ECB populations, resulting in fewer kernels wounds and therefore fewer infection sites.

There have also been similar studies testing the effect of the Bt trait on aflatoxin contamination. Reductions in contamination levels have sometimes been observed, especially in situations with high ECB populations and high overall aflatoxin levels. In these circumstances, reductions have commonly been in the range of 50-75%, substantial but not as large as for fumonisins. It is also significant that in several of these instances, levels of aflatoxin were above the FDA limit for human consumption even in Bt hybrids.

Conclusion
Bt hybrids are not a magic bullet against fumonisins and aflatoxins. However, Bt hybrids expressing the delta-endotoxin in kernels have clearly been shown to reduce the risk of fumonisin contamination in sites with high ECB pressure. They also may reduce aflatoxin risk somewhat should environmental conditions favor aflatoxin contamination.

TIMING OF POSTEMERGENCE HERBICIDES RELATIVE TO CORN GROWTH STAGE
By J. D. Green and James R. Martin

The size of corn is often a critical factor in determining when it is safe to apply postemergence herbicides. Labels of postemergence herbicides often use plant height or growth stage (or both) when discussing timing of applications relative to corn growth. While this may sound simple, there is come confusion on how to determine height or growth stage of corn with respect to herbicide applications.

A common method for determining corn height is done by using free-standing plants. When checking individual plants, measure from the soil surface to the arch of the uppermost leaf that is more than 50% emerged. Because of the variability among corn plants in the same field, it is better to get an average from several plants than relying on just one plant. A temptation for some folks is to measure from the soil surface to the tip of outstretched leaves. The measurements by stretching leaves upward and measuring to the uppermost leaf tip often leads to a greater height than intended by the herbicide label.

The collar stage is another method used to determine the proper timing and method of application of many postemergence herbicides. Staging corn plants in their vegetative growth stage is usually done by counting the number of leaves that have visible collars. The collar is the part of the leaf that joins the leaf blade and leaf sheath and occurs as a discolored line. Collars are not evident until the leaves are well developed and emerged from the whorl; consequently, as you progress up the plant, count only leaves with visible collars and not the uppermost ones that are still in the whorl. For example, a plant may appear to have 5 leaves, but after close examination, it may have only three leaves with visible collars and would be considered in the V3 growth stage.

The first true leaf that emerges during seedling development is characteristically oval-shaped and is the reference point for counting leaves. Once plants reach stage V5 (5 leaves with visible collars), the leaf and ear shoot initiation will usually be complete and a small tassel is initiated in the stem apex tip (i.e. growing point). During tassel initiation, corn will be approximately 8 inches tall and the growing point will be just at or beneath the soil surface. Once plants reach V6, the growing point and tassel will be above the soil surface and the stalk elongation will be rapid. The growth of the stalk and nodal roots will eventually result in the tearing and deterioration of the lowest leaves, thus making it difficult to accurately determine the growth stage.

Staging corn plants that are beyond V6 is possible but may require some practice to become efficient. Dig a plant and cut the stalk lengthwise through the root area. Check for the first elongated internode, which is usually about one centimeter (0.4 inch) in length. The first node above this internode is generally connected to the 5th leaf. Once the 5th leaf has been determined, then use it as the reference point for counting to the uppermost visible leaf collar.

The use of drop nozzles can limit the risk of injury from certain herbicides, especially as the corn canopy develops. Directed applications help in some instances by keeping the herbicide from being intercepted in the top of the canopy where it can be funneled into the whorl and increase exposure to the growing point. This is particularly a problem with certain ALS-type herbicides such as Accent, Spirit, or Lightning. In cases involving contact herbicides such as Gramoxone MAX, the directed sprays must be fairly precise to limit the amount of contact with the corn plants.

The recommended timings for several postemergence herbicides used in field corn can be found in University of Kentucky Extension Bulletin "Weed Control Recommendations for Kentucky Farm Crops" (AGR-6). Always check the product label for specific directions.

For information about corn pests, visit "Insect Management Recommendations".

SOYBEAN RUST CONTINUES TO BE ELUSIVE IN DEEP SOUTH
By Don Hershman

The past week has brought out a new find of soybean rust in Seminole County Georgia, also on volunteer soybean, but the level of disease is very low and spore production is minimal. Extension plant pathologists are having to spend hours observing pustules and spores just to confirm that it is soybean rust. The general understanding at this time is that early symptom expression of soybean rust by anyone will require a great deal of experience and patience. This is unlike full-blown infections which are rather easy to identify.

I encourage you to continue to monitor the USDA public website (www.sbrusa.net) for updates as they occur. I have been changing commentary for Kentucky on an almost daily basis. Other state specialists are doing likewise.

Keep an eye on what happens in Alabama, Georgia, Louisiana, and Mississippi; these are the key states right now as far as Kentucky is concerned.

Disease models are forecasting a very low probability of spore showers of the rust fungus in Kentucky though at least June 6.

WATCHING AND WAITING FOR SOYBEAN APHID
By Doug Johnson

According to Dr. Chris DiFonzo of Michigan State University winged soybean aphids have been moving from their over-wintering host to young soybean plantings in Michigan in the last two weeks. What does this event mean to us?

Generally speaking, soybean aphid populations in the north central states are the source of our infestations in Kentucky. As populations in the northern states get larger, aphids are prompted to move out into new areas. It is this spread that will eventually reach Kentucky but it is hard to predict when this will occur.

Usually, we begin to look for soybean aphids in June and expect to find them in late June or early July. Of course when we find them will depend in great part upon how fast the populations grow, and to some extent the, weather patterns that direct spring cold fronts toward us.

Surveys over the past three years show that soybean aphids can reach all parts of the Kentucky soybean production areas in a given season. Fortunately, thus far this insect has been very little more than a curiosity. However, don't make the mistake of overlooking their potential damage.

If economically important populations do occur, they are most likely to be in our latest maturing beans. This will usually mean our double crop planting, but in fact could be due to any factor that results in delayed maturity. In 2004 for the largest reported populations in Kentucky were found in mid- to late September. A late outbreak was also reported in central Tennessee.

So, do not be too concerned, but do keep your eyes open. Look for aphids while you are looking for soybean rust and other insect pests.

For more information about soybean pests, visit "Insect Management Recommendations".

FIRE BLIGHT-WHAT NOW?
By John Hartman

Fire blight symptoms are appearing in commercial apple orchards and in backyard apple trees throughout Kentucky. Flowering crabapples and some flowering pears (i.e., 'Bradford' and 'Aristocrat' pears) in nurseries and landscapes are also affected. The plant disease diagnostic laboratories have been reporting high numbers of fire blight samples from apples and pears for the last several weeks. In addition, County Extension Agents have been inquiring as to how to best advise their clients with blighted apples and flowering trees. Many growers wonder why the disease is widespread and yet sporadic this year.

• Fire blight is widespread because, for several distinct times this spring, conditions were ideal for infections, especially during bloom when primary infections take place. Depending on the location, if apples or pears were in flower around April 11 & 12 or on April 22, then conditions were good for fire blight infections. Frost in some areas may also have played a role. Readers may recall comments made in Kentucky Pest News, May 16.
• The disease is sporadic because not all trees faced ideal fire blight conditions this spring. Small differences in microclimate based on the tree location or exposure can make a critical difference in disease potential. In addition, timing of bloom in relation to the weather affected whether or not fire blight would be a problem.
• Fire blight has been a threat over an extended period because cool weather interspersed with the disease-favorable warm weather slowed tree development this spring and because some trees may produce many "trailing blooms." In nurseries, dormant liners may be placed in the field over a period of several months and some of these liners may bloom, thus extending the primary infection period even more.

Growers and gardeners with infected trees are often tempted to remove infected branches as soon as they see them. In many cases, this would be the wrong strategy, because removing branches can encourage new shoots to develop and these new shoots would also be susceptible to new infections. If fire blight strikes are discovered early, before leaves have turned completely brown, timely removal of infected shoots can help slow the spread of the disease. However, most growers do not discover the disease early enough for this to be helpful. So what is to be done with infected trees now?

• Growers should just let the disease run its course, allowing the tree defenses to stop fire blight spread within the tree. Dead shoots and branches should be removed in winter when there is little chance of spreading the disease.
• Some growers may feel compelled to cut out fire blight infections, possibly for cosmetic or aesthetic reasons. What then? If pruning is begun after obvious symptoms appear, cut back in the direction of a healthy internode of at least two-year-old wood, leaving a stub several inches long. Rely on the tree's natural defenses to prevent further movement into the branch. If needed, paint the stub with bright paint to make it more obvious. This stub can then be safely removed in the winter. Leaving infected stubs rather than pruning all the way back to the main branch reduces the chances for development of undesirable water sprouts in response to pruning.
• The reason not to prune infected branches back to a spur or crotch in summer is because it may not be noticed in winter and could be overlooked. It should not be necessary to sterilize cutting tools between cuts if only blighted shoots are being removed.
• Do not engage in normal summer pruning and training at the same time as fire blight removal without wiping the cutters with sterilizing solutions like Lysol, 70% alcohol or 10% bleach. Don't forget to remove the infected stubs along with dead shoots and cankers next winter.
• Do not apply chemical controls such as streptomycin. They are only effective if used during the normal bloom period.
• Remove trailing blooms to prevent late spring and summer infections.

FIRST REPORT OF BACTERIAL CANKER OF TOMATO FOR 2005
By Kenny Seebold

Bacterial canker was identified last week on a tomato plant sent in to our diagnostic lab in Lexington. The causal agent of bacterial canker is Clavibacter michiganensis subsp. michiganensis (CMM). This is a particularly difficult disease to deal with because there is no cure, and the pathogen causing bacterial canker can be hard to eradicate once it becomes established. The following is a brief review of the disease and its control measures.

All above-ground parts of the tomato plant are susceptible to bacterial canker. In general, first symptoms will appear on older leaves as a marginal browning, or necrosis, called "firing". A yellow margin may border the brown tissue, and affected leaves tend to curl upward. Seedlings affected by bacterial canker may appear stunted, and will often wilt and die. In older plants, wilting is also evident, and open cankers (from which the disease gets its name) can be found on the stems. When split lengthwise, stems will show reddish-brown discoloration of the vascular system, and the pith may be grainy or pitted. Wilting and vascular discoloration are indicative of systemic infection of the tomato plant. The primary symptom on fruit is the presence of raised lesions with a white margin, roughly 1/16th of an inch in diameter, called "bird's eye" spots.

The pathogen that causes bacterial canker is introduced primarily in seed or on infected transplants. Once established, CMM can survive on plant residues for as long as 3 years, and will persist on stakes and equipment for up to 7 months. The pathogen is spread within plantings by splashing rain and by human activity. Warm temperatures (75-90 °F) and high moisture or relative humidity favor development of bacterial canker.

Control of bacterial canker can be difficult once symptoms are observed. Prevention is the best defense. We recommend that growers use certified, disease-free seed or transplants. Tomatoes should be rotated 2-3 years away from crops other than tomato or its relatives. All implements and materials such as stakes should be sanitized; stakes from infested fields should be destroyed. Irrigate early in the morning to minimize the length of time that foliage is wet. Avoid working tomatoes when foliage is wet, as bacterial canker is a highly infectious disease and can easily be spread by workers. Symptomatic plants should be removed from the production area and buried or incinerated. Applications of fixed copper plus maneb or mancozeb may reduce epiphytic (superficial) populations of CMM before symptoms appear, but have generally had little impact on disease control.

DIAGNOSTIC LAB - HIGHLIGHTS
By Julie Beale and Paul Bachi

During the past week, we have diagnosed Rhizoctonia root rot and zinc deficiency on corn; bacterial blackleg, target spot, Pythium root rot, Sclerotinia collar rot, Rhizoctonia damping off, nitrogen deficiency and cold injury on tobacco.

On fruit and vegetable samples, we have seen fire blight on apple (crabapple and pear as well); bacterial leaf spot and nitrogen deficiency on peach; bacterial blackleg on potato; and bacterial canker on tomato.

On ornamentals and turf, we have diagnosed Botrytis blight and Heterosporium leaf spot on iris; Pythium root rot on miscanthus; leaf/flower gall (Exobasidium) on azalea; bacterial leaf spot on barberry; Kabatina twig blight on juniper; horned oak gall and jumping oak gall on oak; Phylloxera on hickory; petiole borer on maple; brown spot needle blight on pine; anthracnose on ash and oak; Pythium root rot on bentgrass and bluegrass; and brown patch on mixed turfgrass.

By Patty Lucas, University of Kentucky Research Center

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.

View Princeton trap counts for the entire 2005 season at - http://www.uky.edu/Ag/IPMPrinceton/Counts/2005trapsfp.htm

Fulton County trap counts are available at -http://ces.ca.uky.edu/fulton/anr/Insect%20Counts.htm

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

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