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Southeast Missouri Pest Bulletin May 27, 2003

Based on field observations and moth trap captures, this winter's cold temperatures and wet conditions did not kill off as many insect pests as we would have liked for this field season. These insects may owe their survival to this winter's snow that partially insulated them from the freezing temperatures. Thus far, insect activity has been light; however, some insects (ex. thrips and plant bugs in cotton; bean leaf beetles in soybean; and corn borers in corn) will bear watching in the coming weeks. Since we cannot accurately 'predict' where and to what extent insects will hit your crops, the best approach to detecting pest problems is to scout your fields on a regular basis.I recommend at least once a week, and preferably twice a week when there is an ongoing pest outbreak like the bollworm / budworm problem we experienced last year in cotton. (MLB)

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INSECTS
Cutworms: We have not received many reports about nor observed much cutworm activity thus far in regional corn, cotton, grain sorghum, and soybean fields. Several regional extension specialists and myself have been trapping black cutworm moths in New Madrid, Pemiscot, and Scott Counties the last few weeks, and moth captures in the Portageville area have remained steady the last three weeks at just under 100 moths per week. These crops will remain susceptible to cutting damage until the 4th leaf growth stage. If you observe any clipped plants in your fields, locate the larvae beneath dirt clods or in their burrows. Insecticides should only be applied when cutworm larvae are still present. Since cutworms are nocturnal, recommended timing for insecticide applications is in the morning or late afternoon NOT midday.

COTTON
Thrips: I've received several calls the last two weeks regarding insecticide treatments for thrips in replanted or late-planted cotton fields. I've still recommended at-planting treatments since thrips can quickly infest these fields and damage the crop before being detected, and we can ill afford a further delay in this year's crop since it may be a late one. Thrips have many alternate host plants (ex. weeds, wheat) that have permitted their populations to buildup this spring, thus, thrips will remain a problem until cotton plants reach the 5th or 6th true leaf stage. Any cotton not protected with an in-furrow insecticide or seed treatment should be closely monitored and treated when fields reach the recommended economic threshold of 1 thrips per plant. Under conditions of heavy thrips migration, high numbers of adults can be found in treated fields before they have fed long enough to be controlled; however, the presence of numerous wingless, immature thrips indicates that at-planting treatments are no longer providing adequate control. This is when a foliar application of recommended insecticide should be applied.

Tobacco budworm: Yes, it may seem strange to be talking about budworms this early in the year; however, I did want to make a couple of comments regarding some recent moth trap counts gathered this month. Both in northeast Arkansas and here in Missouri, tobacco budworm moths have already been caught in pheromone traps. On May the 19th we caught 133 budworm moths plus 82 more two days later at the MU Delta Center Lee Farm. This is a good indication that some budworms successfully overwintered. As to what this may mean in a few weeks when cotton starts to bloom, we just don't know at this time. What I can say is if you've planted conventional cotton then it should be closely monitored to quickly bring these and other caterpillar infestations under control since you can not afford to lose much of this late-planted crop.

Along with several regional extension specialists, we'll have several budworm and bollworm traps in Dunklin, New Madrid, Pemiscot, and Stoddard Counties. The trap counts will be reported beginning with next week's issue. Anyone who's interested in running your own pheromone traps, I can supply you with pheromone lures for this summer.

Bt cotton: In light of last year's outbreak of caterpillar pests (especially bollworms and budworms) and the delayed planting due to this spring's wet weather, more Bt cotton has been planted this year in Missouri. It's important to remember that with 1st-generation Bt cotton varieties, this technology provides excellent control of tobacco budworms, good control of cotton bollworms, fair to poor control of armyworms and loopers, and no control of piercing-sucking insects (ex. aphids, plant bugs).

SOYBEAN
Bean leaf beetles: This remains one of the most important soybean pests in the United States, and economic infestations have been increasing the last couple of years in the Bootheel. Initially, early-planted fields near overwintering sites (ex. woodlots and woody fencerows) will be most at risk from seedling damage.

The variable colored (red to tan) and marked (spots, stripes) adults are easily identified by the black triangle at the base of their wings. Bean leaf beetle adults defoliate soybean plants by chewing small, round holes between the major leaflet veins. Even though soybean plants have a great capacity to compensate for foliar damage, seedling plants should not be stressed too much.

The recommended Missouri threshold during the seedling stage is 5 or more adults or one damaged plant per row foot. Adults are easily caught with sweep nets, but they frequently drop to the ground when the plants are disturbed. Recommended insecticides for bean leaf beetle control include: carbaryl, chlorpyrifos, methyl parathion, several pyrethroids, and thiodicarb. You can obtain additional information on the bean leaf beetle by picking up a copy of MU guidesheet G7150 at the Delta Center, your local extension office, or by purchasing one from MU Extension Publications (800-292-0969).

FIELD DAYS
The annual Delta Center Field Day has been scheduled for September the 2nd. Mark it down on your calendar, and we hope to see there.

PUBLICATIONS
The 2003 MU cotton and rice insecticide recommendations have been posted on the MU Delta Center website's (http://aes.missouri.edu/delta/) crop and pest information section. If you have any questions regarding these recommendations, feel free to contact me.

DISCLAIMER STATEMENT
The University of Missouri does not warrant products mentioned in this publication. The use of a trade name does not constitute recommendation of one product over other (generic) products of a similar chemistry.

University Extension does not discriminate on the basis of race, color, national origin, sex, religion, age, disability of status as a Vietnam era veteran in employment or program.