Southeast Missouri Pest Bulletin No. 1, May 18, 2004

It has been relatively quiet this spring on the insect front. Thus far, only a few crop pests (ex. spider mites and thrips in cotton; armyworms in corn; aphids in wheat) have infested fields in the Bootheel. Since we cannot accurately 'predict' where and to what extent pests will hit your crops, the best approach to detecting pest problems is to scout your fields on a regular basis. I think this will be particularly important this year since the weather has not been too favorable for planting and early crop growth. I recommend scouting your fields at least once a week, and preferably twice a week when there is an ongoing pest problem like the plant bug outbreak 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, and soybean fields. David Guethle and myself have been trapping black cutworm moths in New Madrid and Stoddard Counties the past few weeks. Very few moths have been caught in the Portageville area the past three weeks, and at the Stoddard County location the counts have averaged about 70 moths per week since mid-April. But, I wouldn't recommend letting your guard down (particularly in cotton fields) since cutworm infestations are very sporadic. I've also noticed quite a few fields with heavy weed cover vegetation that is still alive, and these fields will be very attractive to the female moths as egg-laying sites. Until cotton reaches the 4th leaf growth stage, plants will be susceptible to cutworm damage. When you burndown the weeds with a foliar herbicide spray, you might consider adding a low, labeled rate of a pyrethroid insecticide to kill any cutworms feeding on the weeds or the crop. Otherwise, I wouldn't recommend spraying for cutworms unless you observe clipped plants and live larvae in the fields.

CORN
Bt corn: The National Corn Growers Association in cooperation with industry and university cooperators has developed the Insect Resistance Management Learning Center (IRMLC). The purpose of this web-based center is to provide training on the following: Insect resistance management for corn borers and rootworms, compliance assurance program, integrated pest management, and an overview of insect resistance to the Bt technology. You can access the IRMLC on the association's website at the following link: http://ncga.com/biotechnology/IRMCenter/index.htm

COTTON
Replanting: It is late enough in May that it is getting much more difficult to replant than earlier in the month. Our data shows lint yields decline dramatically during the latter half of May. In 2003 after May 13th to June 2nd lint yields dropped by 66% or 33.6 pounds per day.

This indicates that even a poor stand planted early may have more yield potential than a late-planted one. We've found that one healthy plant per row foot still has top yield potential. Even one plant per 18 inches yielded within 10% of an ideal stand, but the plants must be healthy and the stand uniform throughout the field. One must always consider the general health of the crop when making replant decisions. Weed control will be more difficult with a thin stand, plus blowing sand and thrips must be managed. An unhealthy crop must be given intensive care just like a patient in a hospital. If you replant at this date in the growing season, you must use an early maturing variety. Replanting is a very serious economic decision so plan carefully. (BP)

Thrips: I've only received a couple of calls regarding thrips infestations since cotton planting began this spring. In light of the present weather and weedy field conditions, I'd certainly watch for a rapid buildup of thrips infestations in the coming days. An in-furrow or seed treatment at planting are still the preferred means of managing thrips, but even in fields receiving these treatments you may still need a foliar overspray because of wet soil conditions. Ideally, you can expect about three and four weeks control with seed and in-furrow aldicarb treatments, respectively; however, the recent heavy rains can leach these treatments in the soil and increase the plants risk to thrips feeding damage. Any cotton not protected with an in-furrow insecticide or seed treatment or was planted more than three weeks ago should be closely monitored and treated when fields reach the recommended action threshold of 1 thrips per plant. The presence of numerous wingless thrips or those with only partially developed wings is a key indicator that at-planting treatments are no longer providing adequate control. This is when a foliar application of recommended insecticide (ex. acephate, Bidrin) should be applied. (MLB)

Bt cotton: Based on information I've seen, it looks like our Bt cotton acreage will remain steady this year. I would remind you that the current 1st-generation Bt cotton varieties will not solve all 'worm' problems; however, this technology does provide excellent control of tobacco budworms, good control of cotton bollworms, fair to poor control of armyworms and loopers, but no control of piercing-sucking insects (ex. aphids, plant bugs).

Another important consideration when planting Bt varieties is refuge areas. This is a valuable tool for controlling various caterpillar pests; however, without the refuge areas these insects can quickly develop resistance to the Bt toxin present in the plants. Additional information on Bollgard cotton insect resistance management recommendations is available on the following website: http://monsanto.com/monsanto/us_ag/content/tools_dir/stewardship/irm/2004/bollgard.pdf

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 few years in the Bootheel. Initially, early-planted fields near overwintering sites (ex. woodlots and woody fencerows) will be most at risk.

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 this insect 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).

WEBSITE UPDATE
The 2004 MU cotton and rice insecticide recommendations have been posted for several weeks now on the MU Delta Center website's (http://aes.missouri.edu/delta/) crop and pest information section (see individual crop subsections). If you have any questions regarding these recommendations, feel free to contact me.

PRECAUTIONARY STATEMENT:
In order to protect people and the environment, pesticides should be used safely. This is everyone's responsibility, especially the users of pesticides. Read and follow label directions carefully before you buy, mix, apply, store, or dispose of a pesticide. According to the laws regulating pesticides, they must be used only as directed by the label.

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.