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Don’t Let Insects Spoil Your Picnic

Scott StewartBy Scott Stewart, Jackson, TN

  • Professor, IPM Specialist at the University of Tennessee.
  • Based at West Tennessee Research and Education Center at Jackson, Tenn.
  • Earned B.A. from the University of Northern Iowa.
  • Earned M.S. from Texas A&M University.
  • Earned Ph.D from Auburn University.
  • Has statewide Extension responsibility for insect pest management in row crops.

We have made great strides in the last 20 years with the eradication of the boll weevil in almost all parts of the Cotton Belt and the adoption of Bt cotton varieties that substantially control caterpillar pests. However, there are still annual battles with insect and mite pests that require our diligence.

Starting at the beginning, thrips management typically requires the use of at-planting insecticides. Almost everyone is using an insecticide seed treatment, and the option for Temik is no longer available. The spreading resistance of tobacco thrips to thiamethoxam, the active ingredient in Cruiser, caught us a little by surprise the last several years. In the Mid-South, this has essentially put an end to the use of Cruiser and other thiamethoxam- based insecticide seed treatments in cotton. We are concerned about going down a similar path with imidacloprid (e.g. Gaucho) as it is being used now almost exclusively.

Alternatives to neonicotinoid seed treatments like Cruiser and Gaucho are not really exciting to our farmers, but we need to be prepared to adapt. For now, I am currently suggesting a foliar insecticide application at about the one- to two-leaf leaf stage, particularly when cotton is growing off slowly and/or there is evidence of thrips injury. Making this application early is better than later. Making two applications is usually a waste of time and money.

Tarnished plant bugs remain the No. 1 problem in the Mid-South. Everyone wants a prediction. I won’t go far out on a limb, but problems tend to intensify when cotton acres are down as we funnel plant bugs into fewer acres. We should pay close attention in 2015. There is no single solution to managing plant bugs. Early planting and selection of early maturing varieties helps the cause, but plant bugs require a good scouting program and the proper selection of insecticides.

viewpoint insectsWe have some good tools. All university Extension programs have a list of top performing insecticides that may include Centric, Admire Pro or other imidacloprid products, Bidrin, Diamond, Orthene and Transform. The key is picking the right product at the right time, depending on the time of season and what other pests might be in the field. The biggest mistakes are usually the result of missing the problem. Don’t be fooled that one insecticide application will last two weeks. Tight spray schedules are important in high pressure scenarios.

You never know about spider mites, but somebody is always going to have a problem. A dry summer can set us up for problems, especially if we are continually knocking back beneficial insects with foliar insecticide sprays. Products such as the pyrethroid insecticides or acephate, particularly when repeated applications are made, greatly increase your chances of flaring two-spotted spider mites (and cotton aphids for that matter). That’s one reason I often suggest delaying the use of particularly disruptive insecticides until the mid- and late-blooming stages.

Of course, I would like to say that these are the only pests on the radar. But we all know other things can take a bite out of the crop. Stink bugs are one example, and even with Bt cotton, there is no guarantee bollworms won’t require some attention. These are other reasons why a thorough scouting program is a must. Cotton is a dynamic crop, which can make it fun but also challenging to manage. There are substantial regional differences in pest populations, insecticide resistance levels and many other factors. It really pays to stay current by attending field days, following on-line news blogs from reliable sources and having the phone number of somebody local that you trust to help make insect management recommendations.

Contact Scott Stewart in Jackson, Tenn., at (731) 425-4709 or sdstewart@utk.edu.