Late Season Caterpillar and Spider Mite Control Decisions

— Written By daherber

It should read “If you understand that you do not need to obtain 100% control of caterpillars to preserve yield, then the use of a pyrethroid might be a better choice.

Pyrethroids are most likely not going to give quite as good of control as Danitol or Steward or others, but unless a grower has really significant worm populations, that is OK. Nothing wrong with knocking back 80% of the population with a less expensive pyrethroid.

Late Season Caterpillar and Spider Mite Control Decisions
D. Ames Herbert and Rick L. Brandenburg

Early August is the time of year we commonly see populations of corn earworms and other caterpillars in peanuts in Virginia and North Carolina. Recent light trap catches would indicate we should see some worms in peanut over the next couple of weeks. Two very appropriate questions have been asked in recent weeks and a quick review of possible answers to these questions is in order.

The first question focuses on the issue of insecticide resistance in corn earworm populations in peanuts. There is some indication that pyrethroid resistance among corn earworms, including the ones we find in peanut fields, is a real concern. However, the pyrethroids cost less than other options and for many growers are the preferred means of control. In addition, pyrethroids are not the best choice for controlling tobacco budworms or fall armyworms in peanuts and control is often less than satisfactory against these pests. The second question focuses on which product to select if the field is also infested with spider mites.

In our opinion, 100% control should not be an overriding goal when treating for caterpillars in peanuts. Good control of corn earworm can still be obtained in most situations with the high rate of pyrethroids. Guidelines for helping determine which type of product to select in peanuts this year might include the following:

  1. Very high populations of worms. If populations exceed 8-10 worms per row foot, then the use of a non-pyrethroid insecticide might be a better choice.
  2. If populations of tobacco budworm or fall armyworm make up more than 25% of the population, then the use of a non-pyrethroid insecticide might be a better choice.
  3. If you understand that you do not need to obtain 100% control of caterpillars to preserve yield, then the use of a non-pyrethroid insecticide might be a better choice.
  4. If spider mites are present, then Danitol or Brigade should be used for caterpillar control. Guidelines are subject to specific local conditions, but in general we believe that pyrethroids still hold value for caterpillar control in peanuts this year. The recent rains certainly helped with the spider mite situation, but temperatures this week will drive populations back up. If caterpillar and/or spider mite populations increase in the coming weeks, we will update you on any changes in our recommendations.

Article first appeared as North Carolina Peanut Note (PNNC-2011-037)

Updated on Oct 24, 2014
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