The next two weeks should be key weeks if indeed we are going to see caterpillars in the peanut crop; so keep your eyes open. The last week or so has been good to many of you with some much needed rains. This really helps with the spider mites. In fact, when we get two consecutive days of cloudy weather and temperatures below 90 F, that really helps a fungus that attacks mites and knocks populations back. However, mites still need to be watched carefully given the hot summer and the forecast for the next week. As we move further along into August you can feel more confident applying a compound like Brigade or Danitol for mites and caterpillars with less concern about a rebound of the mite population. Comite is an effective mite product but can be hard to find in certain areas. The later we get in the season, the more practical it is to spray once for mites and then take a wait and see approach and hope you get favorable weather.

Caterpillar sprays should be considered only if thresholds are met. In fields with normal or better leaf canopies, treat if caterpillar populations reach 4 per row foot; and this increases to 6 per row foot towards the end of August. Many peanut fields are treated when populations are well below threshold, a practice that does not reap any benefit, and could increase the risk of other problems. If plants have poor canopy growth, you may be justified in using a lower threshold, but again, it is important to at least try to determine the number per row foot and abide by the thresholds. Another consideration is what species of caterpillars are present. They all count equally in the threshold, but if fall armyworms are in the mix, a non-pyrethroid may be needed to achieve good control.

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.