Following are ‘collaborative’ comments by Rick Brandenburg, David Jordan (NC State) and me regarding the insect/mite situation on peanuts.
Rootworm: July is the month when we think about spider mites and southern corn rootworm. The two are quite different in that spider mites do best under dry conditions and rootworms do best under wet conditions. Add to that the fact that rootworms must be treated preventively and that if it turns dry, not only will you not have rootworms, you will encourage spider mites with the rootworm application. This situation creates lots of unknowns for growers. Make sure you use the southern corn rootworm advisory to make decisions about rootworm treatments. Light, sandy soils will rarely see rootworm problems but are most prone to spider mite outbreaks. Heavier soils retain soil moisture and are more likely to suffer rootworm infestations. July is the key month to treat for rootworms as we have seen poor performance form rootworm insecticides applied in August.
Spider mites: Keep an eye on the weather. Hot and dry will always equal a threat from spider mites. Also, be very careful with ‘automatic’ pyrethroid applications as these can flare mites. If mites become a problem, there are only three products registered for use in peanuts that provide spider mite control: Comite, Danitol and Brigade. Of these, Comite provides the best control and if applied early in the infestation cycle and has often worked with a single application. But in recent years Comite has become difficult for grower to find, and has no activity on worms. Products like Danitol or products with bifenthrin (e.g., Brigade) should be considered if worms and mites are both present. Both can provide decent worm control and at higher rates can provide mite suppression. But sometimes one application of Danitol (or Brigade) might not be completely effective as they knock down adult and larval mites but not eggs. Last year fields were overwhelmed in some areas and a single application wasn’t enough due to the life cycle and high populations. Two applications spaced 5 days apart may have paid dividends under 2010 pressure.
Corn earworm: We are approaching ‘worm season’ in peanuts. We are in the process of doing our annual field corn survey for corn earworm to determine the extent of that population, as it is a good predictor of what is to come in peanuts, cotton and soybean. Preliminary results are showing a moderate to large population in corn, and one that is a bit ahead of schedule. Moth counts in black light traps are still very low which indicates that adults are not moving out of corn yet. We expect to see this picking up in 7 to 10 days. More will be provided when the survey is completed next week. The latest corn earworm pyrethroid resistance monitoring results from Virginia did not show a large jump in resistance level over the past few weeks, but we are continually monitoring and will keep you updated.