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It started raining. What do we do now for peanut pests?

It started raining. What do we do now for peanut pests?

The July rain in South Georgia will reduce the severity of lesser cornstalk borer infestations in many fields and will at least buy us some time before spider mites become a serious concern. If the rain continues through the remainder of the season, we will likely not have to battle either of these pests over a large area. A return to dry conditions, however, will mean we need to keep a close eye on our non-irrigated peanuts to ensure pests are discovered and managed in a timely manner.

Foliage feeding caterpillars are making an appearance in peanuts across the state, but there have not been any widespread “outbreaks”. Folks are reporting a mix a several caterpillar species, and while populations in most fields have not reached threshold, some have. Peanut can tolerate a lot of defoliation without suffering significant yield loss, but defoliation during pod fill is more likely to result in economic loss than at any other time. Thresholds are 4 to 8 caterpillars per row foot…that is per ONE foot. Use the lower end of the range if vines are small or growing poorly and the higher threshold value when plants are vigorous and rank. Finding caterpillars by the fence row, field path, pivot point, etc does not necessarily mean a field needs to be treated. If the average number of caterpillars per foot of row from at least 10 random samples is less than the threshold, it will not pay to treat.

Is it OK to use a pyrethroid in peanuts now that it has been raining? I personally don’t like to put a pyrethroid in a non-irrigated peanut field unless it is absolutely necessary. We need to weigh the risks. What pest are we trying to manage, and does it really need to be managed? Are there alternatives to pyrethroids? Is the risk of yield loss from the pest we are treating greater than the risk of flaring and battling spider mites? The answers to these questions are not always obvious or even knowable, so we will make our choices based on what we do know and hope for the best.

We can expect to see increasing numbers of velvetbean caterpillar, soybean looper, redneck peanut worm, and three-cornered alfalfa hoppers in the coming weeks. There will almost certainly be a surprise or two as well. As always, the best practice is to scout regularly and make management decisions based on good quality, real time information from the field.