This week I received two reports of lesser cornstalk borer (LCB) in seedling peanuts. LCB infestations in peanut in May are not uncommon, but these reports underscore the importance of scouting fields on a regular basis.
What do you do if you find LCB in your peanuts? If the infestation is at or above the threshold, you should treat the field with an insecticide. There are currently two active ingredients that provide good efficacy against lesser cornstalk borer in peanut: chlorantraniliprole (Vantacor and others) and novaluron (Diamond).
“But Mark, my peanuts are only 28 days old. Surely I can wait awhile before I spray them.” Waiting to treat LCB is rolling the dice. It is possible that the environmental conditions that made your field favorable for an LCB infestation will change quickly and dramatically enough that treatment would not be profitable. If the infestation is barely at threshold and the extended forecast calls for cooler temperatures and significant rainfall over several days, I might be tempted to wait and see what happens before spraying my peanuts. Otherwise, my advice is to treat the pest. In my opinion, LCB is the insect that poses the greatest risk to most peanut growers in Georgia each year. Growers may be looking for ways to save money in 2025, but not treating LCB when thresholds are exceeded is not one of them.
There is no reason for a preventive treatment for lesser cornstalk borer; if the insect is not present in the field, do not treat. Moth traps provide some indication of LCB activity, but there is no treatment threshold based on moth trap capture. We have seen lots of moths in traps in Georgia peanut fields where larval infestations never developed. LCB moths in a trap are a signal to go scout the field if you are not already doing that on a weekly basis.
“My field is irrigated, so I don’t need to spray LCB, right?” Wrong. You cannot water LCB away with irrigation before the canopy closes in the row middles. Irrigated fields with a full canopy are rarely infested at threshold levels, but prior to that, fields are at risk.
If you have any questions about LCB management in peanut, please contact your local UGA County Extension agent.
The video below provides some tips for scouting early season LCB in peanut.
