Written by Mark Abney
We are at the point in the growing season where a lot of Georgia peanut fields are 25 to 35 days after planting. Though thrips pressure has not been particularly high in 2023, it doesn’t take many adults per plant to produce a damaging population of immatures on peanut. Thrips injury typically peaks around 28 days after planting regardless of whether an insecticide was used in-furrow. The difference is that injury will usually be much lower in fields where an insecticide was applied. Most fields that are treated with an in-furrow insecticide will not benefit from an additional foliar application, and fields that were not treated at-plant should have been sprayed around 14 days after planting.
Under good growing conditions growers will typically see noticeable reduction in thrips injury at 35 days compared to 28 days after planting. Peanuts in my trials planted on 2 May that received no in-furrow insecticide look rough right now, but I expect them to look much better by the middle of next week. Why am I taking the time to write this? Thrips injury will reduce yield, and we should manage thrips, but revenge spraying after the damage is done is not going to recover that lost yield. As a reminder, applying a foliar insecticide may kill thrips, but it will not reduce the risk of Tomato Spotted Wilt .
It is the second day of June, and reports of lesser cornstalk borer (LCB) in peanut at threshold levels have been trickling in this week from Southwest all the way to South-central Georgia. Everyone knows that LCB likes it hot, and it has not been hot by Georgia standards this spring. I think the high lesser cornstalk borer pressure we experienced in 2022 and the mild winter we just went through set us up for high risk to this pest in 2023. What happens next will depend on rainfall and temperature. Consistent rains in the coming weeks would greatly reduce the likelihood of a statewide LCB outbreak. On the other hand, dry conditions coupled with increasing temperatures would probably result in economically damaging populations in many of our peanut fields. Since I cannot predict what will happen with the weather, I am going to be scouting my peanuts, and I strongly encourage growers to do the same. Here is a link to a video on scouting for LCB https://site.extension.uga.edu/peanutent/2020/06/early-season-scouting-tips-for-lesser-cornstalk-borer-in-peanut/
UGA research has shown that LCB can be effectively managed with timely applications of recommended insecticides (see the Georgia Pest Management Handbook). LCB infestations at threshold should be managed regardless of the age of the crop, as even young plants are susceptible to yield loss from this pest. Rain will not kill LCB, and irrigated fields are not immune from infestation. One or two rainfall events will make it hard to find the caterpillars, and consistent rainfall over multiple weeks will ultimately result in reduced populations. Irrigated fields are at reduced risk for LCB once the vines lap the row middles, but no amount of irrigation will eliminate the pest while the row middles are still open. The bottom on LCB is this: 1. the insect is currently present in GA peanut fields, 2. we can manage this pest effectively if we are timely and use the correct tools, 3. scouting is the key; spraying every peanut field because some of them might be infested is not a good management decision.
If you have questions about thrips, lesser cornstalk borer, or any other insect pest of peanut, please contact your local University of Georgia County Extension Agent.