June will bring a shift in insect concerns in peanut, and as usual, the weather will play a large role in determining what happens next.
April and May insect questions were primarily about thrips, so I will give a short summary of the 2020 thrips situation. Thrips pressure in my trials was variable with some locations receiving very little injury while others were hit pretty hard. By June, most of the thrips migration will be complete. Early planted peanuts should be growing fast enough that thrips are not much of a concern, and hopefully thrips pressure will have subsided so that later plantings are not severely affected. Growers who are considering foliar sprays targeting thrips in June should check the newest expanded leaves and the folded terminal leaves for thrips presence and signs of feeding injury. It does not matter how ragged the older leaves look, if the new leaves are not being fed upon, there is no need to treat. It is also worth noting that skippy stands are not uncommon this year, and we should not be surprised if we start to see Tomato Spotted Wilt Virus in fields where emergence was spotty.
I got reports of tobacco budworm and lesser cornstalk borer (LCB) infestations in peanut this week. Neither of these is unexpected, but they are good reminders that we need to be scouting fields and managing insects wisely. Foliage feeding caterpillars and LCB can be found in peanut fields every year, but LCB will only be a serious problem later in the season when hot, dry conditions persist. Early season LCB infestations that occur before the plants have covered the row middles are easy to miss, can reduce yield, and can remain active in spite of rainfall and irrigation. While LCB does not survive well in moist soil conditions, we generally can’t keep bare soil wet enough to eliminate an infestation. Once the row middles close, the game changes; at this point adequate moisture in the form of rain or irrigation will generally result in rapid declines in LCB numbers. Managing LCB in early season peanut is important to prevent yield loss and to stop the pest population from increasing.
June is often a quiet month for insect pests in peanut, but no one knows what 2020 will hold. The critical message for growers is to continue to monitor fields, identify problems early, and make informed management decisions.
NOTE: As of 3 June there have been no reports of any new regulations affecting the use of chlorpyrifos on peanut. This is good news for growers who need this active ingredient to manage peanut burrower bug and/or rootworm in peanut.