Hearing that thrips populations are larger than normal in the southeastern states has caused some concern in Virginia. For the past several years our ‘normal’ in terms of thrips numbers and plant damage to cotton and peanut seedlings has been higher than most of our neighbors to the south. Worse than ‘normal’ would be really challenging. This is the first week (May 14-18) that we have been able to systematically assess the thrips situation in our many cotton and peanut thrips field trials, as we finally have 1st true leaf cotton and emerged peanuts. To evaluate the thrips species and abundance, we sample 5 cotton seedlings per plot and in peanuts, 10 unopened terminal leaflets per plot. We rinse the adults and immatures from these plants/leaves and count them under a microscope. We also identify some number of the adults to species, which allows us to keep track of any species shifts that could indicate a problem.
This week’s samples are showing numbers that are pretty much in line with what we would expect for this time of the year. In cotton, we are finding about 10-18 adult thrips per 5-plant sample (2-3 per plant) and about that same number of immatures. In peanuts, we are finding about that same number of adults, but fewer immatures. These numbers are typical of the first sample in May. By next week, we will see an increase in the number of immatures to levels that have historically reached as many as 130-160 per 5 cotton seedlings and as many as 60 in 10 peanut leaflets. These immatures are the stage responsible for most of the plant damage. We are just beginning to see the effects of feeding on the plants and by next week, it will be no problem sorting out which treatments are performing best.
A positive observation—so far we are seeing good performance with the treatments that include Admire Pro, Thimet, liquid Orthene in-furrow, CruiserMaxx Peanut, Avicta CP and Aeris/Poncho Votivo in cotton and many others. It is especially important to note that so far, we have not detected any peanut stand emergence delays with Orthene/Acephate liquid in-furrow treatment, and we have several in our field trials.
We will continue to post updates as ‘thrips season’ progresses—and don’t forget that many of these thrips trials will be featured on our annual early season field tour on Tuesday, June 5 beginning at 9 am. We will post the flier next week.