High numbers of thrips continue to be reported on cotton, and this may be a record book year for thrips across the Belt. The bad news is that these high numbers can further delay a relatively late crop.  Seed treatments are not bullet proof to high migration of adults and poor growing conditions. The good news is the hot weather will help push plants quickly past the most susceptible stages (emergence to 3^rd true leaf).  Insecticide treatments may be warranted if you are running multiple thrips per plant when plants have less than three true leaves.  After this point, you need to use some judgment whether treatment is needed based not just on thrips numbers but also on the amount of thrips injury that is present on new leaves. 

As a rule of thumb, treating 4^th or 5^th leaf cotton for thrips is not necessary.  Also, two foliar insecticide applications will only occasionally improve yield (assuming an insecticide seed treatment was used). These late treatments can often cause more harm than good by creating subsequent problems with spider mites or aphids.  Most data shows that thrips treatment after the 3^rd true leaf will not improve yield except in extreme circumstances.  Unlike most producers, I have the benefit of seeing plots with and without treatments.  I’ve include data for selected treatments from a test this year (see below).  You will see that although thrips are present in all treatments, untreated plots have many more thrips and much higher thrips injury.  My point is that seed treatments do provide significant protection.  In fact, in this test, Temik treatment caused some phytotoxicity.  Thus, the Aeris plots were more vigorous despite having a few more thrips than plots treated with Temik.

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Thrips treatment effects in cotton rated on 5/31/11, 22 days after emergence, Jackson.

*Numbers not followed by a common letter are significantly different (P < 0.05).