Alternatives to Acephate for Thrips and Dealing With Lackluster Management
I’ve been fielding a lot of calls concerning the effectiveness of acephate for thrips. Remember that our seed treatments run out at 2-3 weeks after planting (probably closer to two) and we are relying pretty heavily on our sprays. In my opinion, a spray of acephate is still the best option to manage thrips once the seed treatment runs out given its effectiveness and price. Pyrethroids (including bifenthrin) are not effective and other chemicals are generally not as effective. One exception is 3 oz of Radiant plus a surfactant, covered in this article here. In previous screening trials, this has been as effective on tobacco thrips as acephate.
Other folks have been concerned about lackluster performance of foliar sprays. The most important thing to look for is the presence of live thrips after your spray. Do you have immatures present? Adults? Immatures might be Western flower thrips (again, covered here), so consider using Radiant or spraying up to 1 lb. active ingredient of acephate. In this dry weather, you might see some flaring of other pests, such as spider mites behind acephate. Radiant is a much softer chemical and will not flare other pests. Neither chemical will have much residual so we might expect that adults could move in behind the sprays. In this case, your field may simply require a respray if immatures develop from these colonizers. If you are seeing dinged up plants, but no thrips present, you could be seeing injury that happened before your spray or you could be seeing some herbicide injury that only mimics thrips injury (good article on this here). Finally, keep in mind that a good rain will help our cotton jump out of the injury that they are experiencing now.