By Dominic Reisig
Lots of folks are wondering what to use downstream for thrips in cotton. It’s critical to not only get the 1) active ingredient from your dealer, but also to get the 2) rate of insecticide applied to the seed (0.375 mg ai/seed is common for most). This is because brand names change and the active ingredients associated with these brands change over time. Once you have this information, you will be able to make a decision. Active ingredients available for thrips are acephate (not a neonicotinoid), clothianidian, imidacloprid, or thiamethoxam (all neonicotinoids). Some of these may be packaged with nematicides, such as abamectin and thiodicarb, that have some activity on thrips.
Seed treatment. Previous to known thrips resistance, tests from Drs. Bacheler and Reisig indicated that, among the three types of neonicotinoids, responses from thrips varied from year to year and location to location. Dr. Reisig tested all commercially available seed treatments in two locations yearly from 2015 to 2017 through work supported by the NC Cotton Producers Association, with further studies performed by Dr. Kennedy’s program (NCSU Entomology and Plant Pathology Department). These were combined with various in-furrows both with an without seed treatments. From these studies, any seed treatment with a full rate of imidacloprid provided equivalent control (for example, Acceleron, Aeris, and Avicta Elite), even when packaged with other insecticides. Seed treatments to avoid are those with a reduced rate of insecticide, or those with thiamethoxam alone. Acephate (Orthene) seed treatment has provided moderate control in our environment and should be avoided as a standalone seed treatment. Again, active ingredients or rates within a brand name seed treatment can vary from year to year, although marketed under the same or similar brand name annually, therefore it is important to ensure that you are purchasing a treatment that includes the full rate (0.375 mg ai/seed) of imidacloprid.
In-furrow. Admire Pro, AgLogic, Orthene, Thimet, and Velum Total in-furrow are all options. All these products in furrow without an insecticidal seed treatment can provide equivalent control to a seed treatment in some cases. Importantly, they can also completely flop without an insecticidal seed treatment in some cases (with the exception of AgLogic which, depending on rate, usually looks as good or sometimes better than a seed treatment). Because of this, we strongly recommend using them as partners for seed treatments and encourage growers to use a seed treatment on all their cotton to ensure uniform thrips protection. Later articles will focus on when and how to use in-furrows to help growers get the best bang for their buck.