It’s now old news that tobacco thrips in much of the Mid South have apparently developed resistance to thiamethoxam, the insecticide component used in several cotton seed treatments including Cruiser, Avicta Complete, and Acceleron N. Control failures with thiamethoxam were documented in several experiments throughout the Mid South this past season So what does this mean for thrips management in 2014?
1) My recommendation for Tennessee is to avoid the use of thiamethoxam-based seed treatments, specifically in cotton. Impacts will be negligible in corn as tobacco thrips are essentially a non-pest. Similarly, there should be considerably less impact in soybean where we are dealing with a array of early season pests, of which tobacco thrips are just one member of the complex.
2) If Cruiser, Avicta Complete, and Acceleron N are used in cotton, I’m recommending that producers be aggressive in applying foliar applications for thrips control beginning about 5-7 days after emergence and at least one additional application before the second true leaf emerges. Essentially, you will be managing the cotton like it was not treated with an insecticide seed treatment. Alternatively, you could consider an in-furrow treatment with Admire, Admire Pro or an equivalent imidacloprid product (0.26-0.33 lb ai/acre) or Orthene (acephate, 1 lb ai/acre). Most folks are less than excited by in-furrow options, but they have been proven better than relying on foliar applications.
3) You could supplement a thiamethoxam treatment with an acephate seed treatment or hopper box treatment. This will help, but I’m not too excited by these options because labeled rates will not provide much residual control. They are certainly NOT stand alone treatments during a tough thrips year. I’d rather see an over treatment of imidacloprid than relying on these low rates of acephate, in which case you should have ordered this from the beginning.
4) There are no guarantees that imidacloprid seed treatments are completely unaffected even though they have been performing more consistently than thiamethoxam during the past few years. Indeed, there is indication that imidacloprid is at least somewhat affected by the same phenomenon. As a precaution, consider making a foliar application to cotton fields where Gaucho, Acceleron FI or Aeris was used. This application should be made before the third true leaf is visible, and my personal preference is within 14-21 days after planting.
We will be investigating a number of alternative thrips treatments in 2014, but the list of effective and labeled treatments is not long. It does not appear that Temik (or any generic equivalent) is a possibility. Thus, we may need to put more thought into how to preserve the utility of existing insecticide seed treatments in the Mid South.