SOURCE: Dominic Reisig, NCSU ENTOMOLOGY, 4/2/18

Tobacco thrips are the most common thrips species that infest North Carolina cotton. Because most tobacco thrips populations are resistant to the neonicotinoid-group insecticide seed treatments, there has been a lot of renewed interest in different at-planting insecticides. Without a lot of new insecticides available, we can expect the performance of neonicotinoids to continue to decrease over time. However, there are many things to consider before making a decision. Some, though not all, will be covered here. Foliar spray options will be covered in a future post.

Predicting damage potential: The first place to start is the Thrips Infestation Predictor for Cotton (click here). This is a very powerful tool to estimate how much your cotton is at risk for thrips injury based on environmental conditions. To use it, click on the map for a given location and submit an estimated planting date. You should do this for all fields in a given planting window on your farm. Because the tool forecasts risk, it’s a good idea to check one to two weeks before planting and also just prior to planting. Then check after you plant to see if any of the risk windows have changed. Consider more aggressive insecticide management scenarios in high-risk situations and consider using fewer insecticides in lower-risk situations.

No insecticide at planting: Thrips can be managed using foliar sprays alone, but not economically. This is not a recommended thrips management method in North Carolina. Additionally, reliance on foliar sprays alone can disrupt the system, potentially leading to unnecessarily flare-ups of other unwanted insect pests later in the season.

Insecticide in-furrow and no insecticidal seed treatment: Performance of in-furrow insecticides is variable across the Southeast. This is likely due, not only to resistance, but also to environmental conditions and insecticide placement in the furrow. North Carolina data have shown that a well placed in-furrow neonicotinoid, such as Admire Pro or Velum Total can perform as well as (but not better than) an equivalent seed treatment alone for thrips management. Therefore an in-furrow liquid is often insufficient. Seed to insecticide contact is extremely important. Not all soils, seed firmers, orafices, etc., are alike, but small differences in application can influence performance of at-plant insecticides against thrips. Try to contact each seed with as much insecticide as possible for rapid uptake by the plant and use the highest labeled rate. Efficacy of Orthene (acephate) in-furrow has been variable in North Carolina and is not recommended for this reason.

Note, that as mentioned above, thrips are resistant to neonicotinoids in many cotton producing areas in the Southeast. Admire Pro and Velum Total both contain imidacloprid, a neonicotinoid. If seed treatment performance has declined over the past few years, growers should scout fields to see if the insecticides are working. Consider a foliar spray if needed (covered in a future post).

Aldicarb is available as AgLogic 15G Aldicarb Pesticide. From our tests last year, performance is similar to Temik at the equivalent rates.

Insecticidal seed treatments: Most of the commercially available options are neonicotinoid-group insecticides. Because of neonicotinoid resistance in tobacco thrips, performance of the seed treatments has been variable in the past few years. However, because resistance levels are not equal everywhere, in most cases, neonicotinoid seed treatments still provide efficacy and are the most valuable tool we have in our arsenal to manage thrips. Because of this, growers in North Carolina should use insecticidal seed treatments in most situations. However, in some cases, such as in high-risk fields or with very resistant thrips populations, they may need a little help. This can be accomplished using foliar sprays (covered in a future post) or in-furrow insecticides.

We have very little data on the use of Orthene (acephate) seed treatments in North Carolina. The dealer must apply these. See the section above for recommendations on Orthene (acephate) in-furrow.

Insecticide in-furrow and insecticidal seed treatment: For now, this approach is the most effective, assuming resistance levels are not high. However, because of resistance or poor environmental conditions, this is no longer always a one-and-done solution. Also, because of resistance, we can expect efficacy to decline over time. Both a neonicotinoid insecticide in-furrow (Admire Pro or Velum Total) and a neonicotinoid insecticidal seed treatment can be used in combination to boost management in high-risk situations (cool planting conditions or heavy thrips pressure). In lower risk situations, growers may want to forgo the insecticide in-furrow. Finally, Orthene (acephate) in-furrow plus a neonicotinoid seed treatment rarely provides any advantage over the seed treatment alone.