According to Dr. Edmisten and Collins, planting conditions are improving. With planters rolling soon, we urge growers to think about thrips management now. The best source of information for thrips activity is the Thrips Infestation Predictor. This online tool forecasts risk for thrips damage.
Based on which planting dates are at greatest risk, it can help growers know where to aggressively use insecticide and where to hold back, as well as where they might want to start scouting first on the farm. Growers should check this tool now to get a feeling for what infestation risk might look like for a given location and planting date.
Also, since it’s based on local weather conditions, the tool’s accuracy improves closer to planting. So growers should check it just prior to planting, as well as after planting. We also want to demonstrate why it’s so important for growers to check the tool for their farm.
Here is the risk forecast for planting cotton near Hertford (model run 04-26):
This forecast looks nearly identical for locations we ran near Albemarle, Red Springs, Rocky Mount, Swan Quarter, and Wilson (also model run 04-26 and not shown because it looks very similar).
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However, predictions for locations can vary, depending on the year. Also, this forecast is based on expected weather, which we all know can rapidly change. Based on the forecast on 4-26-21, cotton planted at the end of April is at less risk for thrips injury than cotton planted in the middle of May (green = lower risk, red = higher risk).
Growers planting in higher-risk conditions may want to consider an in-furrow insecticide overtop their seed treatment. In contrast growers planting in lower-risk conditions could consider using a seed treatment alone. In addition to driving resistance and hurting the wallet, unneeded insecticides can sometimes cause other problems later in the season like aphids and spider mites.
After emergence, all growers should scout fields and be prepared to spray based on established thresholds (two immatures per seedling). We suggest scouting the fields at highest estimated risk first. Note that insecticide sprays for thrips typically work best when you can peel back the cotyledon and see the first true leaf poking out. After several true leaves have expanded, thrips sprays have diminishing benefit.
This article provides a good overview of how seed treatments, environmental conditions, and thrips populations interact in relation to efficacy.