Project Summaries

12-174GA  Project Manager: P. F. O'Leary

IMPROVED INSECTICIDE SELECTION AND FOLIAR TIMING FOR MITIGATING THRIPS IN SEEDLING COTTON

Michael D. Toews, Georgia Cotton Commission

Thrips of the genus Frankliniella are widely recognized as serious economic pests of southeastern cotton production.  Across the US, seedling thrips infested 8.5 million acres in 2011 and claimed 167,428 bales of cotton.  With expensive seed treatments commonplace and follow-up foliar sprays routinely applied, thrips management control costs can be significant. Injury and damage symptoms can range from leaf curling to delays in crop maturity, reduced yield, and stand loss.  Cotton growers in the southeastern United States, who grow roughly 25% of the US crop, have utilized in-furrow insecticides like aldicarb (Temik 15G) with much greater frequency than their counterparts in other parts of the Cotton Belt.  In addition to providing excellent thrips control, aldicarb confers nematode suppression and residual protection from spider mites and cotton aphids early in the season.  The recent loss of Temik 15G from the marketplace has greatly accelerated the need for new approaches to thrips management in seedling cotton.

This project was broadly aimed at identifying practices, products, and optimal foliar timing for cost effective and efficacious management of thrips.  In three separate experiments we examined heavy rye cover crops with strip tillage, potential in-furrow replacement products, and use of starter fertilizer and a well-timed single foliar insecticide application.  In each experiment, we enumerated thrips populations, measured plant heights, visually rated plots at 28 days after planting, estimated crude biomass accumulation at 42 days after planting, and measured lint yield.

In the heavy rye cover experiment we discovered several issues that will require experience to improve management.  First, stripping into the rolled rye caused build up issues behind the strip till rig that required proper set up and running at faster speeds.  Once the plant stands were established the strip tilled plots did not grow as fast and accumulated less biomass, but experienced significantly less thrips injury and yielded similar to conventionally tilled plots.  In a test of potential in-furrow replacements for Temik 15G, we observed that Counter 20G, Orthene 97 applied as a seed treatment, or Thimet 20G provided similar levels of thrips suppression.  Although none of the insecticide treatments would have required a foliar overspray, 3.5 lb of Temik 15G and 30 oz per cwt of Orthene 97 rated better on a visual injury assessment than the rest of the treatments.  Finally, the starter fertilizer trial showed that the use of starter fertilizer, Cruiser treated seed, and a single foliar Orthene 97 application at first true leaf all contributed to increased biomass production on loamy sand soils, such as those found at Tifton, GA.  Conversely, the starter fertilizer did not contribute to increased biomass on sandy clay loam soils, such as those found near Plains, GA.  Starter fertilizer never reduced the number of immature thrips present, but on loamy sand may have enabled the plants to grow at a faster rate despite serious thrips pressure.  The use of a single foliar overspray at either 1st leaf or 2nd leaf provided superior thrips suppression compared with no foliar sprays at both Tifton and Plains.  Also, use of an insecticide seed treatment always improved thrips management in early season assessments.

 

Project Year: 2012
 

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