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Comparing potential resistance to seed treatments for thrips in the Mesilla Valley

04-07-2020 - In New Mexico, optimal cotton production is often dependent on managing pre-flowering insect pests including thrips Thrips feed in the terminal bud of cotton and cause leaves to have a crinkled, tattered appearance as they expand. Heavily damaged foliage often is stunted and curls upward at the margins (Figure 1). Another characteristic of thrips damage is a silvery appearance of leaves at the feeding sites. Cotton damaged by these pests may have reduced photosynthesis capacity, attenuated growth, and plant death (Boyd et al. 2004). Reductions in stand density, poor early-season crop growth, and delayed crop maturity can reduce lint quality and cotton yields. These reductions have been observed to vary across cotton production regions, justifying expansion to a multiple location study in New Mexico. Early-season pest management in cotton was primarily achieved with an in-furrow treatment of aldacarb (Temik®). In 2010, the Environmental Protection agency and Bayer CropScience reached an agreement to terminate production and use of aldacarb in the United States (EPA Newsroom, 2010). Consequently, to achieve cotton production goals growers had to adopt alternative practices for early-season pest management. Neonicotinoid insecticide seed treatments have become the primary solution to managing early-season pests of cotton. Thiamethoxam and imidacloprid are two common systemic insecticide seed treatments applied to commercial cotton seed. Although the two insecticides belong to the same insecticide group, their physical and chemical properties vary and may affect mortality among target pests. Resistance to neonicotinoid seed treatments has been reported, particularly in the Southeastern US, thus it is important to evaluate efficacy in New Mexico. Evaluations in Artesia with low thrip pressure (Figure 2) have suggested that the seed treatments are effective there but we don’t now if they are effective in the Mesilla Valley. A one year field trial in 2018 with state support was not definitive. The proposed research will fund further research te determine if seed treatments are effective in the Mesilla Valley where there tends to be higher thrip pressure.