Interaction Between Weed Management and Thrips Management on Peanut Development and Yield

The area planted to peanut has been increasing in Mississippi over the past several years due to lower commodity prices in other crops. Peanuts have become a viable option in a producer’s crop rotation on both irrigated and non-irrigated lighter textured soils. Insect pest management is complex, and numerous species typically feed on peanut. In general, at-planting insecticides are recommended to manage soil insects and thrips. Historical research has shown that foliar control of thrips provides little benefit in peanut. However, some pre-emergence herbicides can cause significant injury under certain environmental conditions, and it is not clear how thrips impact seedling peanuts following herbicide injury. The objective of this study was to evaluate the interactions between applications of Orthene and commonly used pre-emergence and post-emergence herbicides. Treatments were arranged as a split-split-plot within a randomized complete block design with 4 replications. The main-plot factor was flood irrigation at 2 levels, flooded and not flooded. The irrigation factor was included to maximize herbicide injury. The sub-plot factor was herbicide application at 2 levels. They included a pre-emergence application of flumioxazin (Valor®, Valent Co.) or no flumioxazin. The sub-sub-plot factor was thrips management at 4 levels. They included 1, 2, or 3 applications of acephate (Orthene 90S, Valent Co.) and an untreated control. Thrips densities were determined at various intervals after emergence to quantify level of control. Additionally, 5 plants were removed from each plot at 23 days after planting and weighed to determine biomass. Percent canopy closure was measured at 64 and 75 days after planting. At the end of the season, plots were harvested and yields were determined. Applications of flumioxazin and acephate each impacted plant weights and percent canopy closure. In general, these impacts were greater where peanuts were flood irrigated.