Heat Accumulation for Timing Lygus Control Measures in a Safflower-Cotton Complex13

Abstract

Lygus bugs, Lygus hesperus Knight and L. elisus Van Duzee, are major pests of cotton in the San Joaquin Valley, California. A simple method of heat accumulation is described which utilizes only daily maximum and minimum temperatures. The procedure is used to predict the time when 50–70% of the lygus bug nymph population in safflower is in the 3rd–5th stages. This critical stage is reached upon accumulating ca. 16,000 degree days, beginning Apr. 1 and using 52°F (11.1°C) as a developmental threshold. This enables growers to apply a single areawide insecticide treatment to their safflower fields before the Lygus begin to disperse to other crops. This treatment largely eliminates the Lygus threat to cotton on the west side of the San Joaquin Valley.