Toxicity of pyrethroids to larvae of the Egyptian cotton leafworm, <i>Spodoptera littoralis</i> (Boisd.). II. Factors determining the effectiveness of permethrin at ultra‐low volume

Abstract

Abstract Factors determining theeffectiveness of permethrinat ultra‐low volume against larvae of Spodoptera littoralis (Boisd.) were investigated using a modified Potter tower. Higher mass application rates for 95 % control were necessary when permethrin was used as a residual deposit compared with direct contact plus residual deposit action. Mortality was increased by adjusting droplet density, although the optimum number of drops/ unit area depended on the mass application rate. When mass application rate and droplet density were held constant, mortality increased inversely with the mean droplet diameter. The implications of these results for field applications are discussed.