Fate and persistence of residues on wheat used to explain efficacy differences between deltamethrin suspension concentrate and emulsifiable concentrate formulations

Abstract

AbstractTo help explain the increased residual activity of a deltamethrin suspension concentrate (SC) formulation against grasshoppers, the persistence, location and nature of residues from the SC and an emulsifiable concentrate (EC) formulation have been compared. Wheat plants were sprayed in a cabinet sprayer at 7.6 g ha−1 for the EC and 5.6 g ha−1 for the SC, then weathered outdoors for 16 days. With the SC formulation, residues were more persistent, more residues were located on the exterior of the leaves, and less deltamethrin was converted to inactive isomers. Eight days after spraying, the exterior deltamethrin residues were 0.13 μg plant−1 from the SC versus 0.06 μg plant−1 from the EC. Thus, more residual deltamethrin is available to grasshoppers with the SC formulation.