Rain‐washing of mimic®, RH‐5992, from balsam fir foliage following application of two formulations
Abstract Two formulation concentrates of the insecticide, RH‐5992 [N'‐t‐butyl‐N'‐(3,5‐dimethylbenzoyl)‐N‐(4‐ethylbenzoyI) hydrazine], an aqueous flowable (2F) and an emulsion‐suspension (ES), were diluted with water to provide spray mixes containing dosage rates ranging from 35 to 150 g of the active ingredient (AI)/ha. The mixes were sprayed in a laboratory chamber, onto balsam fir branch tips collected from field trees and greenhouse‐grown seedlings. Droplet spectra and spray mass recovery were determined on artificial samplers. Simulated rainfall of two different intensities was applied at different rain‐free periods, and rain droplet sizes were determined. Foliar washoff of RH‐5992 was assessed after application of different amounts of rain, and the increase in soil residues was evaluated. A direct relationship was indicated between the amount of rainfall and RH‐5992 washoff. The larger the rain droplet size, the greater the amount washed off. Longer rain‐free periods made the deposits more resistant ...