Persistence of Diflubenzuron on Soybean Leaves

Diflubenzuron [Dimilin™, N-[{(4-chlorophenyl)amino}carbonyl]-2-6-difluorobenzamide] is an insect growth regulator that is highly effective and provides residual control (up to 54 days) against velvetbean caterpillar, Anticarsia gemmatalis Hübner, on soybean, Glycine max (L.) Merrill, in Louisiana. We conducted a study to quantify the field persistence of diflubenzuron residues on soybean leaves when applied at 0.035 kg/ha, a rate used in preventive programs for velvetbean caterpillar. Day of application (day 0) concentration of the insecticide on the leaves was 206 ± 41 ng/cm². By 14 days after treatment insecticide leaf coverage had decreased to about 20 ng/cm², where it remained for the remainder of the study. This persistent low level residue on the soybean leaves is consistent with the extended diflubenzuron efficacy toward velvetbean caterpillar that has been documented in Louisiana.