This study was conducted as part of our ongoing monitoring program to assess the performance of Larvin^® brand thiodicarb and Sherpa^® brand cypermethrin against B. virescens collected from different sites in the cotton belt.

Our 1990 foliar spray test results show that the two insecticides were highly effective against H. virescens populations obtained from sites in North Carolina and Texas. Larvin and Sherpa performed poorly, however, against larvae obtained from one site in Mississippi and three sites in Louisiana.

We evaluated the two insecticides under more practical conditions and found that field rate of Larvin provided good control of the larvae collected from sites in North Carolina, Texas and Mississippi but performed unsatisfactorily against the larvae collected in Louisiana. Field rates of Sherpa demonstrated poor control against both Louisiana and Mississippi larvae but performed well against the larvae collected in Texas and North Carolina.

A comparison between our 1989 and 1990 results indicates no major change in performance of Larvin or Sherpa against larvae collected in North Carolina. Conversely, we detected a significant decline in the toxicity of both insecticides against the larvae collected in Louisiana.