EFFICACY OF UNSYNERGISED DELTAMETHRIN AND DELTAMETHRIN PLUS CHLORPYRIFOS-METHYL COMBINATIONS AS PROTECTANTS OF STORED WHEAT AND STORED CORN (MAIZE)

Soft red winter wheat and ''Pioneer 3320'' corn (maize) were treated with either 0.5, 0.75, 1.0 ppm deltamethrin, 0.5 ppm deltamethrin + 6.0 ppm chlorpyrifos-methyl, 1.0 ppm deltamethrin + 6.0 ppm chlorpyrifos-methyl, or 6.0 ppm chlorpyrifos-methyl, and subsequently stored for 10 months. Bioassays were conducted every 2 months during this storage period. Rhyzopertha dominica (F.) and Sitophilus oryzae (L.) did not survive on the combination treatments applied to wheat. Survival of R. dominica in the three deltamethrin treatments was variable throughout the storage period but no F1 adults were detected. S. oryzae survival on wheat treated with 0.5 ppm deltamethrin ranged from 0 to 84.5%. Maximum survival in the 0.75 and 1.0 ppm deltamethrin treatments was 26.2 and 3.5%, respectively. Sitophilus zeamais (Motsch.) or Tribolium castaneum (Herbst) did not survive in the combination treatments applied to corn. Maximum S. zeamais and R. castaneum survival in the three deltamethrin treatments was 23.5 and 18.7%, respectively, but there were no significant trends during storage and F1 production was minimal.