ABSTRACT
Six insecticides of different chemistries were evaluated against the cotton bollworm (Helicoverpa zea [Boddie]) in conventional (Deltapine® 'DP 5415', Deltapine® 'DP 5415RR') and transgenic Bacillus thuringiensis (Berliner) (Deltapine® 'NuCOTN 33B', Deltapine® 'DP 458 B/RR') cotton. In 1998, treatments consisting of three rates each of a pyrethroid (Karate-Z®), spinosyn (Tracer®), carbamate (Larvin®), pyrrole (Pirate®), oxadiazine (Steward®), and avermectin (Proclaim®) were established in a non-irrigated field. In 1999, treatments consisted of three rates each of Karate-Z®, Tracer®, Larvin®, and Steward® in an irrigated and a non-irrigated (dryland) field. The highest rate of each insecticide corresponded to normal grower-use rates. Tracer® and Larvin® controlled H. zea in conventional cotton, whereas other materials were less effective. Even though H. zea is becoming increasingly resistant to pyrethroid insecticides, Karate-Z® was highly effective in dryland B. thuringiensis (B.t.) cotton. Tracer® and Larvin® were equally effective. Data indicated that reduced rates of Karate-Z®, Tracer® and Larvin® could be used for control of H. zea in dryland B.t. cotton systems. However, reduced rates of these insecticides in an irrigated B.t. cotton system did not provide adequate control.
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