Efficacy of Bacillus thuringiensis - chemical insecticide mixtures for cotton bollworm, Helicoverpa armigera (Hubn.) control
1997
Domo, M.C. | Solsoloy, A.D. (Cotton Research and Development Inst., Batac, Ilocos Norte (Philippines))
The efficacy of commercially prepared Bacillus thuringiensis (BT) mixed separately with different chemical insecticides at sublethal dosages was determined for controlling cotton bollworm, Helicoverpa armigera (Hubn.) at field conditions, at the CRDI Central Experiment Station, Batac, Ilocos Norte, Philippines. At three days after spraying, BT + 1/2 Recommended Rate (RR) of thiodicarb or metamidophos or cypermethrin-cyfluthrin-cypermethrin sequence or carbaryl was comparably effective with deltamethrin, the check insecticide against H. armigera. On the other hand, BT + 1/2 RR thiodicarb or carbaryl was comparable with deltamethrin at five days after spraying. The number of bolls produced was significantly higher from cotton sprayed with deltamethrin or BT + 1/2 RR chemical insecticide mixtures than BT alone or untreated check. The seedcotton yield was comparable for all treatments except BT alone which yielded lowest like untreated check. Boll weight and plant height were not affected by the treatments. The highest net benefit was derived from cotton sprayed with deltamethrin, followed by that from BT + 1/2 RR thiodicarb, then by BT = 1/2 RR cypermethrin-cyfluthrin-cypermethrin sequence and finally Bt = +/2 RR carbaryl. The reduced rate of chemical insecticides mixed with B. thuringiensis gave an effective bollworm control relative to BT alone. The full application of deltamethrin gave the superior control of the pest
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