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Studies of loss estimation and relative susceptibility of genotypes of sorghum to earhead caterpillar (Heliothis armigera Huebner) (Abstract. An estimation of the avoidable loss of sorghum grains due to damage caused by Heliothis armigera was carried out with applications of endosulfan 0.05% at the early milk stage on CSH-5 and CSH-9 hybrids. The larval population was considerably lower in the protected crops compared to the unprotected one. Further, the hybid CSH-5 has a lower level of larval infestation compared to CSH-9. A significantly higher grain yield was obtained in the protected plot than the unprotected one. Losses of 6.65 q/ha (14.51%) in CSH-9 and 5.18 q/ha (12.87%) in CSH-5 were recorded. The overall loss for the two crops was 5.92 q/ha (13.72%). In CSH-9 the cost-benefit ratio was 1:12.70 compared with 1:9.89in CSH-5, with the mean ratio being 1:11.30. The most commonly recommended insecticides, endosulfan spray and BHC dust, were applied at different earhead stages to determine for control of H. armigera, which combination provided the best level of control. The application of insecticides at the early milk stage was highly effective; recording a low number of larvae and a high grain yield. The next earhead stages, in order of merit, were the full flowering and dough stage. The endosulfan spray was more effective in reducing the larval population size and increasing the grain yield than use of the BHC dust. The cost-benefit ratio was 1:31.02 in endosulfan at the early milk stage, and 1:25.06 for the BHC dusting. Among the 36 genotypes, the entries SPV-772, PSYH-2, PM-11344, SPV-756, SPV-690, SPV-790 and MSH-62 of losse earhead type sorghums were found to be less susceptible to the pest compared with the remaining entries from semicompact and compact earhead types.

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