Comparison of various directional insecticide sprays against Busseola fusca (Lepidoptera: Noctuidae) and Chilo partellus (Lepidoptera: Pyralidae) in sorghum and maize

Abstract

Three methods of directional insecticide application against Busseola fusca and Chilo partellus infestations in the late growth stages of sorghum and maize were compared over two seasons. An insecticide mixture consisting of endosulfan and deltamethrin was applied 10 days after artificial inoculation of plants with newly hatched larvae of both species. Treatments consisted of insecticide applications, directed into the whorl (during the flag-leaf stage), onto the sides of plants, or a split application directed both into the whorl and onto the sides of plants. The last treatment was also applied at double the dosage rate, to determine the possible dilution effect resulting from split applications. Reduced dosage rate into the whorls, resulting from the split application, did not result in reduced efficacy of control. Species x treatment interactions occurred in maize and sorghum. Side applications of insecticide were ineffective in both crops. Whorl and split applications were effective and showed similar control of larval numbers in maize, while whorl applications provided best control in sorghum. Split applications resulted in the lowest yield losses in maize and sorghum. The efficacy of the various treatments is discussed in relation to ecological differences between the two borer species.