Effect of larval diets on the survival and development of larvae in the cotton bollworm, Helicoverpa armigera Hübner (Lepidoptera: Noctuidae)

Abstract

This study examined the influence of seven natural diets (cotton boll, cotton leaf, okra fruit, soybean seed, tomato fruit, tomato leaf, and corn kernel) and an artificial diet (Insecta LF) on the larval survival rate, larval duration, frequency of larval stadium types and pupal weight in Helicoverpa armigera. On most diets, the survival rate was notably lower in the early larval stage compared to the late one. The percentage of larvae that survived from the 1st-stadium to the end of the larval stage was highest on okra fruit and Insecta LF (>60%). Less than 60% of the larvae fed on the other diets completed their larval period. The mean larval period was significantly shorter for individuals reared on plant fruits or seeds as well as on Insecta LF than for those reared on plant leaves. The shortest larval duration was recorded on cotton boll while the longest was seen on cotton leaf. The number of larval stadia ranged from 5 to 6 on cotton boll, soybean seed, corn kernel and Insecta LF, 5 to 7 on okra and tomato fruits, and 6 to 7 on cotton and tomato leaves. The five-stadium type was dominant on cotton boll, okra fruit, corn kernel and Insecta LF, while the 6-stadium type was common on soybean seed, tomato fruit, cotton leaf and tomato leaf. Mean pupal weight was greatest in individuals fed on Insecta LF and least in those fed on tomato leaf.