Effect of Natural and Artificial Diets on the Biology of Tomato Fruit Worm (Helicoverpa armigera H.)

Tomato fruit worm, Helicoverpa. armigera (Noctuidae: Lepidoptera), has been identified as the most harmful and destructive insect pest of tomato crop. Mass rearing of this insect is necessary to obtain enough culture for conducting different bioassays i.e., to screen insecticides as tools for insect pest management under laboratory conditions. For this purpose, five artificial diets were prepared by substituting basic ingredients as flour of chickpea, mung bean, soybean, maize and common bean and tested for biological parameters of H. armigera compared with natural food i.e., okra fruit. The current study was conducted in the Laboratory of Plant Protection Division Nuclear Institute for Food and Agriculture (NIFA) Peshawar, Pakistan. The investigations revealed that chickpea flour based-diet produced healthy larvae and pupae that completed development within the minimum duration of 12.7 and 10.5 days, respectively, while artificial diets based on maize and common bean flour increased larval and pupal duration up to 17.5 and 13.4 days, respectively. Likewise, the minimum and maximum larval length of full-grown larvae ranged from 34.2 to 29.8 mm was recorded on common bean flour-based diet and chickpea flour-based diet, respectively. Mortality of larvae was maximum (20%) on natural okra diet. However, mortality was minimum (4%) on chickpea flour-based diet. Percent male and female emergence was varied in all treatments. Apparently maximum adult emergence of 86% was achieved on natural diet, followed by chickpea (83%), soybean (80.3 %), common bean (78%), mung bean (82%) flour based artificial diets while minimum of 68% was recorded on maize flour-based diet. Longevity of adults ranged from 7.6 to 9.4 days in males and 10.2 to 13.3 days in females were recorded among all tested diets. Pre-oviposition, oviposition, postoviposition, fertility and fecundity were also found better in chickpea flour based artificial diet. The male to female sex ratio obtained after feeding the larvae on different diets differ significantly and was found maximum (1:1.8) on chickpea and minimum (1:1.4) on common bean flour-based diet. Therefore, it is concluded from the findings that chickpea flour-based diet is very conducive to maintain good quality culture of H. armigera. Moreover, mung bean and soybean flour-based diets can also be used for successful rearing of H. armigera.