Effect of dust formulation of milkweed (Calotropis gigantea R. Br.) different plant parts against Helicoverpa armigera (Hubner)

Helicoverpa armigera (Hubner) (Noctuidae: Lepidoptera) is known as American bollworm and is one of the most destructive pests of various crops and more or less of universal occurrence except in regions where extremes of climate prevails. It has been reported to feed on more than 120 cultivated food plants all over the world. Host species for H. armigera come from a broad spectrum of families and include important agricultural crops such as cotton, maize, chickpea, pigeon pea, sorghum, sunflower, soyabean and groundnuts. Management of H. armigera using insecticides has become difficult because of the development of resistance. Therefore alternate measures of control that are more efficient, more economical and safer need to be developed. Botanical insecticides have long been touted as attractive alternations to synthetic chemical insecticides for pest management. Taking all these into consideration, investigations were undertaken to obtain precise information on the effect of C. gigantea plant parts on different developmental stages of H. armigera. Fresh Calotropis gigantea R. Br plant parts viz., leaves, stem, flower and roots were collected and allowed to shade dry to prevent the loss of active principle from the plant parts. The shade drying process was continued until the plant materials were dried enough to be powdered. The dried plant materials were taken individually and ground into powder with the help of a Willey mill. The percent mortality of second instar larvae of H. armigera was directly proportional to the concentration of plant part dust. The leaf dust proved its superiority over other plant parts dust by giving 86.66% of mortality at 10% concentration followed by 8% (60.00%), 6% (53.33%), 4% (43.33%) and 2% (33.33%) mortality, respectively. Followed by flower dust treatment recorded the maximum mortality of 66.66% at 6%. Next to flower dust, the whole plant dust and stem dust evinced maximum mortality at 10% concentration (63.33 and 43.33%), root dust exerted low mortality percentage in 2% concentration. Leaf dust at 10% recorded maximum mortality rate of 83.33% against third instar larvae whereas 8, 6, 4 and 2% recorded mortality of 76.66, 46.66, 40.00 and 26.66%, respectively. Next to leaf extract, flower and whole plant dust at 10% concentration proved its superiority by causing 76.66 and 73.33% mortality, respectively. Stem dust showed the maximum mortality at 10% (56.66%). Root dust was found to be least effective.