First Report on Identification of Volatiles from Egg and Larval Frass of Indian Strain of the American Bollworm Helicoverpa armigera (Hübner)

Abstract

Globally Helicoverpa armigera, a polyphagous pest of many economic crops, has developed resistance to almost all groups of insecticides presently in used for its control. In cotton, its larvae cause severe damage and feeds on all plant parts including young leaves, square, flowers and bolls which in turn cause economic damage. Recent reports on development of its resistance to transgenic cotton which has Cry1Ac and Cry2Ab (Bt cotton) has given an indication of future threat to cotton growers. Therefore, use of semiochemicals as management strategy for these insects would be a great alternative as ethological pest management within insect pest management (IPM) to control this menace. These semiochemicals/volatile organic compounds can be present in insect (egg, larva, female) as well as in the host plant. In the present study, a total of seven volatiles have been identified from methanol extract of eggs and faecal pellets, out of which two volatiles; methyl ester of octadecanoic acid (methyl stearate) and methyl ester of hexadecanoic acid (methyl palmatate), were detected in egg samples. From faecal pellets five volatiles were identified namely octadecanoic acid (stearic acid) and its methyl ester, hexadecanoic acid (palmitic acid) and its methyl ester, tetradecanoic acid (myristic acid), caryophyllene and its oxide, phytol. Interestingly, methyl ester of octadecanoic acid and methyl ester of hexadecanoic acid were detected in both the samples. Volatiles observed in common may be used as effective semiochemicals in ethological pest management of Helicoverpa armigera. However, further study is needed to validate the competency of these fatty acids under field conditions.