Epicuticular wax chemicals ofLablab purpureussubsp.bengalensisinfluence short-range attraction and oviposition responses inAphis craccivoraandAphis gossypii

Abstract

AbstractLablab purpureussubsp.bengalensis(Jacq.) Verdc. is an important legume of India and Africa. Both aphids,Aphis craccivoraKoch andA. gossypiiGlover (Hemiptera: Aphididae), are important herbivorous pests of this legume crop. These viviparous females lay nymphs on the leaf surface of this legume plant. Therefore, it is of considerable interest to study whether leaf surface wax chemicals (long-chain alkanes and free fatty acids) of this legume plant served as short-range attractants and oviposition stimulants in both females to lay nymphs. Twenty-onen-alkanes fromn-C12ton-C35and 11 free fatty acids from C12:0 to C22:0 were identified in leaf surface waxes. Nonacosane and nonadecanoic acid were the most abundant amongn-alkanes and free fatty acids, respectively. Both females were attracted towards one leaf equivalent surface wax against the control solvent (petroleum ether) in short Y-tube olfactometer bioassays. A synthetic blend of tetradecane, pentadecane, tetracosane, tridecanoic acid, tetradecanoic acid, and heneicosanoic acid comparable to one leaf equivalent surface wax served as short-range attractants and oviposition stimulants inA. craccivora; whereas a synthetic blend of tetradecane, hexadecane, docosane, nonadecanoic acid, and arachidic acid comparable to one leaf equivalent surface wax acted as short-range attractants and oviposition stimulants inA. gossypii. These results can provide the basis for efficient pest management strategies ofA. craccivoraandA. gossypiiagainstL. purpureussubsp.bengalensisusing host plant leaf surface wax compounds. Further, SEM studies of antennae and forelegs of both aphids were conducted to observe sensilla structures, which help in chemoreception.