Leaf waxes from Lathyrus sativus: short-range attractant and stimulant for nymph laying in a viviparous insect

Lathyrus sativus L. (Fabaceae) is an important pulse crop of Asia, Europe, and Africa. Infestation by the aphid, Aphis craccivora Koch (Hemiptera: Aphididae) causes stunted growth of plants and reduces seed production. Females lay nymphs on the leaves and flowers of L. sativus. Hence, it is relevant to study the importance of leaf wax compounds (long-chain alkanes and free fatty acids) from two cultivars [BIO L 212 Ratan (BIO) and Nirmal B-1 (NIR)] of L. sativus as short-range attractant and stimulant for nymph laying in the aphid. The TLC, GC-MS and GC-FID analyses of n-hexane extracts from leaves of two cultivars revealed 18 n-alkanes from n-C-15 to n-C-36 and 14 free fatty acids from C12:0 to C22:0. Pentadecane was predominant among n-alkanes in both cultivars. Palmitoleic acid and pentadecanoic acid were predominant free fatty acids in leaf waxes of BIO and NIR, respectively. Females were attracted towards leaf waxes of both cultivars compared to the control solvent (n-hexane) in Y-tube olfactometer bioassays. A synthetic blend of either pentadecane, tridecanoic acid, and linoleic acid at similar amounts present in one leaf equivalent wax of BIO, or pentadecane, docosane, pentacosane, heptacosane, tritriacontane, and linoleic acid at similar amounts present in one leaf equivalent wax of NIR acted as short-range attractant and stimulated females to lay nymphs. But, the latter blend was more attractive and stimulated females to lay more nymphs than the former blend, and hence, this latter blend could be employed in the development of baited traps in pest management strategies.