The Role of Green Gram Plant Volatile Blends in the Behavior of Arctiid Moth, Spilosoma obliqua.

Abstract

This study investigated effects of volatile blends released from undamaged (UD), insect-damaged [ID, plants fed by larvae of Spilosoma obliqua Walker (Lepidoptera: Arctiidae)] and mechanically-damaged (MD) plants of three green gram cultivars [PDM 54, Pusa Baisakhi and Samrat] including synthetic blends on the behavior of conspecific adult moths in Y-tube olfactometer bioassays. Females showed attraction towards volatile blends of UD, ID and MD plants of these green gram cultivars against the control solvent (CH2Cl2). The components of volatile blends in UD plants of three green gram cultivars are not similar, but no any difference was found among three cultivars in term of the attractive effect on the insect moths when volatile blends from UD plants of these three cultivars were tested against one another. Females were more attracted towards volatile blends of ID plants of a particular cultivar compared to UD plants of the same cultivar. Total amount of volatiles was higher in ID plants than UD plants. Some herbivore-induced plant volatiles - (Z)-3-hexenal, 1-hexanol, (Z)-3-hexenyl acetate, 2-octanol and ocimene were attractive to the insect moths. Females were attracted towards three synthetic blends resembling amounts present in natural volatile blends of ID plants of these three cultivars in Y-tube olfactometer and wind tunnel bioassays, suggesting that involvement of host-specific chemical cues in long-range host location by S. obliqua females. If attraction of adult S. obliqua to these synthetic volatile blends is upheld by field trials then these blends may find practical application in detection and monitoring of S. obliqua populations.