Identification of 1-Octacosanal and 6-Methoxy-2-Benzoxazolinone from Wheat as Ovipositional Stimulants for Hessian Fly, Mayetiola destructor

Abstract

Bioassay-guided fractionations of a dichloromethane extract of wheat epicuticular wax allowed the identification of 1-octacosanal and 6-methoxy-2-benzoxazolinone (MBOA) as the major components that stimulate oviposition by the Hessian fly, Mayetiola destructor. These compounds were identified by their mass spectral fragmentation patterns and by comparison of their gas chromatographic retention times with synthetic samples. Synthetic samples of 1-octacosanal or MBOA stimulated significant oviposition when compared with solvent controls. In combination, these compounds elicited a synergistic effect on the number of eggs laid by females compared to when they were presented alone. In a choice bioassay, a mixture of synthetic 1-octacosanal and MBOA in the approximate concentrations determined to be present in one plant equivalent of crude extract stimulated the same amount of oviposition as one plant equivalent of extract. This showed that together these two compounds appear to be responsible for the major proportion of the ovipositional stimulatory activity of the wheat epicuticular wax extract. Comparison of the activity of five straight-chain primary aldehydes with chain lengths from C₂₂ to C₃₀ revealed a relationship between chain length and the number of eggs laid by female Hessian flies, with 1-hexacosanal and 1-heptacosanal the most active of the aldehydes tested.