Identification of 1-octacosanal and 6-methoxy-2-benzoxazolinone from wheatas ovipositional stimulants for Hessian fly, Mayetiola destructor

Bioassay-guided fractionations of a dichloromethane extract of wheat epicut icular wax allowed the identification of 1-octacosanal and 6-metboxy-2-benz oxazolinone (MBOA) as the major components that stimulate oviposition by th e Hessian fly, Mayetiola destructor. These compounds were identified by the ir mass spectral fragmentation patterns and by comparison of their gas chro matographic retention times with synthetic samples. Synthetic samples of 1- octacosanal or MBOA stimulated significant oviposition when compared with s olvent controls. In combination, these compounds elicited a synergistic eff ect an the number of eggs laid by females compared to when they were presen ted alone. In a choice bioassay, a mixture of synthetic 1-octacosanal and M BOA in the approximate concentrations determined to be present in one plant equivalent of crude extract stimulated the same amount of oviposition as o ne plant equivalent of extract. This showed that together these two compoun ds appear to be responsible for the major proportion of the ovipositional s timulatory activity of the wheat epicuticular wax extract. Comparison of th e activity of five straight-chain primary aldehydes with chain lengths from C-22 to C-30 revealed a relationship between chain length and the number o f eggs laid by female Hessian flies, with 1-hexacosanal and 1-heptacosanal the most active of the aldehydes tested.