Oviposition responses by Hessian fly, Mayetiola destructor, to wheats varying in surfaces waxes

Leaf waxes are known to contain oviposition stimulants for Hessian fly. In dual-choice tests comparing seedlings of each of three nonglaucous lines of wheat with its corresponding glaucous line, Hessian flies laid similar numbers of eggs on each genotype. However, when plants from these genotypes were tested at the flag-leaf stage, Hessian flies deposited 25-100% more eggs on the nonglaucous genotype compared to normal wax genotype in each pair. Leaf waxes extracted from the genotypes in one of these pairs (Avalon and nonglaucous Avalon) at the seedling and the flag-leaf stage and tested on paper leaf models elicited oviposition responses similar to those observed on the intact plants. Scanning electron microscopy showed differences in crystal density on nonglaucous and glaucous genotypes only at the flag-leaf stage, Gas chromatography-mass spectrometry of the leaf wax extracts showed that fly oviposition responses were associated with differences in the chemical composition of the waxes. This is the first report of Hessian fly oviposition responses varying among genotypes of wheat with different surface wax composition.