Chemical and ultrastructural analysis of corn cuticular lipids and their effect on feeding by fall armyworm larvae

The cuticular lipid composition of lower and upper leaves of five genotypes of field-grown corn,Zea mays L., was determined by combined gas chromatography-mass spectrometry. Surface lipids of the upper leaves had a higher proportion ofn-alkanes (45-52%) than the lower leaves, while the lower leaves had higher percentages of fatty alcohols (12-18%) than the upper leaves. Scanning electron microscopy showed that the upper leaves of two corn genotypes, MpSWCB-4 and Cacahuacintle X's, had a smooth amorphous appearance, while the lower leaves had a dense array of wax crystals.Spodoptera frugiperda (J.E. Smith) larvae weighed more and developed more rapidly when they were reared on diet containing corn foliage from which the cuticular lipids had been removed than when they were fed untreated foliage. However, growth was not inhibited when larvae were fed diet containing the cuticular lipid extracts or individual cuticular lipid components.