Mechanical interaction between larvae of the Colorado potato beetle and glandular trichomes ofSolanum berthaultii Hawkes

The rate of accumulation of glandular trichome exúdate ofSolanum berthaultii on the tarsi of Colorado potato beetle (Leptinotarsa decemlineata) larvae depended on larval size (instar), with large larvae bearing the hardened, darkened exudate on more of their tarsi than did small larvae. In greenhouse studies, third instar larvae accumulated large amounts of exudate regardless of which of 2S. berthaultii accessions they were exposed to, but exudate accumulation by first instars was influenced significantly by plant accession. Tarsal accumulation of exudate was lower in field plots of bothS. berthaultii accessions, but tended to increase with time of exposure. The significant differences in exudate accumulation among larvae exposed to the 2 accessions in the greenhouse were not evident in the field. The density of type A glandular trichomes on the abaxial leaflet surface differed significantly between the 2 accessions in both greenhouse and field. Despite these effects of host and environment on the accumulation of readily observed amounts of trichome exudate on larval tarsi, no larvae were trapped by the adhesive exudate.