Host acceptance behaviour of Colorado potato beetle larvae influenced by potato glandular trichomes

In no‐choice tests, larvae of the Colorado potato beetle, Leptinotarsa decemlineata (Say) (Coleoptera: Chrysomelidae), avoided contact with, and were less frequently observed feeding on, excised foliage of the resistant wild potato Solanum berthaultii Hawkes than on leaves of the cultivated potato, S.tuberosum L. For older larvae, reduced feeding was a consequence of less frequent contact with S.berthaultii leaves. However, first instars appeared unable to penetrate the adhesive barrier presented by glandular trichomes of S. berthaultii , and those that remained on the leaflets fed less often than did first instars on S. tuberosum. Removal of the trichome barrier by wiping leaflets with tissue paper did not attenuate the apparent repellent effect of S. berthaulti foliage, but led to increased incidence of feeding by first instars. Inhibition of larval feeding may therefore rely on a mechanical barrier provided by the glandular trichomes of S.berthaultii.