Feeding on glandular and non-glandular leaf trichomes negatively affect growth and development in tobacco hornworm (Manduca sexta) caterpillars

Trichomes, the hair-like projections on plant leaves, have been well studied as an herbivore defense. However, whether variation in trichome type can have negative effects through the different stages of caterpillar life cycle is poorly understood. Using Solanum elaeagnifolium that produce non-glandular stellate trichomes, and Solanum lycopersicum that predominantly produce glandular, non-branched trichomes, we examined how trichomes affect choice and growth of Manduca sexta, a specialist herbivore of plant species belonging to the Solanaceae. To accomplish this, we removed leaf trichomes and added them into artificial diet for caterpillars, and allowed the caterpillars to grow and develop. Our results show that trichomes negatively affected caterpillar body mass and mass gain, although there was no preference or aversion for them in choice assays. Non-glandular trichomes were particularly damaging, as the consumption of non-glandular trichomes resulted in suppressed mass gain and increased time to pupation. While the consumption of glandular trichomes also affected growth, the effects were significantly lower compared to the consumption of non-glandular ones. Taken together, our results show that feeding on solanaceous trichomes can have negative effects on herbivore larval growth and development, and should be examined further