Attraction of herbivores and their natural enemies to horse nettle (Solanum carolinense L.) plants

Horse nettle (Solanum carolinense L., Solanaceae) is an agriculturally important herbaceous perennial weed found throughout the United States. Previous studies have suggested that inbreeding decreases plant fitness, resistance to herbivory, and the production of volatile organic compounds (VOC’s; Casey et al., 2008; Jorge et al., 2008). This study investigates variation in the diversity of herbivores and parasitoids on horse nettle based on their genotypes (inbred and out bred) and herbivore damage (no damage Vs tobacco hornworm; Manduca sexta) damage. Damaged and undamaged, inbred and out bred plants from three maternal families were placed in cages in an agricultural field, and a sample of the insects attracted to these plants were collected on three different traps. Our data suggest that damaged plants attract significantly higher number of hymenoptera, diptera and coleoptera insects. We also found that damaged outbred plants and undamaged inbred plants attract significantly more flea beetles and aphids with a family X breeding X damage effect. To address the speculation that the variation in the attractiveness is mainly due to the differences in the production of VOC’s, we collected VOC's from these treatments and our data indicate that damaged outbred plants produce significantly higher amount of VOC's (total volatiles and volatile blend) with a family X breeding X damage effect suggesting a broad sense heritability for these traits with a severe effect of inbreeding depression.