Susceptibility ofHeliothis zea (Boddie) larvae toNomuraea rileyi (Farlow) Samson : Effects of α-tomatine at the third trophic level.

To determine the impact of α-tomatine at the third trophic level, the following model was developed:Nomuraea rileyi (Farlow) Samson, the secondary consumer, acting onHeliothis zea (Boddie), the primary consumer, fed an artificial diet modified with α-tomatine. In vitro, the allelochemical inhibited colony formation and growth of the fungus. The in vivo test revealed that larval growth and developmental time were affected by α-tomatine andN. rileyi. Detrimental effects on pupal development were observed in larvae fed diet containing α-tomatine and also treated withN. rileyi (LC90). The fungus was detected in the hemolymph and tissue of larvae treated with two lethal concentrations (LC50 and LC90) ofN. rileyi, including those fed α-tomatine. At the LC50, α-tomatine protected larvae againstN. rileyi and increased survivorship; at the LC90, it inhibited the development ofN. rileyi, thereby reducing production of conidia. Thus, the allelochemical α-tomatine retains its antifungal qualities beyond the second trophic level, inhibiting the development ofN. rileyi inH. zea.