Sesquiterpene carboxylic acids from a wild tomato species affect larval feeding behavior and survival of Helicoverpa zea and Spodoptera exigua (Lepidoptera: Noctuidae)

Abstract

The sesquiterpene carboxylic acids (SCA), (+)-(E)-α-santalen-12-oic, (-)-(E)-endo-α-bergamoten-12-oic, and (+)-(E)-endo-β-bergamoten-12-oic acid, are produced in glandular trichomes of Lycopersicon hirsutum f. typicum Humb. & Bonpl. accession (LA) 1777, which is highly resistant to a range of pests of cultivated tomatoes, L. esculentum Mill. Exposure of the larvae of two key tomato pests, tomato fruitworm [Helicoverpa zea (Boddie)] and beet armyworm [Spodoptera exigua (Hübner)], to these compounds in diets and on leaf surfaces resulted in reduced development rates and survival and deterred feeding. These effects were observed when levels of SCA, in artificial insect diet, applied to leaflets of susceptible cultivars, or synthesized in trichomes of leaves of plants, exceeded 2 mg SCA/g of diet or fresh leaf weight. This study suggests that cultivated tomatoes capable of synthesizing SCA, at 2 mg SCA/g of leaf tissue or greater, on their leaves and fruit would display enhanced host plant resistance to H. zea and S. exigua and other insect pests.