Toxic Effects of a Lactone-Containing Fraction of Cyrtocymura cincta (Asteraceae) on Sitotroga cerealella (Lepidoptera: Gelechiidae)

Abstract

Sesquiterpene lactones play an important role in protection of plants against herbivores. Cyrtocymura cincta (Griseb.) H. Robinson (Asteraceae) is widespread in tropical South America and may contain compounds that provide protection against phytophagous insects. We isolated 2 sesquiterpene lactones from the surface of leaves and flowers, that also were found in the lactone fraction of a chloroform extract of ground air-dried flowers and leaves. Three concentrations of the lactone-containing fraction were incorporated into the diet of the stored grain pest Sitotroga cerealella Olivier, and the effects on its life cycle were evaluated. Larval feeding behavior was not altered, but a concentration of 250 ppm of the lactone mixture in the diet lowered the percentage of adult emergence and produced malformations in adults compared with controls. The most drastic effects were observed in the oviposition capacity and viability of eggs laid by females who fed on treated diets as larvae. None of the eggs laid by females exposed to the 500-ppm concentration produced viable offspring; thus, the lactone fraction contains compounds that produce chemical sterilization.