Efecto de dos nematodos entomopatógenos sobre Cosmopolites sordidus (Coleoptera: Dryophthoridae)

Abstract : The black plantain weevil Cosmopolites sordidus is one of the pests that most severely damages this crop. Entomopathogenic nematodes (EN) of the genera Steinernema and Heterorhabditis are biological control agents of the insect with the possibility of being incorporated into IPM programs. The objective of this study was to evaluate the virulence of Steinernema carpocapsae All Strain and Heterorhabditis bacteriophora on adults and last instar larvae of the weevil. The bioassay used was individual infection in multiple well plates with paper filter in concentrations of 10, 100, and 1.000 infective juveniles (IJ)/25 ml. Every 12 h the number of dead individuals per plate was recorded up to a maximum of 120 h for larvae and 228 h for adults. The cadavers were put in a drying chamber (development of the nematode inside the insect) and later in a “white chamber” (emergence of IJ). The variables studied were mortality of the stages, IJ multiplication and emergence duration. Under the conditions evaluated, both adults and larvae were susceptible to the attack of both nematodes, responding differentially to the increase of dose. Typical symptoms of infection and multiplication in larvae were observed for the nematode species evaluated. Conditions such as the limited niche of the insect and high humidity in plantain corms that are favorable for nematode survival, as well as the high mortality registered with low IJ concentrations and the capacity to develop especially in the larvae, make these agents promising tools for the control of the pest in the field.