Autocontamination trap with entomopathogenic fungi: a possible strategy in the control of Rhynchophorus ferrugineus (Olivier) (Coleoptera Curculionidae)

Abstract

An experimental autocontamination trap was devised to infect Rhynchophorus ferrugineus (Olivier), the Red Palm Weevil, adults with entomopathogenic fungi. The aim was to develop an autocontamination device to support integrated R. ferrugineus control programs. In laboratory bioassays, the delivery system successfully attracted, infected and released weevil adults after they contacted cereal substrata inoculated with indigenous strains of Beauveria bassiana (Balsamo- Crivelli) Vuillemin and Metarhizium anisopliae (Metchnikoff) Sorokin. Tests carried out with the experimental traps showed that M. anisopliae was the more virulent pathogen, causing 75% cumulative mortality in adults, while B. bassiana gave a 45% cumulative mortality. Infectivity of M. anisopliae was not affected by different cereal substrata, i.e. wheat and rice, since curculionid cumulative mortality (95%) and treatment efficiency (95% Abbott) were very high on both of them and Red Palm Weevil LT50 was reached within the same time (15 days). Conidial persistence and germinability of M. anisopliae grown on the rice substratum were examined in field conditions inside traps located in sunny and shady positions in spring, summer and autumn. The results showed that the traps preserved fungal inoculum stability longer in spring and summer than in autumn. No significant difference in M. anisopliae conidial persistence was found between sunny and shady traps during the various seasons.