Sustainable pest management requires the use of ecosystem-friendly control options (e.g. entomopathogens) coupled with target-specific application methods. Here we investigate the susceptibility of the sorghum chafer (Pachnoda interrupta, Olivier) to Metarhizium sp., isolated from dead P. interrupta under field conditions over several years. Target-specific trapping was achieved using Japanese beetle traps or locally made autoinoculation devices, with methyl salicylate or banana as an attractant. Of the attracted and infected beetles, 49% mortality was achieved during October 2005 and 71% during July 2006, while the corresponding mortality in control treatments was 13 and 5%, respectively. We further confirmed that the mortality of the beetles was due to the fungal treatment as 50 and 80% of the dead beetles showed mycosis, respectively. The performance of the pathogen was also investigated in an autodissemination device in 2008 and 2009, where the beetles that were attracted passed through an inoculation chamber. Of the attracted and infected beetles in the autodissemination device, 58.5% (October) and 90.9% (July) were dead within 15 days after treatment. Control mortality was only 3 and 2%, respectively. The potential for horizontal transmission was investigated, where 47% (October) and 59% (July) of the beetles exposed to the pathogen through horizontal transmission were killed. The pathogen was found to be viable for more than 3 days in the field. Our results show that Metarhizium sp. has potential as a biological control agent, and for achieving autodissemination using the target pest as the vector.

Rhynchophorus ferrugineus (Coleoptera, Curculionidae) is the most threatening pest of palms worldwide. The potential of gamma-irradiated males to spread a pathogenic strain of the entomopathogenic fungus Beauveria bassiana (Ascomycota: Clavicipitaceae) to control this pest was studied. First, the effects of gamma irradiation (15 and 25 Gy) on the mating success and performance of adult males irradiated at age one day were studied in the laboratory. Although male longevity decreased after irradiation (118.6 vs. 244.7 days for irradiated and control males, respectively) and their testes suffered from the treatment, fecundity of mated females did not depend on the irradiation status of the male (86.8 ± 5.5 eggs in 15 days). However, egg hatching was significantly lower in couples with irradiated males (31.4% vs. 86.5% for irradiated and control couples, respectively), and this value decreased after a second mating (6.1% vs. 85.9%). Therefore, irradiation did not affect male sexual competiveness but sperm quality. Second, a semi-field assay was carried out to evaluate infestation in young Phoenix canariensis caused by different combinations of couples with irradiated and/or B. bassiana-challenged males. The number of immature stages found in infested palms was significantly higher when females mated with untreated males and lower when mated with irradiated males (either B. bassiana-infected or not). Some females from the fungus-challenged treatments showed post-mortem hyphal growth, and this horizontal transmission proves that irradiated males could act as a vector for B. bassiana and should be considered as a new method to improve the biological control of R. ferrugineus.