Laboratory efficacy against neonate larvae of the banana weevil Cosmopolites sordidus of two indigenous entomopathogenic nematode species from the Canary Islands (Spain)

We evaluated the efficacy, against neonate larvae of the banana weevil, Cosmopolites sordidus (Germar) (Coleoptera, Curculionidae), of two indigenous entomopathogenic nematode species of the families Steinernematidae and Heterorhabditidae. The nematodes, isolated in the Canary Islands (Spain), were Heterorhabditis bacteriophora (TF19) and an undescribed species (TF135) of the Steinernema feltiae- group. Exposure of C. sordidus neonate larvae to 5 concentrations (2.5, 5, 25, 50 and 100 infective juveniles/cm2) in Petri dishes with sterile sand resulted in 100% mortality, with each of the two nematode species at all concentrations tested. The lowest median lethal time (LT50) for Steinernema sp. was 2.6d at a dose of 25 infective juveniles/cm2 and 3.6d for H. bacteriophora at a dose of 2.5 and 5 infective juveniles/cm2. The penetration rate was also evaluated as an indicator of entomopathogenic nematode infectivity. The highest values for penetration rate were recorded at lowest concentrations of infection in Steinernema sp. and in H. bacteriophora, but rates differed regardless of the LT50. Our results suggest that these two nematode species may improve the biological control of neonate larvae of C. sordidus in banana crops.