Susceptibility of Diaprepes Abbreviatus (Coleoptera: Curculionidae) Larvae to Different Rates of Entomopathogenic Nematodes in the Greenhouse

Abstract

The Diaprepes root weevil, Diaprepes abbreviatus, is an important field and nursery pest of citrus and ornamentals in Florida and the Caribbean. Entomopathogenic nematodes, Heterorhabditis indica Poinar, Kanunakar, and David and H. bacteriophora Poinar, and Steinernema riobrave (Cabanillas, Poinar, and Raulston) were compared at different rates for their ability to parasitize D. abbreviatus under greenhouse conditions. Nematodes (0, 11, 22, 54, and 108 infective juveniles per cm2) were applied to Candler sandy soil (9% moisture = approximately -0.035 bars), contained in plastic pots with one D. abbreviatus larva, and a citrus seedling for food. The experiments were conducted at two temperature ranges (22-25C and 26-30C). Steinernema riobrave caused higher larval mortality compared with H. bacteriophora and H. indica, and was more virulent at higher temperatures. At the higher temperature, smaller larvae (ca. 7th instar) were more susceptible to S. riobrave and H. bacteriophora than later instars (ca. 11th instar). Our results indicate that, under greenhouse conditions, S. riobrave has the potential for achieving >90% weevil control at a rate of 22 infective juveniles per cm2.