Infectivity by nematode–bacteria association on the potato weevil Phyrdenus muriceus

Abstract

Bacteria of the genus Photorhabdus (Enterobacteriaceae) are motile, gram-negative, symbiotically associated with juveniles of entomopathogenic nematodes from the genus Heterorhabditis (Heterorhabditidae). Nematodes retain the Photorhabdus bacterial cells in their intestine and transport them into an insect host. Upon locating an insect host, Heterorhabditis penetrates through natural openings (mouth, anus, spiracles), or directly into the hemocoel via the integument, subsequently releasing bacteria into the hemolymph. Once in the hemolymph, Photorhabdus begins multiplying simultaneously releasing toxins virulent enough to kill the insect within 24 hrs. Phyrdenus muriceus (Coleoptera: Curculionidae) is a pest of cultivated Solanaceae affecting egg-plant, potato and tomato. Considerable damages on these crops are produced by this pest affecting both the aerial and underground parts of the plants. Infectivity of the entomopathogenic complex Heterorhabditis bacteriophora and the symbiotic bacterium Photorhabdus luminescens isolated from soil samples collected from an orchard of La Plata was tested against pupae of P. muriceus.