The lethal and sub-lethal consequences of entomopathogenic nematode\ud infestation and exposure for adult pine weevils, Hylobius abietis\ud (Coleoptera: Curculionidae)

摘要

Entomopathogenic nematodes (EPN) frequently kill their host within 1–2 days, and interest in EPN\udfocuses mainly on their lethality. However, insects may take longer to die, or may fail to die despite being\udinfected, but little is known about the effects of EPN infection on insects, other than death. Here we investigate\udboth lethal and sub-lethal effects of infection by two EPN species, Steinernema carpocapsae and Heterorhabditis\uddownesi, on adults of the large pine weevil, Hylobius abietis. Following 12 h nematode–weevil\udcontact in peat, S. carpocapsae killed a significantly higher proportion of weevils (87–93%) than H. downesi\ud(43–57%) at all concentrations tested. Less than 10% of weevils were dead within 2 days, and weevils continued\udto die for up to 10 days after exposure (LT50 of 3 days or more). In a separate experiment, live weevils\uddissected 6 days after a 24 h exposure to nematodes on filter paper harbored encapsulated and dead\udnematodes, showing that weevils could defend themselves against infection. Some live weevils also harbored\udlive nematodes 6 days after they had been removed from the nematode infested medium. Feeding\udby weevils was not affected by infection with, or exposure to, either species of EPN. We discuss these\udresults in relation to the use of EPN in biological control against H. abietis.