Effect of Timber Condition on Parasitization of Pine Weevil ( Hylobius abietis L.) Larvae by Entomopathogenic Nematodes under Laboratory Conditions

Abstract

The large pine weevil (Hylobius abietis L.) is one of the most important pests in coniferous reforestation in Europe. Larvae develop in the stumps of recently felled trees; the emerging adults feed on the bark of seedlings and may kill them. The ability of the entomopathogeni c nematodes Heterorhabditi s megidis and Steinernema carpocapsae to invade pine weevil larvae in Sitka spruce (Picea sitchensis) buried in moist sand was evaluated. Overall, four times as many H. megidis as S. carpocapsae invaded pine weevil larvae. The two species of nematode diVered in their response to timber condition. The number of S. carpocapsae invading pine weevil larvae was twice as high in billets inoculated with the wood-rotting fungus Phlebiopsis gigantea as in fresh timber, while the number of H. megidis invading was reduced by 25%. Invasion into non-feeding insects (larvae of the wax moth Galleria mellonella) contained in timber disks was also aVected by timber quality, indicating that nematode behaviour was aVected directly by the physical or chemical condition of the timber, though trophically mediated eVects may also have been involved.

Evict or infect? Managing populations of the large pine weevil, Hylobius abietis, using a bottom–up and top–down approach

“…Unfortunately data were not collected on the size of either weevil larvae or parasitoid clutches. Armendariz et al (2002) reported that inoculation of timber with P. gigantea enhanced invasion of insects by S. carpocapsae, but reduced invasion by Heterorhabditis megidis Poinar, Jackson and Klein. In our trials, inoculation of stumps with T. koningii at felling did not facilitate either S. carpocapsae or H. downesi applied 24 months later, indeed, infection levels were somewhat reduced as noted above.…”

“…In our trials, inoculation of stumps with T. koningii at felling did not facilitate either S. carpocapsae or H. downesi applied 24 months later, indeed, infection levels were somewhat reduced as noted above. The facilitation of EPN reported by Armendariz et al (2002) may have been due to the degradation of P. gigantea-treated wood- Fig. 3.…”

“…The fungus used in this trial (T. koningii strain S28A1) was chosen based on its negative impact on pine weevil development and repellence of adults in laboratory assays (Creevey, 1999). The second objective was to determine whether T. koningii affected nematode parasitism of H. abietis, as Armendariz et al (2002) reported possible facilitation of S. carpocapsae by P. gigantea in the laboratory. The third objective was to investigate whether stump treatment impacted on the native parasitoid B. hylobii.…”

Susceptibility and behavioral responses of the dampwood termite Zootermopsis angusticollis to the entomopathogenic nematode Steinernema carpocapsae

“…Furthermore, because Z. angusticollis nests can be partially buried in soil, the possibility exists that soil nematodes can migrate from the surrounding soil and penetrate wood in various stages of decomposition. Indeed, decayed wood appears to be very attractive to S. carpocapsae (Armendariz et al, 2002). Soft decomposed wood might provide a suitable substrate for the typical ambush/nictating behavior of S. carpocapsae and ultimately result in the successful invasion of wood-inhabiting hosts, as has been demonstrated in the pine weevil, Hylobius abietis (Armendariz et al, 2002).…”

“…Indeed, decayed wood appears to be very attractive to S. carpocapsae (Armendariz et al, 2002). Soft decomposed wood might provide a suitable substrate for the typical ambush/nictating behavior of S. carpocapsae and ultimately result in the successful invasion of wood-inhabiting hosts, as has been demonstrated in the pine weevil, Hylobius abietis (Armendariz et al, 2002). Therefore, the lack of foraging behavior outside the nest by Z. angusticollis does not necessarily preclude this termite species from encountering S. carpocapsae or other nematode species in their natural environment.…”