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Research Call

DAFM Reference

Lead(Collaborating)Institution

DAFM Award

DAFM National Call 2010 10/C/720 NUIM €317,324

Project Title:

Multi-agent control options for pine weevil

Project Coordinator:

Dr. Christine Griffin

Project Abstract

The large pine weevil (Hylobius abietis) is the main pest of Irish forestry, and a major obstacle to reforestation. Larvae develop in stumps of recently felled conifers; emerging adults feed on young seedlings, causing their death by girdling. Currently, seedlings are treated with cypermethrin but this will soon be unavailable for this use. Biological control of pine weevil using insect-killing nematodes is under development in Ireland but is not likely to be the full solution.  This project investigates the potential of entomopathogenic (insect-killing) fungi (EPF) as a combinable weapon against weevils.  In addition to testing pre-existing strains of well-known EPF (Metarhizium anisopliae and Beauveria bassiana) we are conducting a survey of native EPF in the clear-fell forest ecosystem. We have recovered EPF from the bark of tree stumps and from the soil around stumps, and most promisingly, we have also found pine weevil larvae in their natural habitat infected with indigenous EPF. At least two native species of Beauveria, including B. caledonica, have been identified by molecular means (sequencing the ITS region). In laboratory bioassay, the mortality of pine weevil larvae due to B. caledonica (isolated from naturally infected weevil larvae) was comparable to that due to existing commercial EPF species. EPF are being tested as stand-alone agents and in combination with nematodes for action against weevil larvae in stumps. In the first year field trials, application of nematodes or a combined treatment of nematodes and the non-native EPF B. bassiana to stumps reduced the number of adult weevils emerging over the subsequent season by about 60% relative to untreated stumps.  In certain other pest-pathogen systems, EPF have been found to act synergistically with other control agents – the combination gives higher mortality than expected based on the mortality due to each agent alone - and it has been suggested that EPF weaken the defences of the insect, making it more susceptible to the second agent. In order to understand the interaction of EPF with other control agents and to develop a method of screening for strains that may be most effectively combined with other agents, we are studying the effects of EPF on insect defences, both their cellular defences and protein components of the blood system.  Alteration was seen in the levels of certain proteins in the insect blood following treatment with EPF, including several with known involvement in the insect immune response. The project also targets the damaging stage of the pine weevil, the adult. The normal way of using EPF is to apply large numbers of spores into the pest’s habitat. However, as spores are relatively short-lived they are best for one-off eradication (as when treating stumps to kill larvae present) but are less useful for longer term plant protection. We have set up greenhouse trials to see if EPF will colonise seedlings to give longer term protection against feeding adults.

Final Report:

Final Report (pdf 499Kb)