Fungi could control pine weevil pest

Research at Swansea University has shown that fungi can help control the pests that damage forests throughout Europe and could help forest managers with an alternative to chemical pesticides.

healthy pine weevil larvaRecent research by Dr Minshad Ali Ansari and Professor Tariq Butt from Swansea University’s Biocontrol and Natural Products Group has focussed on the Large Pine Weevil (Hylobius abietis), which feeds on the bark of conifer tree saplings causing significant damage costing an estimated €140 million per year.

 As well as pine, species hit by this pest include Sitka spruce which is very important to the UK timber and paper industries.  Severe infestations are thought to affect conifer plantations for several years as they can prevent saplings and seedlings from growing.

The research co-funded by the EU IMPACT1 project found the most effective strain of insect killing fungi tested on the large pine weevil larvae, pupae and adult insects was Metarhizium robertsii.

Healthy pine weevil larva

The M. robertsii killed all larvae and pupae in four days and all adult insects in 12 days which suggests that the larvae and pupae were more vulnerable than the adult pine weevil and researchers believe it may be due to their softer bodies which fungi can penetrate more easily.

The researchers also compared wet with dry spores and found that although dry spores were more effective, but they may quickly deactivated by heat or UV light in field conditions.

This has led to researchers to suggest that an effective way to combat this pest would be to distribute wet spores (liquid suspension) to the larvae and pupae during July and August.

Dr Ansari said: “Although the chemical insecticide treatment can be used, European directives2 on the sustainable use of pesticides promote non-chemical methods of pest control.

infected pine weevil larvae “These results are extremely encouraging and are supported by field trials with our colleagues in the IMPACT project. Fungal biocontrol agents have an excellent environmental track record and are commercially available in many countries of the world, including the UK. Further work is needed to assess the full potential of M. robertsii. Existing research has included extensive safety testing, with no harmful effects. We are also carrying out field testing to learn more about the effects of the fungus on its host range in the field and on its potential as a commercial product.”

This research has now been published in Science for Environment Policy: European Commission DG Environment News Alert Service: Ansari, M. A. and Butt, T. M. (2012). Susceptibility of different developmental stages of large pine weevil Hylobius abietis (Coleoptera: Curculionidae) to entomopathogenic fungi and effect of fungal infection to adult weevils by formulation and application methods. Journal of Invertebrate Pathology. 111: 33-40. DOI:10.1016/j.jip.2012.05.006.

Infected pine weevil larva