Possible Role of Hylobius abietis (L) in the Transport of Leptographium procerum (Kendr) Wingf and in the Infection of Scots pine

1993

S. 297-308

30 Lit. Ang.

Unselbständiges Werk

200041751

The aim of this study was to determine the fungus species liable to be conveyed by the pine weevil Hylobius abietis, considered to be the main pest of coniferous reafforestations. The study concentrated mainly on the frequency variations of each isolated fungus in 4 Scots pine stands in the Orleans forest (centre of France) in 1989 and 1990, and in 2 mountainous sites (Vosges and Massif Central) in 1990. Leptographium procerum alone - because of its relatively frequent association with the adult insects during the 2 years and in all trapping sites - appeared to have a link with the pine weevil. The contamination frequency due to this fungus revealed important variations from one site to another, but the contamination also seemed to depend on the collection period during the year. The immature emergents, both male and female, could also be contaminated. This contamination was probably linked to the development of Leptographium procerum in its saprophytic phase. The contamination by Leptographium procerum did not seem to have any effect on the weight of the emergents. The fungus had also been isolated from dead Scots pine (Pinus sylvestris L) seedlings, after feeding damage by the pine weevil. Inoculations at the collar with patches of agar cultures on 12 seedlings with artificial substantial wounding revealed high mortality whereas the wounds alone did not lead to mortality. In that case, Leptographium procerum developed mainly in the root part of the seedlings and rarely in the aerial part. These experiments suggest that Leptographium procerum could increase the mortality rate of seedling after partial feeding damage by the pine weevil.