Open access publications in the SLU publication database

Damages to seedlings by the pine weevil (Hylobius abietis, L.), are one of the major problems when regenerating conifers in Sweden. Insecticide treatment of seedlings has so far been the most common way to protect seedlings from damages. However, the use of protections based on various physical feeding barriers is increasing. This development is partly due to all major Swedish forest companies being FSC-certified. Certified companies are obliged to phase out their use of insecticides. Currently Merit Forest (imidacloprid) is the only approved insecticide that certified companies could get a temporary permission to use.
At the Asa Forest Research Station, replacements to insecticides have been tested for many years in the past and in this large scale study we focus on two promising physical feeding barriers, the coating Conniflex and the shield MultiPro. We also included the insecticide Merit Forest alone and in combination with Flexcoat, a starch product extracted from a European bean plant. All the seedlings were planted in scarification by professional planters, to follow a normal Swedish forest regeneration procedure.
The outcome of the study was hard to evaluate, since the amount of pine weevil damage was low, even for the untreated control. There were no differences in survival between the treatments. The differences in death from pine weevil damages were very small, but both Merit Forest with two applications and Merit Forest + Flexcoat had significantly lower number of seedlings killed, compared to the control. Both Conniflex and Multpro though, had few seedlings killed by pine weevils.