Abundance of pine weevils (Hylobius abietis) and damage to conifer seedlings in relation to silvicultural practices

Different reforestation methods were compared in terms of their effect on conifer seedling damage caused by the pine weevil Hylobius abietis (L.), seedling survival, and weevil abundance as measured by trapping, during a period of up to 6 yrs after clear-cutting. Although attack rates on seedlings and seedling mortality differed greatly among sites, attacks were less frequent on plots scarified in the first year after clear-cutting than in unscarified plots. However, after a fallow period of 2 or 4 yrs, scarification had no effect on attack rates. Mortality due to pine weevils was highest for seedlings planted after 2 yrs and lowest for seedlings planted after 4 yrs. Only small differences in attack rates were found between bare-root and containerized seedlings. Survival of insecticide-treated seedlings planted on scarified ground without a fallow period was almost 90% after 3 yrs compared with less than 70% for untreated seedlings. The number of pine weevils caught in pitfall traps in spring of the second year after clear-cutting was positively correlated with the number of insecticide-protected seedlings attacked during the first year. Many H. abietis were caught in baited traps on clear-cuttings older than 4 yrs.