Conifer stump condition and pine weevil (Hylobius abietis) reproduction

Abstract

Reproduction of the pine weevil (Hylobius abietis (L.)) in stumps of Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies (L.) Karst.) was studied in relation to stump condition. Cut surfaces of stumps were treated to promote or retard microbial colonization. During the 4 months following cutting, chemical and physiological properties of the stumps were monitored. The number of emerging weevils and the estimated proportion of root area utilized by the weevil larvae and other organisms were used to evaluate the influence of the stump treatments on pine weevil reproduction. Stump treatments had no clear effect on pine weevil reproduction. However, fewer pine weevils emerged from stumps treated to retard microbial colonization than from other stumps. Moisture content increased with time and decreased with distance from the cut surface. Pine stumps died faster (content of living cells estimated by dehydrogenase activity) and supported higher levels of pine weevil reproduction compared with spruce stumps. Ethanol contents of both pine and spruce stumps were lower in August than in the preceding months. This lower ethanol content coincided with a lower content of living cells.