ASSESSMENT OF PINE WEEVIL NUMBERS ON CLEAR-CUT AND FOREST SITES WITH SHELTER BOARDS AND PITFALL TRAPS

Field experiments were conducted in 1991 and 1992 on clear-cut and for est sites in four forest areas in southern Sweden with the aim to test possibilities for estimating pine weevil (Coleoptera: Curculionidae) population sizes. More pine weevils (Hylobius abietis and H. pinastri) were caught in baited pitfall traps than under shelter boards. The pr oportions of H. pinastri in the total Hylobius catch were higher under shelter boards than in pitfall traps, indicating a difference between the species in behaviour towards the trap types. Numbers of H. abieti s found on forest sites were lower than those on fresh clear-cut sites , but not those on one year old or older clear cut sites. In mark-reca pture experiments the recapture rates of H. abietis ranged from zero t o 73%; they were zero on fresh clear-cut sites. Recapture rate was not correlated to dispersal distance. Estimates of population size (Schna bel method) were in magnitudes of 150 to 5000 H. abietis per hectare. The estimates did not reveal consistent differences between forest and one-year old or older clear cuttings. Dispersal distances were on ave rage 6.0 m in 1991 and 5.4 m in 1992. Only in one area in 1992 the dis persal distances were significantly different between forest and clear -cut site.