Epsilon Archive for Student Projects

Abstract

Two field experiments were conducted in central Sweden in order to: 1) Determine a relationship between the number of approaching pine weevils (Hylobius sp.) and the number of attacks by pine weevils, in relation to the size of seedlings of Scots pine (Pinus sylvestris). 2) Determine if application of methyljasmonate (MJ) on seedlings of Scots pine will result in higher resistance towards attacks by pine weevils and/or have any effect on the number of approaching pine weevils. The field experiments were designed with two separate parts in close vicinity on the same clear cuttings: a) pitfall traps placed in patches of scarified soil that caught approaching pine weevils at 2.5 cm from the bait, which consisted of different sized seedlings of Scots pine some of which were subjected to application of MJ and b) the same type of seedlings planted out in patches of scarified soil.

The first field experiment was conducted on a 1-year old clear cutting outside Uppsala in east central Sweden and the trapping part of the experiment consisted of 8 blocks with 6 treatments: 1) control, 2) small over-wintered seedling, 3) medium sized seedling, 4) medium sized seedling treated with 0.5 ml 100 mmol MJ 4 days prior to start of experiment, 5) large seedling, 6) vial with 9.5 ml of α-pinene. The trapping experiment lasted for 6 weeks in the early summer. The traps were emptied 6 times and the number of caught pine weevils recorded. 25 of each type of the different seedlings were planted out in patches of scarified soil at the same time as the trapping experiment started. These seedlings were then examined on 4 occasions, throughout the summer, for feeding scars caused by pine weevils.

The second field experiment was conducted on a fresh clear cutting outside Forshaga in west central Sweden. Here, the trapping part of the experiment consisted of 7 blocks with 7 treatments: 1) control, 2) small over-wintered seedling, 3) small over-wintered seedling treated with 0.1 ml 100 mmol MJ 14 days prior to start of experiment, 4) small seedling, 5) small seedling treated with 0.1 ml 100 mmol MJ 5 days prior to experiment, 6) medium sized seedling, 7) medium sized seedling treated with 0.5 ml 100 mmol MJ 14 days prior to experiment. Traps were emptied and the number of caught pine weevils recorded 9 times during a 9 week period, from mid to late summer. Again, 25 of each type of the seedlings used in the trapping experiment were also planted out in patches of scarified soil and these seedlings were examined for feeding scars caused by pine weevils on 3 occasions throughout the summer.

844 and 1177 weevils were caught totally in the two experiments. Data from the trapping experiments was subjected to ANOVA:s (GLM) and no significant differences between the trap catches for different seedling sizes were found. There were however significant differences between different seedling sizes with regard to the number of attacked seedlings, the large seedlings were attacked to a much larger extent than the small, and it was concluded that there was no relationship between the number of weevils caught approaching a seedling of a certain size and the number of attacks. The empty control traps also caught large numbers of pine weevils. About 27 % of the pine weevils caught in both experiments belonged to the species Hylobius pinastri, the rest being H. abietis. It was noted that H. pinastri was significantly less attracted to α-pinene than H. abietis. There were no significant differences found between untreated seedlings and the ones treated with MJ regarding the number of attacked seedlings, the severity of the attacks or the number of caught approaching pine weevils. The seedlings treated with MJ did however grow significantly less than untreated seedlings.