Effect of the timing of application on efficacy of entomopathogenic nematodesin control of Hylobius abietis (L.)

Abstract: The large pine weevil (Hylobius abietis) is a pest of great economic importance,damaging young coniferous plantations. In search for new methods to reduce H. abietispopulations, the experiments were conducted aiming at the evaluation of preferred timing ofapplication (June or September) of entomopathogenic nematodes to decrease the number of pestlarvae developing in Scots pine (Pinus sylvestris) stumps. The treatment with Steinernemacarpocapsae and Heterorhabditis downesi at a rate 3 million specimen/stump.against H. abietislarvae in P. sylvestris stumps applied in June indicated low efficacy. Nematode infection wasobserved in approximately 19% of the large pine weevil larvae collected from the stump. Higherefficacy of treatments at the same rate was recorded when nematodes had been applied inSeptember. Spraying of litter around Scots pine stumps resulted in infection of 85% of the larvaedeveloping in the stumps. These results were influenced by the weather conditions –unfavourable for nematode vitality during summer treatment and favourable during autumntreatment.