Effects of green tree retention, prescribed burning and soil treatment on pine weevil (Hylobius abietis and Hylobius pinastri) damage to planted Scots pine seedlings

Abstract

1 Feeding damage and mortality caused to planted Scots pine seedlings by the pine weevils Hylobius abietis and Hylobius pinastri were studied on burned and unburned sites with 0, 10 and 50 m 3 per hectare levels of green tree retention from the second to the fourth summer after logging and burning of the sites. 2 The rate of severe feeding damage to pine seedlings caused by pine weevils was higher on burned clearcut sites than on unburned ones, whereas burning did not increase the feeding damage rate on sites with groups of retention trees. The damage rate in the fourth summer was approximately the same on burned and unburned sites. 3 Pine weevil feeding was the major cause of mortality of freshly planted pine seedlings on unburned sites. On burned sites, mortality was higher than the rate of severe feeding damage, particularly in the second summer after burning, possibly owing to fungal attack and abiotic factors. 4 At a retention tree level of 50 m 3 , feeding damage to the seedlings was lower than on clearcuts and at a 10 m 3 retention tree level. Furthermore, on sites with 50 m 3 of retention trees, scarification of the soil was found to decrease feeding damage more effectively than on clearcuts and 10 m 3 sites. If the seedlings were situated in the centre of scarified patches, scarification alone was as effective as insecticide treatment on unscarified soil for decreasing feeding damage and mortality. 5 The results suggest that when burning is applied as silvicultural treatment after clear-cuts, retention of trees is recommended to reduce the damages caused by pine weevils on pine seedlings.

Steinernema kraussei, an indigenous nematode found in coniferous forests: efficacy and field persistence against Hylobius abietis

“…The large pine weevil Hylobius abietis L. (Coleoptera: Curculionidae) is a widely distributed pest of plantation forestry occurring throughout Europe and is often regarded as being the most serious pest in conifer reforestation ( Scott & King, 1974;Evans, 1997;Leather et al , 1999;Landmann, 2000;Bratt et al , 2001;Steyrer et al , 2002;Pitkänen et al , 2005 ). Hylobius abietis develop in the stumps and roots of dying and dead conifers and emerge as adults to feed on the bark and cambium of woody plants, showing a preference for conifers ( Munro, 1928;Leather et al , 1994;Manlove et al , 1997;Mansson & Schlyter, 2004 ).…”

Regeneration of European boreal forests: Effectiveness of measures against seedling mortality caused by the pine weevil Hylobius abietis

“…An additional option to reduce damage is regeneration under shelterwood Petersson and Örlander, 2003;Wallertz et al, 2005). Similarly, damage levels can be reduced by retaining groups of trees on clear-cuts, which is commonly recommended for other environmental reasons (Pitkänen et al, 2005).…”

Effects of controlled forest burning and intensity of timber harvesting on the occurrence of pine weevils, Hylobius spp., in regeneration areas

“…A retention level of 50 m 3 ha À1 was found to reduce feeding damage to planted Scots pine seedlings significantly, especially on the burned sites in summer 2002, and highest damage being found on burned clear-cut and burned retention tree sites with a density of 10 m 3 ha À1 (Pitkänen et al, 2005).…”

“…They are known to be attracted to burned sites (Sylvén, 1927;Muona and Rutanen, 1994;Bakke, 1996), where high levels of damage to planted seedlings have been attributed to them (Nenonen and Jukola, 1960;Juutinen, 1962;von Hofsten and Weslien, 1999;Weslien and von Hofsten, 1999;Pitkänen et al, 2005), but the effects of retention trees on their behaviour are unclear, especially when the regeneration areas are burned after harvesting.…”

“…We performed a large-scale field experiment to study the effects of harvesting intensity and fire on biodiversity patterns in Fennoscandian boreal forests (see Hyvärinen et al, 2005Hyvärinen et al, , 2006, including monitoring of the impacts that these factors have on pests (Pitkänen et al, 2005;Martikainen et al, 2006). We focus our attention here on the occurrence of pine weevils during the first years after the timber harvesting.…”