Effects of Mounding on Damage by the European Pine Weevil in Planted Norway Spruce Seedlings
The European pine weevil (Hylobius abietis L.) is not found in northern America so far but is the major pest in conifer reforestation in northern Europe. The effects of mounding on pine-weevil damage and growth in planted Norway spruce (Picea abies (L.) Karst.) seedlings were studied on two clearcut forest sites in Finland. Three different mounding treatments (spot mounding with or without mixing and inverting) were compared to three unscarified treatments with or without vegetation control (mulch or herbicide). Mounding significantly decreased pine-weevil damage, mortality, and growth losses of planted Norway spruce seedlings even if insecticide was used before planting. Seedling growth and survival were poorest with the heaviest feeding by the pine weevil. After the first growing season, the proportion of gnawed seedlings was higher on unscarified spots (76% gnawed), whereas seedlings on mounded spots had hardly any feeding (1%). Seedling mortality was lower on mounded (1%) than on unscarified spots, where it was higher in 1-year-old (27%) than 2-year-old seedlings (10%). After the second growing season, mortality and proportion of gnawed seedlings increased on both mounded and unscarified spots. The study indicates that mounding can provide an effective method of decreasing pine-weevil damage and improving plantation success.
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