Assessing weevil damage in silver birch: species identification and effectiveness of mechanical protection

Weevils are notorious pests in conifer regeneration, yet their impact on broadleaved species such as silver birch (Betula pendula) remains poorly understood. This study investigated the incidence and severity of weevil damage on newly planted birch saplings in southern Sweden and tested the effectiveness of Hylonox, a mechanical coating, against weevil attack. A field experiment was established across fresh and one-year-old clear-cuts and damage assessments were conducted over two growing seasons. Strophosoma melanogrammum was the most frequently observed weevil species, followed by Otiorhynchus carinatopunctatus, Hylobius abietis and Hylobius pinastri. Overall, 62% of the birch saplings showed bark damage by weevils, with mortality reaching 16% among the damaged individuals. Mortality was significantly higher in untreated saplings (30%) than in treated ones (21%). Weevil-associated leaf feeding affected 87% of saplings in 2024 and 49% in 2025, but severity was predominantly minor (<20% leaf area affected). Initial sapling height significantly affected both the incidence of bark damage and mortality, with shorter saplings experiencing higher mortality. Ungulate browsing was frequent (45% of saplings), often affecting terminal shoots. The results of this study suggest that weevils can damage birch during early establishment, although mortality is modest relative to that in conifers.