Efficiency of chemical and mechanical plant protection on sites without mechanical site preparation in Scania

Abstract: An important part of the regeneration after clearcutting is to have a high growth and a high level of survival of the planted seedlings. A big threat to the seedlings is the pine weevil (Hylobius abietis), but the black spruce beetle (Hylastes conicularius) can cause some serious damage too, as well as Strophosoma capitatumn. Mechanical site preparation in combination with some sort of plant protection reduces the damage, but in some cases here in Sweden, mechanical site preparation is not possible due to cultural remains or technical reasons. And, with chemical protections being phased out of Swedish forestry, it’s important to understand the efficiency of mechanical plant protection compared to chemical on sites without mechanical site preparation. Therefore, the objective of this study was to see what the consequences could be when replacing chemical protection with mechanical protection on fresh or one year old clear-cuts. The results showed that seedling mortality caused by pine weevils was 3,5% for mechanical protection and 2,4% for chemical protection. The seedling mortality caused by the black spruce beetle was 3,0% for mechanical protection and 4,2% for the chemical protection. No significant difference was seen between the two treatments when looking at damage caused by pine weevil, black spruce beetle and Strophosoma capitatumn, neither did it affect total height and shoot height.