Field performance of sand-coated (Conniflex®) Norway spruce seedlings planted in mounds made by continuously advancing mounder and in undisturbed soil

Abstract

The pine weevil (Hylobius abietis L.) is among the worst pests of newly planted conifer seedlings in Europe. EU regulations restrict the use of insecticides, the cost of mechanical site preparation (MSP) is high, and it has even been suggested that MSP should be abandoned due to social and environmental causes. The aim of this study was to investigate i) the field performance of Norway spruce (Picea abies (L.) Karst.) seedlings planted in mounds made by a continuously advancing mounder (CAM) and in undisturbed soil in southern Finland, and ii) how well the physical barrier (Conniflex® sand coating) prevented pine weevil damage compared to insecticide-applied and unprotected seedlings. The quality of CAM was generally at an acceptable level. After two growing seasons, mortality, mainly caused by pine weevils, was higher and growth lower in unprotected seedlings than in Conniflex-coated or insecticide-treated seedlings. Mortality was also higher and growth lower in undisturbed soil than in mounds. Even though the quality of soil preparation after CAM was quite good, planting Norway spruce seedlings without any protection could not guarantee a successful planting result (>1500 seedlings ha−1). Conniflex coating and insecticide treatment provided equal protection against serious pine weevil damage.