The Real Christmas Tree Board

Ongoing research led by Dr. Robert Jetton and his PhD student Dominic Manz in the NC State University Forest Health Lab (Department of Forestry and Environmental Resources) is shedding new light on elongate hemlock scale (EHS) biology and management. They recently completed a study that evaluated the phenology (timing of the insect’s life stages throughout the year) of the pest across the North Carolina Fraser fir production region. The data shows that EHS has multiple overlapping generations with all life stages occurring year-round. This means that with even good control of insecticide susceptible life stages, less susceptible life stages will survive to perpetuate infestations. The study also revealed that EHS infestations occur on older needle age classes deep within the dense Fraser fir crown where good insecticide coverage is difficult to achieve. Also evident in the phenology data is that peak EHS egg production each year occurs at the beginning of the annual fall harvest season, adding further evidence to the risk of moving this pest to new areas on tree shipments. All of these outcomes indicate the importance of continuing to test new products that are effective against all EHS life stages and the need to remain focused on true IPM approaches that combine insecticides applications with biological and cultural controls as well as new genetic approaches like those being developed by Dr. Justin Whitehill and the NC State Christmas Tree Genetics Program. Additional ongoing projects are assessing the influence of on-farm management practices (insecticide, fertilization, herbicides application timing, rates, methods) on EHS infestation patterns in Christmas tree fields and the risk of EHS crawler emergence from cut trees during the transport, retail, in-home display, and disposal phases of the tree life cycle. Final data and conclusions from these studies will be shared by the end of 2024.