New hosts and differential susceptibility of five-needle pine species to Dooks needle blight (Lophophacidium dooksii)

An outbreak of Dooks needle blight (Lophophacidium dooksii) in a five-needle pine genetic archive containing nine five-needle pine species and their interspecific hybrids provided an opportunity to observe the differential susceptibility of these pine species to the disease. Survey results indicated that four of the nine species in the archive were susceptible, including new hosts western white pine (Pinus monticola) and Himalayan blue pine (P. wallichiana), as well as previously reported hosts eastern white pine (P. strobus) and Macedonian pine (P. peuce). Japanese white pine (P. parviflora) and Korean pine (P. koraiensis) were seemingly not affected by the pathogen. While P. peuce and its interspecific hybrids showed the highest susceptibility and the heaviest needle damage, P. parviflora and its interspecific hybrids, including those with P. peuce, were rarely infected, indicating a potential strong and dominant genetic resistance to the pathogen. Pinus monticola and P. strobus showed similar levels of susceptibility and needle damage. Implications of these results to forest health in North America and the Balkans are discussed.