Four Hazelnut Pollenizers Resistant to Eastern Filbert Blight

442 Eastern filbert blight, caused by the fungus Anisogramma anomala (Peck) E. Muller, is native to the eastern United States where the wild species Corylus americana Marsh. serves as its host. The disease is believed to have been introduced to the Pacific Northwest on nursery stock imported from the East Coast in the early 1960s. The disease is now firmly established in the northern third of the Willamette Valley, the major growing area, and is a serious threat to commercial acreage of the European hazel, Corylus avellana L. The life cycle of the fungus was described by Gottwald and Cameron (1980). Symptoms include perennial cankers that enlarge 30 to 100 cm·year and can exceed 2 m in length, girdling scaffold limbs and the tree trunk. The canopy of older trees of susceptible cultivars is killed in 7 to 10 years. The most common hazelnut orchards in Oregon are planted to ‘Barcelona’, with ‘Daviana’ pollenizers planted every third tree in every third row. ‘Barcelona’ is considered tolerant of the disease, as infected trees remain productive for several years before eventually dying. ‘Daviana’, however, is highly susceptible. As eastern filbert blight spreads from one orchard to another, it is generally found first in the ‘Daviana’ pollenizers. From there, it spreads to the surrounding ‘Barcelona’ trees. ‘Butler’, the second most common pollenizer, is also highly susceptible. ‘Hall’s Giant’ is considered tolerant and is currently recommended as a pollenizer for ‘Barcelona’, although it sheds pollen later than the ideal time. ‘Gasaway’, which is highly resistant to the disease (Mehlenbacher and Thompson, 1991), sheds its pollen very late in the season and, thus, is a poor choice as a pollenizer for ‘Barcelona’. By replacing the highly susceptible pollenizers in a ‘Barcelona’ orchard with resistant genotypes, it should be possible to delay the time of initial infection and to maintain an infected orchard in a productive state for many years. Four resistant pollenizer selections were