EASTERN FILBERT BLIGHT IN OREGON
Eastern filbert blight is a serious disease which threatens the hazelnut industry in the Willamette Valley of Oregon where 98% of the U.S. crop is produced. The causal fungus, Anisogramma anomala (Peck) E. Müller, was introduced from the eastern United States into southwestern Washington in 1970, and is now firmly established in the northern Willamette Valley. In the host, the fungus colonizes the primary vascular system and produces perennial cankers. Stromata with perithecia appear in sunken cankers 13–14 months after infection, and perithecia mature 4 months later. The disease spreads within trees by both mycelial growth and ascospores. Infected orchards are rendered unproductive in 4–8 years. Ascospores are discharged during rains from fall to late spring, but are only able to infect young vegetative tissue at and up to 3 months after budbreak. Patterns of spread in diseased orchards indicate that spores are spread locally in rain splash droplets and over longer distances in wind-blown rain. Control practices include pruning and burning of infected wood, and chemical applications. Cultivars range in susceptibility from highly susceptible to immune. The development of resistant cultivars is a promising long-term control measure. The importation and consumption of Oregon-grown nuts poses no threat to the health of the European industry.
Mehlenbacher, Shawn A., Pinkerton, Jack N., Johnson, K. B. and Pacheidt, Jay W. (1994). EASTERN FILBERT BLIGHT IN OREGON. Acta Hortic. 351, 551-558