Response of Resistant Hazelnut Cultivars to Eastern Filbert Blight in the Pacific Northwest

Abstract

The hazelnut (Corylus avellana) cultivars ‘Ennis’, ‘Jefferson’, and ‘McDonald’ were inoculated with various doses of Anisogramma anomala ascospores to determine whether high concentrations of ascospores resulted in eastern filbert blight (EFB) cankers. Trees at budbreak or early shoot growth were inoculated with 0, 104, 105, 106, and 107 ascospores/ml, placed in a mist chamber for 72 h, and held for 1.5 years for canker development. Ennis trees became infected when the concentration was at least 104 ascospores/ml whereas resistant trees became infected only when the concentration was 106 or 107 ascospores/ml. The progression of EFB symptoms in a 10-ha Jefferson hazelnut orchard was also documented over a 5-year period from 2010 to 2014. EFB cankers were first observed fall 2010, averaged 7 cm in length, and were characterized by longitudinal cracks and flat or slightly sunken areas on trunks. Some cankers had a few small stromata with viable ascospores. Cankers on 143 trees were measured after leaf fall each year. Comparison between the initial canker size and the final size measured in 2014 indicated that 49% of the cankers continued to get larger but there was no indication of whether the cankers would increase or decrease in size over time. Growers should use fungicides the first few years after planting until trees are established and vigorously growing. Cankers that develop on resistant trees should be removed and destroyed prior to budbreak in the spring.