Diseases of Tree Crops
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Affects both hazelnuts and walnuts.
Walnut blight - Xanthomonas campestris pv juglandis
Bacterial disease causing black lesions on catkins, fruit and leaves. Exacerbated by dampness, but severity can be reduced by copper.
For more information, visit the University of California's Statewide Integrated Pest Management Program.
Hazelnut Blight - Xanthomonas campestris pv corylina
Bacterial disease causing lesions on leaves and bark. Mainly affects young, trees, especially when stressed by frost or lack of water. Exacerbated by humid conditions, but severity can be reduced by copper.
For more information, visit the Oregon State University website or the British Columbia (Canada) Ministry of Agriculture and Lands.