Fusicoccum canker, Phomopsis amygdali

	I. Introduction: Fusicoccum canker, also called constriction canker, is caused by Phomopsis amygdali (Del.) Tuset and Portilla, formerly Fusicoccum amygdali Delacr. The disease is of minor economic importance on peach in the mid-Atlantic and southeastern states and rare and of no economic importance on peach in Michigan. II . Symptoms: Symptoms appear in early summer and become increasingly evident as more blighted shoots appear through late summer. Infected twigs and shoots wilt and die because of elongate, brown, sunken cankers, often with a zonate pattern, at their bases (Photos 126, 127). Constrictions formed at the bases of infected shoots and leaf symptoms produced well beyond the infection site result from a translocatable toxin, fusicoccin. Gumming is commonly associated with cankers, but it is not a good diagnostic characteristic because other canker pathogens also cause gumming. III. Disease Cycle: Darkly pigmented pycnidia (flask-shaped, conidia-bearing fruiting bodies) are produced over the surface of the cankered area. The pycnidia exude conidia in white tendrils during wet weather. Conidia disseminated by rain infect through leaf scars in autumn and through buds, bud scale scars, stipute scars and fruit scars, or directly through young shoots during the growing season. The pathogen may also cause large, circular to irregular, zonate, brown spots in the leaves. IV. Control: Removing twigs with dieback and cankers is important to help control Fusicoccum canker. Fungicides, applied just before budbreak and in autumn, may be needed in problem orchards. Some fungicides used for brown rot and peach scab control during the growing season may help prevent infection. Cultivars vary in susceptibility, with Golden Jubilee, Redhaven, Rio-Oso-Gem and Redgold nectarine being more susceptible than Coronet, Harken and Sunhigh.
Text prepared by A. L. Jones and T. B. Sutton