PHYTOPHTHORA ROOT ROT AND BOTRYOSPHAERIA STEM BLIGHT: IMPORTANT DISEASES OF SOUTHERN HIGHBUSH BLUEBERRIES IN THE SOUTHERN UNITED STATES

Abstract

Southern highbush cultivars are extending the range of commercial blueberry production further south in the U.S. due to their low winter chill requirement, late spring bloom, and early fruit production; however, little is known about their susceptibility to diseases. These studies are part of a series whose objective is to compare the susceptibility of southern highbush blueberry cultivars to two diseases common to the southern U. S.: stem blight, caused by the fungus Botryosphaeria dothidea, and Phytophthora root rot caused by the fungus Phytophthora cinnamomi. The susceptibility of southern highbush cultivars to root rot was determined by growing the plants in soil infested with P. cinnamomi. 'Star', 'Bluecrisp', 'O'Neal', 'Jewel', 'Jubilee', 'Southmoon', and 'Misty' were more vigorous than other cultivars in at least two of three separate trials. The susceptibility of 20 southern highbush blueberry cultivars to stem blight was evaluated using a detached stem assay. Cultivars that developed lesions shorter than those on the susceptible rabbiteye, 'Tifblue', were classified as resistant and included 'Pearl River', 'Southmoon', 'Marimba', 'Star', 'Sebring', 'Ozarkblue', Georgiagem', 'Sapphire', 'Bluecrisp', 'Misty', and 'Emerald'. Those with lesions as long or longer than 'Tifblue' were classified as susceptible and included 'O'Neal', 'Legacy', 'Cooper', 'Bladen', 'Jubilee', 'Magnolia', 'Biloxi', 'Gulf Coast', and 'Reveille'.