![]() The leaf tissue around individual lesions may remain green on the upper leaf surface. This disease can be diagnosed in the field by the characteristic small, necrotic lesions that produce orange masses of uredospores on the underside of the leaf. Rust ( Pucciniastrum vaccinii) is often first noticed as yellowing and defoliation of older leaves. In late season, white fungal growth on the upper surface of leaves may include small black fungal fruiting bodies (cleistothecia) that are the overwintering stage of the fungus. The disease first appears as a faint white fungal layer on maturing leaves, causing pale distorted spots with faint necrotic areas, becoming more distorted and red as the season progresses. Powdery Mildew ( Microsphaera vaccinii) usually does not develop on blueberry leaves until midsummer after the crop is harvested. Prolonged periods of high humidity favor disease development. Leaf symptoms appear as small to medium (1/4 inch) circular to irregular-shaped brown to gray lesions surrounded by a red border. Because of its importance as a postharvest fruit decay organism, an increase of the fungus on blueberry leaves in May can cause increased postharvest decay of fruit. In most cases only lower leaves are affected. It appears on the foliage by mid-summer as small to medium (1/4 to 1/2 inch) dark brown, circular to angular lesions surrounded by a dark border.Īlternaria Leaf Spot ( Alternaria tenuissima) occurs primarily in the spring during prolonged periods of cool wet weather, when spores are produced in abundance. Gloeocercospora Leaf Spot ( Gloeocercospora inconspicua) is of minor importance as a leafspot disease in North Carolina. The dark border surrounding the original lesion persists and the large necrotic area surrounds or is to one side of the original lesion. In late summer, the fungus develops a secondary necrotic area around the original lesion spreading in an irregular to fan-shaped pattern. Stem lesions and leaf spots are most severe on small plants or on the lower parts of large plants.ĭouble Spot (Dothichiza caroliniana) lesions are initially 1/16 to 1/8 inches in diameter. Stem lesions are flat or slightly sunken with a tan to gray center and a reddish brown margin. Small black fungal fruiting bodies may be visible in the center of lesions. Spots on leaves are usually small (1/8 to 1/4 inches across) with a white to tan center and a purple border. ![]() Spores are produced in abundance on new lesions throughout the season. The fungus overwinters in infected leaves on the ground and in stem lesions. Damage can also occur in hardwood rooting beds, causing defoliation and poor growth. Septoria Leaf Spot (Septoria albopunctata) can be seen on most highbush and rabbiteye blueberry cultivars grown in North Carolina. On highly susceptible cultivars such as Duke, Jersey, and Pender, the disease can result in severe dieback. As the lesions enlarge, the affected stems turn brown and eventually become gray and die. Stem lesions first appear on current season's growth as dark red circular to elliptical lesions around leaf scars. Secondary stem lesions can develop from leaf infections by growing through the petiole into the stem, and from bud infections late in the season. Development of lesions results primarily from infection through hydathodes at the margins of the leaf, and to a lesser extent through wounds. The leaf anthracnose stage produces large (1/2 to over 1 inch across) brown to gray lesions that are the most common symptom observed in the field. Leaf and stem flecks do not develop further. Symptoms first appear as small reddish flecks on young leaves and stems of succulent shoots. Gloeosporium leaf spot was first described as a stem and leaf fleck disease of blueberry. Gloeosporium Leaf Spot or Anthracnose (Gloeosporium minus) can produce flecking, leaf anthracnose and stem lesions. Symptoms and Disease Cycles Skip to Symptoms and Disease Cycles
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