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Alternaria
leaf spot and fruit rot
Alternaria
tenuissima (fungus)
Annemiek Schilder,
MSU Plant Pathology
Bill
Cline, NCSU
Plant Pathology
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| Alternaria leaf spot occurs
primarily in North Carolina, but Alternaria fruit rot occurs in
most blueberry-growing regions. |
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Symptoms
Leaf lesions are circular to irregularly shaped, tan to gray,
1 to 5 mm in diameter, and surrounded by a reddish brown border.
In most cases only lower leaves are infected, but a severe
infection can defoliate the plant. On ripe fruit, sunken areas
near the calyx are covered by a dark green, velvety growth.
On stored fruit, a grayish-green mold may appear on the stem
scar or calyx end and spread over the entire berry. Infected
fruit becomes soft and shrivelled. |
| Dark green to black spores on an infected berry in the field. |
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Disease
cycle
The fungus overwinters in old twigs and in plant debris on the ground.
Leaf infections occur in the spring during periods of cool, wet
weather. Fruit infections occur as berries start to ripen. Disease
development is optimal at 68ºF (20ºC). |
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Management
Plant resistant cultivars; reduce humidity in the planting;
apply fungicides from bloom until harvest; harvest in a timely
manner; handle berries dry; cool fruit rapidly after harvest. |
| Fuzzy
grayish green mold on stored berry. |
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