Anthracnose
(Ripe rot)
Colletotrichum acutatum
(fungus)
Annemiek Schilder,
MSU Plant Pathology
Bill
Cline, NCSU Plant
Pathology |
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Anthracnose
is a serious pre- and post-harvest fruit rot in most blueberry-growing
regions. Cane, twig, and leaf lesions are more sporadic.
Symptoms
The fruit rot manifests itself as sunken areas on ripe fruit
with gelatinous, orange spore masses. On young canes, lesions
are dark brown with fruiting bodies in concentric circles.
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| On twigs, dark brown lesions
may originate from infected buds and kill part of the twig. On the
leaves, lesions look reddish brown with distinct borders. Salmon-pink
spore masses may appear on infected tissues under humid conditions. |
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Disease cycle
The fungus overwinters in remnants of old fruiting
twigs and infected canes. In spring and summer, fruiting bodies
release spores which are dispersed by rain and infect flowers, fruit
and other tissues. Fruit infections remain latent until the fruit
starts to ripen. In Michigan, spore numbers peak around bloom.
A second peak occurs when fruit are ripening. Warm humid conditions
favor the disease. |
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Management
Prune out old or
infected wood; create an open canopy to reduce humidity and
increase spray penetration; plant resistant cultivars; limit
overhead irrigation; harvest in a timely manner; cool fruit
rapidly after harvest; apply effective fungicides from pink
bud to harvest. |
| Cane
lesions (left) with fruiting bodies in concentric circles.
Orange spore masses (right) on a dead twig in spring. |
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