I. Introduction: Nectria twig blight is
a minor disease that results in dieback of apple twigs. It is caused by the fungus Nectria
cinnabarina (Tode) Fr., asexual state of Tubercularia vulgaris Tode.
Recognition of the disease is important because it is often confused with fire blight,
which requires different control measures.
II. Symptoms: In late May to early
June, shoot growth on infected twigs begins to wilt and die (Photo 64). Small,
sunken cankers are found at the bases of the wilted shoots. Leaves on infected shoots
appear to die from the base, not from the tip, as with fire blight, and no signs of
blighted blossom clusters remain on the twigs. Shoot death may be extensive (Photo 65). In mid- to late summer, bright orange or coral-red structures (sporodochia) 1/8 to 1/6
inch in diameter appear on the surface of the cankers (Photo 66). Orange
sporodochia are also often associated with pruning wounds and winter-injured tissues on
apple. In autumn, the fungus produces clusters of small, dark red, globular
perithecia, but these structures are rarely present in the eastern United States.
III Disease Cycle: Optimum
fungal growth occurs in culture at 70 degrees F, with moderate growth at 80 to 85 degrees
F and limited growth at 37 degrees F. Wounds from fruit harvest, which probably take a
long time to heal late in the season, combined with prolonged periods of wet weather after
harvest, appear to favor the establishment of infection. The disease has been noted
primarily on cultivars with a large cluster-bud base, such as Rome Beauty, Ben Davis and
IV Control: The disease is not usually severe enough
to require special control measures. As a result, chemical control procedures have not
been developed. Removal of infected twigs helps reduce the carryover of inoculum.
prepared by A. L. Jones and T. B. Sutton
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