Protoventuria (Gibbera) Leaf Spot and Berry Speckle
Economic Information
Protoventuria leaf spot and berry speckle, caused by the fungus Protoventuria myrtilli (formerly Gibbera myrtilli), is considered economically insignificant. The leaves are not affected until middle or late summer, and the speckles on berries are superficial and do not rot the fruit. However, severely affected leaves may drop prematurely. The biological and economic impact of premature leaf drop is not understood.
Symptoms
By early autumn, leaf lesions are distinct, reddish, and irregular in shape. The following spring the lesions are faded and margins are indistinct. Leaves turn yellow and clusters of black pseudothecia are sometimes visible. The biological significance of premature leaf drop is not well understood.
Disease Cycle
P. myrtilli overwinters in lesions on leaves. Ascospore release from mature psuedothecia on the previous year’s leaves, and subsequent infection of the current year’s leaves, occur during middle to late summer.
Control
Little is known regarding the relative resistance of cultivars. Unless vines are severely affected by premature leaf loss, chemical control is not warranted on berries destined for processing. Fungicides applied to control fruit-rotting pathogens will also control myrtilli. Applications should be made to coincide with ascospore release, which usually occurs from mid-July through mid-August.
Questions or comments? Please contact Dr. Patty McManus.
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Fruit Pathology
University of Wisconsin - Madison 