Fungi
Black spot of elm
Stegophora ulmea
Thomas Cech
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Fig. 1. Stegophora ulmea, leaf spots
DETECTION PERIOD:
April to August (leaf symptoms and leaf shedding); twig cankers: all the year.
DESCRIPTION:
At first small yellow spots of about 1 mm diameter appear on the leaves in spring. They develop into dark spots of up to 5mm size (Fig. 1): on these stromata are produced. In early August premature shedding of leaves follows and sometimes also twig dieback and death of fruits occur.
HABITAT:
Various species of elms, also European ones! Forests and urban sites.
STATUS:
Widespread in North America, only single cases reported from Europe; species with quarantine status in the European Union.
IMPACT:
In North America mainly a problem in nurseries (defoliation and dieback).
SIMILAR SPECIES:
Other leaf diseases of elms as for instance Phloeospora ulmi (Fig. 2).
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