DISEASE: Apple scab
PATHOGEN: Venturia inaequalis
HOSTS: apples and flowering crabapples (Malus spp.), hawthorn (Crataegus spp.), mountain ash (Sorbus spp.), firethorn (Pyracantha spp.), and loquat (Eriobotrya japonica). Pear (Pyrus spp.) is infected by a related fungus, Venturia pirina, which causes nearly identical symptoms.
Fruit with symptoms of apple scab. (Courtesy J. Hartman)
Apple scab occurs everywhere in the world where apples are grown and causes more losses than any other apple disease. It is most serious in areas that have cool, wet weather during the spring and may not be economically important in warm or dry climates.