See:
Cause Venturia sp., a fungus that overwinters on old fruit and leaves. It has been reported from Washington on cotoneaster. The apple scab fungus V. inaequalis is reported to occur on cotoneaster but it is unknown if isolates from apple can infect cotoneaster or vice versa. V. tomentosae is also reported to occur on cotoneaster in Switzerland.
Symptoms Symptoms are very similar to those of scab on apple and pear leaves and fruit: dark blotchy spots on leaves and fruit. If the disease is severe, fruit may be covered almost entirely by black blotches, and leaves may turn yellow prematurely in fall.
Cultural control In fall, rake and burn leaves and fruit.
Chemical control
- Banner MAXX at 5 to 8 fl oz/100 gal water may be effective. Group 3 fungicide. 12-hr reentry.
- Protect DF at 1 to 2 lb/100 gal water plus 2 to 4 oz spreader-sticker. Group M3 fungicide. 24-hr reentry.
References Menon, R. 1956. Studies on Venturiaceae on rosaceous plants. Phytopathologische Zeitschrift 27:117-146.
Sivanesan, A., and Waller, J.M. 1974. Venturia inaequalis. CMI Descriptions of Pathogenic Fungi and Bacteria, No. 401. Surrey, England: Commonwealth Mycological Institute.