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within several weeks and dropped by mid-July to mid-August. 



Isolations from the center or edge of these foliar infections 

 onto sterile petri plates of potato carrot agar consistently 

 yielded the fungus Sclerotinia sclerotiorum . This was the first 

 reported isolation of the fungus from apple foliage. Controlled 

 laboratory studies were conducted to determine the conditions 

 necessary for foliar infection by S. sclerotiorum . Results 

 showed that not only would the fungus infect wounded leaves , but 

 that unwounded leaves developed lesions providing that continuous 

 moisture was present. 



The life cycle of Sclerotinia sclerotiorum is well known on 

 beans, lettuce and many other vegetable crops. However, to date 

 no successful studies have been done on how the fungus infects 

 apples. It is presently believed that spores, released during 

 spring rains, infect blossoms. It is further thought that pro- 

 longed wet weather encourages the fungus to continue growth into 

 developing fruit with an end rot resulting. It is likely that 

 foliage infections occurred directly from spores, or following 

 contact with young fruit infected with S. sclerotiorum . It may 

 be possible that fungal spores are present on anthers or pollen 

 grains, thus, explaining many of the foliar infections described 

 above. 



At this time, the fungus does not seem to present an economic 

 threat to apple foliage. However, end rots have been increasing 

 during the past 3 years (FRUIT NOTES 48 (1) : 10- 16) . Current apple 

 scab fungicide programs may not provide adequate control of calyx- 

 end rots and no fungicides are currently registered for the disease 

 When prolonged infection periods exist between pink and first 

 cover, applications of captan and benomyl may be helpful. 



In attempts to gain more information about the disease on 

 apples, the Department of Plant Pathology hopes to monitor develop- 

 ment of Sclerotinia sclerotiorum under controlled conditions in the 

 field next season. 



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