the first row of trees was sprayed only on the 

 side away from the border. The border side of 

 those trees was highly vulnerable to infection 

 by ascospores, being unprotected by fungicide 

 and in close proximity to the blackberries. Yet 

 no flyspeck occurred until late summer, when it 

 also occurred on the sprayed side of the trees as 

 well as in other blocks in the orchard. This 

 coincided with a change in environmental 

 conditions that either stimulated the fungus to 

 grow or promoted an influx of conidial 

 inoculum into the orchard from the borders. 

 This supports our contention that ascospores 

 play little or no role in direct infections on fruit, 

 but instead it is conidia moving from border 

 plants that inoculate the crop. 



In summary, flyspeck ascospores form in 



the orchard borders and surrounding woods 

 rather than in the orchard. Ascospores are 

 released during a single discrete period in the 

 late spring and early summer, making it 

 possible to relate the period of heaviest 

 inoculum dose to apple tree phenology, 

 generally 10 to 14 days after petal fall. These 

 spores probably cause infections on border 

 plants but not on orchard fruit. If any infection 

 occur, sprays aimed at controlling scab will 

 most likely control them. Therefore, ascospores 

 do not seem to play a major role in producing 

 the flyspeck symptoms that are seen in late 

 summer in Massachusetts, and efforts need to 

 be focused on controlling infections caused by 

 conidia from mid-July thru harvest. 



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Fruit Notes, Volume 62 (Number 3), Summer, 1997 



