If infections from the initial cycle of spores 

 are not the primary cause of late season 

 symptoms in the orchard, then conidia must be. 

 We wanted to know if inoculum could be 

 building up in the woods and borders, in the 

 form of conidia, and moving into the orchard 

 sometime later in the summer. 



Previous studies have shown that trees 

 closer to the borders have a much higher 

 incidence of flyspeck {Fruit Notes 61(2): 1-4, 

 1996). But flyspeck symptoms are rarely seen 

 before the end of July and have never been seen 

 early in the season. 



Based on the fact that there are repeated 

 yearly infections of the numerous host plants in 

 the orchard border, we knew that ascopores 

 germinate in the field and cause infections. The 

 typical lifecycle of the fungus begins with the 

 ascospore germinating to form a colorless 

 mycelium which live off the nutrients of the 

 waxy surface layer of its host. Repeating cycles 

 of conidia or asexual spores form on this 

 mycelium, and then the typical flyspeck 

 symptoms appear. 



It is possible that ascospores create local 

 infections in the borders and cycles of conidia 

 proliferate on these hosts creating a reservoir 

 of additional infections and inoculum that can 

 move into the orchard block when environmen- 

 tal conditions are conducive. We know from 

 research conducted by Dr. T.B. Sutton that 

 flyspeck conidia are discharged primarily in 

 the early morning hours, after periods of high 

 humidity or heavy dews or rain, and as the 



levels of high humidity decrease (Sutton, Plant 

 Disease 74:643-646, 1990). 



During the summer of 1997 we attempted 

 to find out if and when asexual spores or 

 conidia were typically present within an 

 orchard in Shelburne, Mass. The trees had 

 been sprayed following a first-level integrated 

 pest management schedule with the last spray 

 of Rubigan and Pencozeb occurring on June 4. 

 Spore traps were placed within the blackberry 

 border, in the first row of trees about seventeen 

 feet from the border, and in the third row of 

 trees about seventy feet from the border. Spore 

 trapping rods were brought back to the 

 laboratory and spores counted twice a week 

 starting in mid-July. 



Actual numbers of spores caught on the 

 traps were too small to analyze statistically. 

 However, the number of conidia trapped 

 increased dramatically during the second week 

 of August, coinciding with an increase in heavy 

 morning dews. The first symptoms of flyspeck 

 were observed two weeks later on August 31. 

 Additional data are needed to be able to predict 

 the environmental conditions that will lead to 

 an increase in conidial inoculum in the orchard. 

 It does seem, though, that there is a period of 

 time between the end of primary scab season 

 and mid-July to mid-August, particularly in 

 dry years, when there are few conidia in the 

 blocks and the likelihood of flyspeck infection is 

 very low. 



In the orchard where spores were trapped. 



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



