Flyspeck Life Cycle 



Ascos pores 

 are discharged 

 in rain 



Late Pink 



Twig and fruit 



tissue infected 



Fruit Set to 



Mid-July 



Conidia produced in 

 lesions spread 

 during rain and 

 cause new infections 



Mid June to 

 Harvest 



Feritheda form 

 in orchard and 

 on wild hosts 



Dormant 

 toPink 



Figure 3. The life cycle of Zygophialajamaciencis, the flyspeck pathogen. 



c) increasing use of sterol-inhibiting 

 fungcides, which have no effect on 

 these fungi, during primary scab 

 season; 

 • As a result of the first two factors, increas- 

 ing inoculum over multiple years. 



Of course, with increased pressure, growers 

 responded by applying more fungicide. The 

 EBDC fungicides were much more effective 

 than any other material, and protected fruit for 

 approximately 45 days. Captan, on the other 

 hand, protects fruit for about 14 days, and add- 

 ing Benlate™ or Topsin-M™ increases the 

 range to about 21 days. It is easy to see, given 

 the fungicides available and a recent history of 

 more summer disease damage, that growers 

 have reason to apply more fungicide. 



To develop a way of maximizing the effec- 

 tiveness of the materials available and perhaps 

 to reduce the amount used, we examined the life 

 cycles of the fungi causing the problems. In 

 Figure 3 the life cycle of the flyspeck fungus is 

 shown. The general observation is that in warm 

 wet climates, incidence is higher than in cooler, 

 drier climates. Optimum conditions for the 

 disease are said to fall between 65° and 80°F 

 where humidity exceeds 95%. The fungi which 

 cause summer diseases generally have a broad 



host range. For example, Z. jamaicensis is 

 known to infect over 100 other species besides 

 apple. It is fair to assume that the inoculum for 

 these diseases is always present in virtually all 

 orchards. However, some alternative hosts may 

 be more important than others, and Turner 

 Sutton of North Carolina State University be- 

 lieves that brambles, particularly blackberry, 

 are preferred hosts of the fungus. 



Previous work has indicated that pruning 

 may affect flyspeck and sooty blotch incidence in 

 North Carolina, where disease pressure is much 

 greater than in New England. Generally, better 

 pruned trees had less sooty blotch incidence. 

 However, the results were not consistent from 

 year to year, and there was no indication 

 whether decreases occurred because there was 

 better air circulation, or better fungicide appli- 

 cation and coverage. 



Work on the epidemiology of sooty blotch 

 and flyspeck has been limited. In 1990, we 

 undertook a small study to determine whether 

 summer pruning alone might decrease sooty 

 blotch and flyspeck incidence. In a block of 

 mature Mclntosh/M.7 trees, a random selection 

 of half the trees was summer pruned, while the 

 remainder was not. No fungicides were applied 

 over the summer. Disease incidence was rated 



Fruit Notes, Winter, 1991 



25 



