largely temperature driven. 



In our study during 1999, while apple infections 

 first appeared between September 15 and 21, the first 

 new thyriothecia (infections) appeared on blackberry 

 canes m the borders of four orchards by August 1 7-24, 

 about 4 weeks earlier. This may indicate that the 

 environment in orchard hedgerows is more conducive 

 to S. pomi growth, or that the infections on these canes 

 occuiTed before those on adjacent apple trees. The 

 latter possibility would support the hypothesis that 

 epidemics originate on alternate hosts in orchard 

 borders and spread to the orchard from there via 

 conidia. 



A significant number of thyriothecia never mature. 

 Over the three years, from 33% to 69% of thyriothecia 

 did not contain any signs of spores at the end of the 

 maturation cycle. Such thyriothecia might have 

 actually been fertile, but when examined, they had 

 released their spores and the spore tissue had 

 disintegrated. Possibly some thyriothecia are damaged 

 over the winter by cold temperatures or desiccation. It 

 takes two different mating types of the S. pomi fungus 

 to produce ascospores, and perhaps some thyriothecia 

 never come in contact with a different mating type of 

 the fungus, so no spores can develop. 



We have answered a couple of the key questions. 

 S. pomi does not produce ascospores throughout the 

 year, but only at one time, and that time is between 

 pink and early fruit set. Unfortunately, we still have 

 not answered the question of where these ascospores 

 cause their infections. We do have some suggestions. 

 A 30-day period between the appearance of inoculum 

 and the first flyspeck symptoms in the field is typical 

 of flyspeck (9). In one of three years in this study 

 (1998) the end of ascospore production was 30 to 40 

 days before first infections were detected. Apples 

 inoculated with ascospores from several wild hosts can 

 cause flyspeck symptoms (1; 2). However, conidia of 

 Z. jamaicensis commonly infect apple and cause 

 tlyspeck (1; 4; 8). Spore trapping and the timing of 

 symptom development also indicated that conidia are 

 a significant portion of the inoculum that causes 

 flyspeck on apple (10). Conidia are common during 

 the period of most rapid symptom development. In 2 

 of 3 years the latency period between the end of 

 ascospore release and the first appearance of flyspeck 

 on apple was 60 to 90 days, and it is unlikely that 

 ascospores do any more than start the epidemic. 



As we said at the beginning of this paper, if the 



initial inoculum of flyspeck epidemics is primanly 

 ascospores, it might be possible to manage the disease 

 by preventing these primary infections, much as apple 

 scab is managed by targeting primary ascosporic 

 infections. However, if most or all of the infections 

 that blemish apples are secondary infections caused 

 by conidia that arise on reservoir hosts in orchard 

 borders, primary infections would have to be stopped 

 in those borders. Given legal constraints on fungicide 

 use off site, and the expense involved in owning and 

 clearing borderareas, such an approach is problematic. 

 Before such treatments could be recommended, it 

 would be necessary to know that the registration 

 changes and expense of these approaches would be 

 justified in terms of SBFS disease reductions. At 

 present we have a better understanding of when primary 

 infections occur. 



A ckn o wledgem en ts 



The authors wish to acknowledge the support of 

 USDA Federal Integrated Pest Management funds, 

 Massachusetts Department of Agricultural Resources 

 Integrated Pest Management Funds, and USDA 

 Sustainable Agriculture Research and Education funds. 

 We also wish to thank Dr. Bernard Roitberg, Simon 

 Frasier University, for assistance on the degree-day 

 model. 



References 



1. Barnes, R.C. 1940. Pathogenicity and hosts of the 



fly-speck fungus of apple. Phytopathology 

 30:2. 



2. Baker, K. F., L. H. Davis, R. D. Durbin, and W. C. 



Snyder. 1977. Greasy blotch of carnation and 

 flyspeck of apple - diseases caused by 

 zygophiala-jamaicensis. Phytopathology 67 

 (5):580-588. 



3. Brown, E. M., and T. B. Sutton. 1993. Time of 



infection of gloeodes-pomigena and 

 schizothyrium-pomi on apple in north-carolina 

 and potential control by an eradicant spray 

 program. Plant Disease 11 (5):45 1-455. 



4. Durbin, R. D., L. H. Davis, W. C. Snyder, and K. F. 



Baker. 1953. The imperfect stage of 

 microthyriella-rubi, cause of flyspeck of apple. 

 Phytopathology 43 (9):470-47 1 . 



5. Hickey, K. D., F. H. Lewis, and C. F. Taylor. 1958. 



10 



Fruit Notes, Volume 69, Summer, 2004 



