at 336 wetness-hours from 10 days after petal fall, 

 and 262 wetness-hours from the previous fungi- 

 cide. Once the first summer fungicide was applied 

 in each section, that section thereafter continued 

 to receive a regular fungicide program. 



Results 



Because of the early accumulation of the thresh- 

 old level of leaf wetness hours, sampling (50 fruit 

 per section per week) began in mid-July instead of 

 early August as planned, but no symptoms were 

 seen even in check trees until mid-August. When 

 flyspeck symptoms began to appear (virtually all 

 the summer disease seen this year was flyspeck), 

 they appeared first in the most lightly-sprayed plots. 

 Despite the early wetness, there was not a signifi- 

 cant level of flyspeck except in the check trees un- 

 til mid-September. 



As can be seen from Table 1, there were few 

 significant differences in summer disease occurrence 

 except between the treated and check trees, but 

 there was a trend toward somewhat higher disease 

 in the 'radical' plot at Alyson's. When Mcintosh 

 fruit were harvested in this plot, a random survey 

 of fruit showed over 40% with flyspeck, which is 

 not commercially acceptable. It was clear that this 

 'radical' option did not provide acceptable control 

 of flyspeck. Because of the advanced season and 

 the dry conditions in August, the fruit in the other 

 two plots were harvested before a proper survey 



could be done, but it was evident that control was 

 satisfactory in these two plots. 



At Clarkdale, there was very little difference 

 between treated plots (the intended check trees were 

 sprayed so the data were not included), and a har- 

 vest survey of 100 Mcintosh per plot showed no 

 significant difference nor any trend between treat- 

 ments. 



Once the Mcintosh had been harvested, it be- 

 came evident that there were differences in flyspeck 

 occurrence between varieties in both orchards. This 

 effect had been masked by the random zigzag pat- 

 tern through the plot adopted when sampling fruit 

 in the regular weekly sessions. At Alyson's, the 

 Empires had much less flyspeck than the Mcin- 

 tosh, whereas at Clarkdale, the Golden Delicious 

 had much more flyspeck than the Mcintosh. These 

 differences were presumably not owing to varietal 

 susceptibility, since the literature indicates that 

 apple varieties are essentially identical in their sus- 

 ceptibility to flyspeck. We believe that the differ- 

 ences were owing to the more open growth habit 

 of Empires vs. Mcintosh at Alyson's, generating a 

 less favorable (lower humidity) environment for 

 the organism, whereas at Clarkdale the strikingly 

 high level of flyspeck throughout all three treat- 

 ments indicates that this entire row did not receive 

 a summer fungicide application - perhaps the last 

 scab fungicide on June 9. 



Mite sampling in the test plots did not show 

 any difference in either pest or predator mite num- 



Fruit Notes, Volume 63 (Number 4), Fall, 1998 



15 



