deviation the more variable the sample was). 

 The mean for the 1995-1996 hygrothermograph 

 data alone was much closer to Brown and 

 Sutton, however, with a mean of 289 hours 

 (standard deviation = 44 hours). Thus, using 

 data most favorable to the Brown and Sutton 

 model, approximately 19 more hours of wetting 

 occurred in Massachusetts, on average, than in 

 North Carolina before flyspeck and sooty blotch 

 symptoms occur. These measurements 



support the idea that the Brown and Sutton 

 model may indeed be useful for disease 

 prediction in Massachusetts. The Campbell 

 data, however, do not provide as much 

 support. In addition, note that the significant 

 events of petal fall, beginning of wetness 

 measurement, and symptom occurrence 

 happened later in Massachusetts than in North 

 Carolina. 



Judging from the differences between the 

 two data sets as well as the previously noted 

 regional differences between New England and 

 the Southeast, it is reasonable to conclude that 

 other factors besides leaf wetness are 

 responsible for the onset of flyspeck and sooty 

 blotch in New England. This certainly could 

 account for the rather large variability in the 



New England data. A regression analysis of 

 other weather measurements like temperature 

 and relative humidity with disease onset may 

 suggest some additional factors. This will be 

 the focus of future research. It is also 

 important to note that there is a disparity 

 between the Campbell weather station wetness 

 data and the hygrothermograph wetness data, 

 and it cannot be ruled out that the measuring 

 instruments themselves may be a source of 

 error. There is no easy solution to this problem, 

 and it may be that different empirical wetness- 

 hour estimations may have to be made for use 

 with different wetness sensors, or an easily 

 accessible, standard weather station will have 

 to be used. 



In conclusion, it is believed that an 

 empirical model predicting flyspeck disease 

 and sooty blotch of apple based upon the Brown 

 and Sutton model should be created for use by 

 New England apple growers. Such a model 

 would be useful to Massachusetts growers for 

 timing eradicant fungicide spraying for these 

 diseases in a more timely and efficient manner, 

 and may also provide researchers with further 

 insight into the ecology of the pathogens 

 involved. 



•^ vL» vL» vL« vL* 

 •^ *Y* *Y* "T* *T* 



Fruit Notes, Volume 62 (Number 4), Fall, 1997 



23 



