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A STUDY OF APPLE SCAB IN NEW YORK STATE 



During the past 27 yaars the incubation periods of appla scab in 

 western New York orchards, in the first important infection period of each 

 year, has been made by W. D. Mills. The following table shows the approxi- 

 mate length of the incubation period over the range of mean temperatures 

 encountered. These figures may be used as a rough guide in determining, 

 after scab spots appear, which rainy period was responsible. 



Mean Temperatures During Approximate Length of 

 Incubation Period Incubation Period 



17 days 

 16 " 

 15 " 

 14 

 13 

 12 

 11 

 10 

 9 



As a result of the rainy period of j^ril 25-27 in Massachusetts, 

 unprotected trees of scab susceptible varieties may be expected to shov/ scab 

 spots around May 11-14, depending upon temperatures, 



POULTRY IIANURE AND APPLE SCAB CONTROL 



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Many Mcintosh growers are of the opinion that poultry manure has some 

 influence on the scab problem. They cite as evidence the scabbiness of the 

 average henyard tree. The situation seems to sum up about like this; A 

 liberal application of poultry manure results in more terminal grovirth, more 

 and larger leaves and possibly leaves into v/hich the scab fungus can more 

 easily gain entrance. The added leaf area requires more spray material if 

 the tree is to be completely covered. Then, too, a dense, leafy tree dries 

 off less readily after a rain. It may stay wet an hour longer than a thin 

 tree. The net result is a more favorable set-up for scab development on a 

 tree liberally fertilized with poultry manure. 



Talking about scab control before a group of Nev/ York growers, 

 A. B. Burrell made this important point, - "Keeping the trees well pro- 

 tected is good, cheap insurance, which pays dividends. Let us not again 

 be caught as most growers were in 1945." 



Most growers can apply 25 to 50% laore tankfuls per day witji present 

 equipment by studying the layout and noting where time is lost. If more 

 than 5 minutes are required to return to the filling station or to get 

 the vmter and materials into the tank, the system needs reorganizing. 



