136 NEBRASKA STATE HORTICULTURAL SOCIETY. 



should be remembered that "apple scab'' is kuown by the 

 botanist to make its best development on the trees during 

 cold, wet, inclement weather. These are the conditions when 

 it thrives best. 



On the other hand, during such weather tJie tree is not mak- 

 ing rapid or vigorous growth. It is at a standstill on account 

 of cold weather preventing its normal functions of growth. 

 It has about all it can do, if kept in perfect healtli, to hold its 

 own during severe inclement weather. The ^'apple scab" 

 then is favored in its development ; it is enabled to get a strong 

 foothold on the leaves and flower clusters to devitalize the 

 tree, by injuring the tree and almost entirely destroying the 

 flowers and young fruit by attacking them and preventing 

 their development. 



Observations in our experiment station orchard, during 

 several past cold springs, indicate that s])riug frosts somewhat 

 rarely kill the flowers if they are kept in good health. Apple 

 blossoms in our experiment station orchard, when fully 

 opened, have passed safely through a temperature of 27 

 degrees F., or 5 degrees below the actual freezing point of 

 water, during a frosty night and still set enough fruit for a 

 full crop, where kept free from "scab" by spraying. In the 

 spring of 1908, some of our trees actually passed through a 

 temperature which for a period of about one hour toward 

 morning Avent as low as 26 degrees F., in the orchard, or 6 

 degrees below the freezing point of water, and still had a 

 fair crop of fruit set. Blossoms which are not fully open 

 may probably pass through even a lower temperature than 

 this, if not too prolonged, and still set fruit, if the trees are 

 in healthy condition. In our section, I would regard, ordin- 

 arily, a temperature of 26 degrees 'as being the critical point 

 below which it is not safe for apple flowers in full blossom 

 to pass, but under ordinary conditions I would regard any 

 temperature above 26 degrees as not being necessarily fatal 

 to apple flowers in full blossom. In fact, they will usually 

 endure a temperature not lower than 26 degrees without 

 anything like the full crop of flowers being killed. 



