32 MANUAL OF FRUIT DISEASES 



(6) Factors having to do with transpiration are concerned in 

 the cause of stippen. 



(7) Intermittent weather conditions favor the development 

 of the disease. A light crop of poorly distributed fruit is most 

 liable to bitter-pit. 



(8) Fluctuating temperature and humidity in storage favors 

 the disease. Uniform, low temperature and dry air are inim- 

 ical to it. 



It is then apparent that growers should everywhere be on 

 guard against this disease. No one can safely assume that his 

 fruit will always escape by virtue of the variety which he grows 

 or of the locality in which it is produced. It is very important 

 that everything possible be done which will tend toward the 

 production of good crops evenly distributed over the tree 

 year after year ; for herein lies a possible solution of the control 

 of stippen. Most growers know that vegetative growth is un- 

 favorable to fruitfulness. On the other hand, injudicious, heavy 

 pruning to eliminate the vegetative growth also favors bitter- 

 pit. It is believed that above all other orchard operations 

 pruning has the most direct effect on the development of 

 stippen. For it may regulate the amount, and to a certain 

 extent the size, and it may determine the distribution of the 

 fruit on the tree. The system adopted should be carefully 

 planned, it should aim at the production of a regular crop of 

 evenly distributed fruit, and should therefore be light. The 

 lateral system of pruning, that is, the retention of laterals, as 

 far as practicable, is to be adopted as a part of the general 

 pruning-scheme, particularly in the case of varieties most sus- 

 ceptible to the disease. For there is some evidence that bitter- 

 pit is much reduced on trees when the fruit is borne on lateral 

 rather than on main branches. Frost at setting is also unfa- 

 vorable to fruitfulness, therefore the question of frost-protection 

 should receive attention in localities where experience has 

 proved its necessity. Regulated sap-flow favors fruitfulness, 



