APPLE POWDERY MILDEW AND ITS CONTROL. 23 



It will be understood that at the same time that this general 

 pruning is being done very careful attention should be given to 

 removing all mildewed tips. In fact, the pruning for mildew can be 

 most conveniently done during the dormant period, because the gray- 

 ish mildewed tips can be most easily seen when the foliage is off the 

 trees. To do it thoroughly requires patience and very careful search- 

 ing for the diseased tips, many of which are not more than an inch 

 long and may occur on short lateral spurs. Even after the most 

 careful work it will be found the following spring that some mil- 

 dewed tips have been left and are sending out diseased shoots. These, 

 however, can be removed with very little extra labor at the time the 

 fruit is thinned. Even when no attempt is made to keep the mil- 

 dewed tips cut out, it has been found that far less of them develop 

 in orchards that are well sprayed and cared for than in those that are 

 poorly sprayed and improperly cared for, and from these facts it 

 should be seen that by giving careful attention to both pruning and 

 spraying the number of mildewed tips can be reduced to a minimum. 



It has been stated that in thinning out the trees large limbs should 

 not be removed. Of course, there will necessarily be some exception 

 to this rule, but in general, especially in the cases of the Yellow Bell- 

 flower and Yellow Newtown varieties, when limbs more than an inch 

 and a half in diameter are cut off there is great danger that a serious 

 wood-and-bark disease locally known as "sappy bark" will develop. 

 This trouble appears at the wound and travels down the limb, even- 

 tually reaching the trunk and killing the tree. It causes a character- 

 istic puffing and sloughing off of the bark, and the wood underneath 

 becomes mushy. Disinfecting and painting the wounds have been 

 found ineffective in preventing the disease, and when once started, 

 cutting below the diseased portion does not eradicate it. The cause is 

 unknown. Limbs an inch and a half or less in diameter can be re- 

 moved without much danger of the disease appearing, and in winter 

 pruning the heavy cutting should be confined as far as possible to that 

 size or smaller. 



In practicing the pruning methods outlined here, it might appear 

 that a considerable proportion of the crop will be sacrificed by cut- 

 ting out bearing wood. It is necessary to thin the fruit thoroughly 

 almost every year, however, and the pruning will serve, in a measure, 

 as a thinning operation. Moreover, the fruit will be found to size up 

 better, especially after the system has been in use for two or three 

 years. 



It is true that a considerable annual expense will be incurred in 

 keeping up the pruning of a large orchard of 20-year-old trees 

 according to the plan outlined here. However, that expense will 

 be greatest by far during the first year, when an extra-large quan- 

 tity of mildewed tips and superfluous branches must be cut out. 



