i>2 BULLETIN 120, U. S. DEPARTMENT OF AGEICULTTJEE. 



PRUNING. 



The subject of pruning demands consideration because of its 

 bearing on the problem of mildew control. 



Attention has been called to the abundance of mildewed tips that 

 can be seen during the dormant period. From the infested buds on 

 these tips large numbers of seriously diseased shoots develop the fol- 

 lowing spring, and the question of eliminating them is a very im- 

 portant one, because on them are produced the enormous numbers 

 of spores which serve to infect the healthy foliage as soon as it 

 appears. Pruning offers the only practical solution of this prob- 

 lem, because, as has been stated, summer spraying is not effective in 

 cases in which the entire twig and its leaves have become badly mil- 

 dewed. The reason is that it is impossible to wet the entire mildew 

 covering thoroughly, the spray collecting in drops, even when the 

 operator is successful in wetting all parts of the shoot and its leaves. 

 Particular attention should therefore be given to cutting out the mil- 

 dewed tips, and that work should be made a part of the regular 

 dormant-pruning operations. 



It has been stated that trees that are growing vigorously and pro- 

 ducing large, thrifty leaves are less seriously affected by mildew than 

 poorly growing ones, even though they are of the same variety. One 

 of the commonly recognized effects of winter pruning fruit trees 

 is the improvement in growth and foliage conditions that result the 

 following year. The apple is not an exception in this respect, and 

 the improvement in vigor that can thus be obtained by pruning 

 should be taken advantage of in combating the mildew. 



To obtain the full benefits of winter pruning in the Pajaro Valley 

 greater attention should be given to thinning out the trees. This 

 should not be done by cutting out large framework limbs, but by 

 priming out far more brush than is ordinarily removed. Interlacing 

 branches should be removed, and the current year's growth should be 

 cut back one-third to one-half, or even more in the case of very young 

 trees or very vigorously growing shoots. There is a tendency to 

 allow the lower branches to become so long that they droop almost 

 to the ground. It is true, as usually claimed, that the best fruit is 

 borne on these lower branches, but that condition has been brought 

 about largely by the fact that the tops of the trees have become badly 

 affected by mildew or have lost their vigor through other causes. 

 For these reasons it is important that the tops of the trees should be 

 cut back as well as thinned out, so as to increase their vigor. The 

 long spindling branches in the lower parts of the trees should be 

 gradually shortened and the vigorous young twigs should be cut back 

 so as to induce fruiting. 



