20 BULLETIN 120, U. S. DEPARTMENT OF AGRICULTURE. 



trees. This deficiency can be largely overcome by using angle 

 nozzles of a type that throw a long, solid cone of driving spray. 

 Such a type of nozzle is illustrated in figure 5. The writers wish to 

 lay particular stress on using angle nozzles, which are so constructed 

 as to throw the spray at an angle of 45° from, the spray rod. Much 

 more thorough work can be accomplished with such a nozzle, for by 

 turning the rod it is possible to spray from below or above and from 

 either side. Care should be taken to cover thoroughly the lower sides 

 of the leaves, since that is where most of the mildew infections take 

 place. 



The spray deposit on the foliage protects the leaves from infection 

 and kills out any patches of mildew that may be present. How- 

 ever, summer spraying is of com- 

 paratively little value in cleaning 

 virulent twig infections, such as 

 are shown in Plate IV, figures 1 

 and 2, and Plate VI, figure 2. 

 This phase of the disease must 

 be dealt with by another method, 

 which will be discussed under 

 " Pruning." 



WINTER SPRAYING FOR STIMU- 

 LATION. 



Two years of experimental 

 FIG A 5 , ,_A Th e T l -T SSL 2 T Tl" w °rk have demonstrated that 



nozzle. The liquid enters the eddy cham- 

 ber through an opening at the side and winter spraying Avitll fungicides 



& < 3Pia£aft2 W#« » °f.™ appreciable value in con- 



this construction a long, slender, solid trolling apple powdery mildew. 



cone of driving spray is produced. Attention has been called to the 



fact that the mildew attacks vigorous foliage much less severely 

 than it does that which is puny and slow growing. In this connec- 

 tion the value of the foliage stimulation obtained from summer 

 spraying has been pointed out, and it is evident that if a stimulation 

 of vigorous spring growth can be brought about by a winter spraj 7 ^, 

 just that much will be added to the success of the mildew treatment, 

 as well as to the improvement of the general condition of the trees. 

 As a matter of fact, it has been found that spraying during the dor- 

 mant period with crude-oil emulsions, as commonly practiced in the 

 Pajaro Valley for scale-insect control, will stimulate a vigorous early 

 growth of foliage the following spring. Occasionally a few buds are 

 injured by the oil, but material damage is very rarely noticeable. 



