TWO EPIDEMICS OF POTATO BLIGHT AXD ROT. I// 



rife, and when the tops cover the ground, covers as a rule less 

 than one-third of the foliage. All the remaining leaves being 

 unprotected are killed with blight and millions of spores are 

 washed down into the soil to infect the tubers. No matter how 

 many times or how often such a sprayer is used on a field the 

 resulting rot may be as great in seasons like those of 1907 and 

 1909, as if it had not been used at all. 



EFFICIENT SPRAYERS AND SPRAYING. 



One nozzle alone to a row should never be used on a potato 

 sprayer when the tops grow as large as they do in Maine, 

 except when the plants are small. W'hen the plants are large, 

 two or more nozzles should be used to the row, so arranged 

 that the cones of spray will interfere with each other as little 

 as possible, thus covering the widest possible area, or a strip 

 at least 3 feet wide when the foliage covers the groun:!. There 

 should be an up and down adjustment, sufficient so that the 

 whole battery of nozzles may be raised as the plants grow taller. 

 A side to side adjustment, to be varied with the distance 

 between the rows is desirable also. Those sprayers which have 

 additional nozzles which direct the spray sidewise into the tops 

 from between the rows possess a distinct advantage in that they 

 not only tend to more thoroughly cover the leaves but they also 

 tend to reach the very ones which are first attacked by blight — 

 the lower and more shaded leaves and those resting on the 

 ground. 



The finer the spray and the greater the pressure with which 

 it is thrown the more effective will be the work. A very fine 

 mist forcibly applied covers the leaf with a thin film which 

 adheres, while even greater applications of spray applied in 

 coarse drops may be less effective, first because it is not so 

 evenly distributed and, secondly, because there is much more 

 danger of the larger drops running together and dripping oft" 

 the leaves. High pressure also tends to drive the mixture in 

 among the leaves thus touching the lower leaves, and more 

 effectually coating both sides of the leaves which is very 

 important. 



The Vermorel type of nozzle appears to be the most satis- 

 factory and is the one most used by our growers. New brass 

 caps should be applied to these each year, however, as the small 



A 



