378 Fruit-growing in Arid Regions 



is removed so as to kill any germs which might adhere and so 

 prevent any possibility of spreading the disease in this way. A 

 solution of alcohol, or of corrosive sublimate, one part to one 

 thousand, or kerosene, may be used for this purpose. Waite 

 reports that he has reduced blight to a minimum in large orchards 

 by carefully following this plan. 



We have already noticed that the most vigorous trees are the 

 most subject to blight, and we have also seen that as soon as the 

 tissues become hardened, the advance of the disease is checked. 

 Here, then, is a hint to induce a slow, hard growth by lessening 

 the food supply. Water is both a food and the conveyor of food, 

 so by regulating the water supply we can in a measure control 

 the food supply. 



One of Waite's experiments proves this so completely that we 

 will be pardoned for quoting him again. Two potted pear trees, 

 both in active growth, were inoculated with pear-blight. After 

 the disease had made good progress in both trees, water was with- 

 held from one of them during a period of two weeks. It received 

 just enough to keep the leaves from wilting, while the other was 

 given the normal amount. " As a result, the blight stopped in 

 the dried-out tree as soon as the water was withheld and pro- 

 gressed no farther, while in the watered tree it kept on until it 

 killed the whole top." 



No experiments have been reported which prove the practica- 

 bility of withholding water, under orchard conditions, as a means 

 of controlling blight. But the writer had an opportunity of 

 studying an orchard in the summer of 1904 which had been 

 without water for two and one-half years. The effect of this 

 enforced drought on checking blight was very marked, and it also 

 showed that pear trees can exist in this location for a consider- 

 able period without irrigation or cultivation. These results 

 would probably Be the same in. all of the pear-growing sections 

 where irrigation is practiced. 



The orchard referred to was located on the side of a gradual 

 slope. All other farms and orchards in the vicinity lay below, 

 so there was no possibility of seepage water reaching these trees. 

 The ditch which supplied the orchard with water broke in the 



