178 MAINE AGRICULTURAL LXPPe;rIME;nT STATION. I 



holes in these soon become worn and throw too coarse spray as 

 a result. In use these nozzles should be carefully watched to 

 see if each and every one is constantly working and throws a 

 spray of maximum fineness. If not the machine should be 

 stopped and the difficulty corrected. In purchasing a sprayer 

 care should be taken to determine if the pump is powerful 

 enough to throw a fine mist when the maximum number of 

 nozzles necessary are in use. Sprayers equipped with hand 

 pumps and designed to cover three or four rows at a time as 

 fast as a horse can walk are not recommended. In practice the 

 pressure usually maintained on these pumps is much too low 

 to do effective work. 



Unfortunately there has crept into our literature on potato 

 spraying the statement, and the notion is quite firmly grounded 

 in the minds of many of the potato growers and apparently in 

 the minds of makers of potato spraying machinery as well that 

 50 gallons of spray per acre is a sufficient and proper amount 

 to apply. A little thought will show how erroneous it is to con- 

 duct spraying operations on such a basis when the object is to 

 cover the entire foliage. When the tops are small 50 gallons 

 will usually do this, but it is absolutely impossible to do thor- 

 ough work with this amount of spray when the plants are full 

 grown. Every leaf should be covered at each spraying, regard- 

 less of whether it takes ^0, 100 or 1^0 gallons of bordeaux per 

 acre. In bad seasons like those under consideration it is advis- 

 able during the times when conditions are very threatening to 

 go over the field twice at each spraying, in opposite directions 

 on the row. However on account of danger of loss from drip, 

 the second application should not be put on till the first is dry. 

 This procedure is by all means recommended in place of using 

 a stronger mixture, if more thorough work is desired. 



WHEN TO SPRAY. 



Very commonly men were found who did not spray during 

 rainy weather as they considered it to be useless. This also is 

 a mistaken notion. As has already been pointed out it is during 

 rainy weather that spore production is the most rapid and infec- 

 tion is most sure to take place. Therefore, it is conceivable 

 that one spraying during rainy weather may be more beneficial, 

 even though it be washed ofif within a few hours as is supposed 



