potato diseases in 1907. 289 



Dust Sprays vs. Wet Bordeaux eor Potato Blight. 



The use of dry or dust sprays is by no means a new idea, 

 but their extended use for potato blights is a matter of quite 

 recent development in Maine. A few dust machines, used in 

 1906, almost without exception as far as the writer can ascer- 

 tain, upon fields where no unsprayed or wet bordeaux checks 

 were saved, and in a season very free from late blight, led many 

 to believe that dusting is an ample protection against potato 

 blights. As a result certain limited sections used dry sprays 

 almost entirely during 1907. 



If equal protection can be secured, dusting has many advan- 

 tages over wet bordeaux, even though the first cost of the 

 necessary materials for the former are much more than for the 

 latter. The advantages lie chiefly in the ease, rapidity and 

 cheapness of application. Very frequently it may be necessary 

 to cart the water for wet bordeaux half a mile or more. This 

 hauling of 1000 or 2000 gallons of water every time a 20-acre 

 field is sprayed is no small item of expense. Furthermore the 

 hauling of a 100-gallon spray tank requires two horses and the 

 services of a second man are necessary for a large part of his 

 time to prepare the spray while the other man is applying it. 

 The dust machines are light, even when loaded to their full 

 capacity. One man with a light, fast-walking horse, can cover 

 as much ground with a dust machine in 1 day as can be done 

 in 2 or 3 days with a pair of workhorses attached to a heavy 

 sprayer. On account of the present scarcity and high price of 

 labor these points in favor of dusting have appealed quite 

 strongly to potato growers. 



For several years the Station has been carrying on experi- 

 ments to test the relative merits of dust and wet sprays. Only 

 part of this data has been published.* 



In all trials previous to 1907 the weather conditions were 

 such that little or no late blight occurred and as a consequence 

 no well marked results were secured. The trials of the past 

 season were conducted upon the farm of and in cooperation 

 with the Commissioner of Agriculture, Hon. A. W. Gilman, 

 of Foxcroft. All of the ingredients of each kind of spray were 



* Woods, C. D. and Bartlett, J. M., Me. Agr. Exp. Sta. Bui. 112, p. 6 

 (1905) and Bui. 126, p. 34 (1906). 



