Jan. 1922] annual eeport. 19 



The following table gives a summary of the results of this season's work: 



Work in Potato Diseases. 



During 1920-21 the farmers of the state, their interest awakened as a 

 result of the severe losses due to late blight in 1920, showed increasing in- 

 terest in potato diseases, especially the degeneration maladies — mosaic and 

 leaf-roll. Messrs. Butler and Doran were therefore called upon to devote 

 much time to field work and lectures upon these subjects. The growing 

 of better seed potatoes was recommended and help was extended in secur- 

 ing choice seed stock. 



The question of seed certification was also given attention, and the ad- 

 vantages of producing certified seed rather than ordinary stock were brought 

 prominently to the attention of growers of seed potatoes. 



Potato Spraying Experiments. In one experiment to determine the effect 

 of pressure on the protection afforded by Bordeaux mixture, Mr. Butler 

 found that, when the pressure used was reduced from 180 pounds per square 

 inch, to 90 pounds per square inch, the protection afforded was reduced 

 one-half. The mixture applied under 180 povmds pressure was more thor- 

 oughly distributed over the plants than that applied under 90 pounds pres- 

 sure; and this probably accoimts almost wholly for the better protection 

 afforded, since the amount of copper applied per acre on doubling a given 

 pressure is not increased by one-third. 



In another experiment potatoes were sprayed on the one hand with a 

 machine carrying two nozzles to the row and on the other with a machine 

 carrying three nozzles to the row; the mixture used was applied xmder 90 

 pounds pressure in both cases. The results obtained were as follows: 

 Effect of Number op Nozzles Used per-Row in Spraying on Late Blight 



Control. 



