HOW TO INCREASE THE POTATO CROP BY SPRAYING. 



13 



"hopperette," or hopperdozer. One of these is shown in figure 15. 



An account of others to be used on a larger scale is furnished in 



Farmers' BuUelin 747, Grasshopper Control. 



During the present growmg season (1917) to date it has been 



astonishing to learn how many growers have used Paris green and 



arsenate of lead as remedies for plant-hce. They are not only 



absolutely worthless against plant-lice, but sometimes they destroy 



some other insects which prey upon and which might otherwise 



greatly reduce the numbers of the plant-lice. Arsenate of lead and 



Paris green are stomach poisons and effective only against pests which 



devour leaf tissue. 



LATE-BLIGHT AND ROT. 



Late-blight is the most destructive potato disease. Origmatmg 4n 

 South America, it has spread to every potato country m the world 

 and has destroyed crops to the extent of causing famine, as in Ireland 

 in 1845. 



In the United States late-blight is most common in the North- 

 eastern States, as in- 

 dicated on the map, 

 figure 16. In the 

 shaded areas in bad 

 years 50 per cent of 

 the crop in ims pray- 

 ed fields may be de- 

 stroyed. It occurs 

 every year in north- 

 em New England, 

 and usually visits 

 New York and parts 

 of the adjacent 

 States ; in wet seasons 

 it extends as far west 

 as Iowa and Minne- 

 sota. It occurs to 

 some extent in the 

 south Atlantic truck- 

 ing sections from April to June and in the southern mountaui region 

 in autumn. The moist, cool climate of portions of the Pacific coast 

 favors its development; but it is seldom or never fomid in the Great 

 Plams, the Rocky Mountains, and other dry or hot parts of the country. 



APPEARANCE OF LATE-BUGHT AND ROT. 



Late-blight develops after the blossom period and does its greatest 

 damage toward the end of the growing season. It appears as purplish 

 black or brownish black spots on the leaves, which, if examined when 



Fig. 15.— a successful I j-pe of horse-drawn hopperdozer. (Milliken.) 



