212 MANUAL OF GARDENING 
Potato diseases. — There are different kinds of potato blight and rot. 
The most important are early blight and late blight — both fungous 
diseases. Early blight affects only the foliage. Late blight kills the 
foliage and often rots the tubers. Two serious troubles often mis- 
taken for blight are: (1) Tip burn, the browning of the tips and mar- 
gins of the leaves due to dry weather; and (2) flea-beetle injury, in 
which the leaves show numerous small holes and then dry up. The 
loss from blight and flea-beetles is enormous — often, one-fourth to 
one-half the crop. For blight-rot and flea-beetles spray with bordeaux, 
5-5-50. Begin when the plants are 6 to 8 in. high and repeat every 
10 to 14 days during the season, making 5 to 7 applications in all. 
Use 40 to 100 gal. per acre at each application. Under conditions 
exceptionally favorable to blight it will pay to spray as often as once 
a week. 
Scab is caused by a fungus that attacks the surface of the tubers. 
It is carried over on diseased tubers and in the soil. In general, when 
land becomes badly infested with scab, it is best to plant it with other 
crops for several years. (See page 190.) 
Raspberry diseases. — Anthracnose is very destructive to black 
raspberries, but not often injurious to the red varieties. .It is detected 
by the circular or elliptical gray scab-like spots on the canes. Avoid 
taking young plants from diseased plantations. Remove all old canes 
and badly diseased new ones as soon as the fruit is gathered. Although 
spraying with bordeaux, 5-5-50, will control the malady, the treat- 
ment may not be profitable. If spraying seems advisable, make the 
first application when the new canes are 6 to 8 in. high and follow 
with two more at intervals of 10 to 14 days. 
Cane-blight or wilt is a destructive disease affecting both red and 
black varieties. Fruiting canes suddenly wilt and die. It is caused 
by a fungus which attacks the cane at some point and kills the bark 
and wood, thereby causing the parts above to die. No successful 
treatment is known. In making new settings, use only plants from 
healthy plantations. Remove the fruiting canes as soon as the fruit 
is gathered. 
Red-rust is often serious on black varieties, but does not. affect red 
ones. It is the same as red rust of blackberry. Dig up and destroy 
affected plants. 
