212 MANUAL OF GARDENING 



Potato diseases. — There are different kinds of potato blight and rot. 

 The most important are early blight and late bhght — both fungous 

 diseases. Early blight affects only the foliage. Late blight kills the 

 fohage 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 w^hen the plants are 6 to 8 in. high and repeat every 

 10 to 14 days during the season, making 5 to 7 appHcations 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. 



