256 HORTICULTURE FOR SCHOOLS 



access to the plant if injury is to be prevented. The sprays 

 most commonly used are bordeaux and lime-sulfur, applied 

 in the early spring. 



367. Anthracnose occurs on a large number of plants. 

 On the bean it produces dark markings and blotches on the 

 pods, stems, and leaves. These blotches gradually spread 

 until they produce large irregularly shaped markings. The 

 raspberry and other berries are frequently affected, the dis- 

 ease appearing as purplish spots which gradually become 

 larger and sunken in the center. A form similar to that on 

 the raspberry has done an immense amount of damage to the 

 grape. Legumes other than the bean are also affected by the 

 disease and a large number of other plants are not immune. 



Spraying does not suffice in the control of the disease. The, 

 affected parts should be removed and burned, and care should 

 be taken that only healthy plants are set out. Since the 

 spores are apparently carried by seed, especially of beans, that 

 source of infection must not be overlooked. When the dis- 

 ease appears, a rotation of crops is desirable that will use for 

 four or five years such vegetables and other plants as are 

 immune to the attacks of the organism. 



368. Root-rot. A number of diseases are grouped under 

 the general name of root-rot. These are produced by several 

 different fungi, called as a class Rhizoctonia. As these diseases 

 progress, the smaller roots, or indeed the whole root system, 

 may be killed, although the observer has no knowledge of 

 what is happening until the top withers or even dies. These 

 diseases are especially prevalent on heavy soils, or when the 

 drainage and aeration are not good. A thorough cultivation 

 of the soil, together with proper drainage, is the easiest and 

 cheapest way to protect the roots. Various plants have been 

 reported as subject to these diseases, among which are alfalfa, 

 the orange, cotton, and the grape. Among the vegetables, 

 the bean, pea, potato, tomato, beet, radish, and certain 

 others are susceptible. 



