544 L\ SECTS AFFECTING VEGETATION 



In older plants, sometimes stumps nearly full size may be seen 

 that have shed all their leaves. This deciduous nature of the leaves 

 is very characteristic of the Fusarium wilt. No broken lesions are to 

 be noticed on the stems and roots unless decay (bacterial and fungous 

 complication) follows, which does occasionally take place. 



Parasitic diseases of field crops which are also persistent soil 

 organisms seldom admit of definite treatment economically. In the 

 case of club-root of cabbage the causal organism gradually succumbs 

 to heavy applications of lime. Potato scab, on the other hand, is in- 

 creased by lime. In the case of cabbage wilt (Fusarium) no specific 

 treatment is known. (Ohio E. S. B. 228.) 



CELERY DISEASES. 



Leaf-Spot or Leaf Blight. This is a prevalent condition upon 

 celery plants. This is at times attributed to the fungus above named, 

 or others, and is also produced by other causes, as by excess of water 

 during overflow and the like. During certain seasons the loss from 

 the leaf-spot or leaf-blight troubles is very much greater than during 

 others. This is clearly explained when the conditions giving rise to 

 the leaf troubles are apparent. But this is by no means a common 

 fact, and in some years there is much blighting after the celery has 

 been boarded up for blanching. Usually the fungus is discoverable 

 in diseased areas of the leaves. The use of fungicides, such as Bor- 

 deaux mixture, is likely to prove beneficial, especially to protect the 

 plants in the seed bed until transplanted. (Ohio E. S. B. 214.) 



Celery Root Rot. The disease seems to affect the main roots 

 rather than the fibers. They rapidly rot off near the crown, so that 

 the plants may be readily taken from the ground. Sometimes a few 

 of the larger roots may be severed an inch or two from the crown, 

 which, for the most part, alone remains and tapers to a more or less 

 rounded point. 



It seems clear, that whatever part Rhizoctonia plays in celery 

 Root Rot, in the later stages of decay with which it is known to be 

 associated, the primal cause is to be found in poorly drained soils. 

 More thorough underdrainage, with sufficiently deep main ditches, 

 is suggested as the best preventive. (Ohio Cir. 72.) 



CUCUMBER AND MELON DISEASES. 



Several diseases attack the leaves of cucumbers and melons in 

 this country. Downy mildew, leaf-blight, and anthracnose are the 

 most common, though there are several others of less importance. 

 The parasitic fungi which cause these troubles are quite distinct in 

 their nature, but produce rather similar effects on the foliage. From 

 the standpoint of the farmer they may be considered together, since 

 the treatment for all is practically the same. It is well to know 

 their exact characters, however, especially since there are a number 

 of other maladies, due to bacteria, soil and climatic conditions, and 

 to insects, which do not yield so readily to spraying, and may be 

 confused with the diseases to be described. 



Downy Mildew. Dow r ny mildew, the most destructive of all 

 cucurbit diseases, is especially injurious to cucumbers, but also at- 

 tacks melons, squashes, pumpkins, gourds, and other related vines. 



