DISEASES OF CULTIVATED PLANTS 547 



caused by a species of bacteria, Bacillus tracheiphilus, which enters 

 and clogs the water-carrying vessels of the stem. This wilt disease is 

 spread by leaf-eating insects and probably also by soil infection. Ro- 

 tation of crops is advised, together with the addition of an insecticide 

 like Paris green to the Bordeaux mixture. The Bordeaux mixture 

 itself acts as a repellant to the insects and helps to check the spread 

 of wilt. There is experimental evidence showing the value of spray- 

 ing for wilt, but it should not be expected that this disease will be 

 as fully controlled in this way as the leaf-blights. It is also import- 

 ant to pull and burn diseased vines as soon as they begin to wilt, in 

 order to lessen the spread of the disease. 



It should be emphasized that success in spraying for mildews, 

 wilts, etc., is a question of methods. Success is almost wholly de- 

 pendent upon intelligent oversight, suitable apparatus and thorough 

 application of solutions having the right strength. Since adequate 

 apparatus must be available before spraying can be practiced, its se- 

 lection is all-important. A poor sprayer and poor methods are costly 

 and extravagant at any price. 



Disease Resistance. The possibility of securing strains or varie- 

 ties of cucumbers and melons resistant to the leaf-blight fungi has 

 been considered and some experiments have been made. In connec- 

 tion with experiments recently made at Charleston, S. C., all obtain- 

 able varieties of cucumbers and muskmelons were planted and left 

 unsprayed to determine their relative susceptibility. All were at- 

 tacked, and while differences in degree of infection were noted, all 

 were badly injured. One kind of cucumber, the Japanese climbing 

 variety, was more resistant than the others and remained living after 

 they were dead. (F. B. 231.) 



Wilt (Another Account}. The bacterial wilt of cucurbits is 

 prevalent in the North and West, and is mentioned to avoid confu- 

 sion with the leaf-blights already described. When a melon, cucum- 

 ber or squash vine suddenly wilts throughout its length and dies 

 without appreciable spotting of the leaves, the trouble is usually 

 caused by Bacillus tracheiphilus, and this enters and clogs the 

 water-carrying vessels of the stem. This wilt disease is spread by 

 leaf-eating insects and probably also by soil infection. Rotation of 

 crops is advised, together with the addition of an insecticide like 

 Paris green to the Bordeaux mixture. The Bordeaux itself acts as a 

 repellant to the insects and helps to check the spread of wilt. There 

 is experimental evidence showing the value of spraying for wilt, but 

 it should not be expected that this disease will be as fully controlled 

 as the leaf-blights. It is also important to pull and burn diseased 

 vines as soon as they begin to wilt to lessen the spread of the disease. 



Fusarium Wilt. Another wilt disease of cucumbers and musk- 

 melons similar in appearance to the above, is due not to bacteria, but 

 to a fungus related to the one causing the watermelon wilt, yeocos- 

 mospora vasinfecta, var. nivea. This has been little studied, but is 

 apparently not of great importance. -Spraying will not prevent this 

 form of wilt, and rotation of crops is essential. There is also a form 



