INSECTS, FUNGI, PLANT DISEASES, ETC. 171 



several inches below the point of attack, so that all 

 mycelii will be taken out, otherwise the trouble will 

 make its appearance again. 



Phytophthora infestans (DeBary). Potato rot; late blight, 

 or downy mildew. The leaves turn a brown color in large, 

 irregular spots, the unattacked portions of the leaves 

 remaining green. The tubers are also destroyed by this 

 disease, and become a dark color, shrivelling up and, 

 where the attack is rapid, giving out considerable moist- 

 ure in the rotten portions. 



The remedy is to spray the vines several times with the 

 Bordeaux mixture, beginning when the plants are only 

 a few inches above the surface of the ground, and repeat- 

 ing at intervals of two weeks. 



Blight of the Orange.* Wilt or leaf curl. This is a 

 common disease in Florida, and it is considered to be 

 incurable. It attacks most of the citrus fruits; but it 

 does not generally make its appearance until the tree is 

 old enough to bear fruit. It is a peculiar disease found 

 only in Florida, and it is widely distributed over the 

 State. The blight conies rather suddenly, and its pres- 

 ence is at first manifested by the wilting of the leaves, 

 followed by their falling, until the branches are denuded 

 of foliage. 



Inasmuch as there is no remedy for this disease, the 

 tree affected must be cut out at once and destroyed, be- 

 cause the healthy trees" in the grove will soon become 

 infected, and the entire orchard will die. It is useless to 

 treat blighted trees, and money and time will bo wasted 

 by adopting any remedy recommended; the only sure 

 method is the heroic one of cutting out and burning all 

 trees affected. 



♦Bulletin 8, Vegetable Physiology and Pathology, U. S. Dept. Agri 



