39 



chosen. According to the best information obtainable, the disease is 

 a fungus one, but it acts in a way not clearly understood, and should 

 be met with extreme measures at its first appearance. 



Characteristics. — Usually the first sign of the disease is a loss of 

 color, the leaves changing from green to red, then yellow, and finally 

 brown and withering. The withering begins at the tip as a rule, and 

 as it passes down the leaf loses its stiffness and drops, producing the 

 wilted appearance which gives the disease its name. If the attack 

 is not too severe the plant may produce a fruit, but it is usually of 

 poor quality and ripens prematurely. 



On cutting off the plant at the base the roots can be traced as dark 

 brown or black points in the stem tissue. A more careful examina- 

 tion shows the whole root system to be diseased. Under the micro- 

 scope the root hairs are seen to be abnormally developed, and in the 

 diseased parts the fungus threads can often be found, showing that 

 the disease enters from the soil. 



Cause. — It is often impossible to tell just how the trouble starts, 

 as it may break out simultaneously in widely separated places. It 

 can probably exist in the soil under some conditions for long periods, 

 and it may be carried from plant to plant by ants and other insects. 

 Its presence is usually due to faulty soil conditions, though Australian 

 investigators claim that it also occurs where a field is cropped too 

 long, and by adhering to one source for supply of plants, as well as 

 poor cultivation and fertilization. They claim that plants grown 

 under different conditions should replace the old ones every few 

 years. In Porto Rico fields have not been running long enough to 

 test these points under our conditions, and the spread of the disease 

 here is probably due to improper soils or faulty cultural methods. 



Remedies. — The first precaution to be taken is one of prevention. 

 Never plant a slip that could possibly be already diseased. Second, 

 if the disease should appear, pull out all plants affected, burn them 

 on the spot, or cover with quicklime; also cover the soil with lime 

 and leave exposed to the sun for a few weeks, stirring it from time 

 to time. After a month or six weeks strong, healthy plants may be 

 reset in the vacant places. Third, keep the plants growing vigorously 

 and the soil in the best possible physical condition. 



SPIKE OR LONG LEAF. 



Characteristics. — Any tendency to spike is quickly evidenced by the 

 leaves becoming long and slender. As the disease progresses, the 

 plant becomes more and more like a bundle of rod-like leaves. In 

 the final stages the central leaves of the plant do not unfold, and 

 thus in their long spikelike form give the name to the disease. A 

 plant at all badly affected rarely produces any fruit; if any is formed 



