40 



it is small and practically valueless. Plants that are but slightly 

 affected produce very poor, small-sized fruits. 



Cause. — In most cases spike is apparently induced by improper 

 fertilizing. Acid phosphate in the fertilizer is one of the most 

 common causes. Wood ashes and any poorly proportioned mineral 

 fertilizer will cause it. 



This disease is apparently readily transmitted, and suckers or slips 

 from diseased parents should never be planted. Experiments have 

 shown that fully TO to 80 per cent of slips from spiky parent plants 

 failed to produce marketable fruits. 



Remedies. — First, never plant a slip that is in the least affected 

 with the disease. 



Second, for nitrogen and phosphorus fertilizers use tankage, dried 

 blood, bone meal, or other organic forms. If necessary to use acid 

 phosphate, give a good application of lime, 300 to 500 pounds per 

 acre, shortly afterwards. Thomas or basic slag may serve as a source 

 of phosphate, though results from it thus far are not definite. 



Third. Cultivate well and often, keeping the soil in the best pos- 

 sible physical condition and plants growing vigorously. 



Aside from the above diseases there are several that appear locally, 

 but thus far they have not proved dangerous. Their exact nature has 

 not been fully determined, but they are being thoroughly investigated 

 by the station pathologist. 



LEAF SPOT. 



The first of these local diseases of the pineapple, which we may 

 call "leaf spot," has occurred quite frequently in many plantations, but 

 onty once has it threatened serious damage. It is a leaf disease char- 

 acterized in the first stages by small brownish spots usually not 

 more than one-eighth to one-fourth inch in diameter. They are 

 regular in outline, but not of definite form. These spots rapidly 

 increase in size, and as they spread the center loses all color as well 

 as turgidity of the cells and becomes like straw-colored parchment. 

 This colorless part is surrounded by a more or less clearly defined zone 

 of the brownish color, indicating the spread of the disease. In its 

 spread the spots usually enlarge faster along the leaf veins, thus 

 assuming a long oval shape. In many cases the edge of the leaf is 

 affected, but any part may be attacked. In time the leaf succumbs 

 and dies. 



Cause. — The disease is not fully worked out, but its spread and 

 development is undoubtedly aided by atmospheric conditions. Dur- 

 ing rainy periods, especially where drainage conditions are not the 

 best, the development of the disease is quite rapid, but is checked by 

 dry weather and culture. - 



