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JOURNAL OF AGEICULTURE OF P. R. 



the terms psoi-osis or California scaly bark are to be preferred to 

 simply scaly bark for the Porto Rican disease. 



The trunk and large limbs are the principal areas attacked, al- 

 though in very severe cases the smaller branches and even the twigs 



will be affected. The disease is marked by 

 the scaling off in flakes of the outer bark, 

 a characteristic which accounts for the name 

 of the disease. These diseased areas com- 

 mence as small spots, often a fraction of an 

 inch in diameter only, on tlie trunks or larger 

 limbs. They increase slowly in size, ultimately 

 coalescing to involve areas often several feet 

 in length, and more or less completely gird- 

 ling the trunk or ])ran('h. Some gumming 

 accompanies tlie scaling off of the bark, l)ut 

 is more marked as gum jjockets in tlu' af- 

 fected bark tissues than as an exudation on 

 the surface. 



New bai'k, irregular and much roughened, 

 forms beneath the dead bark patches, so that 



I'*"" verv soon the ulcerated areas, due to a suoces- 



■■ — '■ '' " •^' sion of he-^liug and breaking out anew and so 



Fig. 3. — Psurosis, or characteristic of the disease, appear. Tlti- 



scaly bark. On branch a i • 4.1 i ii i 1 t 



of orange matelv, in the larger areas the bark dies 



througli to the wood, ami the res\iltin<j open 



wounds ar(> snou infected by var-ious wood-rotting fungi. 



Aifeeted trees after some time, often several years, begin to show 

 signs of until riftiness by a yellowing of leaves and the presence of 

 dead wood. Limbs here and there are completely girdled and die. 

 destroying the synnnetry of the tree. Death of the entire tree, how- 

 ever, is generally long delayed, and it may linger on as long as ten 

 years, bearing more or less fruit each season. 



Cause. 



No cause has ever been found. Certain fungi have been noted 

 at times in connection with disease lesions — for example, the Corti- 

 cium of pink disease — but there is no evidence that there was any 

 causal relation. The malady is held by most workers to be due to 



