120 REPORT OF THE COMMISSIONER OF AGRICULTURE. 



the leaves and removing and destroying all those that show any sign 

 of infection. The fungus cannot be destroyed when it has secured a 

 development within the tissues of the leaves without destroying the 

 latter, and the sooner those that are diseased are removed the better. 

 What fungicide may be found useful in preventing the germination 

 of the spores must be determined by experiment. Any ordinary ap- 

 plication of lime or sulphur will have little or no value for this pur- 

 pose. I would hesitate to recommend the application of solutions 

 containing the salts of copper on this vegetable for hygienic reasons. 

 A solution of penta sulphuret of potassium, or liver of sulphur, 1 to 

 2 ounces to a gallon of -water, sprayed upon the plants at the first ap- 

 pearance of the blight, may arrest its progress. This preparation 

 deserves a trial in this case. A shelter of cloth over the plants is 

 said to have preserved them comparatively free from blight in local- 

 ities where plants not so shaded v,^ere badly diseased. 



Orange-leaf Scab. 



Cladosporium sp — . 

 (Plate VI.) 



The following notes on a disease affecting the leaves of sour orange 

 and lemon trees, which I have named Orange-leaf Scab, are essen- 

 tially those read before the Botanical Club of the American Associa- 

 tion for the Advancement of Science, at the Buffalo meeting, and 

 published in the Bulletin of the Torrey Botanical Club for October, 

 1886. Since then no new light has been thrown on this obscure dis- 

 ease, and it is not likely that more will bo discovered until it can be 

 studied in the field. 



So far as I am aware there is no published account of this disease 

 other than that referred to above, and there is a probability that it is 

 of recent origin; it is at least of recent appearance in Florida. The 

 statements of correspondents and the samples which have been sub- 

 mitted for examination show but too plainly its serious character. 



Mr. Charles W. Campbell, writing from Ocala, Fl^., July 29, 1886, 

 says that "the disease first made its appearance last summer, and 

 seems to be increasing the present season, particularly on young trees 

 making vigorous growi:h. It seems to be confined to sour stocks, al- 

 though this season it has appeared on lemon trees. No sweet-orange 

 trees have been affected, nor the sweet buds on sour stalks, even when 

 growing side by side with trees badly affected. It is very destructive 

 to the growth of trees and ruinous to young nursery stocks, so that 

 fears are entertained that it will seriously affect the orange interest 

 unless means are discovered for checking it. Last season and this 

 have been exceedingly wet, and the appearance of the fungi may be 

 due to this fact." 



From letters received from Mr. C. F. A. Bielby, of De Land, Fla., 

 we draw the following conclusions: (1) That the trees most severely 

 affected with this leaf disease last season suffered during the winter 

 more than those not affected ; (2) trees affected last season are the ones 

 first attacked this spring, although the foliage of these is entirely new 

 growth; (3) so far as observed sour trees alone are affected; (4) loca- 

 tion and nature of the soil or of the fertilizers used have no influence 

 on the disease; (5) the most vigorous as well as the "sickly" trees 

 are alike affected; (6) if a tree is diseased in part, the tendency is for 

 the whole tree to become so; (7) the malady does not appear to spread 



