LEAF ROT. Koleroga, CAN. The name given to a diseased condition of the leaves of the coffee plant, caused by an epiphyte growing and develop ing upon the leaf, to which it is superficially attached. The most serious of the diseases under which the coffee plantations in Ceylon have so long been suffering, is time red rust or leaf disease, Hemileia vastatrix. It a true endo phyte, developing in the tissues of the leaf, and expanding outwards, as is the case with the red rust of corn and grasses. Mr. Graham Anderson says (Treatise, p. 2) the leaf disease is a fungoid disease originating in, or at least affecting the cellular tissue, and causing a fungoid efflorescence or eruption on the leaf. Whereas the leaf rot is a fungoid deposit from without, assisted by the impaired condition of the system of the plant. Under the microscope, leaf disease is found to consist of innumerable minute fungi, which aro forced out of the pores of the leaf ; whereas the tenacious fungoid web, which in ' rot' completely creeps over the lower surface of the leaves, is evidently a mildew deposit caused by atmospheric action, coupled with a passive submission of the leaf to the insidious attack, owing to the vital energy of the plant being impaired. The leaves of the coffee plants have been covered with spots of apparent dust, which, spreading from leaf to leaf, front branch to branch, and from tree to tree, has ravaged large areas of country, until the plantations, instead of presenting a bright deep green colour, have assumed a dark orange hue ; the health of the trees has suffered, and the pro duction of berries deteriorated both in quality and quantity. Picking off the diseased leaves,
sponging with a solution of Condy's fluid, and an emulsion of kerosene oil. After many remedies, such as paraffin, dilute sulphuric acid, etc., had been used in vain, the experiment of dusting the leaves with finely-powdered sulphur was tried, with extraordinary success. The fumigation of the trees, by placing a large umbrella or tent-like structure over and round them, and burning sulphur within the closed space, has been almost equally efficacious, though naturally more cumber some and difficult of application. Trees so treated are reported to have quickly assumed a healthy appearance, and if these effects are permanent there is every probability of the disease being stamped out. Whether the same remedy will at the same time kill the spider, the white grub, and other insect pests which have combined in their attacks on the coffee plantations, remains to be seen. See Coffee ; Insects.