A Bark Disease of Coffee in East Africa

Abstract

A disease of the bark of young leader shoots of arabica coffee occurs in the Usambara Mountains of Tanganyika Territory. The disease may be important when “stumping” is practised in the regeneration of old plantations. A brown sunken lesion, formed of dead extra-cambial tissues, usually gradually extends and rings the shoots; after a period varying from a few days to several months after complete ringing the foliage above wilts and dies. A leaf spot is also due to the same cause. The fungus, Fusarium lateritium Nees var. longum Wr., among several isolated from lesions, has been shown to be capable of reproducing the disease by pure culture inoculation. A proportion of the experimental inoculations resulted in the ringing and death of the shoots; many of the lesions, however, after a time ceased to advance and became callused at the margin. Similar recoveries from the disease were observed in the field. Field observations and experiments demonstrated that a common mode of entry of the fungus into the stem tissues was through freshly exposed leaf scars, and occasionally from a leaf-spot down the petiole of a leaf. Many shoots also in the field became diseased as the result of the fungus passing to them through the tissues of a stump from the base of a dead shoot. Coffea arabica alone, of a number of coffee species tested, was susceptible to any extent to this disease. Excision of the affected bark of a stump was effective in checking the spread of the fungus through the stump. The operation, however, is not considered to offer a practicable means of control in the plantation.