Black Arm Disease in Uganda

Abstract

There are no certain records of the occurrence of this disease in Uganda be fore 1925, though there are strong grounds for assummg that it was present here for some few years before that date. In 1925 Snowden definitely identified it as present, and stated that it was of com mon occurrence. In the following year the leaf form of the disease was almost universal east of the Nile, and extremely common in Buganda; the stem form was common at Suere Plantation, following a severe hailstorm in September. In the following s~ason the leaf spot form was practically universal, though the stem form was much less common than in the previous year. In 1 928- 29 the crop of parts of Teso District was severely at tacked by both forms of the disease, and a very poor crop was obtained. The 1 929-30 season is still referred to as the .. Black Arm Year". In this season the disease was very severe in T eso, Bug, were and Lango, and in more limited areas in Busoga and Buganda. The loss of crop is estimated at from 50,000 to 70,000 bales of cotton, but in the light of later research it is difficult to estimate what proportion of this loss is directly attributable to the disease. In the £ollow ing season the disease was much less severe. The seed supply for the areas severely affected during 1 929-30 was ob tained from the less severely attacked areas of Busoga. In spite of this change of seed, the leaf form of the disease was present in almost every plot shortly after germination, and gradually spread to every plant. The stem form was reported from many places, but never became severe, and in this season the disease had little effect on the crop. In 1931-32, in spite of prolonged wet weather in most