Bacterial Canker of Tomatoes in Kenya

Abstract

The "bacterial canker" disease of tomatoes caused by * Corynebacterium michiganense (E. F. Smith) Jensen, is widely distributed throughout the world. It was first recorded and described from North America, where it was known, from the locality of the first outbreak, as the Grand Rapids disease in 1909 by E. F. Smith, who named the bacteria causing it Aplanobacter michiganense. The disease was reported from South Australia in 1924 and from New Zealand in 1936. In view of the virulence of the disease and the popularity of the tomato, its spread round the world seems to have been comparatively slow. In England it was not recorded until 1942 although it was present in Europe as early as 1929. The first occurrence of the disease recognized in Kenya was near Nairobi in June, 1945. This attack caused the almost complete loss of a small plot at the Soott Laboratories. Dr. W. J. Dowson, to whom a culture of the organism from 'this plot was sent, confirmed the identification as that of Corynebacterium michiganense. As far as is known, this is the first record of the disease in East Africa and it is believed not to have been recorded either from the Union of South Africa or the Rhodesias. In most countries where it occurs the bacterial canker is considered to be a disease of major importance but its destructive capacity seems to be somewhat variable. In New Zealand, Reid (1938) states that the disease was not then of major importance, while Cunningham (1941) lists it as one of the three major diseases of the crop in that country. In South Australia (Colquhoun and McCarthy, 1943) where the disease is widespread, cankers do not occur and the name Grand Rapids disease is retained. In Kenya, its status is not yet known but judging from the initial outbreak it must be considered capable of causing very serious loss.