Browsing by Author "Nattrass, R.M."
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Item Bacterial Canker of Tomatoes in Kenya(1946) Nattrass, R.M.; Ciccarone, A.; Department of Agriculture, NairobiThe "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.Item The Bulb Eelworm Disease of Narcissus in Kenya(1950) Nattrass, R.M.The Bulb Eelworm disease of Narcissus species has long been the cause of serious loss Europe. It has only recently (1949) been recorded in Kenya. In appearance the disease symptoms are similar to those usually associated with fungi or bacteria. It is, however caused by an elworm Anguillulina dipsacngItem The bulb eelworm disease of narcissus in Kenya(1950) Nattrass, R.M.The Bulb Eelworm disease of Narcissus species has long been the cause of serious loss to commercial growers of these plants in bulb to Europe. It has only recently (1949) been recorded in Kenya. In appearance the disease symptoms are similar to those usually associated with fungi or bacteria. It is, however, caused by an eelworm Anguillulina dipsaci. This is quite distinct from the Root Knot eelworm Hederodera marioni which causes swellings on the roots of a large range of plants and with which most gardeners are only too familiar.Item The "Canker" Or "Black Leg" Disease of Cabbages and Cauliflowers(1951) Nattrass, R.M.The disease of cabbages and cauliflower caused by the fungus phoma lingram (Fr.) Desm .known a. ''Canker'' in Britain and as "Black leg:' in the United States and elsewhere, has long been present in Europe. An early description of the fungus appeared in Germany in (791 and it was described as a disease of cultivated BNJukos in France in 18411. II was established in Australia and New Zealand by 1987 and was first reported in the United States in 1911. In South Africa the disease is recorded as occurring in Natal in 1913 and in the United States in 1911 it did not reach Kenya until 1944, when damage was caused to cabbages being grown for seed at an altitude of 7,700 feet. There is a little doubt that the fungus was brought to Kenya in consignment of seed from abroad.Item The Cutting and Treatment of Seed Potatoes(1945) Nattrass, R.M.During the present war the need for economy in material and transport has focused attention on the use of cut sets for potato seed.Item Disinfection of Cereal Seed(1944/1945) Nattrass, R.M.; Department of Agriculture, KenyaWith the exception of the Loose Smuts of wheat and barley all the important seed-borne Diseases of cereals can be controlled by one or other of the chemical treatments which, in normal times, are available to the farmer. The cost is small compared with the benefits obtained. Routine seed disinfection is an in- surface with an absurdly low premiumItem Loose Smut of Wheat(1950) Nattrass, R.M.Loose Smut of wheat (Ustilago tritici (Pers.) Rostr.) is of comparatively rare occurrence in Kenya, but there is some indication that it may be on the increase. The disease is easy to recognize in the crop as the smutted ears are already black when they emerge from the sheath. The spore masses are protected only by a thin membrane which quickly ruptures on emergence of the head, allowing the spores to be blown away. The bare blackened central stalks of the ears are characteristic of the disease.Item Potato Blight(July, 1944) Nattrass, R.M.; D.I.C., KenyaThe disease of potatoes known as "Blight" (Phytophthora infestans) has been present in East Africa since 1941, and must now be considered as an endemic disease likely to break out with greater or lesser intensity wherever the crop is grown. Blight belongs to the class of fungi commonly described as the "water moulds". In contrast to many other parasitic fungi which thrive under dry conditions, these have retained many of the characteristics of an aquatic environment. The reproductive bodies, sporangia and swarm spores, are produced during periods of high humidity and a film of moisture is necessary for their germination. It is easy to see, therefore, that the initiation of, and severity of, an epidemic outbreak are, to a very great extent, determined by the weather.Item A Preliminary Note on the "Woodiness" Disease of Passion Fruit in Kenya(September 1939 ) Nattrass, R.M.; Department of Agriculture Kenya ColonyAs a garden or ornamental plant, passion fruit (Passifiora edulis) has been grown in Kenya for a number of years, but large-scale cultivation for the manufacture of juice is a comparatively recent development. It was first planted on a commercial scale in Trans Nzoia in 1933 and in Sotik a few months later. The area devoted to this crop has since been considerably extended and is now approximately 1,000 acres, the chief districts being Trans Nzoia, Sotik, and, to a lesser extent, the neighbourhood of Nakuru. The" woodiness" disease appears to have attracted attention early in the life of the industry." Small leaf" was responsible for some loss in Trans Nzoia as easly as 1935. In the Annual Report of the Department of Agriculture for 1936 Ill" woodiness" is recorded as a new plant disease for Kenya and its virus nature is indicated. Early in 1938 Dr. Storey, of the East African Agricultural Research Station, Amani, visited the Colony and obtained material from Trans Nzoia with which he subsequently proved that the disease was caused by a virus which could, under certain conditions, be transmitted by pruning and handling with contaminated hands and knives. In Trans Nzoia the disease has spread extensively and has now assumed alarming proportions. How the disease originated is not known, but it has possibly always existed on some wild host and passed thence to the cultivated passion fruit. It is unlikely that mechanical transmission carries the disease beyond the confines of a single plantation, but there
