CAB129-37 — Page 348

Page 348

The question of the place of livestock in a mechanised semi-arid tropical system of farming must of necessity be approached in the same way. The first task of the Corporation in this direction is the provision of animal products for the feeding of the European and African staff of the project. The development of the necessary herds and flocks, together with that of the food and water supplies they will need, is already under way. The experience gained from this work will make it possible to consider whether long-term economic advantage is to be expected from the incorporation of livestock in the main rotation policy, and to devise the necessary experiments.

It may be said at once that the Department does not accept the view that the inclusion of livestock in the rotation is essential on technical grounds such as the maintenance of soil fertility. Livestock are unquestionably needed for nutritional reasons, as suggested above, but the land required to maintain the necessary numbers on each Unit is a small fraction only of the area of the Unit. It would be most dangerous to apply preconceived or sentimental notions on this subject, derived from experience in temperate or even sub-tropical climates to fully tropical and semi-arid conditions in Tanganyika without sound experimenta- tion and full proof that the proposed system would succeed technically and economically.

8. PLANT PROTECTION

Work in this field has been largely confined to the entomological investigations conducted by Dr. Evans, since it has not been possible to secure an appointment to the vacant senior post of Plant Pathologist. However, Dr. Wallace, of the Tanganyika Territory Department of Agriculture (Coffee Research Station), and Mr. Sellschop (Potchefstroom School of Agriculture), on visits to Kongwa, gave invaluable help on plant pathology.

Plant Pathology

Groundnuts. The virus disease Rosette, which is probably the most serious disease of groundnuts occurring in Africa, is dealt with under Entomology (below). Black or crown rot (Aspergillus sp.), was serious on some areas of Unit 2, at Kongwa, and was present on Unit 1, where scattered individual plants were noted to be attacked at various stages during growth. On some of the wetter areas of Unit 2 it was estimated that up to 30 per cent. of the plants were affected. The incidence of the disease would appear to be correlated with inadequate burying of grass. Localisation of the disease to former grassland areas supports this view, but there are probably other factors such as local moisture conditions on lower lying areas.

Leaf-spot (Cercospora personata Ellis) appeared on the mature plants just before they were ready for harvest, but probably caused little or no reduction in yield. A bacterial root rot of the main root some 2-3 inches below the collar was also found.

On certain areas it was suspected that a fungus attack on the early matured nuts during March caused them to germinate. At harvest time a count of germinated and ungerminated nuts was made on the varieties Natal Common, Spanish Bunch and Valencia in the 25 variety experiment at the Kongwa Experi- ment Station. The association of germination with either fungus or insect attack or with no obvious cause was recorded. The results show that a mean attack of 10 per cent. by fungi and 2 per cent. by insects had occurred, and that approximately 15 per cent. of the nuts attacked by fungi or insects germinated and only 1 per cent. of the healthy nuts. In the latter case germination was almost entirely confined to one variety, Spanish Bunch. It is clear that germina- tion is greatly increased by insect or fungus damage to the pods.

An experiment to test the value of a range of seed dressings was unsuccessful since a dry spell followed the planting of certain treatments and had an adverse effect on germination. It was, however, clear that certain treatments, including percentage establish-

trimethyl thiupam disulphide dust, had a beneficial effect Pa

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