CROP-PLANTS 369 



methods of cultivation and control of insect pests by spraying and 

 fumigation are in progress. 



Viticulture is increasing in the Union of South Africa. Grape 

 variety trials are in progress at the Paarl viticultural station in 

 the Transvaal and the Oliphants river settlement. Improved 

 methods of cultivation are studied, and in particular irrigation, 

 since water is essential to this industry. Brak-resistant varieties 

 of grapes are studied at the Oudtshoorn experimental station, and 

 measures for controlling Botrytis rot of grapes are tested at the 

 Stellenbosch-Elsenburg College of Agriculture. Here also experi- 

 ments to determine the effect of root-stocks on the keeping quality 

 of grapes are in progress. The correct export temperatures for 

 different kinds of grapes are studied at the Capetown low tem- 

 perature research laboratory. 



MISCELLANEOUS 



Tobacco (both N. tabacum and N. rustica) is an early introduction 

 from America to Africa. It was a product of domestic importance 

 long before Europeans attempted its cultivation outside Africa, 

 and is still so in West Africa. 



The chief producing country in Africa is Southern Rhodesia 

 which, in 1935-6, produced 22 million lb., but it is not by any 

 means confined to that region. Production in the Union amounted 

 to 18 million lb. in the same period, and in Nyasaland to 17 

 million lb. Tobacco requires good drainage, and consequently ter- 

 raced hill sides or sheltered tops of hills are best for its cultivation. 

 It is also very liable to diseases caused by virus, eel-worms, and 

 insects {see Chapter X). Some of these have been controlled by 

 special legislation, for example, in Southern Rhodesia the Tobacco 

 Pest Suppression Act was passed in 1933 to enforce the destruction 

 of all plants left over from the previous season, which might har- 

 bour insects. The careful choice of rotation crops is another 

 method of controlling disease, as in South Africa, where Rhodes 

 grass as a rotation crop has been advocated by African Explosives 

 and Industries, Ltd. (1935), since it is useful for fodder and is 

 immune from eel-worm. 



A study of the problems of cultivation in South Africa has been 

 made by H. W. Taylor (1924). Until recently Rustenburgh has 



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