28 TORREYA 



thetic rubber program might not be developed as rapidly and as well as it has. 



In 1944 continued research on the minor rubber yielding crops is of im- 

 portance — first, because some of them hold real potentialities for development 

 as natural rubber sources, and because studies of all of them yield data which 

 are of value in work on the more important ones. There is a considerable 

 amount of controversy with reference to the performance of synthetics in 

 automobile tires. There seems to be ready admission of the fact that in large 

 bus and truck tires and those for military vehicles which must travel over 

 very rough terrain, synthetic rubber is unsatisfactory unless it is combined 

 with a large proportion of natural rubber and even then the product is 

 not as good as a pure natural rubber tire. We have been using natural rubber 

 from a stock pile which was none too large at the beginning of the war and 

 which has been diminishing very rapidly. 



In his last report the Rubber Director estimated that our imports of 

 natural rubber during 1943 would total 60,000 tons. 



Recent directives have been issued from the Office of the Rubber Director 

 and the War Production Board further curtailing the use of natural rubber. 



The manufacture of synthetics from petroleum products is based on the 

 use of materials of which, even now, there are predictions of exhaustion of 

 supplies. The manufacture of synthetics from alcohols involves growing plants 

 for the production of carbohydrates, fermenting the carbohydrates, and then 

 by complex processes producing a rubber substitute. Even if the synthetics 

 prove to be as good as natural rubber this procedure must compete economi- 

 cally with a product formed directly by the plant. 



Add to all of this the fact that consumption of rubber is undoubtedly go- 

 ing to increase very markedly after the war, when a tremendous deficiency 

 of tires and other rubber articles will have to be filled, and there would seem 

 every justification for very strong continued emphasis on the development of 

 sources of natural rubber in the Western Hemisphere. Of these sources Hevea 

 brasiliensis is most important and guayule has good possibilities. Kok-saghyz 

 holds a potential rubber yield of perhaps 400 pounds per acre, the attainment 

 of which presupposes the solution of several biological and production prob- 

 lems. It has the added feature of being the only crop from which good rubber 

 can be obtained in a very short period. 



Continued research on all of these crops is yielding valuable information, 

 not only for rubber production, but for the production of other crops as well. 

 In addition the development of the Hevea project is laying the basis for a 

 more complementary trade with our Latin American neighbors after the war. 



Bureau of Plant Industry, Soils and Agricultural Engineering 

 Agricultural Research Administration 

 United States Department of Agriculture 

 Beltsville, Maryland 



