Worldwide distribution of soybean-cyst nematode and its economic importance.

Soybean-cyst nematode (Heterodera glycines) was first reported from Japan in 1915. It has since been reported from Korea (1936), Manchuria (1938), the United States (USA) (1954), and Egypt (1968). It is of major concern to soybean producers only in Japan and the USA. Soybean was a major crop in the Orient by 1915 but it was grown very little elsewhere. Since that time its cultivation has spread, and in 1974 there were 37.6 million ha with a production of 51.7 billion kg. As soybean cultivation has spread, the soybean-cyst nematode has been more widely found. Soybean is one of the major food sources for feeding the increasing world population. Soybean-cyst nematodes have been spreading rapidly in recent years and are a major threat to this very important crop.