Disease in onions due to the stem eelworm, Anguillulina dipsaci, causing a soft rot of the bulb and a general stunting of the plant, commonly called “bloat,” has been known for many years. Its symptoms and pathology were fairly fully described and figured by Bos (1888–92). More recently a considerable amount of investigation on the disease has been carried out in U.S.A., particularly by Newhall and Chitwood [see Newhall & Chitwood (1940), Chitwood, Newhall & Clement (1940), Newhall (1941) and (1943)]. It is not intended to discuss this work here but merely to indicate that our knowledge of the disease set up both in the seedling plant and in the grown bulb is now fairly full and detailed.
Certain gaps in out knowledge of the bionomics of the disease have, however, remained, particularly those relating to its sporadic incidence in areas where onions have' not previously been grown or have not been grown for many years. One possibility which needed exploration was whether the parasite could be seed-borne. Bos (1889, ṕ. 346) provided a note on this matter. He said that in seed harvested from a diseased crop of onions and sent to him in the spring of 1886, he was able on close examination to see that some of the seed contained eelworms but only in small quantity.