Abstract
A preliminary publication recording the discovery of mustard as a factor influencing the cyst formation of Heterodera schachtii, and describing various experiments to demonstrate the effects of this factor, has already been made. Mustard seedlings grown to a height of about three inches and then broken down in soil in which a potato plant was immediately thereafter grown, were found to exert some influence on the development of the nematode, which partially inhibited the formation of cysts on the roots of the potato plant. The reduction in the number of cysts developed on the roots of a plant so treated, as compared with a plant grown in infected soil without mustard, was found to average over 60 per cent.