Abstract
Previous work showed that, in the presence of root excretioci of certain crucifen, larvae of the potato‐root eelworm do not emerge from the cysts when stimulated by potato‐root excretions; a similar lack of response is also shown in the presence of dilute solutions of allyl isothiocyanate, the mustard oil of black mustard. The present paper describes a small‐scale field trial in which this mustard oil is applied with peat to the drills at the time of planting. An increase in yield of about 100% resulted from a dressing of the oil equivalent to o.1 cwt/acre.