The Effects of Sub‐lethal Doses of McPa on the Morphology and Yield of Vegetable Crops

Summary. The effects of sub‐lethal doses of MCPA‐sodium on the morphology, yield and maturity of French beans, and on the morphology of broad beans, were studied in field and glasshouse experiments. Epinasty in French beans developed at 0.002 lb/ac a.e., but formative effects were not seen at less than 0–1 lb/ac. With doses up to 0.4 lb/ac there was no significant reduction in yield or haulm weight, but at 1.0 lb/ac and above, yield was reduced and some of the plants sprayed at an early stage of growth were killed. There were characteristic modifications of the roots and stems and of those leaves which were at a susceptible stage of development when sprayed. Broad beans were only slightly injured by 0.2 lb/ac but were generally killed by 2.0 lb/ac. Abnormalities were noted in the germination of seed produced by affected plants. Effets de doses sub‐léthales de MCPA sur la morphologic et le rendement des cultures légumières IV. Haricots verts et fèves