Experiments in 1986–88 compared the spring field bean cultivars Alfred, Minden, Ticol and Troy, grown on clay-with-flints soil at Rothamsted, at row spacings of 12 and 48 cm, and compared two pest and pathogen control programmes based on (i) ‘standard’ control of Ascochyta fabae, Ditylenchus dipsaci and seed-borne viruses and (ii) ‘enhanced’ control of Sitona lineatus, bean leaf roll virus via the vector Acyrthosiphon pisum, Botrytis fabae and Uromyces viciae-fabae in addition to the pests and pathogens in the ‘standard’ control.
With standard control, Minden had the largest mean seed yield of 4·6 t/ha; with enhanced control, Alfred was best with 6·1 t/ha.
The yield benefits of enhanced control ranged from 0·2 t/ha on Ticol in 1986 to 2·4 t/ha on Alfred in 1988. They were related to the control of weevils (S. lineatus), chocolate spot (B. fabae) and rust (U. viciae-fabae). At 1989 prices, the cost of materials used for enhanced control would be repaid by a yield increase of 0·3 t/ha.
The closer row spacing increased yields by 0·15 t/ha on average but effects differed greatly between years. Benefits were largest in 1986 when plants were shortest and in that year were largest for the shorter cultivars.
It is suggested that trials of field bean cultivars should always include a test of pest and pathogen control.