Effects of crop mixtures on chocolate spot development on faba bean grown in mediterranean climates

Chocolate spot incited by Botrytis fabae is a serious faba bean disease of worldwide distribution. The increasing interest in sustainable tools for disease control, together with the lack of sufficient levels of genetic resistance triggered our interest in the use of intercropping as a tool for the management of this disease. The effect of intercropping on chocolate spot severity was studied in field experiments performed in Egypt, the Palestinian Territories, Spain and Tunisia, in which a susceptible faba bean cultivar was grown as a monocrop or with two mixed species intercrops of either barley, oat, triticale, wheat, pea or common vetch, or with three mixed species intercrops of wheat and berseem clover. Chocolate spot was significantly reduced when faba bean was intercropped with cereals, but not when intercropped with legumes. Suppressive effects can be ascribed to a combination of host biomass reduction, altered microclimate and physical barriers to spore dispersal.

► Intercrops with cereals can be an effective strategy for control of chocolate spot in faba bean.
► This beneficial effect varies with the associated species, being higher for barley and oat.
► Cereal species were more effective at reducing chocolate spot severity when intercropped with short faba bean cultivars.
► In contrast, pea and vetch had little or no significant effect on chocolate spot reduction in faba bean.