Alternative Herbicide to Address the Constraint of Parasitic Weed of Faba Bean in North Africa

Abstract

Faba bean, Vicia faba is a key temperate legume grown for food, feed, and as part of cereal-based cropping systems in North Africa. However, its production is severely constrained by parasitic weeds, particularly Orobanche crenata, leading to increased cereal monocropping and higher dependence on imports. Management options are limited, with partial resistance in varieties and the use of herbicide-tolerant cultivars or sublethal glyphosate applications practiced on a limited scale. Recently, the post-emergence herbicide Corum® (480 g/L bentazone + 22.4 g/L imazamox) combined with the adjuvant Dash® has been registered in Morocco and Tunisia for controlling broadleaf and grassy weed control at the vegetative stage of faba bean. Notably, imazamox has an active ingredient against parasitic weeds. This study aimed to evaluate herbicide rates and application timings for parasitic weed control in faba bean in Morocco. Experimental treatments included glyphosate (360 g/ha) applied twice at 15-day intervals during flowering, and Corum with Dash® at three rates (1.5, 0.75, and 0.37 L/ha) applied at vegetative and flowering stages. Non-sprayed plots served as controls. The designed experiments were conducted over two seasons (2023–2025) at the ICARDA Marchouch Research Station under high Orobanche crenata pressure using susceptible registered Morocco varieties. Corum herbicide caused visual injury, but plants recovered within a week. Glyphosate significantly reduced Orobanche shoots, increased nodulation, and resulted in the highest yields. The lowest Corum dose (0.37 L/ha) also suppressed Orobanche and improved yield compared to the higher rates. Non-treated plots showed 64 Orobanche shoots/m² and produced no yield due to early plant death and herbicide treated plots produced less than 5 shoots/m2. These findings suggest that low-dose Corum application can aid in Orobanche management. Large-scale demonstrations are needed to raise farmer’s awareness. Further research is also needed to understand the effects of post-emergence herbicides on faba bean nodulation.