Agronomic and economic assessment of intensive pest management of dry bean (Phaseolus vulgaris)

Two common production constraints of dry bean (Phaseolus vulgaris) in Ontario are annual weeds and anthracnose (caused by Colletotrichum lindemuthianum). Dry bean is not considered a competitive crop and weed interference can result in substantial yield losses, while anthracnose is considered one of the most devastating diseases in dry bean production. A study conducted in Ontario Canada, examined the effect of two herbicide programs on weed management, thiamethoxam insecticide treatment on plant enhancement and three fungicide programs on anthracnose development in a navy bean cv. ‘OAC Rex’. The premium herbicide program (s-metolachlor + imazethapyr) reduced percent weed ground cover relative to the economic herbicide program (trifluralin) in five of six locations. Thiamethoxam increased emergence and vigour at only one location, which contradicts reported benefits of thiamethoxam on plant health. The herbicide or thiamethoxam treatments did not affect anthracnose disease severity, visible seed quality, net yield or economic return. The fungicide seed treatment was often superior to the untreated control, for a number of the parameters measured. The application date of the foliar fungicide, relative to the onset of disease, varied between site-years. This dramatically influenced the fungicide’s effectiveness. Foliar fungicides increased seed quality and net economic return compared to the control when applied prior to disease development. The combination of fungicide seed treatment followed by a foliar fungicide provided the largest reduction in anthracnose severity.