Edible Bean School: Knocking out nightshade

Photo: Mike Cowbrough, OMAFRA

Nightshade can be a nightmare for edible bean growers.

The weed can play havoc with the crop as mature berries produced by the eastern black nightshade plant cause edible bean staining and mud tagging, and can even gum up cleaning equipment at the processing plant.

On this episode of the RealAgriculture Edible Bean School, Ontario Ministry of Agriculture, Food and Rural Affairs weed specialist Mike Cowbrough shares strategies to control the troublesome weed.

Cowbrough’s first management tip for growers is to always take a look at field history before planting edible beans. “If you have a history in a field of moderate to high nightshade pressure, I would strongly discourage you from growing dry beans there because we have limited tools to manage those fields.” He also notes that testing has shown that 75 percent of the nightshade in Ontario is resistant to Pursuit herbicide, a foundational weed control program for edible beans, that is now unlikely to offer anything in terms of nightshade control. (Story continues after the video.)

A two-pass program that combines a pre-plant incorporated, soil-applied herbicide followed by a post-emergent product gives growers the best opportunity to control the weed. Dual and Frontier are Cowbrough’s top herbicide choices for best control.

“To minimize the risk of crop injury, we need to pre-plant incorporate both of those products,” says Cowbrough. “Unfortunately, that might lower our nightshade control a little bit. So we (need to) make sure that our rates are high… And then the key thing is after those programs go down, we need to be scouting probably two weeks after application almost every few days to see if we get little seedlings coming up.”

If nightshade seedlings break though the ground and emerge after the pre-plant application, growers only have one remaining options — Reflex herbicide. The application window for that product is the two to four-leaf stage of nightshade. “So that’s smaller than a quarter. And the window is super tight so we need to be on that,” says Cowbrough who also stresses the need for growers to use higher rates, high water volumes and adequate adjuvant to get the job done effectively.

In the video, Cowbrough also shares how some growers are looking for any edge they can get to improve weed management in dry beans, including incorporating winter cover like cereal rye to reduce the amount of weeds in the field and create an inhospitable environment for seed production.

Click here for more Edible Bean School videos.

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