Weed control

Basic Principles of Weed Control for Dry Beans

Yield losses typically reach around 55% when weeds are not properly managed in edible beans. To minimize any yield losses from weed competition in edible beans they should be kept weed free from emergence to first flower.

Research by the University of Guelph (Ridgetown campus) has demonstrated that weed control is maximized in edible beans when a soil-applied herbicide program is used that targets the most prominent weeds in a field, followed by regular scouting commencing 10–14 days after application to look for new weed seedling emergence, so that herbicides can be applied to those weeds between the 4–8 leaf stage of growth when they are most susceptible.

Imazethapyr (e.g., Pursuit) and halosulfuron (Permit) are considered foundational soil applied herbicides in edible beans because they control a wide range of grass and/or broadleaf weeds. However, in the last 20 years, populations of weeds that are resistant to both of these “Group 2” herbicides have become more prominent, requiring other herbicides be tank mixed, or post-emergence broadleaf herbicides be applied to pick up any deficiencies in weed control.

To minimize the risk of crop injury from herbicides applied in edible beans, the University of Guelph (Ridgetown campus) has found that:

  • Dual II Magnum and Frontier when applied pre-plant incorporated offer better crop safety than when applied pre-emergence.
  • There is a range in sensitivity to imazethapyr among the edible bean market classes grown in Ontario. The following rates of imazethapyr have been shown in field trials to minimize crop injury while maximizing yield and weed control when tank mixed with other herbicides (e.g., Prowl, Treflan, Dual, Frontier or Eptam):
    • Adzuki beans — (Pursuit: 126 mL/acre)
    • Large seeded edible beans (e.g., cranberry, kidney, yellow-eye) — (Pursuit: 100 mL/acre)
    • Small seeded edible beans (e.g., white, black, pinto) — (Pursuit: 75 mL/acre)

It is recommended that you discuss herbicide programs with the organization you have contracted your edible bean crop with, as they will have the most experience with the best regional weed control strategy.

By Mike Cowbrough

Weed Management Specialist, OMAFRA

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