Dry Edible Beans: Weed Control

Excerpt from Agronomy Guide for Field Crops (Chapter 7)

Order OMAFRA Publication 811: Agronomy Guide for Field Crops

Table of Contents

1. Introduction
2. Critical Period for Weed Control
3. Crop Losses Due to Weeds
4. Mechanical Weed Control
5. Integrated Weed Management
6. Updates on Dry Edible Beans: Weed Control
7. Related Links

Introduction

The critical period to control weeds in white beans is from the second trifoliate leaf stage to the first flower stage.

Critical Period for Weed Control

Season-long weed control is not necessary to protect yield. Research has shown that maintaining good weed control throughout the critical period will result in less than 5% yield loss. Later-germinating weeds have minimal impact on yields and have relatively low production of weed seeds.

The product label for postemergent herbicides indicates the growth stage of the weeds when optimum control can be obtained. The timing of weed control should optimize the critical period for the crop and the optimum growth stage of the weed.

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Crop Losses Due to Weeds

Research in other crops has found that some weeds are more competitive than others. While the loss levels due to specific weeds have been well documented for corn and soybeans, crop loss data for edible beans have not yet been determined. Crop scouting is essential to determine the species present in the field and the weed populations. Consider the effect of weeds on crop quality and harvestability when making decisions on the level of weed control needed.

Mechanical Weed Control

Consider cultivation, rotation and other effective cultural practices for weed control along with herbicide treatments when developing a weed control program. Any single method of weed control or the continuous use of the same chemical can lead to the build-up of weeds resistant or tolerance to that control method. Rotation to other crops and/or other control methods will reduce the chance of developing new or unique weed infestations.

High-speed (10-20 km/h or 6-2 mph), shallow (2.5-3 cm or 1-1^1/4 in.) cultivation with a rotary hoe when the beans are in the one- to two-leaf stage will help control small weed seedlings. Under dry soil conditions, rotary hoeing 7-10 days following planting will help control emerging weeds. It can also help activate soil-applied herbicides by mixing the chemical with moist soil. Rotary hoeing during mid-day when bean plants are more flaccid will reduce stand loss. Rotary hoeing is unlikely to remove many weeds that are past the two-true-leaf stage.

Inter-row cultivation may be required when weeds escape herbicide treatment; weeds should be considered as escapes when they are 5-7 cm (2-2^3/4 in.) high. Cultivation should be shallow to prevent exposure of untreated soil and germination of new weed seeds.

Band treatment of chemicals over the row will reduce costs by one-half to two-thirds, depending on the row spacing and width of band. Shallow inter-row cultivation will be required to control weeds between the bands.

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Integrated Weed Management

Weed control in the bean crop is influenced by:

• crop rotation
• row width
• variety characteristics
• tillage practices

In general, the agronomic practices that produce a healthy, fast-growing crop will allow it to compete best with weeds.

Crop rotations can be effective in reducing certain perennial weeds that grow best in a particular crop. Narrow rows and higher populations tend to increase the crop canopy and reduce the growth of weeds, but care should be taken to balance the benefits of weed control with other requirements of the crop.

Equipment can carry weed seeds from field to field. Combines, tillage equipment and soil erosion also transport weeds. Weeds can also infest a field from manure application or other soil amendments. Proper sanitation and cleaning of equipment along with maintenance of field border areas all affect the long-term weed management in the field.

Refer to OMAFRA Publication 75, Guide to Weed Control, for more information including herbicide products and rates. (Order OMAFRA Publication 75)

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Updates on Dry Edible Beans: Weed Control

Refer to OMAFRA Publication 75, Guide to Weed Control .
(Order OMAFRA Publication 75)

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Related Links

• Weed Control
• Dry Edible Beans
• Field Crop Protection Guide - Publication 812

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