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Dry Bean Production Notes
June 19, 2006


Dry Bean Rooting Depth and Water Use

Dry bean roots typically grow laterally 8 to 12 inches and downward to a depth of 3 feet or more, although root distribution is concentrated near the soil surface  about 90% of the roots will be found in the top 2 feet.  Over the course of a growing season, only about 10% of the water used by the beans will be obtained from the soil below 2 feet. Average dry bean water use rates will increase from about 0.05 inches per day soon after emergence to over 0.25 inches per day during pod development.

Be Wary of Unlabeled Herbicides

Make sure youre using products labeled for use on dry beans.  Using a non-registered/unlabeled herbicide may result in an illegal residue which, if detected, could cause condemnation of the crop.

Symptoms of Herbicide Damage

Symptoms can include puckering of leaves, swollen basal stems, stunting, death of the growing buds, cauliflowering of plants, and leaf burning. Besides directly affecting plants, the herbicides may leave plants more vulnerable to disease such as root rots.

If you conclude that herbicides are the probable cause of crop injury, try to determine why the injury occurred. Misuse of high rates, wrong chemical, contaminated spray tank, improper method of application, nonuniform application, overlaps, improper applicator adjustments and tillage operations that concentrate the chemical are some causes of herbicide injury. Some varieties/hybrids are more susceptible than others. Navy beans are generally less tolerant to herbicides than other dry beans types or soybean.

Dont be too hasty to evaluate the effects of herbicide injury; give the plants a chance to recover. Check growing points to see if the plants have potential for recovery. Compare injury effects and weed control benefits. Stand counts and injured plant counts are important considerations. Consider digital photos of initial symptoms to document damage and to help gauge possible recovery. Unbiased yield checks later in affected and unaffected similar areas of the same field are the best estimates in damage losses.

Summary  of influences of various factors on spray drift.

Scouting for Insects

Key insect pests to watch in the Northarvest bean growing area include the potato leafhopper, seedcorn maggot and grasshoppers. Occasionally, various caterpillars infest bean plants and can cause some level of defoliation, but usually less damage than warrants insecticide treatments.

In dry edible beans, field scouting to assess insect populations is based on either the number of insects per foot of row, insects per plant or the level of defoliation.

Insects per foot of row are determined by shaking plants over the inter-row space, on which a strip of cloth has been laid. Count the total number of insect pests per foot of row that fall on the cloth.

Percent defoliation is determined by estimating the amount of leaf loss based on visual inspection of randomly selected plants. The growth stage of the plant is important. Under most conditions, moderate defoliation early in the season has little effect on final bean yield. As plants reach the flowering and pod filling stages, then defoliation poses a greater threat to yield. For example, research indicates that the soybean plant can sustain a 35% leaf loss prior to the pre-bloom period. From pod-set to maturity, the plant can tolerate only a 20% defoliation level.

Diagnosing plant problems

Local agronomists and county extension agents/educators are an excellent resource for diagnosis; the following plant labs can also help diagnose plant pests and problems. Contact the lab for instructions before submitting plant samples.

NDSU  Waldron Hall, Room 206, PO Box 5012, Fargo, ND, 58105, ph 701.231.7854, email:, web site: Fee-based services include insect, weed, disease identification and control recommendations, herbicide injury diagnosis, and soybean cyst nematode screening.

UM - Plant Disease Clinic,
St. Paul, ph. 612.625.1275.
Web site: Fee-based services include plant disease, virus ID, nematode analysis, as well as seed quality testing. Link to more private and public testing labs can be found online:


These labs (as well as professional crop consultants/certified crop advisers) can help determine key factors that affect crop productivity, such as:

Soil organic matter tests  Knowledge of the organic matter level will serve as a guide in selecting an effective herbicide and rate of application, as well as helping to assure crop safety. Testing once every five years should be adequate.

Herbicide spray water analysis  High salt levels in spray water can reduce weed control in nearly all situations. Calcium, and to a lesser degree, magnesium, are antagonistic to 2,4-D and MCPA amine , dicamba, and glyphosate.

Plant tissue analysis  This indicates the nutrient status of plants at the time of sampling, serving as a monitoring tool for determining the adequacy of current fertilization practices. Plant tissue analysis will also detect unseen nutrient deficiencies and may confirm visual symptoms of deficiencies. Toxic levels also may be detected. Combined with soil test information, a plant analysis report can help a producer tailor fertilization practices to specific soil-plant needs.

Online Resources

NDSU Crop Production Page -- With links to 2006 NDSU Herbicide, Fungicide, and Insecticide Guides, as well as other crop production bulletins and NDSUs weekly crop/pest report.

University of Minnesota Extension Service -- Click on the Farm link.

Pesticide Labels -- Excellent resource on all current pesticide and adjuvant labels, with links to pesticide manufacturers --

Northarvest Bean Growers Association Research & Production Library --

Root Rot in Dry Beans - Using bin-run seed and short rotations with crops such as sugarbeets and soybeans will increase root rot susceptibility in dry beans.  Upper plant symptoms are more obvious when drought or other field conditions prevent lateral (secondary) root development.  The disease is most commonly observed during mid-to-late season.  Colorado State University has a root rot backgrounder online at


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Northarvest Bean Growers Association | 50072 East Lake Seven Road | Frazee, MN 56544
Ph: 218-334-6351 | Fax: 218-334-6360 | Email: