Suggested weed management practices
- Plant crop seed that is certified free from weed seed. Otherwise, you might introduce new weed problems to a field.
- Reduce weed seed population in the soil by:
- Encouraging weed seed germination by using shallow cultivation, or any other method that will bring the seed into moisture in the top 0.5 inch of soil.
- Controlling weeds before they set seed.
- Eradicate perennial weeds. Eradicate small patches before they spread. Use cultural, mechanical, and chemical methods as appropriate.
- Rotate crops.
- If winter annual weeds are increasing, rotate to a spring-seeded crop. A spring cereal such as barley will produce well, and weeds such as jointed goatgrass and downy brome will be less of a problem. Moreover, many winter annual broadleaf weeds will not be a problem in a spring-seeded crop.
- In areas where more diverse crop rotations are possible, planting alternate crops, such as pulse or oil seed crops, is even more effective for controlling certain weed populations than planting spring-seeded cereals.
- Control weeds along edges of fields.
- Keep weeds along edges of fields and other idle areas from maturing and producing seed. Some of these weed seeds are likely to move into the field. Any number of methods, including mowing, spraying with a herbicide, or cultivating can be effective.
- Establishing a perennial grass cover is very effective in controlling most weeds. After establishment, weed control often requires minimal additional inputs.
- Use this handbook as a guide to help select an herbicide treatment, then study the herbicide label(s) for appropriate use.
- Control weeds as soon after germination as possible and stop early weed competition with crops.
- Avoid using an herbicide if the grain crop is under stress.
Important information about herbicides
Herbicides may be water-soluble, oil soluble, or water suspensions. Those with the first two properties are formulated as water-soluble concentrates or as emulsifiable concentrates. They require little agitation to keep them evenly distributed in the spray tank. However, water suspension herbicides require additional attention as follows:
Continuous mechanical agitation in the tank is needed to keep wettable powders (WP), liquid suspensions (4L), flowables (4F), water-dispersible granules (WDG), or dry flowables (DF) in suspension. If it is necessary to shut down the application equipment with spray suspensions in the tank, use the following procedures:
- Place equipment where flushed herbicide will not damage desired vegetation.
- Shut off valve from spray tank to boom.
- Flush booms and nozzles with clean water to remove the suspended material.
It is difficult to get the settled material redispersed when you start up again. Do the following:
- Run the agitator for a few minutes.
- Shut off equipment and check for caked material at the bottom of the tank.
- When satisfied dispersion is complete, continue spraying.
Directions and notes for applying herbicides
- Use at least 20 gal/A water carrier for ground application and 5 gal/A water for aerial application (unless stated differently on the label) to ensure even distribution of the spray solution.
- Avoid applying to wheat seeded less than 1.5 inches deep. If the wheat develops roots in the herbicide zone, the wheat plants can be damaged.
- Apply only to recommended soil types. Precipitation can move the herbicide deeper in coarse soil types, and crop damage can result.
- Do not apply to frozen soil. If the soil is frozen, rain or thawing could move the herbicide laterally, causing crop injury from herbicide concentration in some areas and lack of weed control in other areas. However, application can be made if the soil frosts at night and thaws during the day.
- Do not apply to cracked soil; the herbicide may move down the cracks into the root zone of small grains.
- Clods and crop residue reduce herbicide effectiveness as weeds escape from under clods and residue intercepts the spray.
Note If reseeding is necessary due to crop winterkill, reseed (increase seeding rate by 15%) without mechanical seedbed preparation. Cultivation could move the herbicide residue into the crop root zone. Use a deep furrow opener drill and seed at least 2 inches deep. The opener will move the surface soil out of the way and the seed will be planted below the herbicide residue. Do not reseed to any crop other than wheat. Crop may be injured in fields previously treated with metribuzin or other soil active herbicides such as diuron, flufenacet or pyroxasulfone.
Selective herbicides to control weeds in small grains can often be applied by either ground or aerial equipment. See label for any restrictions.
Accurate application is essential for safe and effective weed control. Use equipment that is in excellent condition. Equipment must be properly calibrated. Applying more than the recommended dosage could injure the crop. Application must be within 5% of the recommended rate. If not, take steps to correct the equipment and recalibrate.
Uniform coverage is essential, so do not use less than the recommended gallonage of water carrier per acre. Continuous mechanical agitation is a must when using wettable powders, liquid suspensions, or water dispersible granules to keep the particles evenly dispersed in the spray solution.
The information provided in this handbook is not intended to be a complete guide to herbicide use. Before using any pesticide or herbicide product, you should read the label recommendations on the container. Before a chemical can be recommended for a specific use, it must be thoroughly tested. Following the recommendation on the manufacturer’s label can prevent many problems arising from the improper use of a chemical.