Cereal Crops: Introduction

Introduction

• Apply all treatments in 100-200 L/ha (40-80 L/ac) water except where otherwise noted.
• Crop rotation is a valuable technique used to prevent the build up of weed populations associated with small grain production. Wild oats can increase in population and severely limit production on fields where small grains are grown continuously. Some weeds (e.g., proso millet) will be well controlled by cereal competition.
• Blind harrowing with a light harrow, before emergence of cereals, can help to control small germinating weeds. A light harrow can also be used in cereals up to the 3-leaf stage, or a weeder harrow (L shaped flexible tines) at the 4-leaf stage to provide better control of small annual broadleaf weeds. The timing of these harrowing operations is critical. The weeds must be small and the soil surface must be dry and easily worked.
• Weeds must be emerged from the soil surface and in early stages of growth to be killed by the rates of the herbicides used on cereal grains. Weeds which are growing during early periods of cereal growth (up to 5-leaf stage) have the greatest effect on the cereal yield.
• The growth stage for maximum safety varies with the cereal and the herbicide. Check the label for appropriate timing. When counting the leaves on cereal plants, some confusion can occur if tiller leaves are present. These leaves are not counted. Figure 8-1 is useful for identifying the cereal leaf stages that are mentioned in this chapter.
• Cereal grains have an advantage in that they do not make use of the full growing season. This is particularly true of the winter cereals where preplant cultivation and postharvest cultivation can be used to stimulate germination of weed seeds and reduce perennial weed populations.
• Herbicide Application Timings:
  • Soil Applied Treatments:
    • Preplant (PP) - Also see Special Methods: Preplant - Site Preparation Prior to Any crop for details of products, rates and remarks.
    • Preplant Incorporated (PPI) - Two incorporations at right angles operating at a depth of 10 cm using a double disk (7-10 km/hr) or vibrating shank S-tine cultivator (10-13 km/hr) are required unless otherwise stated. Cultivation-type equipment used for herbicide incorporation is known to spread perennial weeds to previously uninfested areas. Special attention should be directed toward machinery cleanliness, and/or treating fields with perennial weeds last.
    • Preemergence (PRE) - Rainfall of 15-20 mm within 10 days after application is necessary to activate preemergence treatments. Shallow cultivation, rotary hoeing or harrowing will control weed escapes and improves herbicide activity in the absence of rainfall.
  • Postemergence (POST): Leaf stage of the weeds is critical for good weed control. Smaller weeds are usually more sensitive to herbicide injury. Apply according to recommended leaf stages. Crop stage is important to optimize crop safety. Adjuvants will frequently improve the weed control when used as directed. Weather or other conditions may influence the optimum rate of adjuvant, see the product label for more details. Always use appropriate drift management technology.

Related Links

• Weeds in Ontario
• Cereal Crops in Ontario - Barley, Oats, Wheat
• Problem Weed Control in Field Crops
• Pesticide Companies and Agents
• OMAFRA Sprayer Calibration Calculator
• Search the PMRA website
• OMAFRA Publication 505: Ontario Weeds
• OMAFRA Publication 75: Guide To Weed Control

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