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Cereal Crops: Introduction
Excerpt from 2010-11 Publication 75, Guide to Weed
Control, Order this publication
Introduction
- Apply all treatments in 100-200 L/ha (40-80 L/ac) of 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 that 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:
- Preplant (PP) - Also see Preplant
Weed Control, Preplant-Site Preparation Prior to any Crop for details
of products, rates and remarks.
- Preplant Incorporated (PPI)
- Preemergence (PRE)
- 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
For more information:
Toll Free: 1-877-424-1300
Local: (519) 826-4047
E-mail: ag.info.omafra@ontario.ca
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