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| 1 Crop Production |
| 1.2 Crop Production Aids |
| 1.2.9 Weed Control |
| Health Canada’s Pest Management Regulatory Agency (PMRA) regulates all products designed to manage, destroy, attract or repel pests (including weeds) that are used, sold or imported into Canada. These products include chemicals, devices, and even organisms, and are referred to collectively as pest control products, or simply “pesticides.” The federal legislative authority for the regulation of pesticides in Canada is the Pest Control Products Act. The use of pesticides is also subject to regulation under provincial/territorial legislation.
Typically pest management strategies include a combination of tools including mechanical, cultural, biological and chemical practices. Mechanical tools include, cultivating, flaming, and hand picking. Cultural practices include, crop rotation, companion planting and mulching. Biological and chemical practices must comply with the Pest Control Products Act. Producers interested in using these measures should ensure that they understand the federal and provincial laws in addition to their certification body’s position on each product’s use. |
| 1.2.9.1 Acetic Acid (CGSB Allowed)* |
| Acetic acid has been recently investigated for its potential as an herbicide. When applied, acetic acid solutions have been found to act as a non-selective contact herbicide. Concentrations of 10, 15 or 20% acetic acid have been shown to be effective against many weeds, especially small annuals. The 5% concentration (supermarket vinegar is 5 % acetic acid) has provided inconsistent levels of weed control. To be permitted for use in organic systems, the acetic acid must be produced and concentrated by approved methods.
Acetic acid is naturally derived from the fermentation of plant products under anaerobic conditions. Commonly, apple cider, wine, and malt are fermented to produce a 5% acetic acid solution also known as vinegar. This acetic acid can be concentrated from 5 % to 15% by distillation and to 30% by freeze evaporation. These processes are permitted under organic standards. * Acetic acid can also be prepared by several synthetic processes, such as the reaction of methyl alcohol and carbon monoxide in the presence of a catalyst, or the oxidation of acetaldehyde or petroleum. These methods are not permitted for use in organic systems. In addition, some acetic acid herbicides may contain prohibited wetting agents. Acetic acid readily degrades in water and shows little potential for bioaccumulation. It is also biodegradable. The application of acetic acid to soil has been shown to lower pH temporarily; however, pH returns to normal in 48 hours. |
| 1.2.9.2 Corn Gluten Meal (CGSB Allowed)* |
| Corn gluten meal is a fine powder created as a by-product during a milling process of corn. Although it is often used to feed livestock, it has recently been developed as a natural pre-emergent herbicide in the US. Corn gluten meal acts on germinating seeds, inhibiting the development of the new root. During periods of water stress, the seedlings wilt and die because they do not have an adequate root system. Corn gluten meal must be applied to the soil before weeds germinate in order to be effective. It has been shown to inhibit root formation in dandelions, curled dock, plantain, lamb’s quarters, foxtail, crabgrass, and pigweed. It has no effect upon weeds that have already sprouted and formed a root system.
Corn gluten meal has approximately 60% protein and 10% nitrogen by weight and therefore is a natural source of slow release nitrogen. * For use in organic systems, the corn gluten meal must not be derived from genetically modified corn. PMRA has granted the temporary registration of a corn gluten meal product for use as a pre-emergence weed seed germination inhibitor for dandelion and smooth crabgrass on established residential laws. The organic status of the product is not determined. This is the only corn gluten meal product registered as a herbicide. Most commercially available products are intended for use as soil fertilizers. |
| 1.2.9.3 Fatty Acid (CGSB Allowed)* |
| A relatively new approach to weed control is the use of natural fatty acids as a foliar spray. Fatty acids can be applied to the leaves of undesirable plants. The fatty acid then removes or "burns" the waxy cuticle on the surface of the leaves, causing the leaves to dry up.
Fatty acids are broad-spectrum and non-selective, meaning that they work on all plants with which they come into contact. They are not systemic, have no residual activity in the soil and do not persist in the environment. It is most effective on weeds that have just emerged or are less that 15 cm tall. For perennial weeds, several applications may be necessary. Care must be used in its application since it can be a skin and eye irritant and will damage any vegetation it contacts. Producers should be aware that fatty acids used for weed control would also target beneficial insects. * Only fatty acids derived from animal or vegetable oils are permitted for use within organic production systems. Some certifiers restrict the use of fatty acids to roadside and right-of-way vegetation control only. |
| Products | Sources | PMRA | PCP# | OMRI | Origin | Safer's Superfast | Woodstream Canada Corporation | R | 24333 |  |
Safer's Topgun | Woodstream Canada Corporation | R | 22245 | |
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| 1.2.9.4 Insects (CGSB Allowed) |
| The biological control of weeds by introducing insects that feed on them is a practice that has been used by various governments including provincial agriculture and forestry departments.
Weeds for which insects have been effectively used as part of a control regime include: Leafy Spurge, Knapweeds, St. John’s wort, Yellow Starthistle, Musk Thistle, Canada Thistle, Tansy Ragwort, Toadflax, Poison Hemlock, and Purple Loosestrife. Insects for the control of weeds are not required to be registered in Canada by the Pest Management Regulatory Agency. |
| Products | Sources | OMRI | Origin | Live Insects | Biological Control of Weeds |  |
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| 1.2.9.5 Mulch (CGSB Allowed) |
| Many producers rely on mulches for weed control. Both organic and inorganic (plastic and fabric) mulches can be used for this purpose. Traditional organic mulches include; hay, straw, bark, wood chips, leaves, grass clipping, sawdust and compost. These materials are generally readily available. Organic mulch can control weeds but also can add nutrients and organic matter (humus and fresh materials) to the soil, protect the soil from erosion, improve soil tilth, improve moisture holding capacity, and serve as great ground cover. With the exception of hay and straw, which require 15-20 cm of material, most mulches should be applied to obtain 5-8 cm of materials. Avoid weed infested material and make sure to supplement your soils with some nitrogen when using carbon rich material such as sawdust and wood chips.
Generally, organic mulches should be applied after plants are well established and when the existing weeds have been controlled. Furthermore, the mulch should be applied when there is adequate soil moisture and before the hot conditions arrive. It may be necessary to wait for a rainfall before mulching your crop because the mulch could reduce the water infiltration once applied. |
| Products | Sources | OMRI | Origin | Brite'Nup | Adcock Manufacturing | |
Orchard Mulch Non-synthetic | Agri Service Inc | |
Plastic Mulch | RECOTEK |  |
Maple Leaf Farm & Building Supplies Ltd | |
Culture Plastitech Inc | |
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