Pests & Disease

Weeds Control in your Gardens or Landscape

Weeds Control in your Gardens or Landscape

Weeds Control

Weeds control program must take advantage of a combination of cultural methods, mechanical, and chemical adapted to the situation. The effectiveness of the methods of weed control depends on the weather conditions, the type of soil and cropping history. Before adopting any corrective action, identify the weeds present and learn about the characteristics of their growth. Pesticides are now classified in eleven categories for the purposes of sale and use. Exceptions are provided for agricultural uses (including the production of nursery plants). Once the weeds are identified, it is to reduce to the minimum the infestations before the plantations, to eliminate possible sources of infestation and prevent the establishment of weeds.

Principles of weeds control

You can avoid a lot of infestations by using seed and plants free of weeds and preventing weeds from setting seed. Monitor the growth of weeds in both the culture and in the non-crop areas nearby. Increase the activity of soil organisms (bacteria, fungi, earthworms, insects, etc.) is a good way of defense against weeds since this increases the force of the culture and active the decomposition of weed seeds in the soil. Cropping practices favoring the biological activity of the soil (e.g. manure application or plant waste composted, use of cover crops) can reduce weed problems.

Reduction of infestations before the plantations

use of cover crops to curb the growth of weeds when a field of a nursery is put out of production, it must cultivate plants louvers or a green manure before putting it back in production. Of cultures that are buried as rye, red clover, buckwheat, the herbaceous sorghum, millet and oilseed radish are examples of cover crops. These cultures limit the growth of weeds by competition and by allelopathy (in exuding of chemicals that affect the germination of the seeds of weed). They also have the effect of reducing the erosion due to the wind, and the residues that they leave enrich the soil with organic matter. The soil is significantly more piece of furniture in a culture that follows a culture of coverage.

Fight against perennial weeds

many perennial weeds are harmful to crops of nurseries, including quackgrass, bindweed, vetch, wild vine, the perennial nightshade, the thistle, the ground ivy, the glutton, horsetail, toadflax, milkweed, aster, the Souchet, fireweed, and goldenrod. The following are points to consider:
• Always strive, in the year preceding the plantations, to reduce to a minimum (or eliminate) the perennial weed.
• The need, apply a systemic herbicide such as Roundup, on perennial weeds the year preceding the plantations. Respect the mode of employment specified on the label and always use the recommended dose against the weed in question. To ensure a long-term elimination, apply the herbicide in the good growth stage of the weed (e.g. just before flowering in the case of most of the perennial species of broad-leaved).

• It may be difficult to combat of perennial weed in established stands because of the sensitivity of the culture to some herbicides and the impossibility of weeding to bottom of nurseries established.
• A repeated weeding also gives good results against certain perennial weeds such as bindweed. Rid the farmer of the debris of weeds before the use of soils free of weeds.
• Use of non-selective herbicides (as Gramoxone and Roundup) before planting a culture of green manure and before the Bury. The herbicides at low remanences, such as 2,4-D, can be used in combination with green manure crops, tolerant. However, we must avoid the use of herbicides which expose the following plantings to residues in the soil.

Crop Rotation Crop

rotation is an important element of the strategy Long-term control of weeds. After burying a culture of coverage, it is preferable to install of nursery stock different from the previous culture. For example, do follow a culture of conifers by a culture of hardwoods. This rotation leads to an alternation of the methods of work of the soil, spacing, systems of crop and herbicides employees. The rotation contributes to interrupt the cycle of weeds and reduce their proliferation. Short rotations using several cultures allow increasing yields and the profitability of each of the cultures. Choose a culture that opposes a strong competition to weeds identified.

The Technique of False Seedlings

the technique of false seedlings is to prepare the seedbed at the very beginning of the season of growth. It leaves the weeds to germinate. It kills a few weeks later with the help of glyphosate or paraquat. Once the weeds destroyed, it sows or Spade’s culture in the bed of a plantation in ensuring to stir the ground the least possible.

Preparation of beds intended to receive containers

Prepare the area intended to receive containers in y extending a layer of gravel or by covering the ground with a film of black plastic or a geotextile membrane opaque. It is important that the material used intercepts the light rays in order to stop any germination. These materials can be reused for a number of years before having to be replaced. Keep the bed of containers and the aisles free of weeds in y tearing the seedlings or by chemically destroying. Remove and discard all weeds pulled away from the area of culture so that the seed can be scattered in the neighboring containers. Rid the containers of weeds existing before that they do not flower.

Once plant flowers, it risk of disseminating hundreds of catapultées seeds or washed away by the wind. A good number of species of weeds infesting the containers are of annual who rely on several generations of seedlings per year given that their seeds have not need to overwinter before germinating. In the fall, well remove weeds in full growth of containers because the greenhouses plastics are covered. This will avoid that weeds do not overwinter with success in the sheltered that offers the plastic greenhouse. Be sure to remove the rosettes of winter annual, as the bourse-to-Pasteur and the Canada fleabane, as well as established plants and seedlings of chickweed and chickweed. Otherwise, these plants will bloom in May or even before.

Control of Sources of infestation

reduce to a minimum the sources of infestation by resorting to methods of mechanical weeding, cultural chemical or below:
• the use of mechanical or chemical methods to kill weeds that have escaped the treatments before they do rise in a seed.

• Prevent weeds to mount in seed in the surrounding areas not cultivated.
• Mow at regular intervals to prevent weeds to flourish.
• Use a mower to nylon yarn to some places, particularly along fences.
• Search the Sources of weeds, such as the popular, willows, the fireweed and Canada fleabane, which infest cultivation areas in full field or in containers.
• Combat weeds around the basins of irrigation in order to avoid that very small weed seeds are not paid in the containers at each watering.
• Keep a canopy of dense grasses around the basins of irrigation to ensure the stabilization of the shoreline and to avoid infestations of weeds.
• Install a filter in the irrigation network in order to delete the weed seeds in the irrigation water.

Mechanical Methods of Weeds Control

It is possible to reduce weeds and the homes of infestation by mechanical methods. Ensure that the seedlings and transplants are free of weeds before transplanting. Before moving on to another field, rid the hardware of the debris of weeds. Work in last infested fields.

Rotary Hoe

the teeth of the rotary hoe raise malaxate and the land, uprooting as well the weed seedlings. The rotary hoes usually cause less damage to crops that the harrows. They also allow to break the soil crust and to incorporate the herbicides applied in the surface, which activates their chemical action and improves the destruction of weeds.

Use the rotary hoe at the end of the before-noon or the afternoon when the heat of the sun makes fade the uprooted weeds. In addition, the plants are grown more flexible during these periods of the day, and Damage is thus reduced. To obtain good results, maintain a sufficient speed, usually 10 to 20 km/h. A forward speed too slow does not generate a force sufficient to raise the weeds out of the soil and the risk of further damage to crops. On light soils or furniture, it is necessary that the work of the rotary hoe is superficial.

Weeding hoeing or of the between-rank

the superficial job between the ranks of cultures in lines and uprooted weeds Young and cut the most developed. Various types of equipment may be used. When it was a use of bridles, there must be 50% overlap to obtain a complete weed control. Use caches to avoid to bury the small cultures. The first hoeing is, without a doubt, the most important, because the weeds that escape them will reach usually their full maturity. The complete weeding a marvelous herbicide treatment. A superficial weeding (2.5 to 5.0 cm) prevents harm to the action of the herbicide applied (the maintenance of the layer of herbicide will prevent the weed seedlings to lift and to establish themselves in the soil).


Haying or mowing helps to reduce weed populations. The best time for Mowing perennial weeds is at the stage of the floral button, before their roots accumulate reserves and that the stalks rise in a seed. If a herbicide application is planned for later in the season, it must let elapse enough time for the bad grass regrowth after mowing.

Management of Herbicide Resistant Weeds

There are more than 120 species of herbicide-resistant weeds a little everywhere in the world. Refer to the OMAFRA Factsheet, weed resistance to pesticides, to obtain the list of weeds resistant observed in Ontario. The herbicides must be used reasonably.

Delaying Herbicide Resistance

The resistance to a herbicide is the result of repeated applications of this herbicide. The speed with which appears a resistance to different types of herbicides is extremely variable of a weed species to another and from one stand to the other. Here is a series of measures that contribute to reducing to a minimum the number of weeds resistant:

Identification and vigilance.

Nothing distingue appearance the weed resistant, if this is that they do not undergo the destruction and damage observed in plants of the same stand. It is known that it is frequent that weeds” escape ” to chemical treatments. We do note sometimes the appearance of a resistance that when 10 to 30 percent of weeds are insensitive to the treatment. It is, therefore, necessary to inspect the fields regularly and use of diagnostic methods to detect a problem before it gets worse.

Prevention of the spread of weeds.

Out of a field, clean the equipment. Do not allow the rise in a seed of weed resistant.

Use the mechanical weeding.

To the extent possible, make a mechanical weeding with the help in particular of the rotary hoe or the farmer.

Crop rotation and herbicides.

Do not use the same herbicides year after year after year. Practice crop rotation and spray on the new culture of herbicides with modes of action or sites of action different. Use of tank mixes or commercial mixtures registered to contain multiple active ingredients and that can fight a same bad grass in different ways.

Keeping of registers.

Keep accurate records of crop rotations practiced and herbicides used in each of the fields. Well kept records facilitate the planning of long-term strategies for the fight against weeds. Communication. Inquire with associations of producers, universities, extension specialists, agri-businesses, friends and neighbors about resistance problems which they are witnesses. Inform the provincial inspector of weeds or the representatives of the manufacturers of plant protection products of cases of resistance observed so that appropriate measures can be taken to prevent the spread of resistant strains.


The appearance of a resistance is not the only reason that can explain the ineffectiveness of a herbicide. It is important to eliminate the other causes of the inefficiency of a treatment, including errors in the application, the adverse weather conditions, a treatment carried out at the wrong time and outbreaks of growth of weed after the application of a herbicide without residual effect. If, after analysis, it still retains the possibility of a resistance, make the checks that follow:

• The treatment has it been effective against other weed listed on the label of the product? In the event of the emergence of resistance, it is very likely that it would develop in a field that in a single species of weed. Accordingly, if it remains many weeds are normally susceptible to treatment, it must move to again review the other possible causes of the failure of the treatment.

• A-T-we noticed the previous year to a same place in the field the same herbicide or herbicides belonging to the same chemical group and having the same mode of action have been ineffective?

• Was there year after year after year in the field an intensive use of the same herbicide or herbicides belonging to the same group?

If you answered yes to one or the other of the foregoing questions, it is possible that the weed is resistant to the herbicide. Use a herbicide belonging to a different group or to resort to a method of the fight other than chemical. Prevent weed to mount in the seed. Communicate with the provincial inspector of weed as well as with the supplier of herbicides and the manufacturer of pest control products

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