Robust, well-maintained plants will better resist disease, unwanted insects, and competition from weeds. The adoption of winning conditions will also help avoid recourse to pesticides in the yard and on houseplants.
Distinguish between natural allies and undesirable organisms
When the presence of an unwanted organism is suspected, the first step is to identify it. Make sure that it is not a natural ally that enhances the environment, pollinates plants, or eats undesirable organisms or parasites.
Identify natural allies
Below are allies to be protected and some of the benefits they provide.
- Bees and other insects pollinate tree and plant flowers.
- Spiders eat several insects and larvæ each day.
- Ladybugs eat roughly 50 aphids a day in the adult stage and up to 150 a day in the larval stage.
- Toads eat slugs, earwigs, and other insects.
- Dragonflies eat several insects and larvæ a day.
- Millipedes, centipedes, and woodlice decompose organic material.
- Insectivorous birds such as swallows and chickadees eat several insects and larvæ a day.
- Earthworms aerate the soil and decompose organic material.
Several plants produce pollen and nectar, which natural allies love. To attract natural allies, include plants such as dill, fennel, and cosmos in the yard. Also promote biodiversity in the yard by maintaining ground cover such as clover on the lawn and avoiding wildflowers such as dandelions. Such plants are useful to pollinators, which will forage for nectar and pollen.
Identify unwanted insects, weeds, and diseases
A number of insects, diseases, and weeds can pose a problem on plants or in yards.
The presence of unwanted insects can occur in diverse ways. You may see the insect, such as an aphid or a white grub, and/or the damage such as yellowing leaves that it causes to the plant.
Several fungi can cause diseases on indoor and outdoor plants. Depending on the disease and its stage of development, signs may appear on the leaves such as white powder, brown or black spots, and curling and drying leaves.
Weeds are easier to identify in the adult stage and some are better known than others, such as poison-ivy, which can cause painful skin inflammation, and ragweed, which triggers allergic reactions.
Identifying insects, diseases, and weeds can be complicated, but several resources are available:
- For garden plants, the weeds, insect pests, and plant diseases (in French only) page explains the digital tools and services available.
- For flowerbed or garden plants, trees, and shrubs, please consult The Green Pages .
- For trees, please consult the fact sheets on insects (in French only) and the fact sheets on diseases (in French only).
Tolerate undesirable organisms
If they do not cause problems, learn to tolerate the presence in the yard of a few unwanted insects or weeds.
It is preferable to consider other solutions before resorting to pesticides to get rid of them.
For example, rely on:
- physical control, using manual methods such as cutting branches and manual weed control;
- biological pest management, by means of living organisms present naturally or voluntarily introduced into the environment.
Natural predators such as birds and certain insects will often help. The same applies to certain plants, which some people deem harmful, and others deem beneficial.
The growing conditions of houseplants usually differ from those of plants in their natural environment.
Basic rules for promoting the health of indoor plants
To keep indoor plants healthy and more disease- and insect-resistant, provide suitable light, humidity, and temperature.
Choose plants according to the conditions in the room where they are situated. Consider light, the most crucial factor. At least three hours of exposure to sunlight is usually suitable for full sunlight plants and shade plants. Maintain ambient humidity between 50% and 60%.
Respect each plant’s watering and fertilization requirements. Remember that such requirements vary during the year and that moderate watering is the key to success. Remember that plants prefer soil that dries between waterings.
Use sterilized potting soil adapted to the type of plant when repotting, usually in the spring or as needed. Inspect your plants with each watering to detect problems. Immediately quarantine a diseased or infested plant and look after it.
Before you purchase a plant, carefully inspect it to detect insects or diseases. Keep the plant away from other plants in the house for three weeks and examine it regularly. If necessary, remove diseased parts or insects using a rag, a Q-tip, or a brush, and soak the foliage.
Control undesirable organisms without pesticides
Once you have identified the unwanted organism, analyze the other viable solutions before resorting to pesticides.
- Dislodge the insects: use a shower nozzle to remove aphids and a Q-tip dipped in alcohol to remove mealybugs.
- Install sticky insect traps: use yellow or white traps against aphids, yellow ones against whiteflies, and blue or yellow traps against thrips.
- Rely on prevention methods: regularly spray the foliage to prevent spider mite populations.
Residential yard plant and lawn maintenance
Having healthy plants is the best strategy to prevent problems.
Basic rules for promoting the health of flowerbeds, trees, and shrubs
Consider requirements such as hardiness, light, and soil type to choose plants and their location in the yard. Follow these basic rules to promote healthy flowerbeds and avoid undesirable organisms.
- Make sure that the soil is fertile and well drained.
- Properly aerate the soil by turning it over in the spring before planting.
- Weed manually or with tools.
- Preferably water in the morning.
- Avoid watering the foliage.
- Diversify the species planted.
- Choose an area of the yard that receives adequate sunlight for the plants selected.
- Use mycorrhizæ, beneficial fungi that stimulate the growth of the plants with which they are associated.
- Add mulch to flowerbeds and the base of trees and shrubs to prevent undesirable plants from growing and retain soil moisture. Gradually add a layer as the mulch decomposes naturally. Do not incorporate it into the soil. Put 2.5 cm to 5 cm of organic mulch such as compost, leaves, sawdust, and mowing residues in flowerbeds. Put a 5-cm to 10-cm layer of wood chips and bark around trees and shrubs.
- In the fall, remove plant residues since unwanted insects and fungi that cause diseases can winter there.
Basic rules for promoting a healthy lawn
Adopt preventive measures.
- Prepare the soil before seeding. A layer of at least 15 cm of earth is necessary for a lawn.
- Re-seed areas where there is little or no lawn in the spring or late summer to avoid the development of weeds.
- Plant diverse types of plants in the lawn. It will be less sensitive to diseases and insect pests. For example, you can add white clover to your lawn seed mix. This plant supports trampling and drought well and, unlike conventional lawn, it can fix nitrogen in the air, which reduces its fertilizer needs. You can also plant ground cover .
- Have a soil sample analyzed to ascertain its pH. Aim to maintain it between 6 and 7 to enable the lawn to properly assimilate nutriments. Correct the pH of overly acidic soil, i.e., below 6, by applying dolomitic quicklime in the fall.
- Aerate the lawn to promote the activity of microorganisms in the soil and add compost (in French only). In the spring, aerate the soil using a fork or a soil aerating drill bit. Also fertilize the soil in the spring and/or fall depending on the nutritive element needs and the recommendations on the fertilizer packaging.
- Maintain a mowing height of 6 cm to 8 cm, above all during the hottest months. The shorter the lawn is, the more receptive it will be to weeds and unwanted insects. Frequently change mowing direction to reduce the accumulation of mowing residues. Sharpen the lawnmower blades after every eight hours of use to ensure clean mowing and more disease-resistant grass blades.
- Water moderately, early in the morning or late in the afternoon. This will reduce moisture loss stemming from evaporation.
- Wait at least one week after heavy rain to water the lawn.
- Abide by your municipality’s watering restrictions.
- Only water when the soil is dry at root level at the rate of 2 cm to 3 cm of water on the yard’s surface, which promotes deep rooting and allows for less frequent watering.
- Avoid watering and mowing the lawn when it turns yellow during drought. It is dormant and will grow green again when normal precipitation resumes.
Control undesirable organisms without pesticides
The unwanted organism must be clearly identified to select the appropriate control method.
You can dislodge insects in flowerbeds, trees, and shrubs.
- For example, remove lily leaf beetle larvæ and adults by hand from the plant. You can also collect caterpillars in rolled leaves on trees and shrubs. Use a powerful water jet to dislodge aphids.
- Prune the tree or shrub. When mealybug populations are significant, cut the branches affected to reduce the populations. Pruning an apple tree affords better aeration, which avoids scabs.
- Choose resistant varieties. Certain plant varieties are more resistant to certain diseases, e.g., fire blight, rose diseases, Dutch elm disease, and apple scab.
The appropriate lawn maintenance will allow you to control diseases such as powdery mildew, dollar spot, and the appearance of stemmed mushrooms. To control weeds, pull them by hand or with a dandelion weeder.
Biological pest management can prevent unwanted insect populations from increasing. For example, instead of replacing lawn in areas affected by hairy chinch bugs or sod webworms, use resistant lawn seeds in which endophytic fungi are naturally present. To control white grubs, you can apply nematodes, which live as a parasite on these insects. Request advice from specialists at your garden centre.
Last update: February 23, 2023