Harmful insects and plants

Harmful insects and plants

What should you do if you discover poison ivy on your property? How can you reduce the risk of being bitten by a tick?

Saint-Lambert is home to several species of insects and plants that can be harmful to your health, such as ragweed, or to your property or garden, such as Japanese beetles.

This page offers you some tips and resources to prevent or limit damage to your property or risks for your health.

Tick (Lyme disease)

Lyme disease can be transmitted through the bite of an infected tick. The number of infected persons in the Montérégie region is on the rise. Tick populations are now established in the region and are found primarily in forests, woods and tall grass.

The risk of tick bites is highest from May to August, but caution is advised well into the spring and the fall months.

Adults, children and even animals who engage in outdoor activities in or near a forest (hiking, biking, tree cutting, wood gathering, camping, hunting, gardening, etc.), and certain types of workers (road workers, camp counsellors, etc.) are more likely to be exposed to ticks.

To lower your risk of infection while you continue to enjoy the benefits of outdoor activities, we recommend the following precautionary measures in tick-prone areas:

  • Wear long pants, closed footwear and socks, and apply a icaridin or DEET-based insect repellent, following the instructions on the product label.
  • Shower as soon as you get home.
  • Look for ticks on your body. Remove any ticks you find as quickly as possible. The risk of contracting Lyme disease within the first 24 hours of exposure is minimal. However, the longer a tick stays attached to your skin, the greater the chance of infection.
  • Call Info-santé at 8-1-1 if you have been bitten by a tick. You may be advised to consult a doctor or pharmacist to determine if you should take antibiotics to prevent developing the disease;
  • Seek medical attention promptly if you develop any symptoms of illness (fever, headache, fatigue, rash more than 5 cm in diameter) within 30 days of a tick bite. Lyme disease can be treated successfully with antibiotics.
  • Look for ticks on your animal and contact a veterinary if you find any tick.
  • Prevent tick populations from building up around your house by keeping your lawn mowed.
Find out more on the Santé publique de la Montérégie website

Japanese beetle and white grubs

The Japanese beetle is an invasive exotic insect native to Japan. The adult Japanese beetle attacks more than 250 species of plants, several tree species and many fruit and vegetable plants. Examples include the elm, maple, grape vine, peach, apple, apricot, cherry, plum, rose, zinnia, corn, asparagus, soybean, blueberries, raspberries and blackberries.

The larvae of the Japanese beetle, commonly called “white grubs,” are a real scourge for lawns. In the larval stage, the beetle feeds mainly on the fibrous grass roots, leaving behind brown patches of dead grass.

The biological cycle of the Japanese beetle has 4 stages: egg, larva, pupa and adult. The adult beetles are very active for six to eight weeks during the summer. They prefer to feed on hot, humid days and to rest on rainy days.

The females lay their eggs about 8 cm beneath the turf surface. The larvae hatch from the eggs and feed on the grass roots, as do June bugs. The larvae develop and spend the winter in the form of pupae.

The adult emerges at the end of June or in early July and feeds on the flowers and foliage of many plants, including vegetable plants and certain tree species.

Cycle de vie du scarabée japonais

Skunks, racoons, and some bird species such as starlings and blackbirds are natural predators of white grubs. Certain species of insects also help control white grubs by feeding on them.

As a general rule, the key to successful prevention is having a healthy, vigorous lawn. It is also the most effective long-term solution.

In the spring and fall

Even if a lawn has been scavenged by skunks or racoons looking for the little insects they love, various prevention measures can be taken, depending on the condition of the turf.:

  • Aerate the soil using a carrot-type aerator;
  • Add organic matter (commercial compost);
  • Diversify the plant species that make up the lawn by including ryegrasses with endophytes (microscopic fungi that live inside some plants and produce substances repellant to certain insects), fescues and forage plants like white clover;
  • Reduce nitrogen fertilization (particularly chemical);
  • Choose 100%-natural fertilizers whose nitrogen, phosphorus and potassium (N-P-K) content is less than 10 for each element;
  • Keep your grass tall: mow the grass to a height of not lower than 3 inches (7.5 cm);
  • Leave grass clippings on the lawn (slow-release fertilizer);
  • Reduce watering in early June to allow the earth to harden;
  • Keep the soil’s pH level between 6.5 and 7.0.

During the summer

  • Keep the grass long and dry during the egg-laying period, from July to August (minimum three weeks). Dry soil partially hinders the development of the eggs and larvae;
  • Turn off the lights on your property because they attract the adult beetles.

At the end of the summer

The application of nematodes (parasites) is effective from mid-August to mid-September. This is the time when the white grubs are often found at the soil surface feeding off the turf roots. Follow this procedure:

  • The soil temperature must be between 15oC and 30oC (preferably around 20oC). It’s useless to apply nematodes in May because the soil is not the right temperature. Also, in May and June, the larvae turn into pupae. At this stage, they are no longer feeding.
  • One of the most effective nematodes against European chafer larvae is the Heterorhabditis bacteriophora. It’s best to do the treatment during a long rainy period. Never apply the treatment when it’s sunny because the UV rays are fatal for nematodes.
  • Remove the filter from the sprayer or make sure that the holes in your watering can are big enough to let the nematodes through so they reach the soil.
  • Shake the solution of water and nematode powder regularly to make sure the nematodes don’t die due to lack of oxygen.
    • Remove as many adult Japanese beetles as possible by hand and put them in soapy water to kill them. It’s easier to capture them in the early morning because the dew makes it harder for them to fly. Some people use a small vacuum.
    • Attract birds by putting out a birdhouse and food.
    • Plant toxic plants in your flower beds. Examples are fescues, ryegrasses, cultivated geraniums, larkspur, castorbeans, and horse-chestnut flowers.
    • Spread compost, because white grubs prefer sandy soils.
    • Crush the dead Japanese beetles in a little water and spread them around plants. This acts as a natural repellant.
    • Spray the patches of infested lawn with a nematode solution. These microscopic small grubs are parasites that feed on white grubs. They are already present in the soil, but you want to increase their density.
    • Install light traps, because they attract insects.
    • Pheromone traps (controversial for small spaces). According to one study, the female beetles are attracted to the general location of the trap rather than to the trap itself. The waste of the females on adjacent plant leaves then becomes more attractive than the trap for the males looking for mates. See this link for more details: http://www.ncbi.nlm.nih.gov/pubmed/19610405

You are strongly advised NOT to use chemical pesticides in your vegetable garden. First, the insecticides are never effective in the long term because the next generation of insects becomes resistant. As well, you risk killing beneficial insects like ladybugs and staunch warriors like aphids and flower thrips.

The application of pesticides is also subject to By-law 2006-14 concerning the use of products containing pesticides.

Find out more on the website of the Canadian Food Inspection Agency Find out more on the Government of Canada website


Sneezing, blocked noses and itchy, watery eyes: ragweed allergy sufferers know these symptoms all too well. Ragweed is a plant that grows from 10 cm to 1.5 m high with green leaves that resemble those of a carrot. When in bloom, it has yellowish green flowers that grow in clusters. The allergen in ragweed that causes hay fever is its pollen.

Herbe à poux

If you want to eliminate ragweed, you have to know where it grows. It loves to grow in clumps in sunny spots. Ragweed has a preference for badly maintained, poor quality soil such as that found along railway tracks, next to sidewalks, on construction sites, on neglected lots, on patches of bare land, where road salt has killed off a lawn, in a corner of the garden, or where soil has been disturbed.

Only individuals who are allergic to ragweed experience symptoms: sneezing, congestion, irritated eyes and throat, etc.

Even if over-the-counter antihistamine pills and decongestants provide some measure of relief to sufferers, this respiratory allergy gives rise to many health problems and carries huge social costs due to medical expenses and work absenteeism.

This problem requires a radical solution: eliminate it at the source—uproot every ragweed plant that you can find!

  • Pull up the plants manually or mow them before they bloom towards the end of July and again around the third week of August.
  • Use mulch to prevent the plant from growing.
  • Improve soil quality (topsoil, fertilizer).
  • Plant seeds or other plants to compete with ragweed.
To prevent a wave of allergies and stop the plants from reproducing, it is recommended that you mow them before they flower, which they usually do around the end of July and the end of August.

If you see any ragweed growing on City-owned public land, you can notify our environment agent, by email at patrouille-verte@saint-lambert.ca.

For several years now, the Ville de Saint-Lambert has been taking increased action to reduce the presence of ragweed on its territory and its negative impacts on the health of people who are sensitive to it.

One of the actions taken by the City is the annual assessment of ragweed’s presence on our territory. This assessment provides an accurate picture of the situation and allows us to better target our priority actions. The ragweed map identifies the critical sites with high plant density. The City can then control the presence of this allergen in priority areas through twice-monthly mowing and targeted uprooting campaigns.

Find out more on the website of the gouvernement du Québec

Poison ivy

Poison ivy grows from 20 cm to 1 m high and can appear in various forms: bushy, creeping, or climbing. Its shiny foliage is wine red in spring, dark green in summer and multicoloured in the fall. This plant contains a poisonous sap that causes inflammation of the skin, even in winter. Poison ivy grows mostly near wooded areas.

Anyone who has been in contact with the poisonous sap can react to poison ivy. The symptoms are: red skin inflammation, strong itching, and the formation of blisters on the affected areas.

  • Wear gloves when handling the plant and avoid any contact with the skin.
  • Pull the plant up by the roots.
  • Place dead plants in garbage bags or bury them very deep in the soil.
Never compost or burn poison ivy. Inhaling the smoke from the burning plant material can cause a severe pulmonary reaction.
Find out more on the gouvernement du Québec website

Common Buckthorn

Common Buckthorn is an exotic invasive species native to Eurasia, which mainly prevents Québec woodlands from regenerating. Its bark is brown with small lenticles (lines). Its leaves are oval or elliptical, green, and very shiny on the upper surface. It flowers and produces berry-like fruit over several months. The flowers are yellow or white, and the fruit changes from green to red to black. The shrub can grow from 2 to 8 meters tall.


Common Buckthorn can produce large quantities of fruit, ranging from 430 to over 1,800 berries, each containing several seeds.

Buckthorn seeds can remain dormant in the ground for up to three years. This means that even if the seeds fall on the ground, they can remain viable and germinate later, thus contributing to the plant’s continuous spread.

This reproductive capacity, combined with the fact that birds transport the fruit and spread the seeds, makes Buckthorn a highly invasive plant.


The presence of Common Buckthorn has negative impacts on fauna, flora, agriculture and the economy:

  • When the parts of the Buckthorn plant decompose (leaves, stem and fruit), they release a toxic compound called emodin. When large quantities of this compound accumulate in ponds, this can harm the health of embryos and cause malformations.
  • Due to its rapid growth, Buckthorn shrubs can quickly grow to tree size, thus blocking light – essential to other species in the same habitat – and suppressing their growth.
  • Its large root system competes for the water and nutrients in the soil, in turn affecting the reproductive capacity and hindering the growth of young seedlings of other nearby species.
  • Common Buckthorn also has negative economic consequences due to its capacity to spread quickly and form dense thickets on agricultural land, in forested areas and in natural areas.

There are several ways to get rid of Common Buckthorn:

  • Cut the shrub at the base as close to the ground as possible.
  • Dig out the roots to prevent the plant from growing back.
    • For small trunks, dig a hole with a 30-centimeter diameter (minimum) by hand around the trunk.
    • For big trunks, use mechanical machinery to dig a hole with a 1-metre diameter (minimum) around the trunk.
  • Monitor the area and do regular maintenance to remove any new seedlings.
  • When the stem or trunk is more than 5 cm in diameter, it is also possible to use the girdling technique. This involves removing a 5- to 10-cm strip of bark around the entire circumference of the plant’s trunk or stem right near the base, i.e. within the first 50 centimetres above the ground.
When there is a major infestation, the shrubs can be cut at the base and a herbicide applied on the stumps. However, it is important to note that the herbicide you use must be approved by the City and requires a permit.

You can write the Environment Division by email at foresterie@saint-lambert.ca to obtain specific advice on the best approach for controlling Buckthorn in your particular situation.

Emerald ash borer

The emerald ash borer (Agrilus planipennis) is an invasive insect native to Asia that threatens all species of ash trees.

Infested trees generally die after two or three years, but severely attacked trees may die in only one year.

Here are a few signs that might indicate a tree is infested. Note that the first signs will be exhibited at the crown:

  • Abnormal crown thinning, premature yellowing of foliage, progressive crown dieback, and dead branches at the top of the tree (1);
  • Unusual and heavy samara fruit production;
  • Growth of shoots in unusual places on the lower portion of the trunk (2);
  • Vertical cracks in the bark (3)and S-shaped galleries under the bark (4) caused by feeding larvae;
  • D-shaped holes in the bark where the beetle exits the tree (5);
  • Irregular notches in ash leaves caused by adult insects feeding (6);
  • Increased presence of woodpeckers, who feed on the larvae, and feeding holes.
Signes d'infestation - Agrile du frêne

It can be difficult to identify the signs of an emerald ash borer infestation. Some symptoms may be caused by other diseases.

If you suspect your tree has an emerald ash borer infestation, we recommend you consult a qualified expert (arboriculturist, horticulture specialist, forestry engineer, tree pruner, etc.). You can obtain a list of experts from the website of the Société Internationale d’Arboriculture Québec inc. (SIAQ) at www.siaq.org.

If 30% of an ash tree is suffering from dieback, the infestation is generally considered to be too far advanced to treat and save the tree by treatments such as TreeAzin®. This product can effectively control an emerald ash borer infestation, though it cannot guarantee the tree’s survival and must be repeated every two years.

The tree must be cut down between October 1 and March 15 to prevent the emerald ash borer from spreading. Outside this period, it is strongly recommended to avoid cutting down a tree unless it poses a potential danger, due to the high risk of spreading the infestation.

To cut down a tree, you must generally obtain a permit from the Town Planning, Permits and Inspection Department. They can be reached at 450-672-4444.

Find out more on the website of the Canadian Food Inspection Agency

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