Insect pests and lawn issues

Check out the information below as well as the downloadable documents (on the left) and the town’s By-Laws.

Also known as the hairy chinch bug, this tiny insect attacks your lawn, piercing every blade of grass to suck its sap, which then kills it. When there are many of these insects in your lawn, irregular yellow patches of varying sizes will appear.

Generally speaking, damage becomes visible by late June though the time it first appears can vary depending on the weather, and if the season has been wet or dry. Unfortunately, by the time visible damage is significant (late July or early August), it is often too late to act because, by then, the chinch bugs have already reached the adult stage.

In fact, to keep the problem from intensifying, it is important to act at the larval stage, which is when these pests do the greatest damage. Although the larvae are quite small (no larger than aphids), they are visible to the naked eye; just spread the blades of grass apart in an affected area and look closely. The reddish colour of the young larvae helps you identify them in the lawn.

The following photograph, taken from the website of the New Brunswick Horticultural Trades Association, shows the five different larval stages, from the evolution of colours to the appearance of white wings in adults. Note that the two insects at the far right are shown for comparative purposes only, and are not harmful.

When the presence of the insect is identified early in the season, it is possible to effectively reduce its population. In fact, if you treat the chinch bugs at the larval stage, they will not have time to grow into adults and lay eggs. Furthermore, at this stage, they are much more sensitive to the effects of detergent than adults, which have a thin shell. If your property has been infested in the past, it is important to detect the presence of these insects early in the season (between late-May and mid-June) and, if needed, to apply a low-impact control product.

You will find below the different products that can be used between early June and late July to fight chinch bugs. Regardless of the treatment selected, it must be repeated at least 3 times at 5 to 7-day intervals. Furthermore, if it rains within hours after the treatment has been applied, it will have to be repeated.

Remember that, as the season progresses and the yellow patches grow, the effectiveness of the various treatments diminishes. At the adult stage (end of July, August), when the cinch bugs climb up foundation walls or the sides of the pool in quest of heat, a "Shop-Vac” type of vacuum cleaner can be used to eliminate as many of these pests as possible.

Various treatment options and their respective instructions:

Use the unit that connects to your watering hose and set the concentration level according to the product’s instructions. Do not hesitate to ask your nurseryman for advice, as needed. Note that, depending on the thickness of the stubble, for optimal results, dethatching may be necessary before applying the treatment.

  • Lemon Sunlight liquid dishwashing detergent, in a 5% to 10% concentration (i.e. 50 to 100 ml per litre of water): apply abundantly in late afternoon, on a warm, sunny day, to effectively reach all insects.


  • End-All or Trounce (pyrethrine) by Safer’s: apply very early in the morning or at the end of the day, after 6 p.m., or on a cloudy day. With End-All: water the lawn a few hours before using a formula that contains vegetable oil.


  • Neem: use 8 ml of the product plus 2 tablespoons of dishwashing detergent per litre of water: water the lawn a few hours before applying the mix. Apply abundantly in late afternoon, on a warm, sunny day, to effectively reach all insects.

Regardless of the treatment you use, since dead grass will not grow again, you would do well to thicken your lawn at the end of the summer by spreading seeds containing endophytes (ex.: Herbionik or Vert Éternel).

The best preventive measure remains the adoption of good gardening methods, since chinch bugs are particularly fond of short, overly fertilized lawns. If you have problems identifying the chinch bugs or don’t know what is causing the patches of dead grass on your lawn, contact the Town’s eco-consultant, at 450 621-4640, ext. 3305.

For additional information:

  • Lévesque Micheline, 2008. L’écopelouse – Pour une pelouse vraiment écologique. Bertrand Dumont Éditeur Inc. 192 pages.
  • Lévesque Micheline, 2005. Le guide complet des pesticides à faible impact et autres solutions naturelles. Isabelle Quentin Éditeur, Ville Lasalle, Qc. 214 pages.
  • Website of Health Canada

Have some of your perennials been ravaged by insects or disease? Before deciding on a treatment, you must first identify the source of the problem (what insect? what disease?) In many cases, you can reduce the presence of the destructive species without resorting to a low­-impact pesticide. This will allow you to spare a large number of other insects, which are beneficial to your garden, including some natural predators. If a treatment is necessary, before heading to the store, you should first check the Botanical Garden’s homemade formulas.

The following sources provide very helpful ideas:

Here are a few tips for identifying the most common diseases or insects:

The lily leaf beetle

The lily leaf beetle is an insect that attacks mainly Asian lilies and varieties of European lilies. Introduced in North America in the 1940s, in Montreal, it is easily recognized by its bright red colour and the many holes it leaves in your lilies.

You should keep a close eye on your lilies in early spring (early May) to eliminate adults that will lay eggs on your plants. The most effective and environmentally sound method is to remove the adults by hand before they can lay eggs and to either crush them or throw them in soapy water. Larvae then develop from May to early July, a critical period during which your lilies can be almost entirely devoured. As a last resort, if there are just too many beetles, you can sprinkle a rotenone-based powder on the lilies and their base in mid-May.

Black spots on rose bushes

Black spots on rose bushes indicate a fungal disease (diplocarpon rosea) whose scope can vary from season to season, depending on the temperature and more importantly, the humidity. Some rose bushes are much more sensitive than others. Before buying, get information on the rose bush you are considering.

Rose bushes planted in a dry location with abundant sunlight will be less vulnerable than those in the shade with wet bases. Watering also has a considerable impact: avoid watering the foliage of your rose bushes, particularly in the sun.

Some low-impact fungicides can be used, but they must be applied as a preventive measure, i.e., shortly before the spots usually appear.

One formula calls for mixing horticultural dormant oil and liquid lime sulphur (both from the Terre Verte company), according to the manufacturer’s instructions and applying the mixture before buds emerge in the spring, when it is not raining and there is no risk of frost in the following hours.

N.B.: Follow the instructions carefully when using dormant oil, since this product can be toxic to plants if not properly used.

The rose chafer

The rose chafer belongs to the bettle family, like the ladybug and the chafer. The damage it causes is visible as of June, when adults start to feed on the leaves, buds and roses.

The rose chafer is more likely to be present where the soil is rather sandy, although it can be found elsewhere. Check your rose bushes as of mid-June and knock the little pests off into a bucket of soapy water.

Contact the Town of Rosemère’s eco-consultant if you encounter a problem with rose chafers.

Powdery mildew

Not to be confused with "mildew", powdery mildew or oidium is also a fungal disease. It is visible on the surface of the leaves of various plants, which take on a powdery white look, hence the name. This disease primarily affects the aesthetics of the plant and no treatment is necessary. Sometimes, the problem arises because the plant is simply not in the right location, making it more sensitive. For example, a lilac bush that is not in the sun will certainly develop this problem. First, ensure that your plant is in the right location or choose species that are not sensitive to this fungus. If your soil is moist and shaded, avoid planting lilacs, Oswego tea, peonies and phlox.

Possible treatment: to keep powdery mildew on your plants to an acceptable level, take preventive measures before symptoms appear. These treatments should be applied in the spring, at two-week intervals. Try the Botanical Garden’s sodium acid carbonate, milk or horsetail infusion formulas.


Aphids attack several types of plants, like the rose bushes, linden, and lupine, to name but a few. They can be of different colours: black, green, or red.

You can detect an infestation of aphids by an increase in ant activity near the plant or, in the case of a severe infestation, by the presence of ladybug larvae.

Aphids have no shell, which can make them easier to control. On the other hand, they reproduce very quickly, which means that you have to act immediately. Nurseries carry a number of low-impact products for this purpose, but several homemade formulas can also reduce their population. Check out the Botanical Garden’s homemade formulas or purchase an insecticidal soap. Regardless of the treatment you choose, it should be repeated often at the beginning, in order to destroy the largest number of pests. If you have opted for an insecticidal soap containing pyrethrine, avoid using it in the sun.

Slugs (and snails)

Slugs hide during the day and are active at night. They favour moist areas with vegetation debris under which they can hide. Among the visible damage: holes in hosta leaves.

Ideally, you have to maintain an environment that is not conducive to slugs. Therefore, you should avoid watering close to flowerbeds at night and not leave too much vegetation debris under the plants. You can also raise the flowerbed to improve drainage, especially if the soil is heavy. To keep slugs at bay, you can regularly place pieces of eggshell or ashes at the base of the plants. Different types of slug traps are available, but if you are squeamish about handling the slugs, you won’t like emptying the traps!

As a last resort only, you can use a low-impact iron phosphate-based pesticide. 

The Japanese Beetle

The Japanese beetle (Popillia japonica) attacks a large number of plant species (approx. 300!), from perennials and annuals to shrubs and trees. It attacks vines, hibiscuses, malvas, viburnums, dahlias, and polygonums, to name but a few.

This insect is a beetle, which originated in Asia and is quite similar to the European chafer. Its larvae, which are also white worms, can damage grass roots and other vegetation, but the key difference with the chafer lies is the fact that the adult beetle is quite voracious, devouring plants in its path. While this beetle has not been observed as much here as it has in other parts of Québec, you could well encounter it in your yard at some point, since its proliferation has been constant in recent years.

To limit the damage it could potentially cause in our area, you should be aware that the adult emerges from the soil at the start of summer, around early July. This is the best time to install a trap containing pheromones as well as a floral fragrance, which can be purchased from most good nurseries. This trap must be installed far from vegetation favoured by the Japanese beetle (to avoid attracting more beetles to these plants), as of the end of June.

To better control this insect, remember to empty your traps weekly until early September.

Should you have other questions about pests and diseases that could ravage your garden or on the products to use, do not hesitate to contact the Town’s eco-consultant, at 450 621-3500, ext. 3305.


  • Lévesque, M. 2005. Le Guide complet des pesticides à faible impact et autres solutions naturelles. Isabelle Quentin Éditeur, Ville Lasalle, Qc. 214 pages.
  • Renaud, V. 2004. Parasites : les traitements bio. Éditions Rustica\ FLER, Paris, France. 80 pages.

Lawns ravaged by white grubs are a relatively new problem in Québec. Although more problematic in cities where the soil is quite sandy, it has proven to be a significant problem here in Rosemère as well, despite the fact that soil on much of the territory is rather clayey.

The insect that damages lawns is actually the larva of the European chafer, commonly known as the "white grub" as is the larva of the common June beetle, which is indigenous to Québec and the Japanese beetle, which was introduced here. You need a magnifying glass or binoculars to tell one type of white grub from another, although the one that has been seen to cause the greatest damage to lawns in the Greater Montréal area is the European chafer. Generally speaking, white grubs feed off the roots of several types of plants (grasses, deciduous trees and conifers), but they have a preference for grass roots, killing large patches of lawn. The number of grubs per square metre is not directly proportional to the damage visible on the lawn. In fact, the type of soil, the initial length of the roots, the presence of pests and the biodiversity of the soil can all have an impact on the intensity of the visible symptoms. Should you happen to come across white grubs while gardening, don’t worry; it doesn’t necessarily mean that your lawn is in danger…

The insect’s life cycle

In Québec, the adult European chafer emerges from the soil in mid-June, i.e., a few days before the Saint-Jean-Baptiste or when the catalpas are in bloom. It then mates in nuptial flights, between 8 and 10 p.m., after which the female will lay from 20 to 50 eggs some 10 cm below the surface of the ground. The eggs will hatch in July and the larvae (typically "C" shaped) develop slowly where they hatch, feeding off the grass roots. The larvae go from stage 1 to 2 towards the end of August and from stage  2 to 3 in October. As of stage 3, they begin to do the most damage. Before the first frosts, they burrow more deeply into the ground, where they hibernate. The following spring, when the ground warms up, the larvae (stage 3) move back towards the surface and become active again. At that point, they are quite large and attract skunks, raccoons and crows, who feast on them. Then, as mid-May approaches, they once again burrow more deeply into the ground where they become pupae (the nymph stage lasts approximately one month), which represents the ultimate transformation to adulthood. The cycle then starts over when the adult emerges from the ground and mates.

What can you do?!

If you notice damage from white grubs on your property in late fall or early spring, you’ll have to wait patiently until May to reseed the lawn, as soon as weather permits. It is very important not too wait too long because, by late May, the seeds of weeds are floating around, looking for bare patches where they can take hold. Ideally, to repair a damaged lawn, you should use an ecological seed mix containing a variety of grasses (ex.: hard fescue, chewing fescue, red fescue, Kentucky bluegrass, perennial ryegrass, etc.) to increase the biodiversity of your lawn. Some mixes contain a small proportion of white clover while others contain "endophytes", fungus toxic to some pests such as chinch bugs. Adding good compost (forest, vegetal, etc.) to your mix of soil and seed would also be beneficial when putting in a new lawn. Ask a consultant at your nursery about it.

If your lawn has been damaged by white grubs for several years, or if you have reason to believe that beetles have laid eggs on your property, you can detect the presence of larvae as of August. Simply lift patches of lawn at different places on the property and dig through the earth near the roots to locate the white grubs. But don’t look for large grubs… At this time of year, they measure no more than a few millimetres.

If you find several per square foot, you can opt for a nematode-based biological treatment. Sold in nurseries, you can apply this treatment yourself from early August to mid-September, or simply call on the services of a lawn care contractor. Bear in mind that the application of nematodes must be carried out by the book to ensure satisfactory results. Here are a few important tips:

  • Nematodes must be kept cool (never leave the box in the sun or heat).
  • Nematodes must be applied at the end of the day or on a cool, overcast day.
  • It is important to use the right type of sprayer (no filter, right size spout). The watering can or sprayer must be stirred throughout the application to oxygenate the solution (hydrated nematode powder).
  • Watering the soil 24 hours before application and for 10 consecutive days following treatment is crucial. To obtain a temporary watering permit from the Town Hall, present proof of purchase of your nematodes. Note that, in the event of a complete watering ban, it will not be possible to issue a permit.

Note: Nematodes are effective when all application conditions have been met (this includes 10 days of watering), when the temperature of the soil ranges from 15 to 22°C, and when the type of soil is adequate (not overly compact!) The effectiveness of the treatment is drastically reduced if either of these conditions is not met. Regardless of what you choose, make sure you follow instructions to the letter and if you have the slightest doubt, contact the eco-consultant at the Public Works Department.

The best means of prevention remains the adoption of good gardening methods, since grubs prefer to lay eggs in a shorter, sparser lawn. What’s more, if the lawn is healthy, the roots will be longer and more capable of withstanding a larger quantity of white grubs.

What about pesticides?

Chemical pesticides available in Quebec for fighting white grubs are all subject to municipal regulations. In addition, they can only be applied by contractors.

If you are still considering this option, however, you must first contact the Town’s eco-consultant at the Public Works Department. He will check out the damage, either in the fall or early spring, and will issue, if needed, a permit to spray insecticide. You must also be able to demonstrate (ex.: with bills) that you have used good gardening methods or a nematode treatment without success.

For additional information

Digger wasps, also known as sand wasps, can be found in growing numbers in parks, drawn by the presence of loose sand and heat. Their activity is most intense during a few days in July and is characterized by their comings and goings as they dig easily visible tunnels to lay their eggs.

Unlike other wasps, diggers are not aggressive and the risk of being stung by one of them is quite low. To date, no stings have been reported.

There is currently no ecological method for controlling these wasps. Aerating and sifting these appear to be the only way of reducing the size of the wasp population. Adding an extra layer of sand in playgrounds could also imprison them.

To avoid being stung, you should always wear shoes in parks and avoid disturbing wasps at work.

June is the time to start fighting the Japanese beetle. If your plants or those of your neighbours have been ravaged by this shiny little beetle with a voracious appetite, the time has come for you to purchase a pheromone trap from a nursery.

A tip: place it a good distance from your favourite plants and add a few geraniums or white pelargoniums to your landscaping, as these are toxic to the beetle. See our complete information sheet on perennial pests.

Warning: we are noticing the presence of a number of beetles that appear to be parasitized by eggs of the Istocheta aldrichi fly. This small fly, a natural predator of the Japanese beetle in its native country, lays its eggs on the insect's thorax and quickly kills the insect in this way.

If you catch Japanese beetles at home, take note that it can be useful to leave parasitized beetles on plants to help the population of this small predatory fly. Although the fly may not be able to control the entire Japanese beetle population, its presence to reduce the number of these beetles is encouraging!

What’s happening

  • Former Golf Course Dossier
  • New registration platform with Voilà! Rosemère
  • Send us your water meter reading
  • Roadwork-Info
  • 2021 Elections