The Online Gardener's Handbook 2010
Chapter 7: Lawns
Insect Control on Lawns

Table of Contents

  1. Introduction
  2. Anthills
  3. Hairy Chinch Bugs
  4. Grubs
  5. Webworms
  6. Turfgrass Scales
  7. Bluegrass Billbugs
  8. Learn More


In this chapter, a description of various lawn pests will be provided along with suggested management options. These management options will not include the use of pesticides. Some biopesticides and certain reduced risk pesticides are still available to the homeowner for controlling weeds and pests in lawns and gardens. For more information, refer to Chapter 2 of this handbook and the Ministry of the Environment's website. For suggestions on managing specific weeds and pests, consult local horticulturalists, Master Gardeners or your local garden supply centre.


Anthills do make lawn surfaces uneven and can be unsightly, but they do not injure lawns. Specific treatments against ants are not necessary.

Management Options

None. Keeping grass higher will help keep anthills hidden.

Hairy Chinch Bugs

Hairy chinch bugs suck juices from grass, causing it to wither and die. Adults overwinter in protected areas under hedges, in flower beds or near foundations and begin laying eggs in late May and early June. They are visible in early August when they emerge to feed. Adults are quite small (5 mm). Their bodies are black and white, with reddish-brown legs and wings that fold over the back of the insect. The wingless nymphs are even smaller than the adults. They are red with a white stripe across their backs when first hatched in late June, turning grey as they begin to feed and grow through July.

In July, when weather is warm and dry, an infested lawn develops dead, sunken patches that seem to spread from hedgerows, trees or flower beds. Damage is most severe in August after continued hot, dry weather.

Chinch bugs are hard to detect early in the year. If you suspect that you have a problem, push a large can (bottom removed) into the lawn and fill it with water. The chinch bugs will float to the surface after a few minutes.

Management Options

Avoid fertilizing excessively, as chinch bug infestations often occur more quickly on lawns with lush growth. Watering will help suppress chinch bug populations. Cinch bugs prefer hot, sunny areas and may be less problematic if lawns are shaded with trees or shrubs. The cinch bug is also susceptible to some naturally occurring predators and pathogens, which may help reduce populations.


Grubs are the larvae of a number of different beetles that feed on the roots, rhizomes and crowns of grass. Their most active time is usually from September to the end of October; they resume feeding in the spring until the end of May and beginning of June, before pupating.

When irregular patches of lawn gradually turn yellow, then brown, and loose mats of dead or dying turf result, you should suspect a grub problem. Spring and early summer are often when the results of their feeding are observed, and when other animals dig up the lawn.

To examine for grubs, cut three sides of a 30 cm square and pull back the grass. If there are five or more grubs per square, or if the lawn is being dug up by skunks and small mammals feeding on grubs, you have a problem, and should consider applying an insecticide.

The June beetle larva, or white grub, is C-shaped with a brown head and three pairs of long legs. It requires three years to develop into an adult, and during this time it feeds under grass. The adult beetle is dark brown or black and 2.5-3 cm long. Large numbers of beetles can often be seen at night near lights in late May and early June, during which time females are laying eggs. They feed on the leaves of trees and shrubs, causing considerable damage to oak, maple and ash trees. Damage to the lawn can occur in mid-to-late summer of the second year when the grub has been feeding since early spring.

The Japanese beetle larva is similar to the June beetle larva but is only half as big when mature. It completes its life cycle in one year. The adult beetle, which is metallic green and bronze in colour, emerges in early July and the female lays its eggs in the lawn. It eats a variety of fruit, vegetables, trees and shrubs. Grubs hatch in mid-July, with damage occurring from early to late fall. The European chafer larva also resembles the June beetle grub, but it is smaller and completes its life cycle in one year. Adults are also similar, though the European chafer is smaller and lighter in colour. It does not feed on trees and flowers to any extent. The adult chafer swarms in trees on late June and early July evenings, when females lay their eggs in the surrounding lawn. Damage occurs from early to late fall. Infestations of chafers have been reported in most of southwestern Ontario, as far north as Barrie and as far east as Peterborough.

A grub infestation can be devastating, and a complete lawn renovation is often the best solution. Renovation could include cultivating the soil after killing or removing the turf, and then seeding or sodding. If working in an area with very little soil depth (often a problem in subdivisions), additional topsoil may be required.

This can be a very expensive and time-consuming task. In many cases, renovation may only require overseeding with newer grass cultivars that are more resistant to grub infestations.

There are no hard and fast rules as to when a lawn should be renovated, though for older lawns, renovation can often be very beneficial. Grubs may be a problem for several seasons, after which the grub infestation passes, or one very bad year can be enough to destroy your lawn.

Management Options

Once grubs have been detected, water and fertilize during warm, dry periods to keep lawn healthy and to compensate for root damage. Rake lawn after mowing to remove clippings, as excess thatch decreases stress tolerance and makes it more difficult for control products to penetrate. Mow grass a little higher to encourage root growth. Some species of parasitic nematodes have been shown in some studies to be effective in controlling white grubs. Apply nematodes after soil temperatures have warmed and use sufficient water to flush nematodes down into the root zone of the turf. Always check with suppliers for the availability of species and methods of applications. For nematode treatment to work, read the label very carefully and make sure that all the environmental conditions necessary are met.


Young webworms skeletonize grass blades; older worms cut them off completely. The lawn develops irregular brown patches, growing as damage increases. The first visible symptom resembles the damage done by grubs. With webworm damage, however, the dead grass easily pulls away in clumps, revealing masses of silk with bits of soil and green excrement. The silk is produced by the webworm caterpillar, a 2 cm long insect, with a dirty white body sparsely covered with hair and a dark brown head. Small, buff-coloured adult moths darting out of grass in late May and June warn that damage may begin to occur within two weeks, though damage is most common in early fall. A vigourous, healthy lawn can tolerate a considerable number of sod webworms.

Management Options

Plant endophyte-enhanced cultivars of perennial ryegrass, tall fescue and fine fescue, as these varieties resist webworm feeding.

Turfgrass Scales

Turfgrass scales are small, oval, 3-4 mm long, yellow-brown sap-sucking insects found in Kentucky bluegrass and red fescue lawns. Female scales lay eggs in cottony masses that hatch in late June and early July. Hatched crawlers are red and about the size of the head of a pin. In Ontario, this insect overwinters as mature nymphs. No serious damage is caused to lawns, although infested grass may green-up slowly in the spring, and crawlers leave red stains when crushed.

Management Options

None required.

Bluegrass Billbugs

Bluegrass billbug adults are black and 5 mm in length, with distinctive long curved snouts and boat-shaped posteriors. They are members of the weevil family. The larva, which is very small, legless and white with a brown head, feed on roots and crowns of grass plants, resulting in small patches of lawn turning yellow, wilting and dying. Large areas may turn yellow and die. A sawdust-like substance (frass) remains in the thatch to indicate their presence. Whereas the larvae feed on the crowns and roots of grass, adults feed on individual blades, giving them a shredded appearance. Damage occurs in July and at the beginning of August.

Management Options

Plant endophyte-enhanced cultivars of perennial ryegrass, tall fescue and fine fescue, as these resist billbug feeding.

Learn More

For more information:
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