The Online Gardener's Handbook
Chapter 7: Lawns
Insect Control on Lawns
Table of Contents
- Hairy Chinch Bugs
- Turfgrass Scales
- Bluegrass Billbugs
- 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
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
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,
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.
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
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
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
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
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
Plant endophyte-enhanced cultivars of perennial ryegrass, tall
fescue and fine fescue, as these varieties resist webworm feeding.
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.
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.
Plant endophyte-enhanced cultivars of perennial ryegrass, tall
fescue and fine fescue, as these resist billbug feeding.