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Lawn pests and diseases

White grubs, root feeders insect pests, can cause damage to the lawn
Photo: Jean-Michel Bernard
White grub

Even with an organic lawn, you may encounter problems such as lawn pests and diseases. In any case, take the time to identify the source of the problem. The damage may simply be the result of poor growing conditions, like compacted soil, close mowing, thatch build up, deicing salt or even dog urine, and not due to insect pests or disease at all. In most cases, changing your growing methods is usually enough to allow your plants to adapt to the various stresses in their environment.

Insect pests

Two groups of insect pests may be found in your lawn:

    • root feeders (white grubs and sod webworms)
    • leaf and stem feeders (hairy chinch bugs, etc.).

Damage caused by insects is first noticed in irregularly shaped patches of yellow grass of varying dimensions. Here are a few tips that can help you to detect their presence.

If you tug on the grass where it is damaged and  a clump of sod lifts up, you can be fairly certain that white grubs are involved. The damage generally appears in May and June and in September. If the grass pulls out like hair, sod webworms are probably responsible (grayish-beige larva, generally in August and September).

In hot and dry weather, in June and July, watch for hairy chinch bugs. An easy way to find them is to vigorously rub the yellowed grass patches during hot, dry and sunny weather. Little orange, black or red insects will rush about on the rubbed surface.


Although not common, most of serious grass diseases are caused by microscopic fungi and a precise diagnosis is essential in order to determine how to attack them. Watch carefully for the signs and symptoms left by the disease (wet, discoloured or brown patches, presence of mycelia, etc.).

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