Many lawns in Greater Vancouver are already showing signs of chafer beetle infestation this month, a little earlier than usual.
The larvae that develop from chafer eggs laid earlier in summer have developed quickly because of the mild weather and have fattened up and lie just below the surface of grass.
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Lawn damaged by crows and raccoons digging for chafer grubs
The grubs have been feeding on the roots of the grass and causing it to show signs of distress.
This has attracted the attention of crows that have begun pecking at the grass to find the grubs.
Skunks and raccoons have noticed the disturbed grass and joined the party, digging in the grass and yanking back turf to expose the white chafer grubs.
This problem is not normally seen until early spring, but this year it is appearing a lot earlier.
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Attempt to protect lawn by putting down plastic mesh
Sophie Dessureault, integrated pest management controller with the Vancouver parks department, says despite best efforts to treat lawns with nematodes – microscopic worms that feed on chafer grubs and infect them with a bacteria – the problem persists in many parts of town, including some parks and sports fields.
“The crows are intelligent creatures. They can quickly spot when grass is under stress.
“They can see even the slightest changes in colour due to an infestation. And they start by just popping by to check it out.
“If you see a couple of crows on your lawn pecking away, you know they are checking out the site for possible chafer grubs.
“If they find them, they will call down the whole gang and then you are really in trouble.”
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Attempt to protect lawn by putting down plastic mesh
In my neighbourhood in Burnaby, I noticed some lawns are very badly affected.
Some homeowners have put up images of owls and other predatory birds in a bid to scare away crows. It doesn’t work.
Others have covered their lawns with plastic mesh, staked over the grass, in an attempt to make it more difficult for skunks and raccoons to get to the grubs. It doesn’t seem to be working either.
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Perfect lawn only feet away from one ruined by chafer beetles
Other lawns close by are surprisingly unaffected and appear to be flourishing. Experts tend to agree that lawns that are well maintained, and where the grass is not cut too short, seem do better than neglected, unmaintained lawns.
Sophie Dessureault says experiments are continuing to see if thicker, more deeply rooted, tall fescue grass as well as lawns that comprise a mix of micro-clover and fescue grass are more resistant to chafer infestations.
Both these approaches seem to be somewhat successful.
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Chafer grubs in lawn
Treating lawns with nematodes during a two-week window of opportunity at the end of July is also a recommended treatment.
Spraying lawns with powerful pesticides such as Merit, although effective, is generally viewed as a negative approach because of the potential damage it can do to the bee population and environment in general.
The most realistic approach is for homeowners to allow crows and raccoons to do their worst and when they are finished to stomp back in place as much ripped up turf as possible and then to reseed in the spring.
From this point on, it is a matter of carrying out routine maintenance – fertilizing, watering, aerating and liming – and not cutting grass too short.
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