Waging war on grubs
Can homeowners win the battle over the lawn-destroying invaders? Patrick Langston goes digging for answers.
By Patrick Langston, Ottawa Citizen
Photograph by: Jean Levac , Ottawa Citizen/Postmedia News
OTTAWA — Barry Biner has had a rough spring.
Last fall, the Manotick homeowner noticed dead spots on his lawn, but didn’t think much of it — grass goes dormant for part of the year, after all.
This spring, when the snow retreated, the horror show began. Crows, skunks and other marauders tore up half his lawn in search of white grubs, the insects that had produced those dead spots in the fall by consuming the grass roots. The grubs, having overwintered, were now back with a vengeance, killing even more grass where they weren’t picked off by animals turning over the sod in search of a tasty meal.
“I took it hard,” says Biner, who’s now faced with lawn repairs and reseeding costs of about $6,000. “If I’d had a shotgun, I would’ve shot the crows.”
Homeowners across Ottawa feel his pain.
“It’s not just a bad year — it’s a horrendous year. We’re inundated with calls,” says Thom Bourne, owner and general manager of Nutri-Lawn in Ottawa.
He says the grub problem is the worst he’s seen in his 24 years in business and that European chafers, an invasive species, are producing most of the damage.
“I go to a lot of meetings,” says Bourne. “Usually people talk about their kids. Now it’s grubs.”
So what’s causing the invasion and can homeowners do anything about it?
Know thy enemy
First some background.
Grubs are the larvae of the European chafer, June beetle and Japanese beetle (the latter is mostly restricted to southern Ontario). Two to four centimetres long with pale, wrinkly C-shaped bodies and six spiny legs, they’re something only a mother could love.
The grubs that have attacked Biner’s property started out as eggs laid in the grass last summer. The eggs hatched in August and the larvae started feeding on the grass roots, causing only minor damage when small but growing quickly and eating more.
When the cold weather arrived, they burrowed into the soil only to return and begin feeding in the spring before the snow melted. They were hungry and, it turned out, so were the skunks, racoons and other animals.
Those that have survived the animals will soon pupate into flying insects, mate and lay eggs to start the nasty process over.
There are no statistics on how many Ottawa lawns have been damaged, but anecdotal reports suggest that on some streets the majority of homes have been hit to varying degrees.
Province-wide, severe grub damage has occurred in pockets, says Pamela Charbonneau, turfgrass specialist with the Ontario Ministry of Agriculture and Food/Ministry of Rural Affairs. Orillia and Barrie seem especially hard hit this year, she says.
Why the spike in grubs?
Some blame the province for banning, in 2009, the use of most pesticides for cosmetic purposes, like killing weeds or grubs in lawns, parks and other areas. No pesticides, they say, means more pests.
However, insect outbreaks are never a simple affair, according to Jeremy McNeil, a visiting professor in Western University’s biology department.
Last summer’s drought left grass weakened and more susceptible to serious damage from munching larvae.
A heavy snow cover this winter meant the ground stayed relatively warm and more grubs may have survived.
“Like most insect outbreaks, you need a particular combination of ecological conditions,” says McNeil. Grub outbreaks tend to be “sporadic, not cyclical.”
What’s the solution?
“Grubs are going to be with us for a while,” says Charbonneau. “The tools in our tool box are pretty limited.”
Beneficial nematodes — parasites that kill young grubs — are a popular tool. They are considered a biological, or naturally occurring, pesticide and therefore not subject to provincial bans.
Lawn companies apply nematodes (Nutri-Lawn charges $130 to $150 for an average sized lawn), or homeowners can do the job themselves: $30 worth at Ritchie Feed & Seed, for example, will do a 3,000-square-foot lawn.
In either case, homeowners need to water the lawn before application so the nematodes don’t dry out and again after to wash them into the soil.
They are applied in August or early September and the grubs die within a week of application. Annual applications are recommended.
Charbonneau says that even under the best conditions, nematodes kill only about 50 per cent of the grubs.
She says that fungi, bacteria and other biological pesticides currently being developed may prove effective against white grubs. New grasses may also be more resistant to the grubs.
Rebecca H. Hallett, who teaches in the University of Guelph’s School of Environmental Sciences, says a healthy lawn can better resist grub damage.
She says watering a lawn thoroughly once a week promotes root growth that sustains grass during attacks.
Setting your lawn mower at three inches also helps: chafers and other pests prefer to lay their eggs in short grass. As well, longer grass reduces evaporation from the soil, a bonus for lawns during droughts.
Gazing into the crystal ball
The warmer winters caused by climate change could mean a higher survival rate for grubs, says Hallett. On the other hand, “the eggs are laid mainly in July and they tend to die if the weather is too dry, so if we continue to get dry summers populations may decrease.”
Bottom line: no one really knows what will happen in coming years. In the meantime, a combination of nematodes and good lawn management seems the best way to battle the grubby little beasts.