KEVIN GUTTING Skunks will dig through turf looking for the grubs that lie just below the surface. Many of the grubs will eventually become Japanese beetles.

Pests conspire to ruin your yard

She was talking about the pock-marked patch of parched grass on her front lawn. There's a section of lawn, measuring about 10 by 20 feet, where the once-green grass has turned brown and brittle. I should have watered more, Perry had told herself when she started noticing it last month.

Then about two weeks ago, scratchy, golf-ball-size holes and piles of dirt started appearing here and there in the patch. Tufts of grass were being uprooted. First there were just a few holes, then every morning it seemed there were a few more.

Perry made some calls to local garden and nature centers. The problem, they told her, basically came down to this: Grubs and skunks.

Grubs - even the word sounds revolting - are the soft, thick, wormlike larvae that hatch from eggs laid below the soil surface by Japanese beetles. Grubs feast on grass roots. And skunks thrive on grubs.

One night Perry looked out the window and caught a glimpse of a skunk as he reconnoitered for grubs in her lawn. Though she's not happy about the holes he's made, Perry admits a grudging admiration for the animal's single-minded focus on his nocturnal project.

"I was more curious than anything else," she says.

Skunk on the hunt

Perry's plight is hardly uncommon at this time of year.

Every year brings in a stream of exasperated customers with questions about grub control, says Brian Kelly at Northampton Agway Supplies. It may not mean that there are more pests than ever, he said, but it certainly does reflect many a homeowner's obsession with having a nice lawn - Kelly included, a self-described "lawn freak" who says he'll probably lay down an insecticide soon in his own war against grubs. "I take no chances," he said.

KEVIN GUTTING Skunks will dig through turf looking for the grubs that lie just below the surface. Many of the grubs will eventually become Japanese beetles.

The grubs that are eating the grass roots of Jean Perry's lawn will eventually become Japanese beetles, the scourge of many a gardener in the Northeast.

As their name indicates, Japanese beetles were originally brought to this country from Japan; they were first detected in New Jersey in 1916.

Fully grown beetles usually emerge in early July. So sudden is the influx that it's almost like they're "oozing out the ground," says Tom Giles, owner of the Hadley Garden Center. And they're ravenous. The beetles start feasting on roses, raspberry bushes, grapevines, certain shade and fruit trees and many plants.

Those who have studied Japanese beetles seem hard pressed to say anything positive about them. They don't really do anything constructive at all, like destroy any other harmful insects, according to William Coli at the University of Massachusetts Extension Service. "There's no real benefit to them," he said.

About one-half inch long, the beetles have a metallic-green head and thorax and reddish-brown wing covers. Sometimes described as being gregarious by nature, the beetles will often congregate in hordes on plants they deem especially tasty. Gardeners determined to rid their gardens of the pests are often seen hand-picking the beetles off leaves and sending them to their deaths in cans of soapy water.

But no matter how many are destroyed, the chances are always good that some beetles will manage to burrow back down into the ground from whence they came to lay their eggs.

The larvae, called grubs, that hatch from the eggs will feed on grass roots near the surface, causing the grass to turn brittle and fade to a yellowish brown.

To check for the presence of grubs, Tom Giles of Hadley Garden Center suggests peeling back a piece of sod. If its roots have been eaten by grubs, the grass will tear off easily and you'll see the whitish round forms. It's best to test in several spots to assess the extent of the damage, says Pat Vittum, a professor of entomology at the University of Massachsuetts in Amherst. A dozen or more grubs per square foot, she says, is usually cause for action.

If the damage is serious, affected areas may need to be re-seeded in the fall. All is not necessarily lost, however, says Brian Kelly of Agway. A fertilizer with a high phosphate content to promote root development may bring the grass back, he said.

During winter, grubs hibernate about 3 to 12 inches below ground. Then in spring, the cycle begins again, as they work their way back up to the surface to emerge as beetles.

Skunks are especially active in summer when insects abound that are a staple of their diet, says Colleen Kelley, a science consultant at the Hitchcock Center for the Environment in Amherst. Besides insects, skunks will dine on such fare as mice, fruit, ground nesting bird eggs, frogs and salamanders. And a acute sense of smell is most likely what leads them to food, says Kelley - even to the tiny grubs below ground.

Their presence is actually sometimes welcomed, she says, because it means they're ridding an area of pests. In the meantime, though, as William Coli puts it, the destruction they cause in their search for grubs "can leave a lawn looking like it's been rototilled."

Options

Jean Perry's lawn indeed had those tell-tale signs.

As she discovered, there are several methods available these days to combat grubs:

KEVIN GUTTING Part of Northampton resident Jean Perry's lawn has been damaged by a skunk searching for grubs to eat.

The application of beneficial parasitic nematodes, or organisms that feed on grubs. Though they can remain effective for about two years, they work best if applied every year, according to Tom Giles at Hadley Garden Center. The cost is about $19 to cover 2,000 square feet.

Sprayed on in a liquid solution, the nematodes have no effect on humans, animals or plants and are compatible with beneficial insects such as ladybugs.

By far the most effective species is heterorhabditis bacteriaphora, according to Pat Vittum, the UMass entomologist. They can be applied up to about Sept. 15, she said - and they must be watered in immediately.

Milky spore disease, a naturally occurring bacterium that attacks Japanese beetles and certain other lawn grubs, is often billed as the environmentally friendliest way to get rid of grubs.

Milky spore is applied either in spot fashion - a few teaspoons of powder placed every few feet in a grid pattern - or with a spreader.

Depending on how it is applied, milky spore can require several applications and can take two to three years to get established. Once it is well-established, it can last up to 20 years, according to Giles. It is not a poison and will not affect humans, pets, food crops or birds. A 20-pound bag, enough to cover about 7,000 square feet, costs about $40.

There is a "but," though, and that is that there has always been some question as to its effectiveness," says Giles. Some people claim excellent results with it; others are skeptical of its usefulness. "It's still a controversial topic," says Vittum. And, adds Giles, it can be labor intensive to put down, especially if the project is done by sprinkling the powder by hand in the grid pattern.

Merit is a relatively new grub-control insecticide that is found in lawn care products, such as Grub B-Gon. However, it works best when applied earlier in the season, says Agway's Brian Kelly, rather than at this late date.

Halofenozide, a molt accelerating compound found in Grub-Ex, is probably effective up until about Sept. 5, according to Pat Vittum.

At this time of year, the most effective insecticide to treat a major grub infestation is probably Dylox, according to Giles and Kelly. "You want something that's fast and quick," says Kelly. A bag of Dylox that will treat a 5,000 square-foot area retails for about $22.

The best time to apply it, says Vittum, is shortly after Labor Day.

Whatever product you use, she says, remember to water it in well, at least one-quarter of an inch.

Weighing the choices

Jean Perry has considered her options, but hasn't decided yet on a course of action. Her instinct is to avoid chemicals as much as possible, she says, out of concern for children on her street.

The skunk, meanwhile, continues to do his work, though his pace appears to have slowed in recent days. "I think it's kind of fascinating," she says.

But fascination aside, Perry says she realizes that unless she takes some form of action, the grubs will rise up out of the earth next year as those detested Japanese beetles when early July rolls around.

Suzanne Wilson can be reached at swilson@gazettenet.com.

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