Battle with Grubs
Q: How can I save my lawn from grass-eating grubs?
We have a Kentucky bluegrass lawn with a bad case of grubs. We've treated the grass repeatedly with a grub-control product, but the critters keep coming back. What do you recommend we do?
—Ruth Eversman, Chicago
Roger Cook replies: Grubs are the voracious, root-eating larva of June bugs and Japanese beetles, and are very difficult to control.
The first thing to do is identify the infested areas—you'll typically find them under dead patches of grass—and target only those areas for treatment. There's no need to waste money treating the whole lawn. Grubs tend to gravitate to hot, dry places, so lawns that face south or southwest usually have the most trouble.
Timing is critical. Treating a lawn too early or too late in the season greatly reduces the chemical's effectiveness. Where you live, late June is a good time to go after grubs because the treatment works best when they're feeding close to the surface. Keep in mind that most grub-control products must be watered into the soil within 24 hours of application or they lose their clout.
As an alternative to chemicals, try giving the area extra water, which will encourage the grass to grow, cool the soil, and discourage the grubs. If a small area is extremely sandy or stony, dig it out 6 to 8 inches deep and fill in with topsoil mixed with compost. This mixture may hold enough moisture to discourage the little grass munchers.
Biological controls like nematodes may reduce grub populations in sandy soil. Milky spore bacteria, another biological agent, attacks only Japanese-beetle grubs, and it takes a while to build up and become effective.
Here's another option: Dig up the infected lawn and replace it with a planting bed—a perennial or cutting garden, perhaps—which will handle heat and dryness better than grass.