March 2009
How to fix the top 10 lawn problems
And keep them from coming back
Tougher, more resilient grasses and better ways to fend off crabgrass and other weeds and pests should make it easier than
ever to get a lush, healthy lawn. So why do so many people still have lawn problems--and how do you get rid of them?
We asked our on-staff experts and turf scientists across the country to identify some of the most common lawn weeds, pests, and diseases nationwide, as well as the most common mistakes homeowners make in dealing with them.
Even if your lawn already makes the neighbors green with envy, you’re likely to face a few of those common lawn problems. Knowing how to handle them can mean the difference between working on your lawn and simply enjoying it.
The best way to keep your lawn looking great year after year is to fertilize, water, and mow it properly. While you’ll find a plethora of chemical herbicides and pesticides, the healthiest lawns resist weeds and pests without them. An online survey of our readers conducted by the Consumer Reports National Research Center (see “Growing Great Grass”) revealed what worked--and didn’t work--for them and their lawn services.
Crabgrass
Vigorous, adaptable, and fast-growing, crabgrass thrives best in lawns that are underfertilized and mowed too low. Controlling
it isn’t hard, but timing is crucial; many homeowners apply pre-emergence herbicides in late spring or summer, when it’s too
late for them to do any good.
The remedy: Instead, apply corn gluten meal, a natural option, in the early spring. It helps prevent crabgrass and fertilizes. Your local cooperative extension or nursery can tell you the best time. Check our Web site at www.GreenerChoices.org/lawn-care for more advice. Then keep crabgrass at bay by feeding the desirable grasses with ample water and fertilizer--and by mowing high.
Products with dithiopyr, prodiamine, or pendimethalin are typical chemical alternatives. The EPA considers the latter two as possible human carcinogens, however. If you do use these, as with all herbicides and pesticides, be sure to wear rubber gloves, eye protection, long pants, closed shoes, and a long-sleeved shirt. And follow the directions precisely.
Dandelions
This perennial weed tends to thrive in thin lawns with too little fertilizer. Dandelions develop a long and thick taproot,
so pulling out just the flower isn’t enough. You must remove or kill the entire root, or the plant will resprout. And you
should do so before the flowers mature and spread their seeds.
The remedy: Use a specialized, fork-like tool to pull plants and taproots out by hand. While selective herbicides with a combination of 2,4-D, MCPP, and dicamba are effective chemical alternatives, the World Health Organization's International Agency for Research on Cancer (IARC) considers 2,4-D and MCPP possible human carcinogens. If you decide to use those broadleaf herbicides, apply them in fall, not spring. Use granular products on wet grass, liquids on dry (but not droughty) grass.
Other weeds
Dallisgrass, nimblewill, quackgrass, and tall fescue develop into unsightly patches and clumps. They’re likeliest to invade areas that are drier, wetter, shadier, or otherwise different from the rest of the lawn.
The remedy: There is no selective herbicide or other shortcut for those weeds. While glyphosate and glufosinate-ammonium are effective chemical remedies, the EPA considers glyphosate moderately toxic. What’s more, both chemicals require multiple applications and must be applied during periods of active growth.
Fungus
Experts agree: Fungicides are a waste of time and money. “By the time most fungus disease is obvious, the conditions that caused it have passed. So homeowners wind up treating the symptom--dead grass--not the cause,” says Zac Reicher, professor of turfgrass science at Purdue University. What’s more, that patch of dead grass is likelier to have been caused by your neighbor’s dog than by fungus.
The remedy: Fungus must be diagnosed and treated before grass begins to die--a challenge for most homeowners because it’s hard to spot or identify. Instead, look for typical causes such as too much water, improper mowing, and fertilizing at the wrong time of year. Then replant the dead area with a suitable grass type.
Moss
Spread by spores, moss is an attractive ground cover that many homeowners cultivate. But if you’re reading this, you’re probably
not one of them.
You can kill moss with a spray, but unless you change the conditions that encourage it, back it will come. A healthy colony of moss in your lawn means too much shade; acidic, compacted, or wet soil; or too little fertilizer.
The remedy: For very shady areas, reseed with shade-tolerant grasses such as creeping red fescue or St. Augustine and mow them high to maximize their light-trapping leaf surface. Also keep trees and shrubs properly pruned. For moss in low-lying or moist areas, water only when you see signs of too little moisture (when footprints in the grass remain and don’t spring back, for instance).
If the soil is compacted, have a pro aerate it using a piston-driven aerator. For poor drainage, be sure the area is properly graded. If trees, shrubs, or structures prevent you from regrading the area, use underground drainage pipes or create a sump drain--essentially a hole in the ground with a grate over it.
Also check the soil’s acidity, or pH, and adjust it as needed. Test it yourself using an inexpensive kit or meter, or bring soil samples to a nursery, cooperative extension service, or lab. Raise the pH of acidic soil with limestone, and lower the pH of soil that is too alkaline with sulfur, though the latter is a much slower process. Moss prefers acidic soil but will grow in alkaline soil if shade and moisture are favorable.
Too much shade
Most lawn grasses don’t like shade, even “shade-tolerant” varieties. While pruning most shade trees every three to five years is usually a good idea, pruning too often or too much can damage the tree.
The remedy: Replace lawn beneath trees with bishop’s hat, sweet woodruff, or other shade-tolerant ground cover as the tree grows and creates more shade. Then use shade-tolerant grasses at the edges of the area. Trim back high hedges. Azalea, Canada hemlock, common boxwood, flowering quince, Japanese boxwood, Japanese holly, lilac, myrtle, privet, rhododendron, roses, and winterberry can be cut back as far as needed. Shorten common hedges such as arborvitae, English laurel, firethorn, and Japanese yew only a few inches each pruning, and don’t cut into bare, leafless stems. The best time to prune either is in early spring, before the first flush of growth.
Compacted soil
Soil beneath most lawns eventually becomes hard and compacted, even if you prepared it perfectly before planting. The more you walk on the lawn, the faster the soil compacts. Once soil is compacted, water and fertilizer can’t reach the lawn’s roots, weakening them and allowing weeds to grow. But staying off wet lawns could help delay the inevitable.
The remedy: Soil, or core, aeration is the solution. But it’s a job best left to the specialists. Those professionals use piston-driven aerators with tines that move straight up and down, rather than the lightweight, less-effective aerators you’ll find at many rental yards.
Grubs
Those small beetle larvae live in the soil and feed on lawn roots. A few grubs aren’t a big deal. But too many cause irregularly
shaped sections to wilt and die.
Check for grubs by cutting into the lawn near the edge of a brown area and lifting the sod. If it comes up easily, like rolling up carpet, you’ve got grubs. Odds are, you’ll see those milky-white, worm-like creatures with brown heads and three pairs of legs curled into a C shape.
The remedy: Combine Heterorhabditis nematodes (sold in paste-like form) with water and apply to the soil in the spring or fall. Wait a couple of days and reseed or replant any damaged areas. However, chemical insecticides with imidacloprid or halofenozide aren’t effective on mature grubs. So if you choose to use one of those chemicals, apply it in July and August when grubs are immature.
Dog urine
Small brown spots surrounded by dark green grass is a telltale sign of dog urine. Nitrogen in the urine kills the grass in
the center, where its concentration is highest, while darkening the grass at the edges. Those spots are most likely to show
up during hot and dry weather, when lawns are under greater stress. Don’t bother with animal repellents; they’re of little
or no use, according to the experts we interviewed. A motion-activated sprinkler system might help discourage droppings, but
it won’t distinguish between dogs, deliverymen, and welcome guests.
The remedy: Spots of dead grass will often repair themselves eventually. For a quicker fix, cut out the dead spot and fill it in with plugs cut from a strip of sod. Bring a clump from your lawn to the nursery to match grass types. Or wait until grass-planting time--usually in the fall--and sow fresh seed after clearing away the dead grass and loosening the soil.
Moles
Those bothersome rodent-like critters tunnel through soil searching for earthworms, grubs, and ants. Moles tend to tunnel
closer to the surface in spring when soil is moist, leaving a zigzag trail of raised soil. A barrier of chicken wire that
extends 1 foot deep around your yard might help keep them out. But because moles can dig deeper than that and occasionally
travel short distances above ground, even barriers are only marginally effective.
The remedy: Trapping a mole is the only way to be sure you’re rid of it. While harpoon-type mole traps work best, handling them is risky and requires skill. Once you’ve spotted an active tunnel, you’ll need to depress the ridge of soil and set the trap over it; the mole will trigger the trap as it moves through the tunnel.
Bromethalin, the active ingredient in a new mole bait, is a chemical alternative to mole traps. What’s more, baiting is far more effective than home remedies, according to experts. On the downside, while the mole will die underground, eliminating the need for you to handle and dispose of it, you won’t know whether you’ve killed it.
An easier option: Hire a wildlife-control professional to handle mole problems.
We asked our on-staff experts and turf scientists across the country to identify some of the most common lawn weeds, pests, and diseases nationwide, as well as the most common mistakes homeowners make in dealing with them.
Even if your lawn already makes the neighbors green with envy, you’re likely to face a few of those common lawn problems. Knowing how to handle them can mean the difference between working on your lawn and simply enjoying it.
The best way to keep your lawn looking great year after year is to fertilize, water, and mow it properly. While you’ll find a plethora of chemical herbicides and pesticides, the healthiest lawns resist weeds and pests without them. An online survey of our readers conducted by the Consumer Reports National Research Center (see “Growing Great Grass”) revealed what worked--and didn’t work--for them and their lawn services.
| 1 |
The remedy: Instead, apply corn gluten meal, a natural option, in the early spring. It helps prevent crabgrass and fertilizes. Your local cooperative extension or nursery can tell you the best time. Check our Web site at www.GreenerChoices.org/lawn-care for more advice. Then keep crabgrass at bay by feeding the desirable grasses with ample water and fertilizer--and by mowing high.
Products with dithiopyr, prodiamine, or pendimethalin are typical chemical alternatives. The EPA considers the latter two as possible human carcinogens, however. If you do use these, as with all herbicides and pesticides, be sure to wear rubber gloves, eye protection, long pants, closed shoes, and a long-sleeved shirt. And follow the directions precisely.
| 2 |
The remedy: Use a specialized, fork-like tool to pull plants and taproots out by hand. While selective herbicides with a combination of 2,4-D, MCPP, and dicamba are effective chemical alternatives, the World Health Organization's International Agency for Research on Cancer (IARC) considers 2,4-D and MCPP possible human carcinogens. If you decide to use those broadleaf herbicides, apply them in fall, not spring. Use granular products on wet grass, liquids on dry (but not droughty) grass.
| 3 |
Dallisgrass, nimblewill, quackgrass, and tall fescue develop into unsightly patches and clumps. They’re likeliest to invade areas that are drier, wetter, shadier, or otherwise different from the rest of the lawn.
The remedy: There is no selective herbicide or other shortcut for those weeds. While glyphosate and glufosinate-ammonium are effective chemical remedies, the EPA considers glyphosate moderately toxic. What’s more, both chemicals require multiple applications and must be applied during periods of active growth.
| 4 |
Experts agree: Fungicides are a waste of time and money. “By the time most fungus disease is obvious, the conditions that caused it have passed. So homeowners wind up treating the symptom--dead grass--not the cause,” says Zac Reicher, professor of turfgrass science at Purdue University. What’s more, that patch of dead grass is likelier to have been caused by your neighbor’s dog than by fungus.
The remedy: Fungus must be diagnosed and treated before grass begins to die--a challenge for most homeowners because it’s hard to spot or identify. Instead, look for typical causes such as too much water, improper mowing, and fertilizing at the wrong time of year. Then replant the dead area with a suitable grass type.
| 5 |
You can kill moss with a spray, but unless you change the conditions that encourage it, back it will come. A healthy colony of moss in your lawn means too much shade; acidic, compacted, or wet soil; or too little fertilizer.
The remedy: For very shady areas, reseed with shade-tolerant grasses such as creeping red fescue or St. Augustine and mow them high to maximize their light-trapping leaf surface. Also keep trees and shrubs properly pruned. For moss in low-lying or moist areas, water only when you see signs of too little moisture (when footprints in the grass remain and don’t spring back, for instance).
If the soil is compacted, have a pro aerate it using a piston-driven aerator. For poor drainage, be sure the area is properly graded. If trees, shrubs, or structures prevent you from regrading the area, use underground drainage pipes or create a sump drain--essentially a hole in the ground with a grate over it.
Also check the soil’s acidity, or pH, and adjust it as needed. Test it yourself using an inexpensive kit or meter, or bring soil samples to a nursery, cooperative extension service, or lab. Raise the pH of acidic soil with limestone, and lower the pH of soil that is too alkaline with sulfur, though the latter is a much slower process. Moss prefers acidic soil but will grow in alkaline soil if shade and moisture are favorable.
| 6 |
Most lawn grasses don’t like shade, even “shade-tolerant” varieties. While pruning most shade trees every three to five years is usually a good idea, pruning too often or too much can damage the tree.
The remedy: Replace lawn beneath trees with bishop’s hat, sweet woodruff, or other shade-tolerant ground cover as the tree grows and creates more shade. Then use shade-tolerant grasses at the edges of the area. Trim back high hedges. Azalea, Canada hemlock, common boxwood, flowering quince, Japanese boxwood, Japanese holly, lilac, myrtle, privet, rhododendron, roses, and winterberry can be cut back as far as needed. Shorten common hedges such as arborvitae, English laurel, firethorn, and Japanese yew only a few inches each pruning, and don’t cut into bare, leafless stems. The best time to prune either is in early spring, before the first flush of growth.
| 7 |
Soil beneath most lawns eventually becomes hard and compacted, even if you prepared it perfectly before planting. The more you walk on the lawn, the faster the soil compacts. Once soil is compacted, water and fertilizer can’t reach the lawn’s roots, weakening them and allowing weeds to grow. But staying off wet lawns could help delay the inevitable.
The remedy: Soil, or core, aeration is the solution. But it’s a job best left to the specialists. Those professionals use piston-driven aerators with tines that move straight up and down, rather than the lightweight, less-effective aerators you’ll find at many rental yards.
| 8 |
Check for grubs by cutting into the lawn near the edge of a brown area and lifting the sod. If it comes up easily, like rolling up carpet, you’ve got grubs. Odds are, you’ll see those milky-white, worm-like creatures with brown heads and three pairs of legs curled into a C shape.
The remedy: Combine Heterorhabditis nematodes (sold in paste-like form) with water and apply to the soil in the spring or fall. Wait a couple of days and reseed or replant any damaged areas. However, chemical insecticides with imidacloprid or halofenozide aren’t effective on mature grubs. So if you choose to use one of those chemicals, apply it in July and August when grubs are immature.
| 9 |
The remedy: Spots of dead grass will often repair themselves eventually. For a quicker fix, cut out the dead spot and fill it in with plugs cut from a strip of sod. Bring a clump from your lawn to the nursery to match grass types. Or wait until grass-planting time--usually in the fall--and sow fresh seed after clearing away the dead grass and loosening the soil.
| 10 |
The remedy: Trapping a mole is the only way to be sure you’re rid of it. While harpoon-type mole traps work best, handling them is risky and requires skill. Once you’ve spotted an active tunnel, you’ll need to depress the ridge of soil and set the trap over it; the mole will trigger the trap as it moves through the tunnel.
Bromethalin, the active ingredient in a new mole bait, is a chemical alternative to mole traps. What’s more, baiting is far more effective than home remedies, according to experts. On the downside, while the mole will die underground, eliminating the need for you to handle and dispose of it, you won’t know whether you’ve killed it.
An easier option: Hire a wildlife-control professional to handle mole problems.
