Organic Lawn Problem Solver

Our lawn problem solver offers up safe solutions for lawn weeds, pests, and diseases.

November 26, 2010

Serious problems can arise even in a well-maintained organic lawn. Perhaps the soil is low in nitrogen after a dry summer, causing rust to creep up on the blades. Maybe moss is edging out the turf in a moist, shady area. Whatever the trouble, resist the temptation to blast your lawn with fungicide or insecticide. Though weeds, diseases, and insect infestations are certainly problems, they're also indicative of trouble within the lawn's natural ecosystem. Short- and long-term organic solutions are the safest way to keep your lawn—and yourself—healthy.

A few weeds are perfectly normal in an organic lawn. But a particular weed overtaking your grass is a sign your lawn isn't competitive enough, and you need to discover why in order to modify your lawn-care practices.

What Causes It

Clover, which pulls nitrogen from the air, appears where grass is sparse and the soil is low in nitrogen.

Fast fix: Till soil to remove clover; then add compost to the soil to increase its fertility. Reseed bare spots with grass.

Prevention: Apply a slow-release organic lawn fertilizer in fall and leave clippings on the grass all season.

Dandelions can appear anywhere in your lawn, especially where turfgrass is weaker.

Fast fix: Remove flower heads before they go to seed; dig out roots with a dandelion weeder.

Prevention: Apply corn-gluten meal (a natural "weed and feed") in early spring.

Crabgrass can sprout if you mow the lawn too short, allowing sunlight to germinate the weed's seeds.

Fast fix: Dig plants out completely before they set seed, and sow grass seed in their place.

Prevention: Raise your mower's blade to the highest setting and keep removing weeds from reseeded spots until new grass is established.

Broadleaf Plantain
Broadleaf plantain appears in compacted soil and anywhere grass has a hard time growing.

Fast fix: Pull plants out with a dandelion weeder and reseed with grass.

Prevention: Add compost to loosen the soil, discouraging the weed from returning.

Yellow Grass
This may simply indicate wear and tear, an iron or nitrogen deficiency, or that the grass is going dormant. Before attempting to treat one of these pest infestations, get your soil tested to determine whether organic soil amendments will green up the grass.

What Causes It

Billbugs lay eggs in grass, and their larvae feed on stems, causing yellow circular patches that appear drought-stressed.

Fast fix: Add organic matter and water deeply in spring to discourage billbugs.

Prevention: Reseed or overseed the lawn with resistant endophyte-enhanced grasses. (Check seed package labels for these special varieties.)

Chinch bugs
Chinch bugs suck the sap from grass, which causes yellow circular patches to develop.

Fast fix: Water the lawn well for three to four weeks to a depth of 6 inches.

Prevention: Reseed or overseed the lawn with resistant endophyte-enhanced grasses.


Bare or Ragged Patches
Heavy foot traffic or dog waste may be the culprit. If armyworms are truly the cause, you'll be able to see the pests eating your grass.

What Causes It

Armyworm larvae
Armyworm larvaechew grass blades down to the crown, especially during cool, wet weather.

Fast fix: Apply a solution of parasitic nematodes to the infested area; then water well. Bacillus thuringiensis (BT) is effective when the larvae are small.

Prevention: Rake out dead grass and reseed with endophyte-enhanced varieties.

Red Grass
This is a fairly reliable indication of disease; fortunately, both red thread and rust are easily diagnosed and treatable.

What Causes It

Red Thread
Red thread, a fungus that occurs during cool, wet weather, causes circular patches of dried grass.

Fast fix: Mow regularly to remove infected blade tips, and apply compost.

Prevention: Water deeply and provide regular, adequate nitrogen by leaving the grass clippings on the lawn.

Rust, a fungus afflicting drought-stressed, nutrient-starved lawns, causes reddish spores.

Fast fix: Mow regularly to remove infected blade tips, and leave grass clippings on the lawn.

Prevention: Avoid night watering, which causes a prime damp environment for spores to grow.

Whitish Grass
Unless you're striping the lawn for a football game, white grass signals trouble.

What Causes It

Powdery Mildew
Powdery mildew, which causes small patches of white or gray fungus on grass, is most common in shady, wet areas and on overfertilized lawns.

Fast fix: Spray a solution of one part milk to nine parts water over affected areas.

Prevention: Avoid overfertilizing and overwatering the lawn, and plant shade-tolerant grass in areas that get only partial sun.

Brown Grass
Before you call 911 on a lawn-threatening pest situation, keep in mind that brown grass is often a result of poor maintenance, site conditions, or summer dormancy rather than an infestation. Be sure your lawn isn't being mowed too short and that it is not suffering from soil compaction, drought, or nutrient deficiencies.

What Causes It

White grubs
White grubs chew on grass roots, causing irregular, brown, dead patches in the lawn.
Fast fix: Apply parasitic nematodes (genus Heterorhabditis) to the affected area; then water well.

Prevention: Apply milky disease spores, which parasitize Japanese beetle grubs and survive for several years.

Sod Webworms
Sod webworms cause dead spots by severing grass blades and pulling them into the ground to eat. They prefer new lawns.

Fast fix: Apply BTK about two weeks after moths appear, when pests are in their larval stage.

Prevention: If the problem persists, overseed with endophyte-enhanced grass varieties.

Shabby, Worn-Out Looking Lawn
If your lawn looks weak but you can't identify the cause, get out a ruler and check the depth of thatch. Less than a half inch of thatch acts like mulch. A deeper layer keeps water and nutrients from reaching the grass roots.

What Causes It

Thatch, a springy mat of grass roots and stems on the soil surface, is the result of excess fertilizer use. It is not caused by letting clippings fall onto the lawn.

Fast fix: Scrape out the thatch with a hard-tined rake (special thatch rakes are helpful but not essential).

Prevention: Spread a layer of compost on top of the soil to encourage earthworms to thrive in the soil and break down the thatch layer at the same rate at which it is being formed. Use slow-release organic fertilizers only.

These fungi are among the most difficult of lawn problems to get rid of, since they are signs of a fungal mat under the soil that grows outward.

What Causes It

Fairy Ring
Fairy ring appears in the grass first as dark green circles, eventually sprouting mushrooms that can deplete the soil's nutrients and form a water-repellent mat, causing the grass to die.

Fast fix: Dig out the mushrooms and turn the soil to a depth of 2 feet, mixing in compost as you go, to break up the fungal mat and improve the soil's fertility.

Prevention: Use good maintenance practices, such as discouraging thatch buildup by using only slow-release fertilizers, and watering deeply no more than once a week instead of giving your lawn frequent shallow sprinklings.

Low-growing, soft patches of green spongy growth are particularly common in shady areas.

What Causes It

Moss takes hold in poorly drained sites, often where the soil is acidic.

Fast fix: Rake off the moss and add compost to improve drainage. Reseed bare areas.

Prevention: If moss is persistent, plant a groundcover that thrives in damp, shady spots, such as violets or ajuga.

Though the ridges in the soil aren't harmful to your lawn themselves, they are usually an indicator of a problem underground. The raised areas are difficult to mow and they make your lawn uncomfortable to walk and play on.

What Causes It

Moles tunnel through your lawn to feed on grubs and earthworms, creating ridges and mounds.

Fast fix: Press mole ridges flat with the head of a rake to restore the roots' contact with the soil and even the area for mowing.
Prevention: Remove the food source, and the moles will seek it out elsewhere. In the case of grubs (see "Brown grass"), the best long-term control comes from milky disease spores, which come in a liquid form you apply as a drench to the soil.