Not only do lawns provide a soft green mat to walk on, play on, lie on, or just admire, they also provide an excellent breeding ground for unsightly weeds, militant insects, and grass-destroying diseases. Grassy carpets can become battlefields where we combat one or all of these lawn-destroying elements.
Infrequently, the cause of our sickly looking lawn cannot be blamed on weeds, pests, or diseases. Rather, it’s the result of a physical or mechanical ailment, such as deep shade or soil compaction.
Weeds—The Lawn Spoilers
Technically, weeds are annual or perennial plants growing where they are unwanted. As long as soil provides the necessary environment for plants to grow, weeds will grow too. Most soils already contain dormant weed seeds which only need the right germinating conditions to sprout.
You may wonder why last year’s weed-free lawn has weeds in it this year. Where do the weed seeds come from? First, lawn seed is never 100 percent pure; all lawn seed comes contaminated with some weed seed. Gusty winds can disperse weed seeds for miles. And seed-dropping birds and foot traffic also aid in weed infestation.
Weeds are classified into two groups: broad-leafed weeds and grassy weeds.
The Broad-leafed Weeds: The term “broad-leafed weeds” describes all weeds that are not grass-like. Many of these broad-leafed weeds, like chickweed and spotted spurge, have leaves only the size of large freckles.
Grassy Weeds: Any grass that destroys the even texture and uniform color of a lawn is considered a weed grass. The list of these grassy weeds is long. Some of the most common grassy weeds are annual bluegrass, Bermuda grass, crabgrass, dallisgrass, quackgrass, and rye grass. With the exception of Bermuda grass and quackgrass, you can pul grassy weeds by hand or with a steel weed knife. To combat the more tenacious grassy weeds, you can choose from an assortment of chemical weed killers.
Crabgrass—king of grassy weeds: True crabgrass is king of the grassy weeds. But gardeners everywhere often mistake other grassy weeds for crabgrass. This frequently results in the use of crabgrass-killing chemicals on weeds that won’t be fazed by them. On the other hand, if your lawn really is infested by crabgrass, you should learn how to recognize it and how to get rid of it.
What is crabgrass? Hair crabgrass (Digitaria sanguinalis) is a weedy annual that infests turf areas, lawns, and landscapes. Seeds germinate as early as February in warmer areas, continuing through summer. Small seedlings grow 2 to 4 leaves that finally form large, flat, stem-rooting, weedy clumps in summer. Mature, pale green blades grow 2-5 inches long and 1/3 inch wide, with undersides covered in coarse tiny hairs. Fingerlike flower spikelets arise from 2-6 inches-high narrow stems. The flowers seed heavily, so immediate eradication of the weed is necessary to prevent a crabgrass infestation next year. To control, hand pull the crabgrass or use a specified crabgrass control.
Smooth crabgrass (Digitaria ischaemum) resembles hairy crabgrass, but grows smaller and is not as hairy.
Bermuda grass, a very deep-rooted and invasive grass, is groomed as a lawn in many of the warmer southern regions of the country where it thrives. But Bermuda grass is considered a weed in a cool-season grass lawn. Try pulling out isolated sprigs before roots establish a deep foothold. If the weed infestation gets ahead of you, spot treat the weeds with dalapon—one of the proven chemical controls for Bermuda grass.
Quackgrass flourishes in cool, moist, or dry climates and in almost any soil. It’s a perennial that grows flourishes in cool, moist, or dry climates and in almost any soil. It’s a perennial that grows from scaly rhizomes. A rhizome is a thickened underground stem that spreads by creeping. With quackgrass, these rhizomes branch at almost every node, forming a dense root mass for which the plant is notorious and despised. Any small piece of rhizome left in the soil will grow a new plant. Do not let this grass go to seed, as the seeds are long lived and may lie dormant in the soil for as long as 2 to 4 years, then will suddenly sprout new plans. Leaves are dark green in most climates; in dry areas they are covered with a whitish bloom. The portion of the leaf that sheaths the stem is oten hairy. Hand pick quackgrass from lawns and dig rhizomes from the soil, or treat them with a specified chemical control.
Controlling Weeds
Compared to the old days when every lawn weed had to be removed by hand, prying tool, or steel weed knife, today chemical weed controls simplify the work. Of course, if weeds are scarce, hand pulling with a weeding tool is still a good way to eradicate weeds.
If you use a chemical that kills weeds as they germinate, don’t expect it to work unless you cover every inch of soil. Do not spray selective weed killers in the wind—wait for the wind to stop, then apply the material.
If you use a weed killer that is absorbed by the leaves of weeds, do not apply more than the directions call for. Overdoses may burn the leaves and prevent proper movement of the chemical down to the root system.
It is most important to note that the weed killers mentioned are common chemical names and not brand names. Any weed killer you purchase should have the chemical name, the specific weeds it will kill, and the types of grass you can apply it to listed on the label.
Whatever type of weed killer you decide to use, remember to explicitly follow the directions on the container label.
Weed Killer Applicators
Fortunately there are many ways to apply weed killers. You may use applicator wands designed for spot application for chemicals to individual weeds, or trigger-type squirting oil cans.
Hose-end applicators, available in several styles, can be attached to a garden hose for applying water soluble chemicals. Apply these chemicals at low water pressure so as not to wash all the weed killer off the leaves.
Pressure spray tanks and simple watering cans are excellent devices for applying weed killers. Unfortunately, once they have been filled with a weed killing chemical, they should not be used for any purpose other than weed eradicating.
Dry fertilizer spreaders provide an efficient means for applying dry or granular weed killers.
Pests—The Garden Intruders
Lawn-damaging pests fall into two main groups: those that feed on leaf blades and other above-ground lawn parts, and those that feed on roots and other below-ground parts of grass plants.
Above-ground Pests: Armyworms, cutworms, sod web-worms (lawn moth larvae), skipper larvae, leafhoppers, dichondra flea beetle, frit fly larvae, Bermuda mite, slugs and snails, and chinch bugs (the latter in eastern states) feed above ground. To get rid of those you irst water the lawn, then apply the right insecticide. After this, leave the lawn alone for a few days to allow the insecticide to do its job.
Below-ground Insects: White grubs, billbug grubs, Japanese beetle grubs (mostly in eastern states), and mole crickets are below-ground lawn pests. To rid your lawn of these, apply the correct insecticide and then drench your lawn with water. The water will carry the insecticide down deep to the root zone of the lawn where the menacing insects live.
Choosing the Right Insecticide
Unfortunately, the best method to control lawn insect infestation is through the use of insecticides. Selecting the correct lawn insecticide is easy. Diazinon insecticide works on most turf insects above or below the ground. The following insecticides work on one or more of the lawn-damaging pests: diazinon, dursban, kelthane, malathion, metaldahyde, or mesurol.
Insect Symptoms, Causes and Control
In the paragraphs below we describe the damage caused by leading lawn pests, and effective insecticides to use against them.
Irregularly shaped brown areas: armyworms or sod webworms. Most lawns, no matter what their age, are susceptible to attack by armyworms or sod webworms. These worms feed on grass crowns and bases of blades. In warmer climates they can destroy whole lawns. To control these invading insects, treat them with diazinon spray or granules, or with dursban spray or granules.
Dead spots 1 or 2 inches in diameter, with grass chewed below the mowing level: cutworms. This pest makes a hole about the thickness of a pencil, leading down into the roots. To control the chomping creatures, apply spray or granules of diazinon or dursban.
Orange, brown, and yellow butterflies fly over the lawn during the heat of the day: fiery skipper. Symptoms other than butterflies are isolated round deadspots, 1-2 inches in diameter, eventually fusing and killing large areas of the lawn. Small brownish-yellow worms may be inside and underneath the patches of dead grass. Sometimes white cottony masses show in the lawn. These cottonlike masses are the cocoons of a parasite that preys on the larvae of the skipper. If this biological control is not apparent in your lawn, then apply diazinon in spray or granules.
The following test will tell you definitely whether your pest is just one or a combination of armyworms, sod webworms, cutworms, fiery skipper, or something else.
Mix 1 teaspoon of liquid detergent Vel (University of California at Davis has tried other detergents, but for some reason Vel works best) in a sprinkling can of water. If gray worms or caterpillars wiggle to the surface within 10 minutes, your lawn is infested with any of the above. In matted bent grass, it may take longer for the webworms to appear.
Dead grass in defined patches: white grubs or billbug grubs. Pull on the grass. If it comes up like a wet doormat, it’s probably victim of white grubs. You may even find some grubs underneath the grass that you pull—u-shaped grayish white worms shaped much like fat shrimp. If you are not squeamish, you can hand pick the worms and know that you’ve dealt with them in the most direct way. Replace the mat of brown grass. It may replenish itself from the roots in a few weeks.
For chemical control use diazinon or dursban for white grubs. After applying the chemical treatments, water the lawn heavily. This helps leach the chemicals into the ground where the larvae eat.
Central shoots of grass plants dead: frit fly. The small black frit fly produces four generations of larvae a year. The spring and fall larvae live in young grass stems, eating and eventually killing the central shoots, causing the plant to send out side shoots. Some species of grass are very susceptible to this pest. Control the frit fly larvae with diazinon spray or kelthane.
Tufting and yellowing of Bermuda grass, accompanied by skin irritation when touched: Bermuda mite. Spray with diazinon.
Grass seedlings uprooted, young grass blades severed from their rots: mole crickets. These tiny creatures freeload in moist, light soils of newly seeded lawns. Burrowing into the ground, using their shovel-like front legs, they destroy seedlings as they excavate. To control mole crickets, spray with diazinon.
Slugs and snails on the grass at night. Use mesurol or metaldehyde, or metaldehyde plus sevin. Apply this snail bait in the evening to a sprinkled or damp lawn. The moisture on the grass brings the snails and slugs out and activates the bait.
To control leafhoppers, apply diazinon or malathion spray; use dursban or malathion spray to check flea beetles in dichondra, and chinch bugs in St. Augustine lawns.
Gophers and Moles
The success of a campaign to rid your lawn and garden of these pests often depends more on perseverance than on the type of control you use. The three controls used most frequently are the trap, poison, and gas.
Gophers are slipshod excavators. Their mounds are irregular, often fan shaped, the hole located where the handle of the fan would be. The hole is usually plugged up, but is still discernible.
Moles throw up round, conical mounds composed of loose chunks of earth from their main runs. They force plugs of earth up to the surface, but they do not open the tunnel. The ridges you see in your lawn where soil has been raised are hunting paths, and they are seldom used more than once.
Traps. Traps have two outstanding advantages over poison or gas—you actually see the dead gopher or mole, and trapping is the safest method of control. The Macabee trap is considered the most successful for gophers. The lateral-jawed type is most effective for moles.
Poison bait. Though less reliable than trapping, poison bait is the control preferred by many people because it requires less digging. Also, you can cover large areas faster with bait than with trapping. Pieces of vegetable rot or dried prunes dusted with powdered strychnine are very effective in poisoning gophers. For moles, dried fruit, vegetables, and grain baits with thalium sulfate as the toxic agent have proved to be highly successful.
Gas. Under certain conditions (damp, tight soil; limited runway system), gas either destroys gophers and moles or causes them to move out. It is more expensive than bait. Gasses that have been used successfully on gophers and moles include calcium cyanide, methyl bromide, carbon monoxide, and carbon disulphide.
Lawn Diseases
Often a well-maintained, vigorously growing lawn, supposedly free of insects and other pests, will suddenly turn yellow in random spots and begin to die. If this seems to be the problem in your lawn, it probably has a fungus disease.
A fungus disease is composed of microscopic, threadlike plant life. Fungi cannot produce their own food, so they live off dead or living plant matter. Lawns and their clippings seem a delectable favorite of certain kinds of fungi.
Good Turf Management
Before you decide to apply a fungicide to remedy your yellow, browning lawn, learn to diagnose its trouble.
Professional turf managers first decide if the watering and feeding schedule has been adequate.
Lack of water makes grass turn limp, then dull or smoky green; ultimately it will die. Lack of nitrogen makes grass turn yellowish or pale green. It grows slowly and becomes thin. Lack of either or both of these two essentials can lay a lawn open to all kinds of secondary troubles, including an array of fungus diseases that can ultimately cause death to lawns.
Most of the disease and physical troubles of lawns become apparent by persisting after the lawn has been adequately watered and fed with nitrogen.
When Lawns Look Sick
If your lawn has been watered and fertilized consistently, and still appears sick, then it’s time to examine it for disease.
Rarely does a lawn fungus show the classic symptoms that make identification easy, allowing you to proceed with the specific fungicide cure.
Usually when you inspect a sick lawn and compare its symptoms with book descriptions of fungus diseases, you’ll find that your lawn fungus could have all or none of several symptoms—“brown patch,” “melting out,” “grease spot,” “fusarium patch,” “red thread” or “snow mold”—because the symptoms overlap.
Preventing Disease
Lawn fungus is much easier to prevent than to cure. The best way to avoid fungus diseases is to plant the grass that is right for the particular climate and surroundings in which it must grow.
Next, care for your lawn with a regular routine of maintenance. Most fungi thrive in constant moisture, so water your lawn deeply yet infrequently. Thatch build-up aids in poor drainage and causes water runoff. Dethatch lawns with a thatch cutting machine as needed. Fertilize lawns monthly during their growing season. A healthy lawn will withstand fungus much better than an unhealthy one.
Disease Control
Unfortunately even the greenest and healthiest of lawns can become infested with a fungus disease. When this happens, there are two choices of control: cultural control and fungicidal control.
A cultural control is the best method of control. It includes all good practices of lawn maintenance: deep irrigation, weekly mowing, seasonal fertilizing, thatch removal, and annual weeding. Cultural control can sometimes stretch as far as pruning trees or moving shade-causing structures in order to admit more light to a shaded lawn.
A fungicidal control is the least desirable but often the surest type of control. It checks fungi and its progress only through the use of chemical treatments.
Information accredited to Sunset Lawns & Ground Covers. Page 20-24.
