Lawns & the Environment

John Dolley

Did You Know?

• As much as 62,000 square miles of the Continental U.S. are covered with turf grass, an area larger than the state of Georgia.

LAWNS & THE ENVIRONMENT

–by Erik Bliss, formerly with City of Austin Watershed Protection Department

Nearly everyone wants to have a healthy, attractive lawn. Right? Unfortunately, in their quest for a beautiful lawn, some homeowners go a little overboard with the fertilizers and pesticides. In fact, urban lawns typically have more of these chemicals applied per acre than agricultural cropland.

Overuse or misuse of these chemicals is not good for your lawn or the environment. So get smart about your lawn care, and learn to take care of your yard so that problems are prevented before they start. Take a few minutes to read about an environmentally-beneficial approach to lawn care and pest management.

LAWN CARE

A well cared-for lawn can overcome most disease and pest problems; therefore, make sure your plants are receiving the proper amount of light, water, and organic nutrients. Often improper cultural practices are at the root of a recurring pest problem. Don’t rely on chemical pesticide applications as a substitute for properly caring for your plants. Following are some tips on the best way to have both a healthy lawn and environment.

Take Care of Your Soil

Healthy soil is the best defense against pests and disease.  Plants get nutrients from soil, so the soil must have the right biological, chemical, and physical makeup.  Healthy soil will have lots of organic matter and a diverse population of beneficial microbes.  You should treat your soil as a living organism. If you suspect your soil may be lacking, send a sample to a soil testing service (call the County Agricultural Extension Service for more information).

Topdress Your Lawn

All lawns, especially those that have been neglected or treated only with synthetic chemical fertilizers, will benefit from a regular application of rich organic matter. This organic matter will usually be a bulky material, such as humus, or compost.  Experts recommend spreading a 1/4″ to 1/2″ layer of this valuable soil amendment over the top of your lawn. (500 pounds of compost per 1,000 square feet· yields a 1/2″ layer.) This method of fertilizing is called topdressing. The organic matter will increase the fertility of your lawn by: l) providing “slow-release” nitrogen to the roots of your grass; 2) helping to balance mineral content and buffer soil alkalinity; 3) enhancing the growth and development of beneficial microorganisms in your soil; and 4) improving the structure of the soil.

Soil, just like your body, benefits from a regular dose of vitamins and minerals. Adding organic matter regularly is a safe approach to supplying the types of nutrients that your soil needs. Compost will also tend to moderate the high pH factor of our local soils, which tend to be alkaline, since they were derived from limestone. Alkaline soils have a pH above7.0. Irrigating with potable water will also tend to make the soil more alkaline, since our water tends to have a high pH.

Organic matter supplies raw materials to earthworms and naturally occurring bacteria, fungi, and other microorganisms in the soil. These organisms form a relationship with your plants’ roots that is mutually-beneficial. They assist the plants’ ability to gather nutrients and water (thereby enhancing drought resistance) and boost the plants’ natural immune system. Enriching the soil with organic matter also improves soil structure, which in turn improves the soil’s capacity to hold water and nutrients. Regular use of organic matter will lead to healthy balanced soil that will require less irrigation, and will support plants that are more tolerant of insect and disease problems.

Lawn Aeration and Dethatching

Aerate your soil by punching a lot of deep holes in the lawn using a special tool. These engine or hand-powered tools can be purchased or rented at most lawn and garden centers. Try to do this at least once or twice a year. Aeration revives hard packed soil, allowing water and air to enter and exit.

Thatch is an accumulation of dead, compacted roots and stems that collect at the soil surface. Thatch acts like barrier and can prevent water from penetrating the soil, so you may need to remove it if it gets thick. This can be done with a rake, a special dethatching tool, or special power equipment.

Check with your local lawn and garden center for purchases or rental advice.

Fertilizers and the Environment 

Nutrients are essential to a healthy, thriving landscape. Fertilizers supply nutrients to your plants and are an important part of any yard maintenance strategy.  They can be beneficial to your lawn, but they can also cause problems for our creeks, rivers, lakes, and aquifers.  Fertilizers that wash into creeks, either directly or through the storm sewer system, cause algae blooms.  Algae blooms are a concern because they cause taste and odor problems in our drinking water, and they degrade aquatic wildlife habitat.

Sometimes algae blooms can lead to fish kills by depriving the water of oxygen when the algae decompose.  There are three things to remember when fertilizing that will help you feed your plants properly and prevent damage to the environment.

1. Fertilize only when your lawn needs it. The best fertilizing strategy includes monitoring for nutrients (remember that soil test) and adjusting schedules for changing plant needs. Oftentimes, the available organic material in your soil will supply all the materials needed for growth, especially if you leave grass clippings on the lawn. Generally though, Spring and Fall are the best times to consider adding fertilizer to your yard.

2. Use organic and slow-release fertilizers. For the long- term health of your yard, fertilize moderately with an organic or slow-release type. Do not over fertilize.  Applying too much nitrogen prompts fast, weak growth, which attracts pest insects. Using an organic or slow-release type can prevent this sort of trouble, so check the label to see what kind you are buying.

3. Apply fertilizers with care. When using granular fertilizers, apply them with care and keep the pellets off streets, sidewalks, and driveways. There, they can easily wash into the storm sewer and into a creek.  When solid fertilizers are applied to the grass, water them down into the soil with a garden hose.  Don’t try to let a rainstorm do this chore for you!  Rain can easily wash the fertilizer down the storm drain.

Mowing 

Pay attention to mowing height because grasses have different preferences– short cuts for Bermuda, tall cuts for St. Augustine.  You should adjust the height seasonally for some grasses. Your goal is to remove no more that 1/3 of the leaf blade at any one time. Mow only when the lawn has had enough time to recover from the previous cut.  Proper mowing will produce a tight, dense lawn, which discourages weeds.  The accompanying chart gives some mowing height guidelines for some common Austin grasses.

Watering 

Watering the lawn is not as simple as it sounds.  Doing it the right way is very important to your lawn’s health.  Watering too lightly, too often produces weak plants with shallow root systems.  This makes your lawn susceptible to droughts and pests. Too much watering is wasteful and can wash the nutrients out of the soil.  You will know it is time to water if your footprints remain visible when walking across the grass, the leaf blades curl and become dull green, or if a probe will penetrate the soil only a few inches.

WHEN PESTS APPEAR — USE INTEGRATED PEST MANAGEMENT

No matter how well you maintain your lawn you will at one time or another encounter pests.  In the long run, the best approach is to use the previously described techniques to prevent problems before they arise.  (These are often called “cultural pest control methods.”)  When the inevitable pest problem does crop up, solve it using an approach called Integrated Pest Management (IPM).  This encourages you to use Cultural, Physical and Biological pest control methods before resorting to chemicals.  This is what IPM is all about–integrating these methods toward a goal of more effective, long-lasting pest management.  IPM can be summarized by the following 4 steps.

1. Properly identify the pest – Not all insects are pests; in fact, the vast majority are beneficial. Many pests look similar to harmless varieties. You can get help with the identification from your local nursery, or an identification book. Properly identifying the problem is critical to selecting the safest, most effective control, and if the suspected pest is harmless, you have saved time, money, and avoided unnecessary pesticide application.

2. Get information about the pest’s biology and habits — Once you have the pest correctly identified, use the pest’s unique biology and habits to select the most effective controls and apply them when the pest is most vulnerable. Again, consult a good book on organic pest control, or a qualified nursery worker knowledgeable in IPM or organic techniques. Check out the internet!  (See sidebar for Web sites.)  There are some great resources available on IPM and organic gardening.

3. Decide whether the pest is causing damage – Plants have been coping with pests for millions of years and have devised their own protective strategies. Sometimes pest infestations are so minor it is not necessary to do anything but let Mother Nature take care of the problem. Remember, almost all pests have natural enemies that will try to take advantage of an abundant food source.  Think carefully. Is am minor, temporary problem worth the health and environmental risks associated with the use of pesticides?

4. Use least-toxic, specific, and effective methods – There are different types of control methods available for managing pest problems which are NOT limited to chemical pesticide applications.

Physical Pest Control Methods

Oftentimes, pests can be hand-treated to get a minor infestation under control.  Physical methods are usually safe, environmentally-friendly, and inexpensive.  There are many different techniques for physically managing pests, many specific to one pest species only, but here are a few basic categories to consider:

Water Blasts – A mist of high pressure water from an ordinary garden hose, can be used to knock slow-moving pests from plantings.  Aphids and spider mites are especially easy to control using this method.

Pest Traps – Pests can be lured into traps where they are caught on a sticky substance, imprisoned, electrocuted, or drowned.  Traps commonly use food baits, colors, light, or reproductive hormones to entice pests.  Traps can be purchased ready-made or even constructed at home.  They can be used against wasps, yellow jacckets, whiteflies, snails, flies, pillbugs, and many other common lawn pests.

Hand-Picking – Picking caterpillars, garden snails, and fall webworms from plants and destroying them is a useful pest control method in some circumstances.  Caterpillars and snails are easier to locate after dark.  Use a flashlight to examine damaged plants and drop captured pests in a bucket of soapy water.  Snails and slugs should be crushed underfoot.

Pest Barriers – These are designed to block pests from reaching plants.  Such common sense controls may seem obvious, but they are often overlooked.  Like traps, barriers can be bought at your local nursery or made from materials around the home.  Examples include: seedling collars, greenhouses, window and patio screens, row covers, slick Teflon tapes, and copper strips.  Try barriers for slugs, snails, leafcutter ants, whiteflies, cucumber beetles, mosquitoes, cutworms, and squash bugs.  Barriers may be more practical to apply in a small garden, ornamental bed, or individual plants that may be experiencing repeated pest attacks.

Biological Pest Control Methods

Using Nature’s system of checks and balances to keep insect pests under control is an effective and environmentally-safer way to manage pests in your lawn and garden.  Introducing natural predators (beneficials) into your landscape is easy and fun.  It can also be a great outdoor project for the kids.  You can encourage beneficial insects to visit your yard by planting blooming plants (especially wildflowers and natives) and providing a source of water.  You can also purchase beneficial predators through mail order companies or at local garden centers.  Here are some common beneficial insects you can purchase for your yard.  Remember, some broad spectrum pesticides will kill beneficial insects, so switch to other types of controls or more selective alternatives.

Lady Beetles (ladybugs) are a very commonly used beneficial insect. Blooming plants will encourage ladybugs to visit your yard .. Uses: aphids, mealybugs, soft scales, spider mites

Lacewings are one of the best all-purpose predators. Uses: aphids, mealybugs, spider mites, thrips, others

Trichogramma Wasps are tiny parasites that attack the eggs of over 200 types of insect pests.  Trichogramma can control webworrns that eat the leaves of your pecan trees.

Uses: tomato homworm, armyworm, cutworm

Bacillus thuringiensis (Bt}, a naturally-occurring bacteria, can be used to control several different types of pests.  There are different varieties of Bt, so make sure you check the label to see that the variety you buy is effective against your pest problem.  When ingested by a pest, this bacteria releases a crystalline protein that destroys the lining inside the pest’s gut.  This causes the pest to stop feeding and eventually die.  Animals and other beneficial insects are not harmed by the application of Bt, but caterpillars that will become butterflies can be killed.

Uses: mosquitoes, caterpillars, beetle larvae

Avermectins are antibiotics (including ivermectin and abamectin) that are produced by a naturally-occurring bacteria and can be used against a variety of pests.  Some are fairly toxic to mammals and aquatic life, so they should be used with care.

Uses: fire ants, spidermites, leafrniners

Beneficial Nematodes are microscopic worms that attack a wide range of soil-dwelling pest insects.  These nematodes are not the same as the pest species that attack the roots of plants.  The beneficial species can be bought commercially as a dissolvable paste or powder that can be sprayed or poured directly onto infested soil as a drench.  Nematodes travel through the soil and kill susceptible insect species by penetrating their body cavity and infecting them with toxic bacteria. Nematodes are vulnerable to drying-out and are therefore best applied during wet weather or at least after the sun has set.

Uses: white grubs, fire ants, fleas, mole crickets, termites, and mapy other soil dwelling pests

Environmentally-Friendly Chemical Pest Control Methods

Botanical, mineral, and soap insecticides are an acceptable option after physical and biological measures fail.  Unlike most synthetic chemicals, natural insecticides are either harmless in the environment, or degrade quickly into less toxic substances.  They also tend to be less harmful to beneficial insects than synthetic chemicals.  However, natural insecticides should still be used sparingly, with extreme care, and only as the label directs.

Pyrethrum is one of the most widely used botanical (plant-derived) insecticides.  Pyrethrum is a compound made from the dried blooms of the chrysanthemum plant.  The active insecticidal ingredient is sometimes extracted from the flowers and it is called pyrethrin.  Chemists have also been able to synthesize the active ingredient and the artificially-made compounds are call pyrethroids.  Many pyrethrin and pyrethroid-based products have other chemicals added to enhance their effectiveness.  Be aware, these additives may have health and environmental risks of their own.

Uses: controls many pests– check the label on products you select for a complete listing of pests controlled

Neem is a botanical insecticide that is extracted from  the seeds of the neem tree which grows in parts of Africa and India.  Native peoples have long been aware of the useful properties of this tree.  It is the ingredient in many medicinal remedies.  Neem is unique in that it has a triple action effect on pests.  It acts as a repellent, growth regulator, and insect poison.  It can be used to control a wide range of insects on ornamental plants and shrubs.  Neem is also virtually harmless to beneficial insects like bees, lady beetles, and lacewings. Sometimes Neem products are advertised by the active ingredient, azadirachtin.

Uses: aphids, leafminers, thrips, whiteflies, many others

Insecticidal Soaps (potassium salt of fatty acids) are specially formulated soaps used for pest control.  Their insect killing properties are the basis of the old home remedy of using a solution of dishwashing liquid and water to control pests.  Scientists have discovered that potassium salts of fatty acids, found in soaps, will penetrate an insect’s body and collapse cell walls.  Companies have developed special soap products that contain a high proportion of these insect killing substances.  (Similar products have been developed to kill unwanted plants like poison ivy.)

Uses: aphids, mealybugs, whiteflies, chiggers, fleas, mites, and ticks

Horticultural Oil sprays will smother insects by blocking their breathing apparatus.  Oils can also kill insect eggs by penetrating their outer covering and interfering with their development.  These oils should be used carefully since you might inadvertently kill sensitive plants or beneficial insects.

Uses: scales, aphids, mealybugs, spiderrnites

Boric Acid, derived from the mineral Borax, is a pesticide that is often used in bait formulations.  For lawn and garden applications, it is now available as a weather resistant granular bait.

Uses: carpenter ants, fire ants, crickets, roaches

Diatomaceous Earth (DE) is a powdery, white substance that is actually the fossilized remains of tiny microscopic algae.  Diatomaceous Earth, or DE, sticks to pests and destroys their exoskeleton (the hard outer covering).  It causes the affected pest to dry  up and die.  DE controls a wide range of pests, but it can also be harmful to beneficial insects and spiders.  An important thing to remember when using DE is to keep it dry. If it becomes moist, it doesn’t work as well.

Uses: chinch bugs, carpenter ants, fleas, ticks, chiggers, many other insects.

A FINAL NOTE ON “WEEDS”

Weeds are technically classified as “pests” even though most people think only of insects when they hear the word pest.  The best defense against weeds is a thick lawn and a healthy garden.  As in the jungle, the law in your lawn is only the fittest survive.  Therefore, the best way to control weeds is to give the competitive advantage to your grass and plants and let them choke out the weeds.

One person’s weed is another person’s wildflower.  The same plants that discourage gardeners are used for medicine, culinary seasonings, and provide natural wildflowers.  More can be learned about how to use these plants from the environmental groups listed in the “Trees & Plants” section of this Directory.

Lawns

Broadleaf weeds, like clover, dandelion, sow thistle, and purslane, will gradually die back if kept regularly mowed.  As your lawn begins to grow and thicken in the Spring, it will crowd out these unwanted plants.  Be sure to keep flowering weeds mowed down to prevent their reproduction.  There is no need to apply herbicides such as those in “weed and feed” type fertilizers to control these pests.  Simply stay consistent with the weekly mowing and make sure your lawn has the nutrients and water it needs.  Hand-pulling some of the most weedy areas will help your grass quickly crowd out the pests.

Grass and sedge type weeds, like quackgrass, nutsedge, bermuda, and crabgrass can be some of the most difficult weeds to control, even with herbicide use.  Try to avoid problems with this type of weed by keeping established lawns thick and healthy and hand-pulling any new invaders promptly.  If installing a new lawn, use pure seed stock or good quality sod.  Regularly mowed lawns, even ones with minor weed problems, can still look quite nice, so try giving yourself, and our environment, a break by learning to live with a few of these weeds among your grass.

If certain areas of your lawn are so infested that they are beyond help, instead of waging chemical warfare, you may be better off digging up the area and reseeding or resodding.  Solarize the area (moisten the soil and cover with clear plastic for several weeks) to sterilize the soil and replant.  Be sure to give your new planting a good sprinkling of compost to get the biological activity in the soil going again.  If grass refuses to do well in the area or just can’t out-compete the weeds, replace it with a ground cover or an ornamental bed with plants well-suited to the site.

Basic weed management strategies for lawns will depend on the type of turf you are growing, but may include making adjustments to mowing frequency, mower height, fertilizer applications, and watering schedule.  Supplement these by hand-pulling the remaining weeds and you will be on the right track towards a more attractive lawn.

Gardens and Ornamental Beds

Weeds can pop up everywhere, including your vegetable garden and flower beds.  In these areas, using a mulching material coupled with occasional physical removal will easily keep most weeds at bay.  Three or four inches of mulch will keep most weeds from germinating.  If you have an unusually bad weed problem, place newspapers (about 6 sheets thick) on the ground before applying your mulch.  Once the paper is down, moisten it to make it stick, then spread your mulch on top.  The paper will keep all but the most persistent weeds out.

Physical removal can be done by hand or with a garden tool designed for weeding.  Tools like hoes and cultivators can make quick work of weeds while saving wear and tear on your knees and back.  Many varieties are available at local garden centers.  No gardener should be without one.

There are also weed-killing soaps available on the market that destroy weeds by dissolving their waxy membranes. They act rapidly but tend to kill only the top leafy portion of the plant, so you may experience some root resprout.  However, if you pull or re-treat the sprouts, the roots will eventually weaken and die.  While considered a least-toxic herbicide, these soaps may damage desirable plants if used inappropriately. Please read and follow the label directions.

For more information on ways to maintain a healthy lawn and properly deal with pests, call the City of Austin.

Integrated Pest Management ……… (512) 974-1475
austintexas.gov/department/integrated-pest-management

Urban Landscaping ……………………. (512) 499-3543