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Chemical Basics For Lawn Care and Ornamentals

Perfect lawns don't pop up overnight. They require watering, mowing and other standard maintenance practices just to look presentable in a neighborhood. For really great landscapes, it's a game of fertilizing, aerating and dethatching. Some homeowners and professional lawn maintenance experts go the next level by topdressing and over seeding the lawn. But there's something almost everyone can agree on: It's the added chemicals that really make a difference.


Why Use Chemical Products on Lawns?


A residential or commercial landscape is an ecosystem that's filled with numerous insects, both beneficial and detrimental. Various organisms dwell in the soil, bugs crawl and fly above the ground and wildlife invades on occasion. Some organisms attack grass roots and compromise a lawn from beneath the ground. Certain pests feed on grass blades and ornamental leaves while others build colonies and turn green landscapes into sand mounds.


A lawn doesn't just harbor insects; it's also the ideal environment for weeds. A weed, no matter if it's a dandelion or crabgrass, competes with ornamental plants and turf. It steals vital nutrients, strangles the plants beneath the soil and spreads like wildfire in the right conditions. It's this fight against detrimental pests like weeds and insects that birthed the chemical product industry.


Without the use of maintenance products, either natural or chemical, lawns and gardens wouldn't have a chance to flourish. Insect pests and weeds would be out of control and damage grass and edible crops. Rarely does anyone ever see a lush, emerald green lawn that hasn't had a chemical treatment.


What Defines a Lawn Pest?


A lawn pest can be any organism that negatively affects the health of a plant. It can be anything from sawfly larvae to fungi and bacteria. It can even be a one-celled organism like algae. Other common lawn pests include:

  • Broadleaf and grassy weeds
  • Earthworms, nematodes and roundworms
  • White grubs and sod webworms
  • Spider mites
  • Wildlife such as raccoons, squirrels and deer

Because of the diversity of turfgrass and ornamental pests, numerous chemical products such as pesticides and deterrents exist to combat infestations, to ward off future pests and to maintain healthy plants.


What is a Pesticide?


A pesticide is a chemical or a natural substance that effectively kills, prevents and repels any nuisance pest. It may also attract, sterilize or regulate the pest in question. In the landscaping world, pesticides play an important role in turfgrass and ornamental pest control management.


Some people have a misconception about pesticides and believe that each product contains toxic ingredients. Though some have higher levels of toxicity than others, many of the modern pesticide products contain forms of bacteria, fungi and viruses. Others contain chemically organic compounds that mimic natural pesticides in nature, such as pyrethroids, which are similar to pyrethrins from chrysanthemums.


Pesticides control any plant, animal or disease-causing organisms that damage turfgrass, ornamental plants and any associated greenery throughout the landscape. They not only target and kill turf-damaging pests but also any biting or stinging pests that bother people and animals in the vicinity. However, it's important to note that pesticides should not only be used to kill pests. They're part of a much bigger pest management program and should be combined with cultural practices to limit their use as much as possible.


What is the Best Pesticide?


There really isn't a "best" pesticide – just the right pesticide for the situation. When choosing a product, always consider the problem first. It should target the specific pest with quick action without harming beneficial organisms, people, animals and the environment. Some pesticides leave behind a residue that continues to work; however, it should only last as long as necessary to achieve the desired effect.


The ideal pesticide would also have no odor, making it useful in public places. After all, no one would tolerate the stench no matter how well the product works. It should also have the power to kill the pest in a way that no resistance would occur. The pesticide should also prevent infestations long after it's been applied yet break down naturally without staining surfaces or impacting the surrounding ecosystem.


Unfortunately, it's not always possible to get an all-in-one pesticide that does everything mentioned. Therefore, one should know the limitations of the product and choose a pesticide that controls the specific pest in question. Afterward, it's all about combining the product with other products and using best practices to create a turfgrass management program.


Turfgrass Pest Management


It's important to know the most common pests before creating a turfgrass pest management program. The three common types are weeds, insects and diseases. Each pest affects the landscape in different ways and causes widespread damage if it's not contained, controlled and eliminated.


Weeds are by far the number one cause of unhealthy turfgrass throughout the country, especially in the western states like Colorado and Wyoming. Therefore, the go-to product for killing and controlling weeds in turfgrass and ornamental gardens is an herbicide. Herbicides are separated into two classifications: systemic and contact. Both provide effective weed control but have two different methods of action:

  • Systemic herbicides work in one of two ways: They are either taken in by the roots and circulated throughout the entire plant, or the weed absorbs the herbicide through its leaves and transports the chemical to the roots.
  • Contact herbicides work at the site where the chemical contacts the weed. It's not transported throughout the plant. Instead, it kills the weed on target.

Herbicide Categories and Plant Life Cycles


Herbicides are also separated into two categories: pre-emergent and postemergent. They should be used during a specific time in a weed's life cycle in order to work effectively.


Pre-emergent Herbicides


A pre-emergent herbicide must be applied to the soil before the weeds emerge or the seeds germinate. If it's applied after the fact, it will fail to eliminate the weeds. Once it's applied, the herbicide is taken in by the roots and systemically moved throughout the plant. Timing is everything with these herbicides. Therefore, it's important to know when the target weeds will germinate and emerge from the soil. Applying a pre-emergent herbicide several weeks prior to weed emergence provides the most successful control.


Postemergent Herbicides


A postemergent herbicide works effectively after the weed has emerged from the soil. It's best applied as a contact foliar spray directly on the target weed. Using a postemergent herbicide in an area where the weeds have yet to emerge will result in failure. Postemergent herbicides come in two types: contact and systemic.

  • Contact herbicides are most effective on annual broadleaf weeds. They work on contact and don't harm turfgrass when they're applied according to the label.
  • Systemic herbicides work best on perennials, which can regenerate from their root systems. A systemic herbicide works through the leaves and makes its way to the roots and stems, killing the entire plant along the way. Runoff and drift can kill beneficial plants, so take extreme caution during application.

Herbicide Modes of Action


Herbicides have several modes of action, or unique ways in which they affect the target weeds. To select the right herbicide for the job, it's best to have a general understanding before choosing any herbicide for a given situation.


Amino Acid Inhibitors


Amino acid inhibitors have a mode of action that prevents amino acid synthesis, which is vital for normal plant growth and development. These inhibitors are limited to foliar applications since they become inactive when they're mixed with soil. Some examples of amino acid inhibitors include:

  • Round Up with glysophate
  • Oust with sulfometuron
  • Image with imazaquin

Cell Growth or Cell Division Inhibitors


Cell growth or cell division inhibitors are typically pre-emergent herbicides and applied to the soil. They disrupt the growth of plant tissue and only target certain weed species. Some cell division inhibitors include:

  • Super with paraquat
  • Reward with diquat
  • Basagran with bentazon

Growth Point Disintegrators


Growth point disintegrators target the growing point of turf weeds. They're applied at early postemergence and are effective on both annual and perennial grasses, especially when they're used with an adjuvant. Affected weeds show various symptoms such as yellowing and other discoloration. Some products include:

  • Acclaim with fenoxaprop-ethyl
  • Poast with sethoxydim

Growth Regulators


Growth regulators are available as contact and systemic herbicides. They're applied during postemergence as a foliar spray, disrupting the weed's growth and causing everything from leaf cupping to dark coloration. Drift and runoff can damage nontarget plants. Many growth regulators contain 2,4-D as the active ingredient, but other known regulators include:

  • Banvel with dicamba
  • Turflon with triclopyr

Photosynthetic Inhibitors


These postemergent herbicides are applied to the soil and interfere with photosynthesis, thus preventing food production in the weeds. They provide long-term control and will continue to work for weeks or months depending on the amount that's applied. Some common photosynthesis inhibitors include:

  • Princep with simazine
  • Hyvar with bromacil
  • AAtrex with atrazine

Pigment Inhibitors


Pigment inhibitors work by stopping the formation of carotinoid pigments, which protect the chlorophyll from light. This pre-emergent inhibitor exhibits foliar and soil activity and halts photosynthesis. It's effective on both grassy plants and broadleaf weeds. Some products include:

  • Ronstar with oxadiazon
  • Amitrole T

Disease Management


Turfgrass not only has to fight against competing weeds but also harmful pathogens. Turf diseases occur when these pathogens enter the plant through the root system or the leaves. They disrupt the turf's metabolic process and cause discolored patches in areas of the lawn and spots on individual blades. To fight against turf diseases, a fungicide acts as both a protective and a curative measure.


Fungicides prevent disease-causing fungi from forming and spreading and are grouped by formulation:

  • Inorganic fungicides contain various minerals such as copper and sulfur. They don't easily decompose in nature and are now limited in use.
  • Organic fungicides are carbon based and decompose naturally in the environment, posing little risk of long-term contamination.

Contact Versus Systemic Fungicides


Contact fungicides only protect the part of the plant on which they cover, not the roots. A fungus can still affect parts of the plant that aren't covered, so it's important to apply the product thoroughly. Contact fungicides have broad-spectrum activity, control numerous species and have very few resistance issues. Rain, irrigation and chemical breakdown can render the contact fungicide inactive, thereby shortening its control.


Systemic fungicides, however, do not break down so easily or get washed away by rainfall and irrigation. They're taken in by the roots, and the active ingredients are distributed throughout the plant in a process called translocation. Mowing will not remove the fungicide either since the chemical is stored in the roots and the stems. Even new growth will obtain some of the translocated protectant. Unfortunately, systemic fungicides do have a higher possibility for resistance due to their very specific mode of action.


Classifications of System Fungicides

  • Benzimidazoles: Inhibit cell division of fungi
  • Dicarboximides: Inhibit invasion of hyphae, the invading rootlike filaments of the fungi
  • Sterol Inhibitors: Inhibit growth of the fungi biochemically by disrupting the cell wall membranes

Turfgrass and Ornamental Insect Management


Pest insects vary throughout the country and cause more problems in some places than in others. In the humid South, pests thrive in turf and damage crops, gardens and ornamentals. Pests such as chinch bugs and grubs eat grass roots and cause numerous problems for homeowners who want a lawn without visible damage.


Colorado has a dry, arid climate and fewer insect pests to destroy the turfgrass. However, pests learn to adapt to any environment. Billbugs and white grubs are found in the state and can damage turf or attract skunks and other foragers. The wildlife causes a mess of its own as the animals dig up yards in search of insects in the soil.


Homeowners and lawn care professionals target turf pests with insecticides. These products range in strength and may only target specific pests by using minerals, chemicals, organic compounds or other ingredients. Insecticides are divided into groups based on their modes of action.


Inorganics


Inorganic pesticides have been around the longest and contain minerals as the active ingredients. They have a slow killing mode of action and are used primarily in the structural pest control market. Some types of inorganic pesticides include:

  • Boric acid
  • Diatomaceous earth
  • Silica aerogels

Organics


Organic pesticides range in type and contain either carbon-based or all-natural, "organic" ingredients. Some manufacturers create organic pesticides with sesame oil to combat pests such as spider mites and certain fungal diseases.


Botanicals


Botanical insecticides are often referred to as natural insecticides since they contain chemical compounds that are derived from plants. Some common botanicals include:

  • Pyrethrum
  • Rotenone
  • Ryania
  • Nicotine

Pyrethroids


Pyrethroid insecticides contain six distinct chemical molecules with similar structures. Compared to natural pyrethrum, pyrethroids have an improved mode of action and provide faster knockdown, greater killing power and longer residual effects.


Neonicotinoids


Neonicotinoids contain synthesized compounds that are similar to the nicotine molecule. They provide longer residual effects and systemic activity than similar pesticides of their type.


Insect Growth Regulators


Insect growth regulators affect the growth and development of turf pests. They pose little risk to mammals and disrupt the normal processes of insects at different life stages. Some of the effects include:

  • Disruption of hormones that are responsible for development in immature pests
  • Sterilization of adult insects
  • Inhibition of important enzymes needed for growth

Weed Control Ideas for Colorado Turf


Weeds thrive in the Colorado climate and would take over the landscape if not for the many herbicides on the market. Whether it's a postemergent foliar spray or a pre-emergent granular, it's possible to treat and to prevent weeds with one or more weed-control products. For those who want thicker, fuller and greener lawns, these products can help tame the weeds and improve the look of residential and commercial landscapes.


Pre-emergent Herbicides


Granular formulations may not provide quick results, but they're great for controlling weed growth before it happens.

  • Snapshot has two active ingredients to control more weed species. It's an excellent bedding pre-emergent for early spring applications. Apply it to rock and mulch areas.
  • Pendulum 2G works best on grassy weeds that invade rocky areas and mulch. It's great for early spring applications.

Liquid formulations go to work quickly and yield faster results when compared to granular herbicides. However, it's possible to apply too much and damage the lawn. Following the application rates on the label is recommended.

  • Prodiamine 65 WDG can be applied in the spring and the fall and works effectively on turf and bedding.
  • Pendulum AquaCap has a nonstaining formula and works best on grassy weeds. Apply it in the spring to prevent weeds from emerging from the soil.
  • Surflan is a bedding pre-emergent and provides control for up to six months. Because it's harmful to cool-season grasses, it should not be used on Colorado turfgrass. Apply it to bedding in the spring.
  • Dimension 2EW should be applied in the spring on turf and bedding. It's colorless and has some post-emergent activity.
  • Gallery is a turf and bedding pre-emergent with an increased weed spectrum. Apply it in the spring and the fall, and combine it with label-recommended pre-emergents for even greater weed control.

Postemergent Herbicides


It's not always easy to catch weeds before they emerge. For established weeds in turf and bedding, a postemergent herbicide is the ideal choice.

  • Shredder 2,4-D Amine is a cost-effective product for controlling specific broadleaf weeds. It has greater temperature sensitivity and lower volatility and works well when it's combined in the tank with glysophate to increase the control.
  • Strike Three contains mecoprop, dicamba and 2,4-D as the active ingredients, targeting a wider spectrum of weeds on turf.
  • 4-Speed XT contains triclopyr for increased efficacy on hard-to-control weeds. It provides immediate visual results and helps to kill weeds quickly.
  • Horsepower contains MCPA, triclopyr and dicamba and knocks out hard-to-control, turf-invading weeds without the need to use 2,4-D.
  • Quincept contains dicamba, quinclorac and 2,4-D and helps to knock out invading grasses on turf while providing good broadleaf weed control.
  • Fiesta is an organic-based, selective herbicide that controls weeds in turf. It contains a chelated iron source and kills broadleaf weeds without effecting desired grasses.
Phoenix Environmental Design Inc.
Rob Gar
Rob Gar

Author