Invasions of Pre-Emergent Herbicides Bayer Spring has here, and it is time for lawn care professionals to begin preparing for the annual fights with annual grasses and weeds. Crabgrass, goosegrass, foxtails, and annual bluegrass are the most popular targets of pre-emergence herbicides.
Bayer In lawns and landscapes, annual grasses and some small-seeded broadleaves are the major targets of pre-emergence herbicides. The most typical targets consist of crabgrass, goosegrass, foxtails, and annual bluegrass. These herbicides limit weed emergence, or the growth and development of freshly hatched weed seeds, according to Dean Mosdell, Ph.D., Syngenta’s technical services manager.
Weed Lawn Care | DO NOT USE WEED & FEED (pre-emergent)
“The location of activity varies on the herbicide’s mechanism of action, although all herbicides are most effective when applied prior to weed seed germination.” Some pre-emergence herbicides can suppress freshly emerging weeds, but effects can be uneven; thus, products should be sprayed before germination. 
Which pesticides must be applied to turf?
Grass Weed Control | University of Delaware Your lawn may produce more than the planned amount of lovely grass. It may also promote the growth of weeds, which diminish the appearance of your grass. In addition to diminishing the appearance of your lawn, weeds compete for water, nutrients, and light with the intended turfgrass.
Without weed management, your grass will gradually degrade. Typically, weeds are an indication of a cultural or soil issue in your lawn. Consequently, weed control requires both the removal of weeds and the correction of the conditions that lead to poor grass quality. Cultural Control Growing lush, thick grass is the most effective method for weed control.
Strong, healthy turf prevents the germination of weed seeds by shading them. Select appropriate lawn grasses, fertilize appropriately (mainly in the autumn), lime as needed based on soil test recommendations, mow often, taking no more than one-third of leaf tissue with each mowing, water during establishment and solely to maintain a green lawn during periods of drought.
Be sure to fully soak soil regularly when you water. Frequent, light watering stimulates weed invasion, hinders deep roots, and reduces turfgrass tolerance to environmental stress. Add compost and aerate the soil to enhance its structure. To have a beautiful, healthy lawn, you must have a fundamental understanding of turfgrasses and their cultural needs.
For additional information on cultural lawn care, consult the fact sheets on cultural lawn care. Chemical Management Herbicides, or chemicals that kill or affect the natural development of weeds, can be categorized as either selective or nonselective.
Herbicides that are selective kill weeds without harming attractive turfgrasses. Nonselective herbicides kill all plant life, including turfgrasses, and are used to renovate lawns or eliminate weeds that are resistant to selective herbicides. Herbicides can be further categorized as preemergence or postemergence.
Herbicides administered prior to the germination and appearance of weeds. Typically, they are employed to combat annual weeds. Herbicides used to control weeds that have already sprouted from the soil. They are either contact or systemic in nature. Contact herbicides only impact the plant parts they contact and are not translocated to other weed components.
- Because systemic herbicides are translocated throughout the plant, they are effective against perennial weeds that may produce new leaves from subterranean roots.
- Herbicides may be applied to either vegetation or soil.
- Typically, postemergence herbicides are sprayed to the leaves, whereas preemergence herbicides are applied to the soil.
A foliar herbicide must make contact with and be absorbed by the plant’s foliage. Its effectiveness is diminished if it is washed off the leaf surface by rain or irrigation. Herbicides applied to the soil can be applied as liquids or granules and must be soaked into the soil after application.
The most effective method for managing weeds in lawns is to determine how the weed varies from the desired grass and exploit that distinction as a management method. Annual grass weeds Summer annual grass weeds are typical lawn concerns. They vary from attractive lawn grasses in that they must annually germinate.
Crabgrass and goosegrass are two typical annuals seen in the summer. Before germination or emergence, these weeds are controlled by preemergence herbicides that build a chemical barrier in the soil. The barrier impedes the seedlings’ emergence and regular development.
| TABLE 1. SOME PREEMERGENCE HERBICIDES FOR THE CONTROL OF SUMMER ANNUAL GRASSES*. | |
|---|---|
| Generic name | Trade name |
| Benefin | Lebanon Balan 2.5G |
| Benefin and trifluralin | Team |
| Bensulide | Bensumec |
| Bensulide + oxadiazon | Goosegrass/Crabgrass Control |
| Dithiopyr | Dimension |
| Oxadiazon | Ronstar |
| Pendimethalin | Pre-M, Pendulum, Halts |
| Prodiamine | Barricade |
| Siduron | Tupersan |
All of the chemicals included in this publication can be used on residential lawns, although some are only available to licensed professionals. The majority of preemergence herbicides stay active in the soil for the amount of time recommended on the manufacturer’s label; thus, sowing should be delayed for that period.
- Siduron is the only substance that may be used safely during or shortly after seeding.
- Preemergence herbicide application timing is crucial.
- Springtime applications of preemergence herbicides are most effective 10 to 14 days before the projected germination period.
- Crabgrass begins to sprout when soils are moist and the upper inch of soil reaches 55 to 58 degrees Fahrenheit at dawn for four to five days.
Sometimes, Forsythia petal fall is used as a guidance, however it may not be trustworthy. Crabgrass typically germinates in Delaware between March 15 and April 15. Depending on the substance, time of application, location, and spring precipitation, reapplication within 60 days may be required for season-long control.
If preemergence herbicides are sprayed too late, summer annual grass management may require a postemergence herbicide. Apply postemergence herbicides when crabgrass or other annual weeds are clearly visible and exclusively to weed patches. As crabgrass grows, it becomes increasingly difficult to control.
You may need to reapply sprays every 10 to 14 days, and you should anticipate some yellowing of the preferred turfgrass.
| TABLE 2. SOME POSTEMERGENCE HERBICIDES FOR THE CONTROL OF SUMMER ANNUAL GRASSES*. | |
|---|---|
| Generic name | Trade name |
| Dithiopyr | Dimension |
| DSMA | Methar 30 |
| Fenoxaprop-p-ethyl | Acclaim Extra |
| MSMA | MSMA Turf Herbicide |
| Quinclorac | Drive 75 DF Herbicide |
All of the chemicals included in this publication can be used on residential lawns, although some are only available to licensed professionals. Grass-like weeds Chemically and morphologically, broadleaf weeds and attractive lawn grasses vary. Scientists have developed solutions that selectively eliminate broadleaf weeds without hurting attractive turfgrasses.
- The majority of broadleaf weeds are treated by herbicides that are sprayed after weed emergence.
- These herbicides are administered to the weed’s foliage and are absorbed by it.
- These herbicides can be sprayed or applied as granules.
- For the most effective control of broadleaf weeds, spray the foliage with postemergence herbicides (do not wash off).
For optimal control, granular treatments should be applied to damp (dew-covered) foliage. Postemergence broadleaf herbicides are best effective when weeds are actively growing (spring and autumn) and when temperatures range from 70 to 85 degrees Fahrenheit.
Commonly, two or more distinct herbicides are offered in combination to control as many distinct broadleaf weeds as feasible. Because many of these herbicides are selective for certain broadleaf weeds, it is crucial to identify the weed(s) to be eradicated. These products may cause harm to trees, shrubs, flowers, and vegetables if they come into touch with the leaves.
Since this pesticide is mobile in the soil and may be taken up by tree roots, trees and shrubs are especially susceptible to dicamba. Use none of these herbicides on newly-seeded grass. Wait until the new grass has been mowed at least three times before applying any treatments (usually about 6 to 8 weeks after seedling emergence).
| TABLE 3. BROADLEAF HERBICIDES AND HERBICIDE COMBINATIONS FOR USE IN COOL-SEASON TURF*. | |
|---|---|
| Generic name | Trade name |
| 2,4-D (amine) | Solution Water Soluble, Weedestroy AM-40 |
| Carfentrazone-ethyl | Quicksilver |
| Dicamba (amine) | Banvel, K-O-G Weed Control |
| Fluroxypyr (amine) | Spotlight |
| MCPA (amine) | MCPA-4 Amine |
| MCPA (ester) | MCPA LV 4 Ester |
| MCPP (potassium salt) | MCPP 4K Turf Herbicide |
| MCPP (amine) | MCPP-p 4 Amine |
| Triclopyr (ester) | Turflon Ester |
All of the chemicals included in this publication can be used on residential lawns, although some are only available to licensed professionals. Nutsedge Yellow nutsedge is a widespread plant of turfgrass that resembles a grass but is in fact a sedge.
It has upright, triangular, yellow-green stems with a thick midvein and a waxy surface. The fibrous root structure generates several tubers, which are subterranean food storage organs resembling nuts. Each of these tubers is capable of germination and plant production. Yellow nutsedge thrives in warm, damp environments and is commonly found in low-lying, poorly-drained regions of the lawn.
If there are only a few nutsedge plants, they can be eradicated by hand. Remove the entire plant and its roots by excavating beneath the plant. Herbicides may be necessary in areas with dense populations of nutsedge. Herbicides that will eliminate this sedge without hurting the desired turfgrass have been produced.
- Certified pesticide applicators have access to two herbicides (Basagran (beta an) and SedgeHammer (halosulfuron)) that are particularly effective for yellow nutsedge control: Basegran (beta an) and SedgeHammer (halosulfuron).
- Perennial grass weeds The only difference between perennial grass weeds and attractive turfgrasses is that we do not want them on our lawn.
Due to its soft, fine-bladed, tufty growth pattern, bentgrass, which is extremely attractive on a golf green, is a weed in the lawn. Wiregrass, which is prevalent across the state, spreads swiftly via thorny stems. In the winter, this warm-season grass stays dormant.
As with bentgrass, Nimblewill (Muhlenbergia) is a blue-green grass with tiny blades and wiry stems that forms patches. Multiple species of Paspalum are seen in lawns. One is a coarse, yellow-green, warm-season clump grass called Dallasgrass. Flat, spherical seeds are typical of seed spikes. The only way to control these perennial grasses is to apply a nonselective herbicide, kill the entire weed-infested lawn patch, and then reseed the area with desirable turfgrass.
Glyphosate is a herbicide that may be used for this form of weed management.
| TABLE 4. SUGGESTIONS FOR SELECTIVE CONTROL OF TURFGRASS WEEDS, BY WEED SPECIES.* ** | |||
|---|---|---|---|
| Weed | Material | Apply | Remarks |
| Annual Bluegrass Poa annua This fine-bladed, bright-green low-growing grass grows vigorously in cool, moist weather. It’s the first grass to “greenup” in the spring. Produces many whitish seed heads. Forms patches that may suddenly die out in hot dry weather. | bensulideor | Late summer | Apply just prior to expected annual bluegrass germination (late August or early September). Only effective in reducing populations of the annual subspecies of annual bluegrass. |
| or ethofumesateor | September and October | For use on established perennial ryegrass or Kentucky bluegrass or when establishing perennial ryegrass. Two applications are necessary. Do not mix with liquid fertilizers or other pesticides. | |
| Black Medic Medicago lupulina This and similar species of yellow flowering clovers may invade lawns, forming solid patches. | Fluroxypyr, or dicamba, or quinclorac, or combination of products containing dicamba, or 2,4-D + triclopyr | Spring or fall | Best control when weeds are actively growing. Products containing carfentrazone provide faster burndown of black medic than those without carfentrazone. |
| Chickweed: Common Stellaria media Mouse ear Cerastium vulgatum Common chickweed is a mat-forming plant with tiny star-like white flowers. Thrives in spring and fall when cool and moist. Mouse-ear chickweed is similar but is perennial, has hairier stems and leaves, and is more tolerant of summer heat. | MCPP, or dicamba, or combination of products containing MCPP and dicamba, or or 2,4-D + triclopyr | Spring or fall | Best control when weeds are actively growing. |
| Chicory Cichorium intybus This somewhat woody perennial has bright blue flowers. | 2,4-D, or combination of products containing 2,4-D or MCPA | Spring | Most effective on young weeds. |
| Cinquefoil Potentilla spp. Pronounced “sink-foil”; this common creeping plant reminds people of wild strawberry. But typically has five-part leaves, yellow flowers, and no fruit. Thrives in poor soil. | 2,4-D + MCPP + dicamba, or 2,4-D + dicamba, or 2,4-D + triclopyr | Spring | Difficult to kill. May require repeat applications. |
| Clover Trifolium spp. Spreads by creeping stems, forming conspicuous patches. Blossoms attract bees and other stinging insects. | Clopyralid, or fluroxypyr, or dicamba, or quinclorac, or combinations of herbicides containing clopyralid or dicamba, or 2,4-D + triclopyr | Spring, summer, or fall | Best control when weeds are actively growing. Combinations of herbicides containing carfentrazone provide faster burndown of clover than those without carfentrazone. |
| Crabgrass: Small (smooth) Digitaria ischaemum Large (hairy) Digitaria sanguinalis This notorious lawn weed consists of two types: smooth and hairy. Both are coarse-bladed, yellow-green in color, and spread out in crab like fashion. They are heavy seed producers. Hot, showery summer weather encourages this pest. | Preemergence control: benefin, or benefin + trifluralin, or bensulide, or bensulide + oxadiazon, or dithiopyr, or oxadiazon, or pendimethalin, or prodiamine, or siduron | Early to mid-spring | Best controlled if herbicides are applied about 2 weeks prior to expected crabgrass germination.d. |
| Postemergence control: Fenoxaprop-p-ethyl, or methanearsonates (DSMA or MSMA), quinclorac, or dithiopyr | Early summer | Apply postemergence products only when crabgrass is visible in the stand. Check labels for temperature and plant development restrictions. |
Some of the chemicals included in this book are only available to experts with a licensed applicator certification. * Herbicide recommendations are based on product label information and the results of a limited number of research experiments. Due to the fact that herbicide efficacy can vary based on environmental circumstances, location, and application techniques, the recommendations in this table may not fully adhere to the turfgrass safety and weed control requirements established by research studies.
- References 2004.
- Hart, S., D.W.
- Lycan, and J.A. Meade.
- Weed Management in Home Lawns Cooperative Research and Extension at Rutgers, FS119.
- Revised August 2003.
- Chemical Weed Control, Center for Turfgrass Science, College of Agricultural Sciences, Penn State University.
- Http://plantscience.psu.edu/research/centers/turf/extension/factsheets/weed-management/chemical-weed-control By weed species, suggestions for the selective management of turfgrass weeds in Pennsylvania.
Center for Turfgrass Science, College of Agricultural Sciences, Penn State. Weed Management in Turf | http://plantscience.psu.edu/research/centers/turf/extension/factsheets/weed-management/table-4. College of Delaware
Agriculture Australia Globally, herbicide resistance to Group 1 herbicides has been proven and recorded in more than 40 grass weed species in more than 40 nations. Group 1 resistance is broad and prolific with tens of millions of hectares impacted, in fact it is the second most probable herbicide mode of action to produce resistance with only the Group 2 mode of action more likely.
Group 1 resistance commonly exists across wide areas of Australia in the grass weed species including more than 20,000 populations of annual ryegrass, annual veld grass, more than 5,000 populations of wild oats, phalaris, more than 200 populations of brome grass, crabgrass, crowsfoot grass and more than 200 populations of barley grass.
Resistance has emerged in broadacre and vegetable conditions. As little as six treatments to the same population of annual ryegrass can result in the selection of resistant individuals, according to research. In one season, a population might change from a tiny region of resistant individuals to a failed whole paddock.
Group 1 herbicides FOPs, DIMs, and DENs carry the same significant chance of resistance. Where a Group 1 herbicide has been used on a particular paddock to control any grass weed, avoid applying a Group 1 herbicide to manage the same grass weed in the following season, regardless of the performance of the Group 1 herbicide in the previous season.
Applying Group 1 herbicides often to dense weed populations is the worst possible circumstance for rapidly selecting for resistance Where resistance to a Group 1 herbicide is suspected or confirmed, there is a high likelihood of resistance to other Group 1 and Group 0 herbicides.
- Consequently, a future integrated strategy should use other control strategies and herbicides of various mode of action groups.
- These guidelines should be implemented into a program for Integrated Weed Management (IWM).
- Always attempt to guarantee that weeds that survive any treatment do not produce viable seed.
To diminish the weed seedbank, adhere to the integrated tactics outlined in this pamphlet, including cultural weed management measures. Ensure that you combine and cycle herbicides with distinct modes of action. Prior to use, always examine the product label.
| GROUP 1 | Inhibition of acetyl co-enzyme A carboxylase (/ACC’ase inhibitors) |
| Aryloxyphenoxypropionates (Fops): | clodinafop (Topik ® ), cyhalofop (Agixa ® *, Barnstorm ® ), diclofop (Cheetah ® Gold* Decision ® *, Hoegrass ® ), fenoxaprop (Cheetah ®, Gold*, Wildcat ® ), fluazifop (Fusilade ® ), haloxyfop (Verdict ® ), propaquizafop (Shogun ® ), quizalofop (Targa ® ) |
| Cyclohexanediones (Dims): | butroxydim (Factor ® *), clethodim (Select ® ), profoxydim (Aura ® ), sethoxydim (Cheetah ® Gold*, Decision ® *), tralkoxydim (Achieve ® ) |
| Phenylpyrazoles (Dens): | pinoxaden (Axial ® ) |
List of chemical families, authorized active ingredients, and, in parentheses, the brand name of the first registered product or its successor. Consult the APVMA website for a comprehensive listing of registered items from the PUBCRIS database. CropLife Australia; URL: https://croplife.org.au/resources/programs/resistance-management/specific-guidelines-for-group-a-herbicides-2-draft/; Last updated: 30 June 2022
What three types of herbicides are there?
Every year, several aquatic herbicides are administered to lakes around the United States ( Figure 7 ). Herbicides for aquatic environments come into two broad types. Systemic herbicides are absorbed and carried via the vascular system of the plant, resulting in the death of the entire plant.
Touch herbicides destroy the portion of a plant that comes into contact with the chemical, but the plant’s roots may survive and it may regenerate. Herbicides with a broad spectrum will destroy the majority of plants they meet. Selective herbicides will harm just some plants, generally broad-leaf or dicot plants such as Eurasian water milfoil.
Although herbicides are screened to minimize harm to other aquatic organisms at recommended application rates, it is important to remember that the effect of herbicide breakdown products, herbicide interactions in the environment, and impacts of herbicides on all life stages of all aquatic organisms are not well studied.
Additionally, aquatic creatures inhabiting plants may be harmed by habitat loss. Herbicides have been demonstrated to be successful in reducing noxious weeds, but they can have unexpected consequences such as decreased water clarity, dominance by a non-target invasive species, and resumption of dominance by the target invasive species after just a few years.
In addition to the number of vulnerable and tolerant plant species, the morphometry of the lake, and the lake’s trophic state are other factors for chemical treatment. Figure 7, Aquatic plant herbicide applicator. Read complete chapter URL: https://www.sciencedirect.com/science/article/pii/B9780124095489091028
Artificial turf is more durable and resistant to weeds than real grass. However, it is feasible for weeds to grow through the backing material’s microscopic gaps and along its edges. Occasionally, depending on the type of infill utilized, weeds may grow in the infill.
What weeds commonly invade Bermuda grass?
Common Bermuda Grass Lawn Weeds – There are two major types of weeds: grassy weeds (including crabgrass, nutsedge, Poa annua, foxtail, goosegrass, barnyardgrass, and witchgrass) and broadleaf weeds (includes purslane, pigweed, goosefoot, London rocket, spurge).
Grassy weeds can go unnoticed because they resemble grass, but broadleaf weeds have real leaves and are much more noticeable. Grassy weeds sprout a single leaf from their seeds, whereas broadleaf weeds sprout two leaves. Both forms of lawn weeds are detrimental to your bermuda grass and must be eradicated properly to maintain a healthy lawn.
Dandelion, chickweed, doveweed, white clover, purslane, and spurge are the most prevalent broadleaf weeds in bermuda grass. Dandelion, chickweed, doveweed, white clover, spurge, and purslane are seen from left to right in the image above. Crabgrass, dallisgrass, yellow nutgrass, and annual bluegrass are seen from left to right in the image above.
If you can identify the weeds in your yard, you can make better educated decisions about which products to use by reading the labels. Be cautious to properly examine the product labels to see if the chemical may be applied to your lawn without causing damage. Follow the application directions on the product’s label.
For further information, please see Recognizing Common Lawn Weeds. It is crucial to be aware that there are a number of cultural, non-chemical weed management strategies available.