Weeding Out the Right Ingredients
Weeding Out the Right Ingredients By Brandi D. Thomas

The most often requested "control product" is for lawn, and then garden weed control. If your employees have trouble telling preemergents from post, this guide to active ingredients will help.

A customer approaches you: “Excuse me, I’ve got this awful weed in my yard that I can’t seem to get rid of — it’s almost like a vine, and has started twining itself around some of my shrubs. What should I use to control it?” Do you know enough about weeds to identify this as bindweed? Do you merely point her in the direction of your weed control products, passing the responsibility of finding the right product off to the best-marketed package on your shelves? Or do you walk her over to the department, explaining to her the best ways to prevent weed invasion in the future and asking questions about her problem to help her identify the weed and the best control measure?

You risk losing a customer if you leave her hanging — she could pick the wrong product and end up unsuccessful, upset with the product, and by association, your store. If you can tell her which weed control ingredients will solve her problem, however, chances are she’ll not only get rid of the weeds, but she’ll gladly return for repeat purchases.

Getting down to business

The following 14 active ingredients, when applied as directed, are effective against the weeds indicated.

Benefin. A selective, preemergent herbicide for established lawns. Brand names: Balan, Benefin. Weeds: Crabgrass and some other annual grassy weeds, including annual bluegrass, green foxtail and goosegrass; may give partial control of some annual broadleaf weeds (except spurge). Timing: Apply in spring (before April 15), prior to germination.

Benefin+trifluralin. A selective, preemergent herbicide for established lawns. Brand names: Team. Weeds: Crabgrass, annual bluegrass, goosegrass, barnyardgrass, green foxtail and yellow foxtail; may give partial control of some annual broadleaf weeds. Timing: Apply in spring (before April 15), prior to germination.

Benefin+trifluralin+isoxaben. A selective, preemergent herbicide for established lawns; equivalent to pre-mix of Team+Gallery. Brand names: Prevent. Weeds: Controls the same annual grasses as Team, plus the annual broadleaf weeds controlled by Gallery. Timing: Apply in spring (before April 15) prior to crabgrass germination.

DCPA. A selective, preemergent herbicide for established turf. Brand names: Dacthal. Weeds: Many broadleaf weeds (chickweed, purslane, spurge) as well as crabgrass and certain other annual grassy weeds (annual bluegrass, green foxtail); generally provides better control of grasses than broadleaf weeds. Timing: Apply in spring (before April 15), prior to weed germination; lawns should be watered immediately after herbicide application; second application often needed eight weeks later to control spurge and later annuals.

Isoxaben. A selective, preemergent herbicide for established lawns. Brand names: Gallery. Weeds: Annual broadleaf weeds such as chickweed, filaree, knotweed, mustards, pigweed, plantain, prostrate spurge, purslane and woodsorrel; high label rates provide partial control of annual bluegrass, barnyardgrass and green foxtail. Timing: Apply in fall or spring prior to weed germination; controls only weeds that emerge from seed following application; does not control overwintering annuals, or perennials emerging from crowns or roots.

Pendimethalin. A selective, preemergent herbicide for established lawns. Brand names: PRE-M. Weeds: Crabgrass and most other annual grassy weeds; also provides control of annual broadleaf weeds such as chickweed, knotweed, puncturevine and spurge. Timing: Apply in spring (before April 15), prior to crabgrass germination.

2,4-D. A postemergent herbicide for basic broadleaf weed control in established lawns; sometimes included with lawn fertilizers; applications in both spring and fall may be required to control difficult weeds; do not make more than two broadcast applications per year. Brand names: 2,4-D Amine, Dandelion Killer, Weed-N-Feed. Weeds: Controls or suppresses many annual and some perennial broadleaf weeds, including bindweed, bull thistle, Canada thistle, dandelion, mallow, plantain, puncturevine, purslane and spurge. Timing: Apply when weeds are actively growing, but not if air temperatures are expected to exceed 80° F within three days after application.

2,4-D+2,4-DP+MCPP. A selective, postemergent herbicide for established lawns; more potent and longer-lasting than 2,4-D alone. Brand names: Triamine. Weeds: Most annual and perennial broadleaf weeds, including those listed under 2,4-D, as well as black medic, chickweed, clover and violet. Timing: Apply when weeds are actively growing but not if air temperatures are expected to exceed 80° F within three days after application.

2,4-D+MCPP+dicamba. A selective, postemergent herbicide for established lawns; more potent and longer-lasting than 2,4-D alone. Brand names: Trimec, Lawn Weed Killer, Feed & Weed, Premium Weed & Feed, Weed-B-Gone. Weeds: Most annual and perennial broadleaf weeds, including bindweed, black medic, bull thistle, Canada thistle, chickweed, clover, dandelion, mallow, oxalis, plantain, puncturevine, purslane, spurge and violet. Timing: Apply when weeds are actively growing but not if air temperatures are expected to exceed 80° F within three days after application; do not apply within the dripline of trees or shrubs; active herbicide can leach down into root zone or woody plants and cause injury.

2,4-D+dicamba+MCPP+MSMA. A selective, postemergent herbicide for established lawns; do not use within the dripline of trees and shrubs. Brand names: Quadmec. Weeds: Same annual and perennial broadleaf weeds as Trimec or Triamine, plus crabgrass and certain other annual grassy weeds. Timing: Apply when weeds are actively growing, but not if air temperatures are expected to exceed 80° F within three days after application.

Glufosinate. A non-selective, foliar-active herbicide for control of weeds prior to lawn establishment or for spot treatment of individual weeds in landscape sites. (NOTE: Any desirable plants, including lawn grasses, contacted by this spray will be killed). Brand names: Finale. Weeds: Annual grasses and broadleaf weeds; provides suppression or temporary control of perennial weeds. Timing: Apply when weeds are actively growing.

Glyphosate. A non-selective, foliar-active herbicide for control of weeds prior to lawn establishment, for lawn edging removal or for spot treatment of individual weeds in landscape sites. (NOTE: Any desirable plants, including lawn grasses, contacted by this spray will be killed). Brand names: Roundup, Killzall, Kleenup. Weeds: Annual grass and broadleaf weeds; also effective against quackgrass, orchardgrass, bermudagrass, other perennial grasses and many perennial broadleaf weeds such as field bindweed and Canada thistle. Timing: Apply when weeds are actively growing; applications to perennial weeds are generally most effective as plants enter the flowering stage, or in early fall.

MSMA. A selective, postemergent herbicide for established lawns. Brand names: Crabgrass Killer. Weeds: Crabgrass and certain other annual grassy weeds. Timing: Apply when grassy weeds are small and actively growing.

Triclopyr+clopyralid. A selective, postemergent herbicide for established lawns. Brand names: Confront. Weeds: Annual and perennial broadleaf weeds; particularly effective against clover and black medic. Timing: Apply when weeds are small and actively growing.

Promote prevention

Your customers may not know that weeds are preventable, so it may be to your advantage to provide them with this information. After all, the less time they have to spend worrying about killing the weeds that foil their landscaping endeavors, the more time they can devote to buying and growing your plants.

The first step to a healthy lawn is buying good-quality, weed-free seed or sod, and seed producers are required to show the percentage of weed seed contained in their packages. Of course, even if a lawn begins from high-quality seed, that doesn’t mean it won’t be subject to contamination later on by birds or wind-blown weed seeds. That’s why it’s important to fertilize your lawn regularly to keep the grass thick and healthy, which will keep weeds from establishing easily. Mowing should be regulated, performed frequently without cutting the lawn so low that the mower damages it and encourages weed invasion. Two inches is generally the right height for clipping. The mower blade should be kept sharp, and clippings should not be removed unless they are excessive and will smother the grass. And finally, advise watering according to weather and soil type; whatever the type, the top half-inch of soil should be allowed to dry out between watering to discourage weed seed germination.

Editor’s note: This is a partial list of active ingredients and brand names. Some of these chemicals may not be available in your area. Please follow all labels as the final authority.