Understanding what does MSMA herbicide control is essential for homeowners and lawn care professionals seeking effective weed management solutions. MSMA (monosodium methanearsonate) is a selective, organic arsenical herbicide that has been a trusted tool for controlling grassy weeds in warm-season turf for decades. Knowing its strengths and limitations helps you make informed weed control decisions.

MSMA is primarily effective against grassy weeds, making it a valuable component of integrated weed management programs for warm-season lawns. However, its use is limited to specific weed types and turfgrasses, and understanding these limitations is crucial for successful application. Using MSMA incorrectly can result in poor weed control or turf damage.

This herbicide works by being absorbed through the leaves and translocated to the roots, causing plant death through arsenic toxicity. MSMA is particularly effective on annual and perennial grassy weeds that are difficult to control with other herbicides. However, it is not effective on broadleaf weeds or sedges, which require different active ingredients.

This comprehensive guide examines what MSMA herbicide controls, its application methods, turfgrass safety, and alternatives for weeds not controlled by MSMA. With the right knowledge, you can use MSMA effectively and safely in your lawn care program.

What Does MSMA Herbicide Control?

Primary Targets: Grassy Weeds

MSMA is primarily effective against grassy weeds, including both annual and perennial species. The herbicide is absorbed through the leaves and translocated to the roots, providing systemic control of targeted weeds. MSMA works by disrupting plant metabolism through arsenic toxicity, causing yellowing, stunting, and eventual death.

The most common grassy weeds controlled by MSMA include:

• Crabgrass (Digitaria spp.): Annual grassy weed that forms dense patches in lawns
• Dallisgrass (Paspalum dilatatum): Perennial grassy weed with coarse, tufted growth
• Goosegrass (Eleusine indica): Summer annual grass with prostrate growth habit
• Johnsongrass (Sorghum halepense): Aggressive perennial grass weed
• Bermudagrass (Cynodon dactylon): Can be controlled when it invades other turf types
• Sandbur (Cenchrus spp.): Annual grass weed with spiny burs
• Foxtail (Setaria spp.): Summer annual grass with bristly seed heads
• Signalgrass (Brachiaria spp.): Warm-season annual grass weed

What MSMA Does NOT Control

MSMA is not effective on broadleaf weeds, sedges, or certain grassy weeds. Understanding these limitations is essential for successful weed control:

• Broadleaf weeds: Dandelion, clover, plantain, chickweed, Virginia buttonweed, and other broadleaf species
• Sedges: Yellow nutsedge, purple nutsedge, and other sedge species
• Some grassy weeds: Certain perennial grassy weeds may show tolerance to MSMA
• St. Augustinegrass: MSMA can damage St. Augustinegrass and should not be used on this turf type
• Centipedegrass: MSMA can cause injury to centipedegrass
• Fine fescues: Cool-season grasses like fine fescues are sensitive to MSMA

How MSMA Herbicide Works

Mode Of Action

MSMA is an organic arsenical herbicide that works by disrupting plant metabolism. When applied to the leaves of target weeds, MSMA is absorbed and translocated throughout the plant. The arsenic compound interferes with cellular respiration and photosynthesis, causing the plant to yellow, wilt, and eventually die.

The systemic nature of MSMA ensures that the herbicide reaches the root system, providing complete kill of annual and perennial grassy weeds. This is particularly important for perennial weeds like dallisgrass and Johnsongrass, which can regrow from root fragments if not fully controlled.

Application Timing

MSMA is most effective when applied to actively growing weeds. The best application times are:

• Spring: Apply when weeds are actively growing and temperatures are between 60-85°F
• Summer: Can be applied during summer, but avoid application during heat stress
• Fall: Apply to actively growing weeds before dormancy
• Avoid application: During drought stress, extreme heat (above 90°F), or when rain is expected within 24 hours

Turfgrass Safety: Which Grasses Can Handle MSMA?

Safe Turfgrasses

MSMA is generally safe for use on the following warm-season turfgrasses when applied according to label instructions:

• Bermudagrass: Most tolerant of MSMA, excellent for weed control
• Zoysiagrass: Tolerant when applied at recommended rates
• Bahia grass: Generally safe with proper application
• Kikuyugrass: Tolerant of MSMA when applied correctly

Grasses That May Be Injured By MSMA

• St. Augustinegrass: Highly sensitive; avoid use or apply with extreme caution
• Centipedegrass: May be injured; use only with careful application
• Fine fescues: Cool-season grasses are sensitive to MSMA
• Kentucky bluegrass: May be injured; not recommended
• Perennial ryegrass: Sensitive to MSMA; avoid use

MSMA Application Best Practices

• Read the label carefully: Always follow label instructions for mixing rates, application methods, and safety precautions
• Apply to actively growing weeds: MSMA is most effective when weeds are actively growing and temperatures are between 60-85°F
• Use the correct rate: Apply at the recommended rate for your specific turfgrass and weed target. Over-application can damage turf
• Avoid application during stress: Do not apply during drought, heat stress (above 90°F), or when grass is dormant
• Add a surfactant: Adding a surfactant or spreader-sticker can improve MSMA absorption and effectiveness
• Do not mow immediately: Wait 2-3 days after application before mowing to allow herbicide absorption
• Water in if needed: Some formulations require watering in after application; check label instructions
• Monitor results: Allow 7-14 days for visible results, with complete control taking 3-4 weeks

MSMA Alternatives For Weeds Not Controlled

For Broadleaf Weeds

• 2,4-D: Effective on many broadleaf weeds like dandelion, clover, and plantain
• Dicamba: Broadleaf herbicide with excellent control of many species
• Triclopyr: Effective on broadleaf weeds, including hard-to-control species like Virginia buttonweed
• Combination products: Products containing 2,4-D, dicamba, and MCPP provide broad-spectrum broadleaf control

For Sedges

• Halosulfuron (Sedgehammer): Sedge-specific herbicide for yellow and purple nutsedge
• Sulfentrazone: Effective on sedges and some broadleaf weeds
• Imazaquin (Image): Controls sedges and some broadleaf weeds

For Weeds Not Controlled By MSMA

• Quinclorac: Controls crabgrass, dallisgrass, and other grassy weeds that MSMA may miss
• Fenoxaprop: Controls annual and perennial grassy weeds
• Fluazifop: Controls many grassy weed species
• Clethodim: Controls annual and perennial grasses

Common Mistakes When Using MSMA

• Applying to the wrong weed type: MSMA controls grassy weeds only, not broadleaf weeds or sedges
• Applying during hot weather: MSMA can cause turf injury when applied above 90°F
• Using on sensitive turfgrasses: Do not apply to St. Augustinegrass, centipedegrass, or cool-season grasses
• Over-application: Using too much MSMA can damage turf and cause yellowing or dieback
• Poor timing: Applying when weeds are not actively growing reduces effectiveness
• Incomplete coverage: Failing to cover all weed leaves reduces control effectiveness
• Mowing too soon: Mowing within 2-3 days of application removes herbicide before absorption

MSMA Legal And Environmental Considerations

MSMA is a restricted-use pesticide in many areas due to its arsenic content and environmental concerns. The Environmental Protection Agency (EPA) has implemented restrictions on MSMA use, particularly on golf courses and sod farms. Always check local regulations before using MSMA and follow all label instructions carefully.

Environmental concerns regarding MSMA include potential groundwater contamination, soil accumulation of arsenic, and risks to non-target organisms. Proper application techniques, such as avoiding application near water sources and using appropriate rates, help minimize environmental impact.

Frequently Asked Questions About MSMA Herbicide

1. What does MSMA herbicide control?

MSMA controls grassy weeds including crabgrass, dallisgrass, goosegrass, Johnsongrass, bermudagrass (when invading other turf), sandbur, foxtail, and signalgrass. It does not control broadleaf weeds or sedges.

2. Is MSMA safe for St. Augustinegrass?

MSMA is not safe for St. Augustinegrass and can cause significant turf injury. Avoid using MSMA on St. Augustinegrass lawns. If control of grassy weeds is needed in St. Augustinegrass, use alternative herbicides labeled for that turf type.

3. Can MSMA kill crabgrass?

Yes, MSMA is effective on crabgrass when applied during active growth. Apply when crabgrass is actively growing and temperatures are between 60-85°F for best results. Multiple applications may be necessary for complete control.

4. How long does MSMA take to work?

MSMA typically takes 7-14 days to show visible results, with complete control taking 3-4 weeks. Results may vary depending on weed species, growth stage, and weather conditions.

5. Can MSMA be used on cool-season grasses?

MSMA is primarily for warm-season grasses and can injure cool-season grasses like Kentucky bluegrass, perennial ryegrass, and fine fescues. Avoid using MSMA on cool-season lawns.

6. Does MSMA kill nutsedge?

No, MSMA does not effectively control nutsedge. Nutsedge is a sedge, not a true grass, and requires sedge-specific herbicides like halosulfuron (Sedgehammer) or sulfentrazone for effective control.

7. Is MSMA banned?

MSMA is not banned entirely but is a restricted-use pesticide in many areas. The EPA has restricted its use on golf courses and sod farms. Always check local regulations and follow label instructions before using MSMA.

Conclusion

Understanding what does MSMA herbicide control is essential for effective, targeted weed management in warm-season lawns. MSMA is primarily effective on grassy weeds, including crabgrass, dallisgrass, goosegrass, Johnsongrass, and other annual and perennial grass species. It does not control broadleaf weeds or sedges, which require different active ingredients for effective control.

MSMA is a valuable tool for integrated weed management when used correctly on appropriate turfgrasses. Its systemic action provides excellent control of persistent grassy weeds that are difficult to manage with other herbicides. However, its use is limited to warm-season grasses like bermudagrass and zoysiagrass, and it should never be applied to St. Augustinegrass, centipedegrass, or cool-season turf.

For weeds not controlled by MSMA, alternative herbicides are available. Broadleaf weeds respond to 2,4-D, dicamba, and triclopyr, while sedges require specialized products like halosulfuron or sulfentrazone. By understanding the strengths and limitations of MSMA, you can develop a comprehensive weed control program that addresses all weed types in your lawn.

Ready to use MSMA effectively in your lawn care program? Choose the right product for your specific weed problems, follow label instructions carefully, and combine MSMA with other herbicides for complete weed control. Your efforts will reward you with a healthier, more attractive lawn.