Turf Weed Management Strategies

Turf Weed Management Strategies

Identify Weed Species and Determine Life Cycles

Don’t assume you have the same weed or weeds as your neighbor. You may not even have the same turfgrass.


Weed Identification

Risky method – but quick

Ask your neighbors or friends.

(They sometimes are wrong, and you can end up wasting money on ineffective control measures.)

Turf Weed Management StrategiesWeed Identification

Possible time consuming method – but reliable

Dig up samples and take to your local county cooperative extension office for identification and a control recommendation.

(If they can id at the office, this is not time consuming. If they can’t id, they will send your sample to the weed science department at NCSU. A reply could take days or weeks.)


When sending samples, collect healthy, normal growing weeds if possible and include above ground as well as below ground vegetation.

Wrap weeds in moist paper towels to keep as fresh as possible and put in a plastic bag.

Describe the area where the weed problem exists.


Quickest reliable method

Learn to identify weeds by yourself. A diagnostic kit consisting of a magnifying lens and weed id guide or guides would be helpful.

(The sooner you know the weed population, the sooner you can develop a weed management strategy.)


Weed Identification Guides

To identify mainly from pictures, there are several excellent weed id guides for settings such as turfgrasses, crops, ponds and forests. Many of these guides include control options as well.



Color Atlas of Turfgrass Weeds

• Authors include, McCarty, Everest, Hall, Murphy and (Yelverton – NCSU)

• Includes control options



Univ. of GA Cooperative Ext. Service Website

• Identification and Control of Weeds in Southern Ponds

• Poisonous Plants of the Southern United States

• Weeds of Southern Turfgrasses

• Weeds of Southern United States



The Southern Weed Science Society

• Forest Plants of the Southeast and Their Wildlife Uses

• Weed Identification Guide



Dr. Joe Neal Website - NCSU

• Identifying Seedling and Mature Weeds

• Weeds of Arkansas

• Weeds of Southern Turfgrass

• Weeds of the Northeast



To identify weeds (plants) using keys that give plant descriptions that notice its essential characters, synonyms and place of growth, we at NCSU use books entitled…

New Britton & Brown Illustrated Flora

and also

Turfgrass Pest Management Manual

Turf Weed Management StrategiesWeed Identification Guides

Problems associated with turf managers using botanical identification books such as New Britton & Brown Illustrated Flora…

Identification based on flower and reproductive structures (these are constantly being removed by mowing – so you hardly ever get to see these)

Mowed grasses are sometimes impossible to correctly id.

Turf Weed Management StrategiesWeed Identification Guides

Problems associated with turf managers using books such as New Britton & Brown Illustrated Flora…

You would need to know scientific terminology of flower and reproductive structures, as well as other plant parts.

(What are glumes, lemmas, stamens, pistils, etc…)



An advantage using books such as New Britton & Brown Illustrated Flora…

Contains thousands of grass AND broadleaf plants (you probably won’t have a specimen that is not listed) – Your plant sample can most likely be identified if you are persistent.



Turfgrass Pest Management Manual

• Keys out grasses only (weeds and turf) using vegetative instead of reproductive characteristics

• Photos of grass and broadleaf weeds with general descriptions of growth characteristics

• Consists of plants commonly grown in NC

Weed BiologyTen Most Common Weeds in North Carolina Turf

1. Annual bluegrass2. Crabgrass species (smooth, large)3. Dallisgrass4. Chickweed species (common, mouseear)5. Goosegrass6. Henbit7. Clover species (white, hop)8. Dandelion9. Wild garlic10. Kyllinga species (green, false-green)

2000 Proceedings - SWSS

Weed BiologyTen Most Troublesome Weeds in North Carolina Turf

1. Annual bluegrass2. Dallisgrass3. Kyllinga species (green, false-green)4. Crabgrass species (smooth, large)5. Goosegrass6. Virginia buttonweed7. Purple nutsedge8. Violet species9. Yellow nutsedge10. Wild garlic

2000 Proceedings - SWSS

Grass Vegetative Key

Based primarily on…

1. Leaf vernation

2. Ligule

3. Auricle

4. Collar

5. Sheath

and also presence or absence of rhizomes or stolons


Leaf vernation is the arrangement of the leaves of the budleaf (youngest leaf) and surrounding sheath.

Leaf vernations are either rolled or folded (V-shaped) in the bud leaf.


Grasses rolled in the budleaf include…

Smooth crabgrass

Bahiagrass

Bentgrass

Dallisgrass

Tall fescue

Foxtail species

Annual ryegrass


Grasses folded in the budleaf include…

Bermudagrass

Bluegrass species

Carpetgrass

Centipedegrass

Goosegrass

Perennial ryegrass

St. Augustinegrass


Ligule is a protruding structure from the upper leaf surface where the blade and sheath join.

Ligules can be membranous (shiny), hairy, membranous with hairs or absent.


Creeping bentgrass

Bluegrass species

Smooth crabgrass

Dallisgrass

Tall fescue

Annual ryegrass

Perennial ryegrass

have membranous ligules


Bermudagrass

Carpetgrass

Foxtail species

St. Augustinegrass

Zoysiagrass

have hairy ligules


Bahiagrass

Centipedegrass

Goosegrass

have membranous ligules with hairs

Barnyardgrass does not have a ligule.


Auricle is a pair of appendages protruding from the sides of the grass leaf at the junction of the blade and sheath.

Auricles can be rudimentary (short and blunt), large and claw-like or absent.


Tall fescue has short or blunt auricles.

Annual and perennial ryegrass have large or claw-like auricles.

The remaining previously-mentioned grasses have no auricles.


Collar is the region on the back side of a leaf where the leaf blade and sheath are joined.

Collars can be divided by the leaf midrib or continuous, with shapes ranging from broad to narrow.


Bluegrass species

Smooth crabgrass

Tall fescue

Foxtail species

Perennial ryegrass

have collars divided by a midrib


Bahiagrass, creeping bentgrass

Bermudagrass, carpetgrass

Centipedegrass, dallisgrass

Goosegrass, annual ryegrass

St. Augustinegrass, zoysiagrass

have continuous collars

Why Weeds are Present in Turfgrass

Weeds are the result of improperly managed turf.

What is Properly Managed Turfgrass?

The turf species must be adapted to its environment.

•Should you choose cool or warm season turf?

•Is it shade tolerant?

(St. Augustine, tall fescue, perennial bluegrass)

•Does it require full sunlight? (Bermudagrass)


Turf must be mowed at proper height and frequency.

3 Inch Turf Mowing Height

Tall fescue

Tall fescue / fine fescue / per. bluegrass mixtures


2.5 Inch Turf Mowing Height

Perennial bluegrass / perennial ryegrass mixtures

Bahiagrass

St. Augustinegrass


2 Inch Turf Mowing Height

Perennial bluegrass

Perennial bluegrass / fine fescue


0.75 – 1 Inch Turf Mowing Height

Bermudagrass

Centipedegrass

Zoysiagrass


The turf must be fertilized at the proper time with the proper rate and technique.


Cool Season Turf Nitrogen Timings and Amounts

For all cool season turf, start applications in September – October and finish in February – March. Do not apply nitrogen in the spring or summer because of disease concerns.

3 lbs of N per 1000 sq ft per year is sufficient.


Warm Season Turf Nitrogen Timings and Amounts

Timings and rates vary between species, but generally start in the spring and fertilize through summer. Do not apply nitrogen in the fall or winter.

Total N rates range from 0.5 lb per 1000 sq ft per year for centipedegrass to 6 lbs for hybrid bermuda.


The turf site must be well drained, noncompacted and receive adequate rainfall or irrigation.

Indicator Weeds

Some weeds prefer conditions such as low / high pH, compaction, shade, dry / wet soils, or low / high nitrogen.

Under these conditions, the turf may perform poorly, but these weeds will continually be a nuisance until the underlying problem is corrected regardless of the choice of herbicides.

Indicator Weeds

The presence of an indicator weed suggests a condition but is not proof of a condition.

It is not always feasible or practical to fix the underlying problem because of money, time or human nature.

Indicator Weeds

Herbicides are short-term solutions and can’t compensate for poorly managed turf. Consider them as band-aids or duct tape (temporary fixes).

Herbicides will not eliminate weeds permanently, but correcting the origin of turf stress may.

Indicator Weed Examples

Low soil pH Red sorrel

High soil pH Broadleaf plantain

Droughty soils Spotted spurge, black medic, knotweed, woodsorrel species,

lespedeza, bracted plantain

Wet soils Sedge and kyllinga species, annual bluegrass,

goosegrass, moss, algae

Indicator Weed ExamplesHigh nematodes Spotted spurge, prostrate

knotweed, Florida pusley

Low mowing height Annual bluegrass, chickweed species, algae

Low soil nitrogen Legumes (clover, chickweed and speedwell species, black medic, chicory), broomsedge, bitter sneezeweed

High soil nitrogen Annual bluegrass, ryegrass species, moss

Indicator Weed Examples

Poor (sandy) soil Sandspur, poorjoe, quackgrass

Compacted soil Annual bluegrass, goosegrass, prostrate knotweed, spotted spurge

Shade Ground ivy

Weed Control Procedures

A successful weed management strategy should integrate all of these procedures and not rely heavily on one.

Preventative

Mechanical

Biological

Cultural

Chemical


Preventative

•Good sanitation

Clean mowers, tillage implements and other turf equipment before moving to new sites to remove weed seeds and vegetative material.


Mechanical

•Physical removal by hand or tillage

Effective on annual weeds when the growing point is removed or buried

Ineffective on perennial weeds that have underground storage organs unless done repeatedly


Mechanical

•Mowing

Effective on many annual broadleaf weeds that have an upright growth habit

Ineffective on common broadleaf weeds such as prostrate knotweed, spotted spurge and common lespedeza because of low growth


Mechanical

Mowing (continued)

Mowing prevents seed formation in annuals.

However, mowing is generally not effective on grassy weeds and many perennial weeds. One exception for perennial weeds is yellow nutsedge, which can’t produce tubers with frequent mowings at 1.5 inches or less.


Biological

Biological weed control utilizes natural enemies such as insects, fungi, bacteria and nematodes.

This method is generally limited to large areas where a single weed dominates and other control methods are not practical.

Example – thistle control in rangelands with weevils


Biological

Turf example with limited success: Xanthomonas campestris (bacteria) on annual bluegrass

Mow and immediately apply bacteria which enters the cut surfaces to produce wilt which kills the plant

Biologicals don’t give rapid kill like chemicals. This is not enticing to many consumers. People usually want problems fixed quickly.


Cultural

The best way to prevent weed problems in turf is to properly manage the turfgrass.

•Select an adapted grass species

•Mow at proper height and frequency

•Fertilize at proper time and rates

•Irrigate as needed in morning, not late evening

•Improve soil drainage by adding soil or soil mixes


Chemical

The quickest way to prevent weed problems in turf is to apply herbicides.

Herbicides are short-term solutions. Results can be seen quickly, and people are happy. Herbicides do not correct the problem as to why weeds were present in the first place. As long as the problems are not corrected, the need for herbicides will exist.

Turf Weed Management Strategies

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