David M. Kopec, Extension Turfgrass Specialist

Nutsedge is a very troublesome weed in golf course and parks turf. There are two species of nutsedge that infest turf, which include yellow nutsedge (Cyperus esculentus) and purple nutsedge (Cyperus rotundus). Yellow nutsedge is normally found at higher elevations where Kentucky bluegrass, ryegrass, and fescues grow year round. Purple nutsedge predominates in lower elevations, were bermuda grass is the main turf. In Phoenix, both yellow and purple nutsedge can be found, mainly because of the introduction of yellow nutsedge from landscape plantings.

How they grow:

Both yellow and purple nutsedge grow by sending up a shoot in the spring from underground tubers (nutlets). Each nutlet has 3-5 "eyes", just like a potato.

One "eye" sends up one shoot. When the shoot reaches the surface, green leaves form on the stem. At the base of this stem is a swollen bulb, called a "corm". This corm contains the leaves (like an onion bulb). At the base of the bulb, new runners emerge, to produce another plant 2-3 inches away from the original shoot. This process is repeated until the nutsedge fills in between as many turfgrass plants or open bare ground areas as it can! One "eye" from one nutlet can produce over 150 plants in one growing season!

Nutsedge tolerates mowing, and its fast leaf elongation rate lets the leaves grow over the grass to steal sunlight from the turf. In late summer and early fall, food reserves are moved into the underground shoots, forming new tubers (nutlets). Each nutlet has 3-5 "eyes", which will send up new shoots next spring. You can see how easy it is for nutsedge to spread quickly, and why it grows back after either mechanical or chemical treatments.

Nutsedge Identification:

Since chemical control measures are not the same for yellow or purple nutsedge, it is important to know how to identify which nutsedge you have.

Yellow Nutsedge

1. Underground tubers are ¼ inches or less, roughly round shaped, and smooth

2. Underground tubers are not attached to each other in chains. They exist as a single nutlet at the end of an underground chain

3. Seed heads are yellow

4. Leaves are narrow 1/4 to 5/16 inches, light green/yellow in color

5. Leaves are generally upright (60 degrees or more)

Purple Nutsedge

1. Underground tubers are ¼ to ¾ inches in length, scaly (barklike) and oblong
2. Underground tubers when freshly crushed smell like mahogany wood

3. Underground nutlets are often interconnected on long chains

4. Seed head is purple

5. Leaves are 3/8-1/2 inches wide

6. Leaves are more horizontal (about 45 degrees)

The tuber characteristics are the best identification features when identifying nutsedges.

Control:

Mechanical:

The first time you see nutsedge plants, simply pluck them out of the ground by cutting the bottom of the stem below the ground.

This way you remove the corm, and a new "eye" must be used up from a nutlet for another plant to reach the surface. Don't wait! When there are 10-15 plants by a curb, around a tree, or on a tee bank, just pluck them out. Repeat the process when new shoots emerge. This way you use up the nutlet growing points, and there is never enough plants to make new nutlets at the end of the year. It takes more time talking about what to do, than to pluck out the plants at this stage.

Chemical:

New chemicals have reached the market place which suppress nutsedge, and are safer on turf. No chemical will eliminate nutsedge. It takes repeat applications to remove the foliage, which forces regrowth from existing tubers. You must treat and retreat until the tuber population is exhausted. You can reclaim highly infested areas through diligence.

MANAGE (halosulfuson) Controls both yellow and purple nutsedge, and is safe on almost all turfgrasses. Sprayed on the foliage and absorbed through the leaves, it turns leaves yellow in 3-5 days, followed by leaf necrosis. New shoots emerge 3-4 weeks later. After re-emergence, apply a second application.

IMAGE (imazaquin) Controls purple nutsedge in bermuda grass turf. Will eliminate cool season grasses. Weak on yellow nutsedge. Some foliar uptake, mostly soil uptake. Leaves turn yellow 10-14 days after treatment, then necrotic at 21 days.

New shoots appear 4 weeks after treatment. Reapply after new green growth appears.

MSMA (monosodium methane arsonate):

Safe for bermuda grass, burns the foliage quickly when used with a surfactant. Re-apply every three weeks until seasonal maximum is reached.

Note: Tank mixes of MSMA and Image have provided better control of purple nutsedge than either alone.

Note: Rotating herbicides (on bermuda grass) will allow for up to 6 applications in 1 year without exceeding seasonal application rate limits.

Note: Directed and/or spot sprays save you money, time, and usually better weed control.

Note: Repeat applications for 2-3 years can reclaim highly infested areas.