Plan Your Yellow Nutsedge Control Strategy Now!

Yellow Nutsedge is a problem perennial weed. It is troublesome because it acts like an annual weed that develops from seeds germinating from the soil seed bank. The tubers are like seed since they are distinct, have dormancy and each can produce a plant. However, the seed produced by Yellow Nutsedge plants is not very viable. In some studies, the viability of seed has been as low as 17% and less than 1% developed into plants.

Overwintering Tubers

The real problem in controlling Yellow Nutsedge comes from allowing overwintering tubers to form. Although Yellow Nutsedge produces foliage, roots and rhizomes along with tubers, only the tubers survive overwinter.

Yellow Nutsedge has the following life cycle. Tubers in the soil germinate in the spring in response to temperature and moisture. The shoot from the tuber (actually a determinate rhizome) establishes a crown just below the soil surface. A single tuber can form 1 to 3 plants. The plant then grows foliage, roots and rhizomes. The rhizomes are not like those of quack grass. They do not overwinter and are not the source of the perennial habit. They do not have active nodes that can sprout. Many indeterminate rhizomes are forming throughout the early part of the growing season. They can grow to the soil surface and form secondary plants that can form more rhizomes and subsequently more plants. This is how Nutsedge is able to develop into a weed problem so quickly. The formation of tubers at the ends of these "indeterminate rhizomes" is what leads to the perennial nature of this weed. The formation of tubers is triggered in response to daylength duration. Once we pass the summer solstice and are receiving less then 14 hours of light per day, some physiological response occurs in the plant and tubers begin to form at the ends of the rhizomes. The tubers that form are dormant until at least the next spring.

Yellow Nutsedge has an unbelievable ability to produce. In a study in Minnesota during the 1960's, single tubers were found to yield 1900 plants and 6900 tubers in a single season. They were distributed to a depth of 9" and covering an area of 2 meters in diameter.

| Top of Page

Tillage

Tubers tend to be distributed near the soil surface unless buried by tillage. In one study 45% of tubers were within 1.5", 79% within 3" and 95% within 5" of the soil surface. Tubers also tend to distribute in close proximity to the mother plant since the rhizomes on which they form have not been found to be longer then 24". This suggests that tillage is a primary factor in Yellow Nutsedge movement within and between fields.

Individual tubers are not long lived in the soil (1-3 years), but Nutsedge continues to be a perennial problem because we allow new tubers to enter the soil seed bank each season. Those tubers buried deeper tend to be longer lived.

Tuber germination begins in early May and continues into July. Uniform emergence that benefits control strategies is associated with shallow, even distribution in the soil suggesting that no-till or shallow tillage are best for control of this weed. Many tubers have been found to die overwinter when present on the soil surface or buried very shallow. This occurs because of tuber desiccation and intolerance to the cold temperatures at or near the soil surface. However, the dormancy of Nutsedge tubers often results in uneven germination, complicating control strategies.

Herbicide Control

Yellow Nutsedge is a weak competitor and tends to be more of a problem where the control of other weeds in the field is good. Without the competition from other weeds, Nutsedge is able to get enough light, nutrients and moisture in a crop canopy to allow tuber formation.

Many herbicide programs for weed control in corn and soybeans are effective in controlling Nutsedge during the early part of the season. This allows the crop to establish and compete vigorously with the Nutsedge. However, the herbicide programs often do not provide control of sufficient duration to prevent emergence, foliage development and tuber production during the later part of the season. This late season control of Nutsedge is critical to managing this weed. Obviously, a single season of preventing new tuber formation will not be sufficient since tubers already in the soil can be viable for 1-3 years or more.

Isolate Patches

Yellow Nutsedge tends to start in patches within a field. Since it is such a troublesome weed because of its perennial nature, high tuber production, long germination pattern, and relative ineffectiveness of chemical control practices, it is wise to isolate the patches. Repeated application of post herbicides throughout the season to the patches is recommended. Once the crop is harvested, it is critically important to prevent Nutsedge foliage production. No foliage means no new tubers. Maintaining this late season foliage free situation for 3-5 years should greatly reduce the infestation.

If possible you may want to consider not cropping the area where the Nutsedge is present. You can then use shallow tillage to stimulate germination, remove foliage and prevent new foliage introduction throughout the season. Non-selective or selective herbicides can be used within this system in combination with tillage or to replace tillage.

| Top of Page

Clean Tillage Equipment

Tillage and other equipment that enters infested areas should be cleaned or inspected before moving to other areas of the field or fields that do not have a Nutsedge infestation. Equipment is probably the biggest variable in an infestation spreading within and between fields. Although many will consider patch isolation, multiple passes with management practices and equipment sanitation to be awkward and time consuming, nothing will have a bigger impact on the control of this species. This works well with new infestations that typically occur near field entrances and occupy a very small portion of the field.

Next month will discuss the effectiveness of specific herbicide programs for Yellow Nutsedge management and how to integrate herbicides and other control methods into a strategy.

| Top of Page |