Nutsedge Control in Sugarcane

James Griffin  | 10/9/2015 8:43:48 AM

There is much interest right now concerning what to do with nutsedge showing up in planted fields. Consultants and growers have indicated to me that the nutsedge problem this year is more widespread than in previous years. The problem is partly due to poor control of nutsedge with glyphosate applied during the summer fallow period and also to the rainy period around the time sugarcane was planted. Nutsedge is probably the most difficult weed to control in sugarcane. Purple and yellow nutsedge, often referred to as cocograss or nutgrass, produce underground tubers deep in the soil, making control with traditional soil-applied herbicides nearly impossible. The most-effective means to control nutsedge is through a foliar treatment that is safe to sugarcane. A systemic herbicide that is readily moved within the plant would be desirable because the level of control is directly affected by how much herbicide moves to the nutsedge tubers. A contact herbicide would provide only top growth kill of nutsedge and regrowth from tubers would occur very rapidly.

A common misconception within the industry is that 2,4-D and Weedmaster control nutsedges. We have seen some initial activity from these herbicides, but control is only temporary. When nutsedge is not controlled in the fall in planted sugarcane, weeds can flourish, robbing young sugarcane plants of moisture while giving nutsedge a firm foothold in the field. Because winters in south Louisiana are traditionally mild, a heavy population of nutsedge can be present in the spring as sugarcane is emerging from the winter dormant period. Application of an effective herbicide prior to winter would help lessen overwintering of nutsedge tubers and encourage rapid sugarcane emergence and establishment in the spring. Research conducted here at LSU shows that nutsedge control measures should first be implemented during the summer fallow period to prevent weeds from removing water from the sugarcane beds and to help facilitate planting. The second control measure for nutsedge should be implemented in September or October after nutsedge has emerged following planting of sugarcane or in fields where nutsedge has reestablished following harvest of sugarcane for seed or for early delivery to the mill. Below is information concerning nutsedge control taken from the LSU AgCenter Sugarcane Weed Control Guide.

POSTEMERGENCE WEED CONTROL (SEPTEMBER-NOVEMBER): To control purple and yellow nutsedge in early-planted sugarcane apply Permit at a broadcast rate of 1.0 to 1.33 oz/A with nonionic surfactant at 1 to 2 qt/100 gal of water or crop oil concentrate at 4 qt/100 gal of water. Activity is slow, and four weeks may be needed to maximize control. Other herbicides may be applied with Permit for additional weed control.

We have found a September/October application of Permit herbicide effective in decreasing nutsedge populations the following spring with no negative effect on the sugarcane stand. With the urgency of the current situation, growers are actively spraying 2/3 to 1 ounce per acre of Permit to control yellow and purple nutsedge and to allow sugarcane to establish a stand before winter. The higher rate should be used under a heavy infestation. A new product that we have evaluated extensively this past year is Yukon, a 67.5% water soluble granule formulation. Yukon is a premix of Permit and dicamba, the active ingredient in Banvel herbicide. A 4-ounce-per-acre rate of Yukon, which corresponds to a 2/3-ounce rate of Permit and around 4 ounces of dicamba, has been effective in controlling nutsedges. The dicamba component would also be helpful in controlling small broadleaf weeds. It is my understanding that the cost of Yukon will be $11 per acre for 4 ounces applied broadcast. Yukon should be applied with a nonionic surfactant or crop oil concentrate.

Weed control recommendations for sugarcane and other crops as well as other weed science research and extension information can be found at the Agronomy and Environmental Management Web site.

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