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Fall Panicum: Biology and Control in Sugarcane1
Curtis Rainbolt and Brent Sellers2Fall panicum (Panicum dichotomiflorum) is a native grass that can be found throughout the United States in agronomic and horticultural crops, turfgrass, nurseries, landscapes, and noncrop areas. It grows well in warm wet conditions and is one of the most common grass weeds found in Florida sugarcane.
Biology and Identification
Fall Panicum is an annual that primarily emerges in spring and summer, but seed germination can occur almost year-round in Florida sugarcane fields. However, it tends to be sensitive to shading and is typically not found in sugarcane once canopy closure occurs. In sugarcane, fall panicum typically reaches a height of 1.5 to 4 feet, but has been reported to reach over 6 feet in height. Its growth habit can range from erect to sprawling and it can form large loose tufts. Seedlings and mature plants have different identifying characteristics.Seedlings
Fall panicum seedlings (Figure 1) often have a purple tint and the first few leaves have many hairs on the underside. The sheaths and collars of the first few leaves also tend to be densely hairy. However, as the seedling grows and new leaves emerge they gradually become less hairy. Leaves are rolled in the bud and auricles are absent. Leaf blades are ¾ to 1 ½ inches long and about 1/5 inch wide. Ligules are 1/24 to 1/12 inch long, fringed, hairy, and often fused at the base.
Figure 1. Fall panicum seedling in a sugarcane field. Mature Plants
The leaf blades of mature plants are 4 to 20 inches long by 1/5 to 4/5 inch wide and have a conspicuous midvein. The undersides of leaves on mature plants are without hairs (glabrous) and glossy. Stems are glabrous, round, and sometimes glossy. Nodes along the stem are usually swollen and bent in different directions ( Figure 2 ), which contributes to the rather unusual zigzag growth habit of this weed. Stems are capable of rooting at the lower nodes. The seedhead is a wide, spreading panicle 4 to 16 inches long ( Figure 3 ). Individual spikelets are yellow and approximately 1/8 inch long by 1/12 inch wide. Each spikelet produces 1 smooth, dull-yellow-to-brown seed.
Figure 2. Swollen and bent node of a mature fall panicum plant.
Figure 3. Fall panicum with mature seedheads. Control in Sugarcane
Preemergence or Very Early Postemergence
Fall panicum can be effectively controlled preemergence (PRE) or very early postemergence (VEPOST) with the following treatments:
- Aatrex1and others (atrazine) can be applied PRE or VEPOST to control fall panicum at 6 to 8 pts per acre. If applied VEPOST, fall panicum should be 2 inches or less in height. It can also be applied in combination with Evik (ametryn) at 0.25 to 1 lb per acre. The addition of Evik can increase POST activity, but can also result in increased crop injury to sugarcane. Lower rates of Evik should be used when temperatures are warmer.
- DuPont K4 (hexazinone + diuron) can be applied at 4 lbs per acre PRE or VEPOST to fall panicum and POST to sugarcane less than 18 inches tall. POST applications to actively growing sugarcane may result in crop injury when daily temperatures exceed 80 degrees F.
- Prowl 3.3 or Prowl H2O (pendimethalin) applied at 8 or 7.2 pts per acre, respectively, will provide PRE control of fall panicum. Prowl does not have postemergence activity.
- Sencor1 (metribuzin) can be applied at 1.33 to 2.33 lbs per acre (on muck soils only) PRE or VEPOST for control of fall panicum. If applied VEPOST, fall panicum should be 2 inches or less in height. Sencor in combination with Prowl is also an effective treatment for fall panicum.
1 WARNING: The following information has been added to the atrazine and metribuzin labels. This statement should be heeded by all prospective users and steps should be taken to comply with this label change:
"Atrazine and metribuzin are chemicals which can travel (seep or leach) through soil and can contaminate groundwater as a result of agricultural use. Atrazine and metribuzin have been found in groundwater as a result of agricultural use. Users are advised not to apply atrazine or metribuzin where the water table (groundwater) is close to the surface and where the soils are very permeable, i.e., well-drained soils such as sands and loamy sands. Your local agricultural agencies can provide further information on the type of soil in your area and location of groundwater. In addition, some product label statements include as a further qualification of risky soils, soils containing sinkholes over limestone bedrock, severely fractured surfaces, and substrates which would allow direct introduction into an aquifer."
Postemergence
Fall panicum can be effectively controlled postemergence (POST) with the following treatments:
- Asulox and others (asulam) can be applied broadcast, or directed, in sugarcane at least 14 inches tall at 6 to 8 pts per acre for postemergence control of fall panicum. Apply only once per season and not less than 90 days before harvest. The addition of a non-ionic surfactant at 0.25% v/v is recommended.
- Envoke (trifloxysulfuron) can be applied 0.3 oz per acre to control fall panicum seedlings less than 6 inches in height. It can be applied broadcast in ratoon cane, but can only be applied directed in plant cane. For control of larger fall panicum plants, Envoke at 0.3 oz per acre can be tank-mixed with 4 pt Asulox and applied broadcast to ratoon cane ( Figure 4 ). Envoke should always be applied with non-ionic surfactant at 0.25 % v/v.
Figure 4. Fall panicum treated with an Asulox + Envoke tank mixture.
Footnotes
1. This document is SS-AGR-132, one of a series of the Agronomy Department, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida. Original publication date September 2006. This publication is also a part of the Florida Sugarcane Handbook, an electronic publication of the Agronomy Department. For more information you may contact the editor of the Sugarcane Handbook, R.A. Gilbert (ragilbert@ifas.ufl.edu). Visit the EDIS Web Site at http://edis.ifas.ufl.edu.2. Curtis Rainbolt, assistant professor, Agronomy Department, Everglades Research and Education Center--Belle Glade, FL; Brent Sellers, assistant professor, Agronomy Department, Range Cattle Research and Education Center--Ona, FL; Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, FL 32611.
The use of trade names in this publication is solely for the purpose of providing specific information. UF/IFAS does not guarantee or warranty the products named, and references to them in this publication does not signify our approval to the exclusion of other products of suitable composition. All chemicals should be used in accordance with directions on the manufacturer's label.
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U.S. Department of Agriculture, Cooperative Extension Service, University of Florida, IFAS, Florida A. & M. University Cooperative Extension Program, and Boards of County Commissioners Cooperating. Larry Arrington, Dean.
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