The following information was just released by Oklahoma Secretary of Agriculture, Terry Peach. It is important to note that this is a crisis exemption. Normally this means the exemption is good for 15 days but extenuating circumstances may prolong use.
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Justification for Crisis Determination:
During the 2008 season, Oklahoma submitted an application for the use of Pendamethalin (Prowl H2O) to control sandbur species in Bermuda grass pastures and hay fields in Oklahoma. Before the use season, Oklahoma declared a Crisis to use the product Prowl H20 in order to save thousands of acres of pasture to the noxious grassy weed species of sandbur. The product performed well and was instrumental in saving hay crops on at least 15,000 (fifteen thousand acres). This is the first time in several years that sandbur control was obtained since the product imazapic (Plateau) was withheld from growers and was unavailable for use.
During 2009, growers in south Oklahoma have not been able to use the product because approval came too late in the season. Prowl H20 must be applied before sandburs begin to grow in the spring since it is a pre-emergent herbicide. Once the weed has emerged, it cannot be killed in a grass crop by any product except Pastora. During 2009, the use of Prowl H20 was greatly reduced over what was initially forecast.
The reason being the product was approved so late in the growing season that many thousands of acres did not benefit from this Section 18.
Since it did not rain, Prowl H20 was not applied in many situations. If the application is too late in the season and the field sandbur or the Bermuda grass has emerged or if the Bermuda grass has broken dormancy, the application is lost. This is the case in “all” of Oklahoma now with sandburs actively growing.
If rain does not come or if the sand bur has emerged, then the only way to control them is with a post emergent application of Pastora when the weed is between 1.5 inches tall or at the 3-leaf stage. This treatment is also possible for fields where the grower did not know the weeds were there or growers who did not want to risk an application using Prowl and not knowing if the rain would occur to activate it.
Dr. Paul Baumann, State Weed Specialist of the Texas AgriLife Extension Service at (979) 845-0877, may answer additional questions.
USE DIRECTIONS
This product is a NON-RESTRICTED USE pesticide when used under a Section 18 in Oklahoma.
All restrictions and requirements concerning the proposed use and the qualifications of applicators using Pastora Herbicide (dry flowable granule) [Nicosulfuron (56.2%) + Metsulfuron (15.0%)] are as follows:
All applicable directions, restrictions, and precautions on the EPA label must be followed unless otherwise modified in this authorization document.
Use of this pesticide is authorized to begin on April 17, 2009.
Pastora Herbicide (Nicosulfuron + Metsulfuron) may be applied to improved pastures and hay fields of Bermuda grass grown for forage, hay and grazing in Oklahoma.
Sites to be treated:
Pastures and Bermuda grass hay meadows infested with sand bur.
Method of Application:
Pastora may be applied by ground or air equipment. Refer to the “use directions” for restrictions and application details.
Rate of Application (amount of active ingredient (ai) and product)
Sandbur: For the control of sandbur species, apply Pastora Herbicide at a broadcast rate of 1.0 to 1.5 ounces per acre. This would be 0.035 lb ai Nicosulfuron + 0.009 lb ai Metsulfuron methyl for 1.0 ounce Pastora; or 0.052 lb ai Nicosulfuron + 0.014 lb ai Metsulfuron methyl for 1.5 ounces of Pastora per acre. Do not apply more than 2.5 ounces of Pastora per acre per year or 0.087 lb ai Nicosulfuron and 0.023 lb ai of Metsulfuron methyl of lb. ai per acre per year.
Maximum number of Applications
Do not apply more than 2.5 ounces per acre per crop season. Usually only one application is needed per season; however, since field sand bur can sprout and grow any time during the season, a second application may be necessary.
Total Acreage to be treated:
There are approximately 18.2 million acres of permanent grass pastureland plus an additional 2.8 million acres of improved hay fields that may need treatment (Oklahoma Field office of USDA-NASS 2007 Census and personal communication).
This application assumes that 50% of the growers may need this treatment since it allows growers to wait and see how many acres need treated and where the product is needed. They may need to use it as a rescue treatment where the Prowl H20 treatment was not effective. In this case, 2.5 million acres are needed under this section 18.
Total Amount of Pesticide to be used:
If all 2.5 million acres in Oklahoma were to be treated using the maximum rate of 2.5 ounces per acre per year, a total of 6,250,000 ounces or 390,625 lb. of Pastora would be needed. Since it is almost impossible to quantify how many acres are infested with sandbur, an average is being used to calculate the amount of product and active ingredient needed.
Use Season:
Application should be made when the sandbur is less than 1.5 inches tall and/or across and is actively growing. Make applications to Bermuda grass that is less than 4 inches tall following initial green-up in the spring or after cutting for hay. Tall, dense stands of Bermuda grass can intercept spray and reduce sandbur control. A follow-up application of Pastora may be necessary to control subsequent germination (flushes) of sandbur following the first application.
Sandbur greater than 1.5 inches tall may be suppressed resulting in a reduction in sandbur seed heads. In contrast, sandbur control in areas with thin stands of Bermuda grass may not be satisfactory.
Dr. Paul Baumann has indicated that field sand bur cannot be controlled with any other product once the weed has emerged and after the Bermuda grass has greened up and is growing for the season. This allows Pastora to be used after it is too late for other products to be used. The use season for this product would start in Oklahoma in April and continue into the summer as the weather warms up.
Harvest Season:
Harvest or grazing may begin at any time and continue periodically through the season. There are no grazing or haying restrictions for Pastora for livestock including cattle, horses, sheep, goats, and other animals when Pastora is used as directed.
Section 166.20(a) (3) (VI):
• All applicable restrictions and requirements concerning the proposed use, and the qualifications of applicators using Pastora Herbicide must be followed.
• All applicable directions and precautions on the EPA approved exemption must be followed.
• These ”use directions” must be in the possession of the user at the time of the pesticide application.
• Follow all precautions and restrictions on the labels of all products applied in combination with Pastora Herbicide. Always follow the most restrictive label.
• Pastora shall be applied only by certified applicators or licensed applicators. The licensed applicator must be certified in the category applicable to the application of a pesticide in fields and pastures for weed control.
• Mixers/loaders and applicators must follow the restrictions on the federal label for cleaning and maintaining PPE. If there are no instructions for washables, use detergent and hot water. Wash PPE clothing separate from other laundry.
• Do not apply to newly sprigged or newly planted Bermuda grass. Apply only to established Bermuda grass that is at least one year old.
• Do not allow spray to drift to adjacent crops.
The Oklahoma Department of Agriculture Food and Forestry is responsible for ensuring that all provisions of this exemption are met. ODAFF is also responsible for providing information in accordance with 40 CFR 166.50(b) and will report any adverse effects resulting from the use of this pesticide in connection with this action.
Pastora Herbicide shall be applied only by certified applicators, licensed applicators or by persons under the direct supervision of a licensed applicator. The licensed applicator must be certified in the category applicable to the application of restricted use pesticides in field crops for weed control.
This product must not be used directly adjacent to native habitat where any endangered species occur. An untreated buffer zone of 200 feet is needed adjacent to any habitat where endangered species may occur in the proximity. This is the first year this request has been submitted by Oklahoma.
