published in


August 2010

Pastora Herbicide: A New Tool for Grass Weed Control in Bermudagrass

Dr. Brent Sellers
University of Florida/IFAS

photo of Dr. Brent Sellers

For questions or comments regarding this publication contact: Brent Sellers 

A new herbicide mixture was recently labeled for use in established bermudagrass pastures and hayfields for control of weedy grasses. Pastora is a premix of nicosulfuron (56.2%) and metsulfuron (15%). Though metsulfuron has been used for many years in pastures, nicosulfuron is new to this market and provides new opportunities for weed control. The use rate for Pastora is 1.0 to 1.5 oz/acre per application, with a total maximum of 2.5 oz/acre/year. The amount of metsulfuron in 1.0 and 1.5 oz/acre of Pastora is equivalent to applying 0.24 or 0.37 oz/acre of any 60DF formulation of metsulfuron (MSM60, Accurate, Clean Pasture, etc). Though this rate of metusulfuron may not be sufficient to control blackberry or other woody perennials, it will provide superior control of many annual weeds (red sorrel, Carolina geranium, henbit, and others). There are no grazing or haying restrictions when using Pastora. 

The primary target weed for this herbicide has been sandbur, but Pastora will also control many other grass weeds including barnyardgrass, coast cockspur, johnsongrass, vaseygrass, seedling crabgrass, and several others. In addition to grass weeds, several winter and summer annual broadleaf weeds can be controlled with this herbicide. Dogfennel and tropical soda apple will not be controlled with this product. 

For optimum control of grasses, it is essential to apply Pastora when weeds are small. Sandbur should be approximately 2 inches tall for consistent and complete control. Although preliminary data suggests that1.5 oz/acre will control larger sandbur, it is likely that larger plants will be stunted and seedheads aborted, but not necessarily killed. 

Tall, dense stands of bermudagrass will intercept much of the herbicide spray. Therefore, Pastora should be applied for annual grass weed control when bermudgrass is no taller than 4 inches following initial greenup or after cutting for hay. Considering that rainfall is usually limited after initial greenup, applications may need to be delayed for optimum control until after the initial hay cutting and when rainfall is sufficient for active weed growth. 

Vasseygrass is a tall-growing weed that is common on seasonally wet pastures. This weed is very difficult to control, but Pastora holds promise to reduce the influence of this weed species. Data collected within Florida suggests that Pastora will provide between 65 and 80% control of vasseygrass. These applications were made during bermudagrass greenup when rainfall is generally limited. We anticipate slightly better control of vaseygrass after full greenup, but applications will need to be made fairly quickly or vaseygrass will become too large to adequately control.