Flexstar GT labeled

Chris Boerboom, Extension Weed Scientist

Syngenta has registered Flexstar GT for postemergence weed control in Roundup Ready soybeans. Flexstar GT is a premix of the ingredient in Flexstar (fomesafen) and glyphosate. One use of this premix is to control glyphosate-resistant weeds such as common and giant ragweed and waterhemp. However, to control glyphosate-resistant biotypes, Flexstar GT needs to be applied at an early stage of growth for the Flexstar component to be effective. For resistant weeds, this is often a 2 inch maximum height. Flexstar GT could also be used as a strategy to lessen the risk of resistance as it contains two modes of action. To capitalize on the two modes of action, early postemergence applications also need to be made. Spraying large weeds with Flexstar GT may provide effect control, but defeats the purpose of having the second mode of action if the weeds are too large to be controlled by Flexstar. One advantage of an early postemergence application is that Flexstar has some residual activity if activated by rain. The timing of Flexstar GT should be driven by weed size, but applications cannot be made within 45 days of harvest.

The Flexstar GT rate is limited to 3 pt/a in central and northern Wisconsin (north of Hwy 18 west of Madison and I-94 east of Madison) in alternate years. Check the label for the northern counties that are included. In the central sands, Adams, Marquette, Portage, Waupaca, Washara, and Wood counties are excluded. South of this line, 3.75 pt/a can be used. At these rates, Flexstar GT would provide these equivalent amounts of Flexstar and glyphosate.

Flexstar GT	Equivalent to	Flexstar		Glyphosate	(3 lb/gal generic formulation )
3 pt/a	=	1 pt/a	+	1 lb ae/a	(42 oz/a)
3.75 pt/a	=	1.3 pt/a	+	1.23 lb ae/a	(53 oz/a)

Many of the Flexstar GT use directions are similar to the Flexstar label. Remember that Flexstar is a contact herbicide and through spray coverage is important. Spray volumes of 15-20 gpa and flat fan nozzles are recommended and air-induction nozzles should not be used. Flexstar GT has an adjuvant system, but ammonium sulfate can be added as with most glyphosate products.   Soybean, dry beans, and snap beans can be replanted at anytime, but small grains should not be planted for 4 months and corn (field, seed and sweet) and peas should not be planted for 10 months. Alfalfa and other crops should not be planted for 18 months.