Nursery weed control results for Michigan growers

Research conducted in Michigan nurseries by Ohio State University has led to the approval of two new herbicides Michigan growers can now use in their weed control program, as well as a label expansion for two other products.

Weed control is a key production issue when growing nursery plants either in containers or in field production systems. Michigan growers were the beneficiary of research efforts that were undertaken since 2009 by Hannah Mathers from Ohio State University and with the Michigan Nursery and Landscape Association’s procurement of three Specialty Crop Block Grants that served as the funding source. Michigan State University Extension also played a role in disseminating the research results by hosting two, in-depth weed control workshops, three plot tours and several other weed control discussions in the past three years.

Mathers’ research has assisted with the registration of two new herbicides that Michigan growers can now use in their weed control programs: Biathlon and Marengo. The research has also supported the label expansion for the 2009 registered FreeHand and Tower products by BASF. In addition, several herbicides that are still experimental and are part of the USDA IR-4 program for potential ornamental registration have also been examined. As a result of these efforts, container and field growers in the state now have the four added tools mentioned above and Tower plus Pendulum combinations to rotate with SureGuard and Gallery + Barricade in field weed control programs.

Mathers’ research, assisted by OSU research associate Luke Case, has also examined liverwort (Marchantia polymorpha L.) controls. Liverwort infestations are a common weed problem in nurseries and greenhouses. If uncontrolled, liverwort will lead to reduced plant quality, loss of plant vigor and unmarketable plants at the consumer level. Mathers and Case have shown that SureGuard herbicide at lower rates (3 ounces per acre) on dormant plants will control liverwort and not have any phytotoxicity when used on labeled plants. In addition, via grower input, baking soda applied as a dusting (2.24 grams per square foot) has been proven to effectively control even advanced infestations. Baking soda is not currently labeled for use on liverwort.

Mathers and Case, as a result of these Specialty Crop Block Grants, have submitted two invention disclosures in 2012 for bio-herbicides with commercial potential in nurseries and landscapes to meet the growing demand for clients that want organic or alternative pest control opinions. Currently, in 2013, they are exploring alternatives to fumigation for seedling and liner growers, and pre- and post- emergence herbicides for labeling on extremely difficult weeds in nursery fields.

For more details on Mathers’ herbicide research, please download a copy of her Yearly Research Summary Report 2012 Ornamentals Research, available for download at

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