Morehead State University

Poster Title

Screening for Glyphosate (N-(phosphonomethyl) glycine) Resistance in Horseweed (Conyza canadensis) Populations

Institution

Morehead State University

Abstract

Glyphosate (N-(phosphonomethyl) glycine)is a broad spectrum, non-selective weed killer that is used globally, and has been in use since the mid-to-late seventies. Increased and exclusive use of glyphosate with the adoption of Roundup Ready technology in crops such as corn and soybeans has lead to cases of resistance among multiple weeds globally. A remarkably sudden appearance of glyphosate resistance has occurred in horseweed (Conyza canadensis) in the Eastern United States. Glyphosate resistant horseweed has been reported in several states including Delaware, Pennsylvania, Kentucky, Tennessee, Ohio, Indiana, and Arkansas. Seeds were collected from horseweed plants in Preble and Clark counties in western Ohio that were suspected of being glyphosate resistant. The suspect seeds were germinated in the Morehead State University Department of Agricultural and Human Sciences greenhouse and trans-planted into 2 inch x 2 inch cell pack trays. A CO2 pressurized sprayer was used to apply Roundup Weathermax® at rates of 1,2,4,8, and 16 qts/acre when the plants had matured to cover the 2 x 2 cells. The plants were observed and photographed over the next 30 days and injury data was collected. Resistance was found in the plants from Preble County with two plants surviving the 16 qt/acre rate and showing regrowth at 20 days after treatment. Numerous Preble County plants survived at lower application rates. No resistance was detected in Clark County horseweed selections.

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Screening for Glyphosate (N-(phosphonomethyl) glycine) Resistance in Horseweed (Conyza canadensis) Populations

Glyphosate (N-(phosphonomethyl) glycine)is a broad spectrum, non-selective weed killer that is used globally, and has been in use since the mid-to-late seventies. Increased and exclusive use of glyphosate with the adoption of Roundup Ready technology in crops such as corn and soybeans has lead to cases of resistance among multiple weeds globally. A remarkably sudden appearance of glyphosate resistance has occurred in horseweed (Conyza canadensis) in the Eastern United States. Glyphosate resistant horseweed has been reported in several states including Delaware, Pennsylvania, Kentucky, Tennessee, Ohio, Indiana, and Arkansas. Seeds were collected from horseweed plants in Preble and Clark counties in western Ohio that were suspected of being glyphosate resistant. The suspect seeds were germinated in the Morehead State University Department of Agricultural and Human Sciences greenhouse and trans-planted into 2 inch x 2 inch cell pack trays. A CO2 pressurized sprayer was used to apply Roundup Weathermax® at rates of 1,2,4,8, and 16 qts/acre when the plants had matured to cover the 2 x 2 cells. The plants were observed and photographed over the next 30 days and injury data was collected. Resistance was found in the plants from Preble County with two plants surviving the 16 qt/acre rate and showing regrowth at 20 days after treatment. Numerous Preble County plants survived at lower application rates. No resistance was detected in Clark County horseweed selections.