Skip to main content
ARS Home » Southeast Area » Auburn, Alabama » Soil Dynamics Research » Research » Publications at this Location » Publication #303056
Title: Confirmation of glyphosate-resistant common ragweed in North Alabama

Author
item FLESSNER, M - Auburn University
item MCELROY, J - Auburn University
item BURMESTER, C - Auburn University
item Price, Andrew
item DUCAR, J - Auburn University

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 2/28/2014
Publication Date: 2/28/2014
Citation: Flessner, M.L., Mcelroy, J.S., Burmester, C.H., Price, A.J., Ducar, J.T. 2014. Confirmation of glyphosate-resistant common ragweed in North Alabama. Southern Weed Science Society. CDROM.

Interpretive Summary:

Technical Abstract: Glyphosate resistant common ragweed (Ambrosia artemisiifolia) was first reported in Arkansas and Missouri in 2004 and has since been reported across the mid-west from the Dakotas to Pennsylvania. Objectives of this research was to evaluate common ragweed populations collected from Madison County for glyphosate resistance and compare their tolerance level to a known susceptible population. Common ragweed was collected from the suspect glyphosate resistant population, which was named ‘original field,’ and transplanted in the greenhouse. Glyphosate was applied at 1.12 kg ae ha-1 to the transplants, and seed from plants with the quickest recovery were collected for a population named ‘suspected one’ (S1). Common ragweed from a different field in Madison County was also collected, and this population was named ‘barn-field.’ Lastly, common ragweed seed was purchased from Azlin Seed Service and used for a glyphosate-susceptible population named ‘common.’ Two maturity levels were evaluated. Treatments included 0, 0.14, 0.28, 0.56, 1.12, 2.24, 4.5, 9.0, 18.0, and 36.0 kg ae ha-1 glyphosate applied at 280 L ha-1 (30 GPA). I50 values (glyphosate rate resulting in 50% visual control or fresh weight reduction) were compared between populations using 95% confidence intervals. Data from the large growth stage indicate that original field, barn-field, and S1 were 24, 17, 12 times more tolerant to glyphosate than the common (susceptible) population, respectively. Fresh weight reduction data from the small growth stage indicate that original field and barn-field were 3 to 4 times more tolerant than the common (susceptible) population; the S1 population had a similar tolerance to all other populations. Fresh weight reduction data from the large growth stage indicate that original field and barn-field were approximately 3.4 and 7.9 times as tolerant to glyphosate as the common (susceptible population), respectively, while S1 and common were similar in tolerance. These results confirm common ragweed resistance to glyphosate in Madison County, AL, with a 3.4 to 24 fold increase in tolerance. While the level of glyphosate resistance varied with population and growth stage, it can be clearly surmised that all populations are highly resistant to glyphosate applied alone. On average, original field and barn field had I50 values of 1.1 and 0.71 kg ae ha-1 while the large growth stage had I50 values of 4.8 and 1.8 kg ae ha-1, as estimated by visual and mass reduction data types, respectively. Therefore, if glyphosate is applied at the small growth stage compared to the large, 2.5 to 4.6 times less glyphosate may be necessary for control.