Theses and Dissertations

Issuing Body

Mississippi State University


McCurdy, James D.

Committee Member

Tseng, Te-ming P.

Committee Member

Stewart, Barry R.

Committee Member

Dong, Hongxu

Committee Member

Avila, Luis

Date of Degree


Document Type

Graduate Thesis - Open Access


Plant and Soil Sciences

Degree Name

Master of Science (M.S.)


College of Agriculture and Life Sciences


Department of Plant and Soil Sciences


Quinclorac controls crabgrass (Digitaria spp.) post-emergence in cool- and warm-season turfgrass. A rate response study revealed that two Mississippi smooth crabgrass (Digitaria ischaemum) species (MSU1 and MSU2) are resistant to quinclorac. Following that, field experiments were carried out to evaluate programmatic approaches to control one of these populations. Despite prior study on quinclorac-resistant weeds, to date, quinclorac-resistant smooth crabgrass and its mechanism of resistance have only been reported once in California. The mechanism of resistance of MSU1 and MSU2 relative to susceptible (SMT) was then investigated. The SMT biotype accumulated three times more cyanide than the resistant populations. Glutathione-S-transferase (GST) activity was evaluated as a possible contributor to non-target site resistance. The GST activity was elevated in the MSU1 and MSU2 populations. These findings suggest a non-target site–based mechanism of resistance involving the accumulation of cyanide. Further research is needed to investigate potential target-site mechanisms of resistance.

Available for download on Thursday, May 15, 2025