Herbicide Resistant Weeds

Interference and water use of biotypes differing in sensitivity to MSMA.

Akanda, M. R., R. H. Walker, and G. Wehtje. 1996. Interference and water use of biotypes differing in sensitivity to MSMA. Weed Science. 44: 830-835.

Biotypes of common cocklebur (Xanthium strumarium) which were assumed to differ only with respect to sensitivity to MSMA were identified. Water use of these biotypes when grown as isolated plants in a growth chamber was determined with stem flow gauges. The MSMA-tolerant biotype exhibited less whole-plant sap flow at media moisture levels above 17%. Furthermore, only in the tolerant biotype did sap flow differ between the upper and lower canopy; the upper canopy had greater sap flow. Field experiments were conducted at Auburn in 1991-92 to compare growth parameters, water use and competitive ability towards cotton of the MSMA-sensitive and -tolerant biotypes. Sensitive biotype plants were taller and had greater leaf area than those of the tolerant biotype; dry weight was equivalent. The tolerant biotype used less water and reduced seed cotton yield more than the sensitive biotype.