Submitted to: Weed Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 11, 2002
Publication Date: August 20, 2003
Citation: Papiernik, S.K., Grieve, C.M., Yates, S.R., Lesch, S.M. 2003. Phytotoxic effects of salinity, imazethapyr, and chlorimuron on selected weed species. Weed Science. 51:610-617. Interpretive Summary: The herbicides imazethapyr and chlorimuron ethyl are often used postemergence for the control of weeds in legumes, especially soybeans and peanuts. Depending on the herbicide, plant species, and environmental conditions, stressed plants may have different susceptibility to herbicide damage than non-stressed plants. In controlled greenhouse experiments, we examined the impact of salinization and the herbicides imazethapyr (Pursuit) and chlorimuron ethyl (Classic) on the growth and survival of five weed species. For most tested species, salinization had little effect on plant growth and survival. Observed growth and survival trends were consistent with herbicide label information. For all tested species, most surviving plants were not vigorous and would not be highly competitive with crop plants. A large proportion of irrigated agricultural land is salt-affected, and the reuse of saline drainage water to irrigate salt-tolerant crops is receiving increasing attention. The results of these experiments may help determine herbicide efficacy in these systems, and indicate that weed control aspects of the labels for these herbicide formulations will not require modification for moderately saline soils.
Technical Abstract: Greenhouse experiments were conducted to determine the impact of salinity and herbicide (imazethapyr and chlorimuron) treatment on weed growth. Five species, barnyardgrass, cocklebur, ivyleaf morningglory, common purslane, and yellow nutsedge were grown in potting soil and irrigated with non-saline (EC 2 dS/m) or sulfate-dominated saline (EC 7 dS/m) nutrient solution. Plants were treated postemergence with imazethapyr (Pursuit formulation) at 70 g ae/ha or chlorimuron ethyl (Classic formulation) at 8.8 g ai/ha. Results indicated that irrigation with saline water had no overall impact on the growth or survival of most tested weed species. Growth of yellow nutsedge (maximum height and stem diameter) was reduced for plants irrigated with saline water. Observed growth and survival trends in saline and non-saline treatments were consistent with herbicide label information. Complete control of common purslane was not achieved by either chlorimuron or imazethapyr. Growth and survival of ivyleaf morningglory and yellow nutsedge was greater for plants treated with imazethapyr than with chlorimuron, while for barnyardgrass, growth and survival was significantly greater for chlorimuron-treated plants. Both herbicides affected cocklebur growth and survival in a similar way. For all tested species, most surviving plants were not vigorous and would not be highly competitive with crop plants. The results of these experiments suggest that weed control aspects of the labels for these herbicide formulations will not require modification for moderately saline soils.