Phytotoxic effects of salinity, imazethapyr, and chlorimuron on selected weed species

Greenhouse experiments were conducted to determine the effect of salinity, imazethapyr, and chlorimuron on weed growth. Five species, barnyardgrass, common cocklebur, ivyleaf morningglory, common purslane, and yellow nutsedge, were grown in potting soil and irrigated with nonsaline (EC ∼∼ 2 dS m⁻⁻¹) or sulfate-dominated saline (EC ∼∼ 7 dS m⁻⁻¹) nutrient solution. Plants were treated after emergence with imazethapyr (Pursuit formulation) at 70 g ae ha⁻⁻¹ or chlorimuron ethyl (Classic formulation) at 8.8 g ai ha⁻⁻¹. Results indicated that irrigation with saline water had no overall effect 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 nonsaline treatments were consistent with information on the herbicide label. Complete control of common purslane was not achieved by either chlorimuron or imazethapyr. Growth and survival of ivyleaf morningglory and yellow nutsedge were greater when plants were treated with imazethapyr than when treated with chlorimuron, whereas for barnyardgrass, growth and survival were significantly greater when plants were treated with chlorimuron. Both herbicides affected common 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 information mentioned on the labels for these herbicide formulations will not require modification for moderately saline soils.Nomenclature: Chlorimuron; imazethapyr; yellow nutsedge, Cyperus esculentus L. CYPES; barnyardgrass, Echinochloa crus-galli (L.) Beauv. ECHCG; ivyleaf morningglory, Ipomoea hederacea (L.) Jacq. IPOHE; common purslane, Portulaca oleracea L. POROL; common cocklebur, Xanthium strumarium L. XANST.