TOXICITY, ABSORPTION, AND TRANSLOCATION OF SOIL AND FOLIAR APPLIED IMAZAQUIN IN YELLOW (CYPERUS ESCULENTUS) AND PURPLE (C. ROTUNDUS) NUTSEDGE

Studies were conducted to investigate the toxicity of soil and foilar applied imazaquin in yellow and purple nutsedge. Soil incorporated imazaquin rates from 0.1 to 0.5 ppmw reduced plant dry weight of yellow nutsedge by 92 to 99%, and that of purple nutsedge by 82 to 99%. Imazaquin placement above the tuber was significantly more toxic than placement either around or below the tuber. This suggests that a shallow incorporation of imazaquin at 1 to 2 inch depth should provide effective nutsedge control. Incrementing imazaquin rate significantly increased the number of sprouts when the herbicide was placed above the tuber. This apparent release of apical dominance may be a result of herbicide absorption and translocation from the sprouts to the lateral buds of the tuber at growth regulatory level or a result of the death of the current sprout at lethal concentrations. Three-day old nutsedge propagules absorbed significantly greater amounts of ('14)C-imazaquin from shoot application than from root application (nutrient solution). The emerging shoot appeared to be the major site of imazaquin uptake at early stages of nutsedge plant development.;Under field conditions, yellow nutsedge control with imazaquin was inconsistent. Soil type and weather conditions greatly influenced the performance. Nutsedge control was better in narrow rows than in wide rows. In general, pre-plant incorporated treatments gave better control than postemergence treatments.;Imazaquin activity was slow following postemergence application. Tiller development from the basal bulbs of plants treated with imazaquin indicated that kill was not complete. The rates of 0.188 kg/ha and lower caused significantly greater tillering than the higher rates. Foliar applied ('14)C-imazaquin was absorbed and translocated basipetally in both plant species. Purple nutsedge plants translocated twice the amount of absorbed ('14)C as yellow nutsedge plants at 8 days after application. The rhizomes and roots of yellow nutsedge plants had equal amounts of radioactivity, whereas the rhizomes of purple nutsedge plants accumulated significantly greater amounts than their roots. Foliar applied imazaquin showed greater toxicity on purple nutsedge than on yellow nutsedge. There was greater translocation and spray retention in purple nutsedge plants than in yellow nutsedge plants.