Determination of Methiozolin Absorption and Translocation Using Herbicide Bioassays and Radio-Labeled Methodology.

Annual bluegrass (Poa annua) is a troublesome turfgrass weed. Methiozolin has been reported to selectively control annual bluegrass in desirable turfgrasses. However, little is known regarding annual bluegrass uptake and translocation of methiozolin. Studies were conducted to compare annual bluegrass control from foliar and root exposure to methiozolin and to investigate foliar and root absorption and subsequent translocation using radio-labeled methiozolin. Results indicate methiozolin applied preemergence can effectively control annual bluegrass; however, postemergence (POST) application resulted in < 80% control regardless of foliar versus root exposure. POST applications are more effective at higher rates and smaller growth stages. Foliar-plus-soil methiozolin application trended to result in the best control, compared to foliar-only and soil-only applications. Absorption and translocation data indicate that methiozolin is absorbed by both leaves and roots and translocates upward in the plant toward the leaf tip. Due to the fact that control is limited from a single methiozolin application (as observed in POST experiments), successful field application of methiozolin requires multiple, timely applications directed toward the roots and/or crown of annual bluegrass.