Methiozolin Absorption and Translocation in Annual Bluegrass (Poa annua)

Abstract

Annual bluegrass is a problematic turfgrass weed. Methiozolin is a new, currently unregistered herbicide that selectively controls annual bluegrass in desirable turfgrasses. Studies were conducted to evaluate and compare annual bluegrass control from PRE-applied methiozolin as influenced by rate and soil type and from POST-applied methiozolin as influenced by rate, soil type, annual bluegrass growth stage, and treatment placement. Studies were also conducted to evaluate foliar and root absorption and subsequent translocation of methiozolin by annual bluegrass using radio-tracer techniques. PRE-applied methiozolin controlled annual bluegrass > 99%. POST-applied methiozolin 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 moderately translocates upward in the plant toward the leaf tip with little to no basipetal translocation. Because control is limited from a single methiozolin application (as observed in POST experiments), successful field application of methiozolin requires multiple and timely applications directed toward the roots and/or foliage of annual bluegrass.

Methiozolin sorption and mobility in sand-based root zones

“…The K d values observed are consistent with other soil‐active herbicides (Table ). These data corroborate previous researchers who reported that methiozolin has soil activity for control of annual bluegrass …”

“…Overall, results indicate that ∼24% of applied methiozolin remains available for root uptake, but binds sufficiently to soil so as to resist leaching displacement. Thus, these studies indicate that methiozolin is available in soil for herbicidal activity, which has been observed in selective placement and field studies …”

“…Methiozolin reportedly has both pre-emergent (PRE) and post-emergent (POST) herbicidal activity on annual grass weeds. 2,3,8 Grossmann et al reported that it inhibited tyrosine aminotransferase (TAT), which blocks the production of plastoquinone and tocopherol, both of which are important in membrane protection to oxidative stresses. 9 However, TAT inhibition research was conducted using broadleaf plants (i.e.…”

“…1,10,11 Methiozolin is absorbed by the roots and foliage of annual bluegrass. 2,3,8 Root exposure and subsequent absorption is required for POST control. 2,3,6 Koo et al reported that no herbicidal activity resulted from leaf-only application.…”

“…) is a herbicide of the isoxazoline class . Methiozolin selectively controls annual bluegrass ( Poa annua L.) in creeping bentgrass ( Agrostis stolonifera L.) and hybrid bermudagrass ( Cynodon dactylon × C. transvaalensis Burtt‐Davy) . Currently, there are few options for selective annual bluegrass control in these turfgrasses, especially in golf course putting greens.…”