Fate of Prohexadione Calcium in Annual Bluegrass (Poa annua) and Three Turfgrasses

Abstract

Prohexadione calcium is an experimental turfgrass growth regulator that selectively controls or suppresses annual bluegrass in desirable turfgrass such as creeping bentgrass, Kentucky bluegrass, and perennial ryegrass. To help explain interspecific differences in turfgrass and weed response to prohexadione calcium, two laboratory trials were conducted to measure 14C-prohexadione calcium absorption, translocation, and metabolism in these four species. Annual and Kentucky bluegrass absorbed more prohexadione calcium than creeping bentgrass and perennial ryegrass when averaged over harvest timing and trial. Radioactivity partitioning to other foliage did not differ between species but annual bluegrass and Kentucky bluegrass translocated more radioactivity to roots and evolved more radioactive CO2 than creeping bentgrass and perennial ryegrass. Thin-layer chromatographic separations indicate radioactivity was translocated predominately as prohexadione calcium. When averaged over species and trial, 25 and 16% of recovered prohexadione calcium was metabolized within 1 h after treatment in treated leaves and other foliage, respectively. The rate of metabolic degradation was 0.7% h−1 in treated leaves and 0.4% h−1 in other foliage. Previous research indicates that annual and Kentucky bluegrass growth is suppressed more by prohexadione calcium than is growth of creeping bentgrass and perennial ryegrass. Increased prohexadione calcium absorption partially explained these interspecific differences in growth suppression.

Methiozolin Absorption and Translocation in Annual Bluegrass (Poa annua)

“…Goddard (2009) reported approximately 20% translocation of mesotrione out of the treated leaf. Prohexadione was reported to translocate 11% of applied to the roots and 15% of applied to the foliage beyond the treated leaf (Beam and Askew 2007). These findings suggest that foliar-only application of methiozolin may be ineffective because of minimal translocation to the remainder of the plant.…”

“…Bispyribac (logK ow 5 21.03) reached maximum absorption of 29%, 24 HAT (Lycan and Hart 2006;Senseman 2007). Lastly, 83% of applied prohexadione calcium (calcium salt of 3,5-dioxo-4 propionylcyclohexane-carboxylic acid; K ow unknown) was absorbed by annual bluegrass foliage (Beam and Askew 2007).…”

Growing Degree Day Models for Plant Growth Regulator Applications on Ultradwarf Hybrid Bermudagrass Putting Greens

“…Two commonly used PGRs in turfgrass are trinexapac‐ethyl (TE) and prohexadione‐Ca (PH). These active ingredients are absorbed by turf foliage and inhibit the production of active gibberellic acid (GA) by blocking the late 3β‐hydroxylation reaction of GA 20 to GA 1 (Watschke and DiPaola, 1995; Fagerness et al, 2000; Rademacher, 2000; Beam and Askew, 2007).…”

“…Strategies for using TE on bermudagrass putting greens have been explored for many years; however, research on PH use in turfgrass is limited (Beam and Askew, 2007; Beam, 2004; Marchi et al, 2015). The impact of TE on bermudagrass putting greens varies by application regime and cultivar differences (McCullough et al, 2005, 2006, 2007; Baldwin et al, 2009; McCarty et al, 2011).…”

Growth inhibitors in turfgrass

“…These reductions are equivalent to those caused by trinexapac-ethyl at doses of 0.7, 0.22, 0.60, and 0.27 kg a.i. ha -1 , respectively (Ervin & Ok, 2001;Beam & Askew, 2007).…”