Control ofPoa annuaby Suppression of Seedheads with Growth Regulators

Abstract

Field and greenhouse studies were conducted to determine the degree to which annual bluegrass (Poa annuaL.) could be controlled by inhibiting seedheads. The materials used were: MH (1,2-dihydro-3,6-pyridazinedione); chlorflurenol (methyl 2-chloro-9-hydroxyfluorene-9-carboxylate), plus methyl 9-hydroxyfluorene-9-carboxylate, and methyl 2,7-dichloro-9-hydroxyfluorene-9-carboxylate; and endothall [7-oxabicyclo (2.2.1) heptane-2,3-dicarboxylic acid]. The effects of these materials on pollen quality and the viability of seed produced by treated plants were also determined. For all chemicals used, multiple applications at low rates resulted in better seedhead inhibition than single treatments at higher rates and their effects lasted longer. However, treatments that inhibited seedheads by an amount predicted to reduce annual bluegrass (more than 75%) often caused objectionable foliar discoloration. Endothall, particularly the granular formulation, caused excessive injury at all rates. All growth regulators reduced the number of seed produced, which affected the number of seeds that germinated from soil that was taken from treated plots. The number of seed found in the soil was sufficient to allow the stand to be self-perpetuating. All treatments reduced the percentage of fertile pollen, however, this reduction was not significant because the germination of seed harvested from treated plants was not reduced significantly. Even though these treatments reduced seedheads significantly, the population of annual bluegrass the following year was not reduced.

Suppression of Annual Bluegrass Seedheads with Mefluidide, Ethephon, and Ethephon plus Trinexapac‐Ethyl on Creeping Bentgrass Greens

“…Phytotoxicity caused by PGR applications on turfgrass plants has been documented (Dernoeden, 1984; Watschke et al, 1979). Injury symptoms to sensitive plants include discoloration of leaf tissues and stunted shoot and root growth (Cooper et al, 1987; Eggens et al, 1989; McCullough et al, 2005b).…”

“…A nnual bluegrass is a major weed of creeping bentgrass putting greens (Beard, 1973). The encroachment of annual bluegrass into creeping bentgrass is undesirable due to its poor stress tolerance, susceptibility to most cool‐season turfgrass diseases (Watschke et al, 1979), and unsightly light green color compared to creeping bentgrass. Annual bluegrass is a prolific seed producer and a single plant can produce up to 2200 seeds per season (McCarty, 1999).…”

“…Herbicide options for selective control of annual bluegrass on creeping bentgrass putting greens are limited. As a result, PGRs are often used to shift populations and/or suppress seedhead formation (Inguagiato el al., 2010; Petrovic et al, 1985; Watschke et al, 1979). Commonly used PGRs for seedhead inhibition in turf include mefluidide (N‐[2, 4‐dimethyl‐5‐[[(trifluoromethyl) sulfonyl] amino] phenyl] acetamide), ethephon ([(2‐Chloroethyl) phosphonic acid]), and a combination of ethephon and TE (4‐(cyclopropyl‐a‐ hydroxymethylene)‐3, 5‐dioxo‐cyclohexanecarboxylic acid ethylester).…”

“…Geographic location and management intensity affect the distribution and selection of annual or perennial types; however, in most cases, the two biotypes co‐exist (Slavens et al, 2011). Besides genetic variation, other factors that contribute to the inconsistencies in seedhead control include PGR application rate (Shepard, 2008), application timing (Smith and Askew, 2013; Watschke et al, 1979), and seedhead evaluation methodologies (Danneberger and Vargas, 1984a; Inguagiato et al, 2010).…”

The Effect of Chlormequat and Mefluidide and Their Interaction With Chlorpyrifos on the Herbage Yield of Italian Ryegrass

“…Certain plant growth regulators (PGR) may increase the ratio of vegetative to reproductive tillers in grass plants (1) .…”