First Report of Pronamide-Resistant Annual Bluegrass (Poa annua)

Abstract

A biotype of annual bluegrass with suspected resistance to pronamide was collected from a golf course in Georgia. The objectives of this research were to determine the level of resistance to pronamide and the mechanisms associated with resistance. From POST applications, the pronamide rate that reduced shoot biomass 50% from the nontreated bluegrass measured >10 times higher for the resistant (R) biotype as compared with susceptible (S) biotypes. The R biotype was not controlled by PRE applications of dithiopyr or prodiamine, but was controlled >92% by PRE applications of pronamide at 0.56 and 1.68 kg ha −1 . Mature plants (3-to 5-tiller) of the R biotype absorbed 32% less [14 C]pronamide than the S biotype after 72 h in hydroponic culture and accumulated 39% less radioactivity per gram basis of dry shoot mass. The R biotype metabolized [ 14 C]pronamide similar to the S biotype, averaging 16% of the extracted radioactivity. The resistance to POST pronamide applications in the R biotype is associated with reduced absorption and translocation compared with the S biotype. Nomenclature: Pronamide (propyzamide); annual bluegrass, Poa annua L. Key words: Absorption, mitotic inhibitor, translocation, turfgrass.Annual bluegrass is a problematic weed in turfgrass. It has a light-green color, coarse leaf texture, and produces unsightly seed heads that reduce turfgrass aesthetics (Beard 1970). Annual bluegrass also has poor tolerance to heat, disease, and traffic stress that may further exacerbate reductions in turfgrass quality (Beard 1970;Lush 1989). The decline of annual bluegrass in late spring reduces turf density and predisposes areas to invasion of summer annual weeds. Practitioners can reduce populations by adjusting turfgrass fertility, modifying irrigation regimens, and collecting mower clippings after annual bluegrass seed head emergence (Gaussoin and Branham 1989;Lush 1989). Cultural practices that promote turfgrass competition with annual bluegrass often do not provide acceptable levels of control, and herbicide use may be warranted.Mitotic inhibitors are widely used for PRE control of annual bluegrass in turf. The dinitroaniline (DNA) herbicides inhibit microtubule polymerization by binding to tubulin that restricts chromosome movement during prometaphase of mitosis and causes isodiametric cell formation (Blume et al. 2003;Murthy et al 1994;Vaughn and Lehnen 1991). Dithiopyr is a mitotic inhibitor used for PRE annual bluegrass control in turf that does not bind to tubulin. Rather, dithiopyr binds to microtubule-associated proteins that shorten microtubules during mitosis (Armbruster et al. 1991;Vaughn and Lehnen 1991). Dithiopyr and the DNA herbicides have limited efficacy for POST annual bluegrass control. Application timing before germination is critical to maximize efficacy of these herbicides for PRE control (Bhowmik and Bingham 1990;Toler et al. 2003Toler et al. , 2007.Pronamide (propyzamide) is a benzamide herbicide that provides PRE and POST annual bluegrass control in warm-season turfgrasses (Isgrigg ...

Rotations and mixtures of soil‐applied herbicides delay resistance

“…Thus, we assumed that cross‐resistance between pyroxasulfone and prosulfocarb was the norm in our modelled species L. rigidum despite exceptions to the norm in a variable species such as L. rigidum often being expected . Additionally, resistance to propyzamide appears to be a rare phenomenon, as it has thus far only been reported at very low level in grass weeds such as Poa annua and L. rigidum …”

“…In L. rigidum , resistance to pyroxasulfone has been selected after only three generations of recurrent low‐dose selection in glasshouse studies, but the empirical evidence indicates it is rare in L. rigidum ‐unselected populations in the field with values possibly lower than 10 −7 . Resistance to propyzamide has been recently documented in Poa annua in the USA and Australia, and one relatively old report of reduced propyzamide sensitivity in A. fatua . However, because there is high uncertainty about the initial resistance allele frequencies, we wanted to investigate how varying this parameter would affect results.…”

Incidence of multiple herbicide resistance in annual bluegrass (Poa annua) across southeastern Australia

“…It is therefore likely that the low level resistance identified in P. annua is non-target site based. McCullough et al (2017) reported that resistance to POST propyzamide in a population of P. annua from a golf course in Georgia, USA, was associated with reduced absorption and translocation.…”

“…Similarly, in P. annua, Ser-264 was confirmed to provide resistance to atrazine (Perry et al 2012), Val-219 to metribuzin and diuron (Mengistu et al 2000), and Pro-106 to glyphosate (Cross et al 2015). On the other hand, an NTSR-based mechanism causing reduced absorption and translocation was reported as a mechanism of resistance to POST pronomide applications in P. annua (McCullough et al 2017).…”

Annual Bluegrass (Poa annua) Biotypes Exhibit Differential Levels of Susceptibility and Biochemical Responses to Protoporphyrinogen Oxidase Inhibitors

“…Currently, 28 cases of herbicide-resistant P. annua have been reported worldwide (Heap 2018). Resistance has been confirmed to ethofumesate, glyphosate, sulfonylureas, pronamide, and triazines used for POST P. annua control in turfgrass (Binkholder et al 2011; Hutto et al 2004; Kelly et al 1999; McCullough et al 2017; McElroy et al 2013). Poa annua has also developed resistance to dithiopyr, pendimethalin, and prodiamine used for PRE control (Isgrigg et al 2002; Cutulle et al 2009).…”