Selection of Bioassay Method Influences Detection of Annual Bluegrass Resistance to Mitotic‐Inhibiting Herbicides

Abstract

Dinitroaniline‐resistant annual bluegrass (Poa annua L.) has been reported in several states; however, there are no standardized screening methods for detecting resistance. Research was conducted to evaluate screening techniques (Murashige and Skoog [MS] media, filter paper, hydroponics, and soil based) to detect herbicide resistance to dithiopyr, prodiamine, and pendimethalin in a suspected resistant ecotype of annual bluegrass from Chattanooga, TN (Chattanooga). A senstitive ecotype from Fresno, CA (Control) was also tested. All the bioassays were able to diagnose the ecotype from Chattanooga as resistant to prodiamine and pendimethalin. However, the degree of resistance was highly variable between bioassays. In hydroponics, the amount of prodiamine required to inhibit Chattanooga growth by 50% was 26 times more than Control. Comparatively, in MS media the amount of prodiamine required to inhibit Chattanooga growth by 50% was 80 times more than Control. Minor dithiopyr resistance from the Chattanooga ecotype was detected by the hydroponics, filter‐paper and soil‐based bioassays. Hydroponics provided the most rapid diagnosis of resistance, accessing resistance for a mature plant in 10 d. The MS‐media bioassay had the least amount of confounding variables. These findings highlight the potential variation in results that can occur in mitotic‐inhibiting herbicide resistance detection simply on the basis of how plant samples are assayed.

Confirmation and Control of Annual Bluegrass (Poa annua) with Resistance to Prodiamine and Glyphosate

“…Prodiamine rates needed to reduce dry biomass of the resistant and susceptible phenotypes by 50% were 1,006 and 45 g ha −1 , respectively, equating to a resistance factor of 22 based on dry biomass reductions. These results are similar to research conducted by Cutulle et al (2009), who identified a phenotype of annual bluegrass 26 times less sensitive to prodiamine than a known susceptible phenotype.…”

Use of herbicides on turfgrass

“…While both dinitroaniline herbicides and dithiopyr both inhibit mitosis, dithiopyr does so in a slightly different fashion (Cutulle et al, 2009). Unlike dinitroanilines, dithiopyr has preemergence activity and postemergence activity on certain weeds-primarily Digitaria spp.…”

Herbicide Resistance in Turfgrass: An Emerging Problem?

“…These herbicides disrupt mitosis by preventing the protein tubulin from polymerizing to form microtubules required for cell division (Vaughn & Lehnen 1991). Multiple biotypes of annual bluegrass resistant to the DNA herbicide prodiamine have been reported in the southeastern United States as the result of repeated use of prodiamine for residual control of annual weeds (Cutulle et al 2009;Isgrigg et al 2002;Lowe et al 2001). Certain prodiamine-resistant annual bluegrass populations have also shown reduced sensitivity to another DNA herbicide, pendimethalin (Cutulle et al 2009).…”

“…Multiple biotypes of annual bluegrass resistant to the DNA herbicide prodiamine have been reported in the southeastern United States as the result of repeated use of prodiamine for residual control of annual weeds (Cutulle et al 2009;Isgrigg et al 2002;Lowe et al 2001). Certain prodiamine-resistant annual bluegrass populations have also shown reduced sensitivity to another DNA herbicide, pendimethalin (Cutulle et al 2009). Seed of DNAresistant and -susceptible biotypes have similar germination rates; however, above ground growth of DNA-resistant annual bluegrass and foxtail (Setaria spp.)…”

“…However, repeated use herbicides targeting similar SOAs for control of problematic weeds has led to the development of herbicide resistant biotypes of annual bluegrass (Poa annua), goosegrass (Eleusine indica), and smooth crabgrass (Digitaria ischaemum) in turfgrass systems ( Figures 1-3). Despite the fact that herbicide resistance in agricultural production has been an issue since 1970 (Timmons 1970), several reports of turfgrass weeds resistant to glyphosate, triazine and triazinones (i.e., simazine, metribuzin), sulfonylureas (i.e., foramsulfuron, trifloxysulfuron), and dinitroanilines (i.e., prodiamine) have surfaced within the past five years (Binkholder et al 2011;Brosnan et al 2012a;Brosnan et al 2008;Cross et al 2013;Cutulle et al 2009;McElroy et al 2013a;Perry et al 2012). These data illustrate that herbicide…”