Germinability of annual bluegrass seed during spring in the Eastern United States

Abstract

Soil seedbank management via collecting clippings may be a means of combatting herbicide resistance in annual bluegrass (Poa annua L.) by minimizing recruitment from the deposition of viable seed into the soil. Our objective was to assess the germinability of annual bluegrass seed in spring to determine when collecting clippings would be most impactful. Research was conducted across 2019 and 2020 in five locations: Knoxville, TN; Starkville, MS; Griffin, GA; West Lafayette, IN; and University Park, PA. Annual bluegrass seed was harvested every 100 growing degree-days (GDD 0C ; base 0 ˚C with accumulation beginning on 1 January each year from 400 to 1,100 GDD 0C . Seeds from each harvest timing were placed on moistened blotter paper in petri dishes and randomized in a growth chamber set to a 77:68 ˚F and 8:16 h light-dark cycle. Germination was assessed every 3 d until 21 d of incubation.Cumulative germination percentage after 21 d of incubation increased at research locations in northern latitudes. In Tennessee, germination was greatest from 600 to 900 GDD 0C . In Indiana, germination did not exceed 50% until 600 GDD 0C and increased with GDD 0C accumulation. Clippings should not be collected until at least 600 GDD 0C in these locations. In Pennsylvania, little variation existed among GDD 0C harvest times, indicating that clipping collection may be a valuable practice any time mature seedheads are present. Turfgrass managers should consider geographic location when selecting a time to implement clipping collections and will probably need to conduct multiple clipping collection events. INTRODUCTIONAnnual bluegrass (Poa annua L.; ABG) is a common and problematic weed in turfgrass because of the species' light green color, prolific spring seedhead (inflorescence) produc-Abbreviations: ABG, annual bluegrass; CGP, cumulative germination percentage; GDD, growing degree-days; GDD 0C , growing degree-days with a base of 0 ˚C.

Using survey results to direct future extension efforts in annual bluegrass management

“…(2021), Carroll, Brosnan, McCurdy, et al. (2021), Carroll, Brosnan, Trigiano, et al. (2021), Carroll et al.…”

“…Relating to annual bluegrass emergence, research by Carroll, Brosnan, McCurdy, et al. (2021) determined that in Tennessee (a transition zone climate), the annual bluegrass seed was most germinable from inflorescence tissue at 600 0c and 900 0c , suggesting this is the optimum time for clipping collection in the spring. While these are valuable findings, more research is needed to determine how the environment affects spring germination of annual bluegrass in warm‐season climates, south of Tennessee.…”

Developing and implementing a sustainable, integrated weed management program for herbicide‐resistant Poa annua in turfgrass

“…Herbicide resistance can have severe economic consequences for turfgrass managers and producers by affecting aesthetics, playability, surface stability, integrity of the desired turfgrass species, and yield (e.g., sod and seed production). To control resistant weeds, turfgrass managers must often increase their input costs by purchasing alternative herbicide chemistries and investing in additional labor to remove resistant weed populations using alternative, integrated weed management (IWM) methods (Carroll et al, 2021a(Carroll et al, , 2021bElmore et al, 2023;Johnson, 1994).…”

“…Ultimately, chemical weed control with multiple SOA will be more effective and long-lived than repeatedly relying on one SOA (Cross et al, 2015). Furthermore, chemical control strategies are only one of several integrated approaches to managing herbicide resistant P. annua (Barua et al, 2021;Brosnan et al, 2020;Carroll et al, 2021aCarroll et al, , 2021bGuertal & McElroy, 2018;Imaizumi et al, 1997;Varco & Sartain, 1986).…”

A bioassay to determine Poa annua responses to indaziflam

“…Mature seed from each collection were harvested with scissors, dried in a forced-air oven (Laboratory Oven; The Grieve Corporation, Round Lake, IL), and sieved (Standard Test Sieve; Fisher Scientific Company LLC, Hampton, NH) to remove chaff. After processing, seed were stored in glass vials (40 mL Scintillation Vial; Thermo-Fisher Scientific, St. Louis, MO, USA) at −20˚C for a minimum of four weeks to break any potential dormancy (Carroll et al, 2021b).…”