Turfgrass Renovation Using Dazomet to Control the Poa annua L. Soil Seed Bank

Abstract

<jats:p>Annual bluegrass (<jats:italic>Poa annua</jats:italic> L.) is an invasive weed producing copious amounts of viable seed that compete with seedling turfgrasses during renovation. These field studies were conducted to determine the effectiveness of dazomet (tetrahydro-3,5-dimethyl-2H-1,3,5-thiadiazine-2-thione), a granular soil sterilant that breaks down in soil to release methyl isothiocyanate (MITC), for controlling the soil seed bank of annual bluegrass during turfgrass renovation. Field trials in Urbana, Ill., and West Lafayette, Ind., in Spring and Fall 2000 and 2001 evaluated dazomet rate from 0 to 504 kg·ha<jats:sup>-1</jats:sup> and soil preparation techniques to determine the most effective practices to reduce annual bluegrass reestablishment into a creeping bentgrass (<jats:italic>Agrostis stolonifera</jats:italic> L.) seeding. The interval, in days, between dazomet application and creeping bentgrass planting was also examined to determine the optimal seeding time as measured by the level of annual bluegrass reestablishment. Spring trials generally gave poor results that were attributed to windy conditions resulting in rapid loss of MITC. The annual bluegrass soil seed bank was reduced 46% in spring trials compared to 78% in fall trials. Increasing dazomet rates reduced the absolute number of viable annual bluegrass seeds remaining in the soil. However, significant quantities of viable seed remained, regardless of dazomet rate. Annual bluegrass infested the renovated turf in all trials to varying degrees. Dazomet rates of 420 or 504 kg·ha<jats:sup>-1</jats:sup> yielded the lowest rates of annual bluegrass reestablishment. Trials conducted in the fall at these rates resulted in annual bluegrass cover of 1% to 20% in the resulting turf. Creeping bentgrass planted at 1 day after dazomet application had significantly less annual bluegrass than when seeded at 7 or 9 days after dazomet application. Dazomet is a tool that can help reestablish a new turf with lower levels of annual bluegrass. However, eradication of annual bluegrass with dazomet is not likely and environmental conditions will dramatically affect the success of the sterilization.</jats:p>

Confirmation and Control of Annual Bluegrass Resistant to Photosystem‐II‐Inhibiting Herbicides

“…Given that >80% of viable annual bluegrass seed are found within the top 0‐ to 1‐cm depth of soil (Branham et al, 2004), a large proportion of resistant annual bluegrass seed would be removed when harvesting zoysiagrass sod. However, it is rare for a single production field to be entirely harvested in a single year.…”

Nonchemical annual bluegrass (Poa annua) management in zoysiagrass via fraise mowing

“…In the seedbank analysis, 235 annual bluegrass seedlings were counted indicating that proportionally, the majority of the annual bluegrass seed remained in the soil following fraise mowing. Again, these results were surprising considering published data on cool-season turfgrasses suggest that the majority of the annual bluegrass in the seedbank resides in the top 1 cm (Branham et al 2004) of soil in cool-season golf course fairways or the top 1.3 cm (Green et al 2019) of the soil in cool-season golf course putting greens. It is likely that seedbank dynamics and seed distribution in the soil profile is different between climates with increased annual bluegrass.…”

“…It is likely that seedbank dynamics and seed distribution in the soil profile is different between climates with increased annual bluegrass. Past research on annual bluegrass seedbank dynamics (Branham et al 2004;Green et al 2019;Watschke et al 1979) was conducted in cool-season turf swards in Illinois, Indiana, Michigan, and Pennsylvania with a high percentage of annual bluegrass. Additionally, some of the sites previously studied were golf course turfs that were 90þ yr old.…”

“…Annual bluegrass soil seedbanks have been estimated to be as large as 179,500 seeds in the top 2.5 cm of soil per square meter (Watschke et al 1979), with others reporting that more than 80% of the viable annual bluegrass seed are within the top 0-to 1-cm layer (Branham et al 2004). There is also evidence that most annual bluegrass seed shed in the spring is viable and germinates by late summer (Branham et al 2004). Additionally, Baker et al (2005) reported that annual bluegrass coverage in a perennial ryegrass (Lolium perenne L.) sward was reduced by fraise mowing.…”

Resistance of Closely Mown Fine Fescue and Bentgrass Species to Snow Mold Pathogens

“…Application of dazomet in 1999 likely reduced the amount of P. annua seen in 2000 (4). Large seed banks and long-term seed viability of P. annua allow it to be a successful primary colonizer when existing turf swards are killed by snow mold or other agents.…”