Cutting Edge: Celebration Bermuda Grass, Herbicide Resistance in Poa Anoa

Cutting Edge: Celebration Bermuda Grass, Herbicide Resistance in Poa Anoa

The combined effect of water quality and nitrogen sources on bermudagrass performance in gestation and nitrogen uptake

The diminishing availability of potable water for turf irrigation, even in high-precipitation parts of the United States, has led to exploration of non-potable water resources for golf course irrigation. Reclaimed wastewater has been used as a substitute for potable water to irrigate golf courses. A greenhouse study was conducted during fall 2021 (November-December) and spring 2022 (April-May) at the University of Florida/Fort Lauderdale Research and Education Center to explore the interaction of water quality and nitrogen source on performance and nitrogen intake. Absorbing Bermudagrass celebration.

Nitrogen was applied at a rate of 1 lb N per 1,000 square feet (49 kg per hectare) at the beginning of the study using either water-soluble AMS (21% nitrogen, 0% phosphorus, 0% potassium) or 65% control. – Fertilizer release (42-0-0) compared to the unfertilized control. The lawn was watered twice a week with reclaimed wastewater (3.3 ppm nitrate-nitrogen) or potable water (0.01 ppm nitrate-nitrogen) at gravimetric water content. Turf quality (scale 1–9) and normalized difference vegetation index (NDVI; scale 0.0–0.99) were assessed weekly.

Plot samples were collected weekly, oven-dried to determine dry weight, and subsequently analyzed for nitrogen content and total assimilated nitrogen (TAN). Lawns watered with reclaimed wastewater had higher nitrogen and TAN contents. Fertilized grasses absorbed more nitrogen during the spring than in the fall. Higher cutting productivity (producing more biomass) during spring compared to fall resulted in no difference in leaf nitrogen content between seasons. Overall, reclaimed wastewater increased nitrogen content and had no detrimental effect on turf quality or NDVI. — I. Alexandra Sierra Augustine (iasierra@ufl.edu), Patrick McLoughlin, A. Fernanda Arévalo Alvarenga, Marco Schiavone, Ph.D

Annual bluegrass test patches

The spread of ethofumite-resistant annual bluegrass on US golf courses

Annual bluegrass (Poa annua L.) is the most common weed in lawns. Herbicide options for controlling annual bluegrass on golf courses are limited, and repeated applications are often necessary. Annual bluegrass is a prolific seed producer, allowing for the rapid development of herbicide resistance. Ethofomyces resistant annual bluegrass plants have already been documented in producing weed seeds in Oregon. Therefore, a dose-response trial was initiated to determine the potential level of ethofomysate resistance in Poa annua L. on golf courses.

Seeds were collected from 28 sets of golf courses in Alabama, California, Indiana and Oregon. In addition, two populations, one with known resistance and one with known susceptibility, were identified in preliminary tests and used as controls in this trial. Individual seedlings from each group were transplanted into separate containers and then grown in the greenhouse until they reached 2–3 tiller size, immediately before herbicide application. Ten doses of ethofomisate were applied using a compressed air path spray chamber: .0, .01, .02, .06, .11, .17, .23, .34, .46 and .92 pounds of active ingredient per 1,000 square feet (0, 0.56, 1.12, 2.8, 5.6, 8.4, 11.2, 16.8, 22.4 and 44.8 kg a.i. per hectare), with 0.02 to 0.05 lbs. per 1,000 square feet of a.i. (1.1 to 2.2 kg a.i. per ha) Label application rates for perennial ryegrass.

Plant biomass was collected 28 days after application. Populations with a resistant-to-susceptible ratio of 1.01 to 5.33 have been found on golf courses. The most resistant variety is found in California with ED50.26 lb a.i. per 1,000 square feet (12.74 kg a.i. per hectare). Results demonstrate that annual bluegrass is developing resistance to ethofomycin in managed turf and the need for practitioners to implement resistance prevention measures. — Vera Vukovic (vvukovic@purdue.edu) and Aaron J. Patton, Ph.D.


Darrell J. Pehr (dpehr@gcsaa.org) is GCM's science editor.

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