1998 Iowa Turfgrass Research Report
Effects of Primo on Poa annua Populations in Creeping Bentgrass Maintained at Fairway Height
Barbara R. Bingaman, Nick E. Christians, and Michael B. Faust
The objective of this study was to monitor Poa annua populations through the season in fairway height turf following a routine application program with the growth regulator, Trinexapac-ethyl (Primo).
This study was conducted in a turf area maintained at 1/2-inch mowing height surrounding a practice green at Veenker Golf Course in Ames, IA. The turf in this area consists of Perennial ryegrass and Kentucky bluegrass with a uniform infestation of Poa annua.
The experiment was a completely randomized design. Individual plot size was 5 x 5 ft with three replications. Untreated plots and Primo treated plots were randomly placed in a single row. Primo was applied at 0.5 fl oz/1000 ft2.
Monthly applications were made on June 5, July 10, August 13, and September 4. The liquid was applied at 30-35 psi with a CO2 backpack sprayer equipped with TeeJet™ #8006 flat fan nozzles. All applications were made between 6:30 and 7:00 a.m. The plot was watered with the normal watering schedule in the late afternoon.
Visual turf quality data were taken weekly beginning June 10 and ending September 16, 1997 (Table 1 and 2). Visual quality was assessed on a 9 to 1 scale: 9 = best, 6 = lowest acceptable, and 1 = worst quality. Poa annua control was measured by estimating the percentage cover per plot. Percentage cover data were assessed by estimating the percent area per plot covered by Poa annua (Table 3). Percentage cover data were taken on June 5 and September 11. Additional percentage cover data will be taken in spring, 1998 beginning at greenup. Winter damage also will be assessed in early spring.
The plot and the surrounding area were overseeded with perennial ryegrass twice between late August and early September. By September 11, germinating ryegrass plants were quite numerous throughout the plot.
Throughout the season no Poa annua seedheads were visible in the plot or in the surrounding turf area. Beginning on August 20, the Primo treated plots had a darker blue-green color when compared with the untreated plots and the surrounding area. This color difference was detected through September 11. On September 16, no color differences were detected.
Percentage Poa annua cover data were taken on June 5 and September 11. There was a uniform Poa annua population among the treated and untreated plots on June 5. There were significantly smaller Poa annua populations in Primo treated plots on September 11 when compared with the untreated controls (Table 3). There was a large population of young ryegrass plants in all of the plots.
Table 1. Visual quality of fairway height Perennial ryegrass in the 1997-98 Postemergence Poa annua Conversion Study (June 10 through July 31, 1997).
Untreated control
Primo
LSD0.05
fl oz/1000 ft2
Applications were made on June 5, July 10, August 13, and September 4.
NS = means are not significantly different at the 0.05 level.
Table 2. Visual quality of fairway height Perennial ryegrass in the 1997-98 Postemergence Poa annua Conversion Study (August 6 through September 16, 1997).
Untreated control
Primo
LSD0.05
fl oz/1000 ft2
Applications were made on June 5, July 10, August 13, and September 4.
NS = means are not significantly different at the 0.05 level.
Table 3. Percentage Poa annua cover in fairway height Perennial ryegrass in the 1997 Postemergence Poa annua Conversion Study.
Untreated control
Primo
LSD0.05
fl oz/1000 ft2
Applications were made on June 5, July 10, August 13, and September 4.
NS = means are not significantly
different at the 0.05 level.
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ISU Horticulture:Publications:1998 Turfgrass Report | College of Agriculture |