in Fairway Height Creeping Bentgrass
The growth regulator, Trinexapac-ethyl (Primo), was evaluated for Poa annua control in creeping bentgrass maintained at fairway height following a fall conversion program in this study. It was conducted on a fairway height area surrounding a practice green at Veenker Memorial Golf Course in Ames, IA. The turf in this area consisted of perennial ryegrass with an infestation of Poa annua that ranged from 20 to 0% through the 1998 season. The experimental design was a randomized complete block. Individual plot size was 5 x 5 ft with 3 replications. The plot was overseeded with perennial ryegrass in September 1998.
Treatments were applied to the same plots as in 1997. Primo 1EC was used at 0.5 fl oz/1000 ft2 monthly from May through September. Initial application was made on May 14 and subsequent applications were made on June 17, July 14, August 19, and September 23, 1998. Primo 1EC was mixed with 283 ml of water (3 gal/1000 ft2) and was applied at 30 psi with a CO2 backpack sprayer equipped with Teejetâ #8006 Teeject flat fan nozzles. All applications were made between 6:30 and 7:00 a.m. Following applications, the plot was watered with the normal watering schedule in the late afternoon.
Visual turf quality data were taken from April 22 through October 27 (Tables 1 and 2). Visual turf quality was assessed with a 9 to 1 scale with 9 = best, 6 = lowest acceptable, and 1 = worst turf quality. On each of these dates, the plots were checked for phytotoxicity. Phytotoxicity was assessed using a 9 to 1 scale with 9 = no damage, 6 = moderate tip burn (browning) and 4 = severe tip burn.
All data were analyzed with the Statistical Analysis System (SAS, Version 6.12) and the Analysis of Variance (ANOVA) procedure. Treatment effects were examined with Fisher's Least Significant Difference means separation test (LSD).
Poa annua populations were estimated as the percentage of area per plot covered by Poa annua. Percentage cover data were taken on May 13, May 28, June 12, June 30, July 14, July 30, August 12, August 26, September 10, September 22, October 1, October 14, and October 27 (Tables 3 and 4). Additional percentage cover data will be taken spring 1999 beginning at greenup. Winter damage also will be assessed spring 1999.
Primo treated ryegrass had a darker green color than the untreated ryegrass on May 28 and June 12 approximately 2 - 4 weeks following the first Primo application (Table 1). No further quality differences were noted through the season until October 27 (Table 2). No phytotoxicity was found.
Primo treated ryegrass had less Poa annua than the untreated control from May 13 through July 30 (Tables 3 and 4). The reduction in Poa annua was significantly different on May 13. The reductions were numerically different from May 28 through July 30. By August 19, the Poa annua had all died in the experimental plot. Close examinations of the plot were made from August 19 through October 27 and no Poa annua was found.
Table 1. Visual quality1 of perennial ryegrass treated for the 1997-98 Fairway Height Poa annua Conversion Study (April 22 - August 12, 1998).
|
|
|
fl oz/ 1000 ft2 |
22 |
13 |
28 |
12 |
30 |
14 |
30 |
12 |
|
1 |
Untreated control |
|
|
|
|
|
|
|
|
|
|
2 |
Primo 1EC2 |
|
|
|
|
|
|
|
|
|
|
|
LSD0.05 |
|
|
|
|
|
|
|
|
|
1Visual quality was assessed using a 9 to 1 scale with 9 - best, 6 = lowest acceptable, and 1 = worst quality.
2Primo 1EC applications were made on May 14, June 17, July 14, August 19, and September 23.
-- = Means separation tests are not valid for these data.
Table 2. Visual quality1 of perennial ryegrass treated 1998 Fairway Height Poa annua Conversion Study (August 26 - October 27, 1998).
|
|
|
fl oz/ 1000 ft2 |
26 |
10 |
22 |
1 |
14 |
27 |
quality |
|
1 |
Untreated control |
|
|
|
|
|
|
|
|
|
2 |
Primo2 |
|
|
|
|
|
|
|
|
|
|
LSD0.05 |
|
|
|
|
|
|
|
|
1Visual quality was assessed using a 9 to 1 scale with 9 - best, 6 = lowest acceptable, and 1 = worst quality.
2Primo applications were made on May 14, June 17, July 14, August 19, and September 23.
-- = Means separation tests are not valid for these data.
Table 3. Percentage Poa annua cover1 in perennial ryegrass treated for the 1997-98 Fairway Height Poa annua Conversion Study (May 13 - August 26, 1998).
|
|
|
fl oz/ 1000 ft2 |
13 |
28 |
12 |
30 |
14 |
30 |
19 |
26 |
|
|
|
|
|
|||||||
|
1 |
Untreated control |
|
|
16.0 |
15.0 |
|
|
|
|
|
|
2 |
Primo2 |
|
|
5.0 |
3.7 |
|
|
|
|
|
|
|
LSD0.05 |
|
|
|
|
|
|
|
|
|
1These values represent the area per plot covered by Poa annua.
2Primo applications were made on May 14, June 17, July 14, August 19, and September 23.
NS = Means are not significantly different at the 0.05 level.
-- = Means separation tests are not valid for these data.
Table 4. Percentage Poa annua cover1 in perennial ryegrass treated for the 1997-98 Fairway Height Poa annua Conversion Study (September 10 - October 27, 1998).
|
|
Material |
fl oz/ 1000 ft2 |
10 |
22 |
1 |
14 |
27 |
Cover |
|
|
|
|
|
|||||
|
1 |
Untreated control |
|
|
|
|
|
|
|
|
2 |
Primo2 |
|
|
|
|
|
|
|
|
|
LSD0.05 |
|
|
-- |
|
|
|
|
1These values represent the area per plot covered by Poa annua.
2Primo applications were made on May 14, June 17, July 14, August 19, and September 23.
-- = Means separation tests are not valid
for these data.
 |
ISU Horticulture:Publications:1999 Turfgrass Report | College of Agriculture |