Seedhead Suppression of Poa annua on a Putting Green
Dr. Thomas Watschke and Jeffrey A. Borger at Penn State
This study was conducted on a mixed stand of creeping bentgrass (Agrostis stolonifera) and Poa annua at the Penn State Blue Golf Course in State College, PA. The treatments were applied on March 31, 1998. Treatments 4 and 6 received post applications of MACRO-SORB® foliar alone at a rate of 2 oz/M on April 7 and April 14. The turf was maintained using practices for irrigation, mowing, and fertilization that would be typical for a green. The green did not receive any aerification/topdressing prior to or during the study. Phytotoxicity ratings were taken on April 27 and seedhead suppression was rated on May 6, 1998.
Table 1. Effect of Embark Lite and MACRO-SORB® foliar on phytotoxicity ratings and percent suppression of Poa annua seedheads on a Poa annua/bentgrass putting green.
| |
Trt
No. |
Treatment
Description |
Form |
Rate & Timing of Application1 |
Phytotoxicity2
(April 27, 99) |
% Suppression
(May 6, 99) |
| |
1 |
Check |
|
|
8.0 |
0 |
| |
2 |
Embark Lite |
0.2 L |
40 oz/A (3/31) |
7.8 |
70 |
| |
3 |
Embark Lite +
Ferromec |
0.2 L
L |
40 oz/A (3/31)
5 oz/A (3/31) |
8.0 |
80.0 |
| |
4
4
4
4 |
Embark Lite +
Macro-Sorb foliar
Macro-Sorb foliar
Macro-Sorb foliar |
0.2 L
L
L
L |
40 oz/A (3/31)
2 oz/M (3/31)
2 oz/M (1WAT)
2 oz/M (2WAT) |
7.5 |
82 |
| |
5 |
Check |
|
|
7.8 |
0 |
| ½ rate of Embark Lite + M-S foliar |
6
6
6
6 |
Embark Lite
Macro-Sorb foliar
Macro-Sorb foliar
Macro-Sorb foliar |
0.2 L
L
L
L |
20 oz/A (3/31)
2 oz/M (3/31)
2 oz/M (1WAT)
2 oz/M (2WAT) |
8.0 |
60 |
1 - Treatment application 3/31/98; WAT= Weeks After Treatment application.
2 - Rating scale of 0 = brown, 7 = acceptable, 10 = dark green
Results and Conclusions
Phytotoxicity ratings revealed that treated turfgrass was not different to untreated turf. Although it is common to observe some powerful discoloration after Embark Lite application, this phytotoxicity effect was not observed in this particular study.
Seedhead suppression results showed that Embark Lite by itself did not suppress Poa annua seedheads to an acceptable level. The addition of MACRO-SORB® foliar to Embark Lite followed by post applications of MACRO-SORB® foliar, one and two weeks later, increased seedhead suppression to 82% compared to 70% of Embark Lite alone. These results indicated that MACRO-SORB® foliar increases efficacy of Embark Lite to suppressseedhead of Poa annua and also maintains the quality of the treated turf.
When the rate of Embark Lite was reduced to 20 oz/A, additions of MACRO-SORB® foliar did not improve seedhead suppression to an acceptable level. However, a seedhead suppression of 60% with such a very low rate of Embark Lite (Table 1, treatment 5) suggests that MACRO-SORB® foliar enhances uptake or increases plant utilization of Embark Lite. Such low rate of Embark Lite by itself would not have had this seedhead suppression effect.