1999 Postemergent Broadleaf Herbicide Study
Barbara R. Bingaman, Mark J. Howieson, and Nick E. Christians
The efficacy of Millennium Ultra and numbered research compounds were compared to traditional 3-way herbicides (i.e. Riverdale's Triplet) in this study. It was conducted at the Iowa State University Horticulture Research Station north of Ames, IA in an area of common bluegrass with a heavy infestation of red clover, white clover, dandelions, Canada thistle, and other broadleaf weed species. The soil in this area was a Nicollet (fine-loamy, mixed, mesic Aquic Hapludoll) with 3.5% organic matter content, pH of 7.3, 6 ppm P, and 130 ppm K. The experimental design was a randomized complete block with 5 x 10 ft plots and three replications.
Triplet, Milennium Ultra, Super Trimec, Trimec Classic, and three experimental products (RDL 211, RDL 343, and RDL 414) were screened against an untreated control (Table 1). The materials were diluted into 567 ml of water. This translates to an application rate of 3 gal/1000 ft2. Sprayables were applied at 30-35 psi using a carbon dioxide backpack sprayer equipped with TeeJet #8006 flat fan nozzles.
All products were applied postemergently after dandelions, clover, and other broadleaf species were well established. Applications were made on June 9. It was 86º F and partly sunny with a SW wind at 10-15 mph. There was no drift of the materials. The plot was neither irrigated nor mowed for 24 hours following application.
Weed damage data were taken on June 15 and June 18. Damage was assessed using a 0 to 9 scale with 0 = no damage, 5 = individual plants 50% dead and 9 = 100% dead (Tables 2-4). After June 18, it was assumed that all remaining damaged and undamaged weeds would survive so no additional damage data were taken. Beginning on June 24, weed population data were taken. Subsequent data were taken on June 29, July 9, July 15, July 21, July 27, and August 4. Dandelion and thistle numbers were counted per plot and clover numbers were estimated as percentage cover per plot (Tables 5,7, & 9). To better reflect weed control, weed population data were converted to percentage reductions as compared with the untreated controls (Tables 6, 8, & 10). Percentage crabgrass cover was estimated on July 27 and August 4 (Table 11). On August 4, all other weed species within the study were surveyed. Oxalis and crabgrass populations were large enough to collect data (Tables 11 and 12).
Data were analyzed with the Statistical Analysis System (SAS, Version 6.12) and the Analysis of Variance procedure (ANOVA). Treatment effects were tested using Fisher's Least Significant Difference (LSD) mean separation test.
The plot was examined for phytotoxicity periodically and no phytotoxic symptoms were found. Herbicide treatment did not cause any deterioration in turf quality as compared with the untreated control throughout the study (Table 1). Visual quality remained good throughout the duration of the study.
There was significant damage to dandelions, clover, and Canada thistle on June 15 and June 18 as compared with the untreated controls (Tables 2, 3, and 4). There were some significant differences in the level of clover damage among the herbicide treatments on June 15 and June 18. Differences in thistle damage were significant among the herbicides on June 18.
By June 29, all herbicide-treated dandelion populations were significantly reduced as compared with the untreated controls (Tables 5 and 6). The best control was observed on July 9 when all herbicides reduced dandelion numbers by at least 70%. Mean reductions show that all herbicides significantly reduced dandelion populations as compared to the untreated controls.
Clover control was highly significant from June 24 through the end of the study (Tables 7 and 8). By July 9, clover cover was reduced at least 80% in all treated turf and reductions were > 95% in turf treated with four of the herbicide formulations. Reductions were numerically greater for some herbicides from June 29 through August 4, but the differences among herbicide treatments were not significant.
Canada thistles were initially severely damaged by some of the herbicides but the plants were not killed as shown by the data (Tables 9 and 10). There were no significant differences in thistle numbers among the treatments as compared with the controls. All herbicides reduced thistle counts through June 29 as compared with the control but after this date most treated turf contained more thistles than the untreated.
Because of decreased competition from dandelion and clover, oxalis and crabgrass populations were generally larger in treated turf than in untreated (Tables 11 and 12). Differences in oxalis counts were not significant but differences were significant in percentage crabgrass cover.
Table 1. Visual quality1 of turf treated for the 1999 Riverdale Postemergent Broadleaf Herbicide Study.
|
Material |
Rate product /1000 ft2 |
June 24 |
June 29 |
July 9 |
July 15 |
July 21 |
July 27 |
Aug 4 |
Mean |
|
|
1 |
Untreated control |
NA |
9.0 |
9.0 |
9.0 |
9.0 |
9.0 |
9.0 |
9.0 |
9.0 |
|
2 |
Triplet 49.7% |
1.29 oz |
9.0 |
9.0 |
9.0 |
9.0 |
9.0 |
9.0 |
9.0 |
9.0 |
|
3 |
Millennium Ultra 47.1% |
0.92 oz |
9.0 |
9.0 |
9.0 |
9.0 |
9.0 |
9.0 |
9.0 |
9.0 |
|
4 |
RDL 211 47.4% |
1.10 oz |
9.0 |
9.0 |
9.0 |
9.0 |
9.0 |
9.0 |
9.0 |
9.0 |
|
5 |
RDL 343 46.0% |
1.17 oz |
9.0 |
9.0 |
9.0 |
9.0 |
9.0 |
9.0 |
9.0 |
9.0 |
|
6 |
RDL 414 59.1% |
1.10 oz |
9.0 |
9.0 |
9.0 |
9.0 |
9.0 |
9.0 |
9.0 |
9.0 |
|
7 |
Super Trimec |
1.10 oz |
9.0 |
9.0 |
9.0 |
9.0 |
9.0 |
9.0 |
9.0 |
9.0 |
|
8 |
Trimec Classic 3.4 SL |
1.50 oz |
9.0 |
9.0 |
9.0 |
9.0 |
9.0 |
9.0 |
9.0 |
9.0 |
|
LSD0.05 |
-- |
-- |
-- |
-- |
-- |
-- |
-- |
-- |
1Visual quality was assessed using a 9 to 1 scale with 9 = best, 6 = lowest acceptable, and 1 = worst quality.
Table 2. Damage1 to dandelions in turf plots treated for the 1999 Riverdale Postemergent Broadleaf Herbicide Study.
|
Material |
Rate product /1000 ft2 |
June 15 |
June 18 |
Mean |
|
|
1 |
Untreated control |
NA |
0.0 |
0.0 |
0.0 |
|
2 |
Triplet 49.7% |
1.29 oz |
7.3 |
5.7 |
6.5 |
|
3 |
Millennium Ultra 47.1% |
0.92 oz |
7.0 |
6.3 |
6.7 |
|
4 |
RDL 211 47.4% |
1.10 oz |
6.7 |
6.3 |
6.5 |
|
5 |
RDL 343 46.0% |
1.17 oz |
7.0 |
5.3 |
6.2 |
|
6 |
RDL 414 59.1% |
1.10 oz |
7.7 |
6.0 |
6.8 |
|
7 |
Super Trimec |
1.10 oz |
8.3 |
7.0 |
7.7 |
|
8 |
Trimec Classic 3.4 SL |
1.50 oz |
8.0 |
7.3 |
7.7 |
|
LSD0.05 |
1.6 |
2.2 |
1.5 |
1These figures represent the degree of damage observed on dandelions. Damage was assessed using a 0 to 9 scale with 0 = no damage, 5 = plants 50% dead, 9 = plants 100% dead.
Table 3. Damage1 to clover in turf plots treated for the 1999 Riverdale Postemergent Broadleaf Herbicide Study.
|
Material |
Rate product /1000 ft2 |
June 15 |
June 18 |
Mean |
|
|
1 |
Untreated control |
NA |
0.0 |
0.0 |
0.0 |
|
2 |
Triplet 49.7% |
1.29 oz |
5.7 |
5.7 |
5.7 |
|
3 |
Millennium Ultra 47.1% |
0.92 oz |
5.0 |
6.7 |
5.8 |
|
4 |
RDL 211 47.4% |
1.10 oz |
6.7 |
6.3 |
6.5 |
|
5 |
RDL 343 46.0% |
1.17 oz |
6.0 |
5.7 |
5.8 |
|
6 |
RDL 414 59.1% |
1.10 oz |
6.3 |
5.3 |
5.8 |
|
7 |
Super Trimec |
1.10 oz |
7.0 |
7.3 |
7.2 |
|
8 |
Trimec Classic 3.4 SL |
1.50 oz |
5.3 |
6.3 |
5.8 |
|
LSD0.05 |
1.1 |
1.6 |
1.1 |
1These figures represent the degree of damage observed on clover. Damage was assessed using a 0 to 9 scale with 0 = no damage, 5 = plants 50% dead, 9 = plants 100% dead.
Table 4. Damage1 to Canada thistle in turf plots treated for the 1999 Riverdale Postemergent Broadleaf Herbicide Study.
|
Material |
Rate product /1000 ft2 |
June 15 |
June 18 |
Mean |
|
|
1 |
Untreated control |
NA |
0.0 |
0.0 |
0.0 |
|
2 |
Triplet 49.7% |
1.29 oz |
5.3 |
5.3 |
5.3 |
|
3 |
Millennium Ultra 47.1% |
0.92 oz |
4.7 |
4.3 |
4.5 |
|
4 |
RDL 211 47.4% |
1.10 oz |
4.7 |
8.0 |
6.3 |
|
5 |
RDL 343 46.0% |
1.17 oz |
8.7 |
8.0 |
8.3 |
|
6 |
RDL 414 59.1% |
1.10 oz |
8.3 |
8.0 |
8.2 |
|
7 |
Super Trimec |
1.10 oz |
8.0 |
9.0 |
8.5 |
|
8 |
Trimec Classic 3.4 SL |
1.50 oz |
9.0 |
7.7 |
8.3 |
|
LSD0.05 |
5.1 |
4.3 |
4.5 |
1These figures represent the degree of damage observed on thistle. Damage was assessed using a 0 to 9 scale with 0 = no damage, 5 = plants 50% dead, 9 = plants 100% dead.
Table 5. Dandelion populations1 in turf plots treated for the 1999 Riverdale Postemergent Broadleaf Herbicide Study.
|
Material |
Rate product /1000 ft2 |
June 24 |
June 29 |
July 9 |
July 15 |
July 21 |
July 27 |
Aug 4 |
Mean |
|
|
1 |
Untreated control |
NA |
40.3 |
55.3 |
56.7 |
23.3 |
26.7 |
31.3 |
30.3 |
37.7 |
|
2 |
Triplet 49.7% |
1.29 oz |
20.7 |
32.7 |
16.7 |
14.7 |
15.0 |
14.3 |
21.7 |
19.4 |
|
3 |
Millennium Ultra 47.1% |
0.92 oz |
31.7 |
35.7 |
7.7 |
6.7 |
6.0 |
5.3 |
13.0 |
15.1 |
|
4 |
RDL 211 47.4% |
1.10 oz |
17.7 |
23.0 |
7.0 |
10.7 |
13.3 |
13.0 |
8.3 |
13.3 |
|
5 |
RDL 343 46.0% |
1.17 oz |
18.7 |
32.3 |
16.3 |
16.0 |
16.7 |
22.7 |
15.3 |
19.7 |
|
6 |
RDL 414 59.1% |
1.10 oz |
22.3 |
31.0 |
7.7 |
22.3 |
11.7 |
10.7 |
11.3 |
16.7 |
|
7 |
Super Trimec |
1.10 oz |
19.3 |
24.0 |
1.3 |
5.0 |
6.3 |
6.0 |
6.0 |
9.7 |
|
8 |
Trimec Classic 3.4 SL |
1.50 oz |
15.3 |
24.7 |
7.7 |
10.0 |
8.3 |
6.0 |
7.3 |
11.3 |
|
LSD0.05 |
15.1 |
15.9 |
12.8 |
11.3 |
10.4 |
P>F = 0.06 17.3 |
13.0 |
10.8 |
1These figures represent the number of dandelions per plot.
Table 6. Percentage reductions1 in dandelion populations in turf plots treated for the 1999 Riverdale Postemergent Broadleaf Herbicide Study.
|
Material |
Rate product /1000 ft2 |
June 24 |
June 29 |
July 9 |
July 15 |
July 21 |
July 27 |
Aug 4 |
Mean |
|
|
_________________ Percentage reduction (%) _______________ |
||||||||||
|
1 |
Untreated control |
NA |
0.0 |
0.0 |
0.0 |
0.0 |
0.0 |
0.0 |
0.0 |
0.0 |
|
2 |
Triplet 49.7% |
1.29 oz |
48.7 |
40.9 |
70.6 |
37.1 |
43.8 |
54.2 |
28.5 |
48.6 |
|
3 |
Millennium Ultra 47.1% |
0.92 oz |
21.4 |
35.5 |
86.5 |
71.4 |
77.5 |
83.0 |
57.1 |
59.8 |
|
4 |
RDL 211 47.4% |
1.10 oz |
56.2 |
58.4 |
87.7 |
54.2 |
50.1 |
58.5 |
72.5 |
64.8 |
|
5 |
RDL 343 46.0% |
1.17 oz |
53.7 |
41.5 |
71.2 |
31.3 |
37.6 |
27.6 |
49.4 |
47.7 |
|
6 |
RDL 414 59.1% |
1.10 oz |
44.6 |
43.9 |
86.5 |
4.1 |
56.3 |
65.9 |
62.6 |
55.7 |
|
7 |
Super Trimec |
1.10 oz |
52.0 |
56.6 |
97.6 |
78.5 |
76.3 |
80.8 |
80.2 |
74.2 |
|
8 |
Trimec Classic 3.4 SL |
1.50 oz |
62.0 |
55.4 |
86.5 |
57.1 |
68.8 |
80.8 |
75.8 |
69.9 |
|
LSD0.05 |
37.4 |
28.7 |
22.6 |
48.4 |
38.9 |
P>F = 0.06 55.3 |
42.9 |
28.6 |
||
1These figures represent percentage reductions in dandelion counts per plot as compared to dandelion populations in the untreated controls.
Table 7. Percentage clover cover1 in turf plots treated for the 1999 Riverdale Postemergent Broadleaf Herbicide Study.
|
Material |
Rate product /1000 ft2 |
June 24 |
June 29 |
July 9 |
July 15 |
July 21 |
July 27 |
Aug 4 |
Mean cover |
|
|
__________________________ (%) _________________________ |
||||||||||
|
1 |
Untreated control |
NA |
65.0 |
88.3 |
56.7 |
56.7 |
66.7 |
70.0 |
71.7 |
67.9 |
|
2 |
Triplet 49.7% |
1.29 oz |
20.0 |
26.7 |
3.7 |
10.3 |
11.7 |
16.7 |
9.0 |
14.0 |
|
3 |
Millennium Ultra 47.1% |
0.92 oz |
15.0 |
10.0 |
0.7 |
0.7 |
0.7 |
0.3 |
1.0 |
4.0 |
|
4 |
RDL 211 47.4% |
1.10 oz |
16.7 |
13.3 |
6.7 |
2.0 |
5.0 |
8.7 |
6.7 |
8.4 |
|
5 |
RDL 343 46.0% |
1.17 oz |
33.3 |
26.7 |
8.3 |
6.7 |
8.3 |
13.3 |
8.3 |
15.0 |
|
6 |
RDL 414 59.1% |
1.10 oz |
16.7 |
11.7 |
2.3 |
1.0 |
1.0 |
1.0 |
1.0 |
5.0 |
|
7 |
Super Trimec |
1.10 oz |
18.3 |
13.3 |
0.7 |
0.0 |
0.7 |
1.0 |
0.7 |
5.0 |
|
8 |
Trimec Classic 3.4 SL |
1.50 oz |
26.7 |
25.0 |
10.0 |
8.3 |
11.7 |
16.7 |
8.3 |
15.2 |
|
LSD0.05 |
24.2 |
22.0 |
11.0 |
16.9 |
14.1 |
20.1 |
11.4 |
12.7 |
||
1These figures represent the area per plot covered by clover.
Table 8. Percentage reductions1 in clover cover in turf plots treated for the 1999 Riverdale Postemergent Broadleaf Herbicide Study.
|
Material |
Rate product /1000 ft2 |
June 24 |
June 29 |
July 9 |
July 15 |
July 21 |
July 27 |
Aug 4 |
Mean |
|
|
_________________________ (%) _________________________ |
||||||||||
|
1 |
Untreated control |
NA |
0.0 |
0.0 |
0.0 |
0.0 |
0.0 |
0.0 |
0.0 |
0.0 |
|
2 |
Triplet 49.7% |
1.29 oz |
69.2 |
69.8 |
93.5 |
81.8 |
82.5 |
76.2 |
87.4 |
79.4 |
|
3 |
Millennium Ultra 47.1% |
0.92 oz |
76.9 |
88.7 |
98.8 |
98.8 |
99.0 |
99.5 |
98.6 |
94.0 |
|
4 |
RDL 211 47.4% |
1.10 oz |
74.4 |
84.9 |
88.2 |
96.5 |
92.5 |
87.6 |
90.7 |
87.6 |
|
5 |
RDL 343 46.0% |
1.17 oz |
48.7 |
69.8 |
85.3 |
88.2 |
87.5 |
81.0 |
88.4 |
77.9 |
|
6 |
RDL 414 59.1% |
1.10 oz |
74.4 |
95.8 |
95.9 |
98.2 |
98.5 |
98.6 |
98.6 |
92.7 |
|
7 |
Super Trimec |
1.10 oz |
71.8 |
84.9 |
98.8 |
100.0 |
99.0 |
98.6 |
99.1 |
92.7 |
|
8 |
Trimec Classic 3.4 SL |
1.50 oz |
59.0 |
71.7 |
82.4 |
85.3 |
82.5 |
76.2 |
88.4 |
77.5 |
|
LSD0.05 |
37.2 |
24.9 |
19.4 |
29.8 |
21.2 |
28.7 |
15.9 |
18.7 |
||
1These figures represent percentage reductions in clover cover per plot as compared to clover populations in the untreated controls.
Table 9. Canada thistle populations1 in turf plots treated for the 1999 Riverdale Postemergent Broadleaf Herbicide Study.
|
Material |
Rate product /1000 ft2 |
June 24 |
June 29 |
July 9 |
July 15 |
July 21 |
July 27 |
Aug 4 |
Mean count |
|
|
1 |
Untreated control |
NA |
11.0 |
15.7 |
5.0 |
6.7 |
4.3 |
5.0 |
6.3 |
7.7 |
|
2 |
Triplet 49.7% |
1.29 oz |
4.0 |
4.3 |
5.7 |
6.3 |
6.7 |
8.0 |
8.7 |
6.2 |
|
3 |
Millennium Ultra 47.1% |
0.92 oz |
3.7 |
9.0 |
5.7 |
11.3 |
11.3 |
12.3 |
12.7 |
9.4 |
|
4 |
RDL 211 47.4% |
1.10 oz |
4.0 |
10.0 |
6.0 |
7.7 |
7.7 |
7.7 |
10.0 |
7.6 |
|
5 |
RDL 343 46.0% |
1.17 oz |
2.7 |
5.3 |
2.7 |
6.0 |
6.0 |
6.0 |
6.0 |
5.0 |
|
6 |
RDL 414 59.1% |
1.10 oz |
5.0 |
7.3 |
5.3 |
6.7 |
9.7 |
11.7 |
14.3 |
8.6 |
|
7 |
Super Trimec |
1.10 oz |
3.0 |
12.3 |
8.7 |
11.7 |
13.7 |
19.0 |
18.0 |
12.3 |
|
8 |
Trimec Classic 3.4 SL |
1.50 oz |
5.3 |
13.3 |
11.0 |
12.3 |
13.0 |
17.0 |
13.3 |
12.2 |
|
LSD0.05 |
NS |
NS |
NS |
NS |
NS |
NS |
NS |
NS |
1These figures represent the number of thistles per plot.
Table 10. Percentage reductions1 in Canada thistle populations in turf plots treated for the 1999 Riverdale Postemergent Broadleaf Herbicide Study.
|
Material |
Rate product /1000 ft2 |
June 24 |
June 29 |
July 9 |
July 15 |
July 21 |
July 27 |
Aug 4 |
Mean |
|
|
________________________ (%) ________________________ |
||||||||||
|
1 |
Untreated control |
NA |
0.0 |
0.0 |
0.0 |
0.0 |
0.0 |
0.0 |
0.0 |
0.0 |
|
2 |
Triplet 49.7% |
1.29 oz |
63.6 |
72.4 |
0.0 |
5.5 |
0.0 |
0.0 |
0.0 |
19.0 |
|
3 |
Millennium Ultra 47.1% |
0.92 oz |
66.7 |
42.7 |
0.0 |
0.0 |
0.0 |
0.0 |
0.0 |
0.0 |
|
4 |
RDL 211 47.4% |
1.10 oz |
63.6 |
36.3 |
0.0 |
0.0 |
0.0 |
0.0 |
0.0 |
1.7 |
|
5 |
RDL 343 46.0% |
1.17 oz |
75.8 |
66.0 |
46.7 |
10.4 |
0.0 |
0.0 |
4.8 |
35.7 |
|
6 |
RDL 414 59.1% |
1.10 oz |
54.5 |
53.3 |
0.0 |
0.5 |
0.0 |
0.0 |
0.0 |
0.0 |
|
7 |
Super Trimec |
1.10 oz |
72.7 |
21.4 |
0.0 |
0.0 |
0.0 |
0.0 |
0.0 |
0.0 |
|
8 |
Trimec Classic 3.4 SL |
1.50 oz |
51.5 |
15.1 |
0.0 |
0.0 |
0.0 |
0.0 |
0.0 |
0.0 |
|
LSD0.05 |
NS |
NS |
NS |
NS |
NS |
NS |
NS |
NS |
||
1These figures represent percentage reductions in thistle counts per plot as compared to thistle populations in the untreated controls.
Table 11. Oxalis populations1 in turf plots treated for the 1999 Riverdale Postemergent Broadleaf Herbicide Study.
|
Material |
Rate product /1000 ft2 |
August 4 |
|
|
1 |
Untreated control |
NA |
1.3 |
|
2 |
Triplet 49.7% |
1.29 oz |
3.7 |
|
3 |
Millennium Ultra 47.1% |
0.92 oz |
4.3 |
|
4 |
RDL 211 47.4% |
1.10 oz |
1.7 |
|
5 |
RDL 343 46.0% |
1.17 oz |
3.0 |
|
6 |
RDL 414 59.1% |
1.10 oz |
2.0 |
|
7 |
Super Trimec |
1.10 oz |
2.0 |
|
8 |
Trimec Classic 3.4 SL |
1.50 oz |
2.7 |
|
LSD0.05 |
NS |
1These figures represent the number of oxalis per plot.
Table 12. Percentage crabgrass cover1 in turf plots treated for the 1999 Riverdale Postemergent Broadleaf Herbicide Study.
|
Material |
Rate product /1000 ft2 |
July 27 |
August 4 |
Mean |
|
|
_________________ (%) _____________ |
|||||
|
1 |
Untreated control |
NA |
5.3 |
5.3 |
5.3 |
|
2 |
Triplet 49.7% |
1.29 oz |
8.3 |
3.3 |
5.8 |
|
3 |
Millennium Ultra 47.1% |
0.92 oz |
23.3 |
25.0 |
24.2 |
|
4 |
RDL 211 47.4% |
1.10 oz |
18.3 |
11.7 |
15.0 |
|
5 |
RDL 343 46.0% |
1.17 oz |
16.7 |
25.0 |
20.8 |
|
6 |
RDL 414 59.1% |
1.10 oz |
18.3 |
15.0 |
16.7 |
|
7 |
Super Trimec |
1.10 oz |
7.0 |
8.3 |
7.7 |
|
8 |
Trimec Classic 3.4 SL |
1.50 oz |
30.0 |
28.3 |
29.2 |
|
LSD0.05 |
11.9 |
14.2 |
11.1 |
||
1These figures represent percentage reductions in percentage crabgrass cover per plot as compared to populations in the untreated controls.
|
Index Page - Turfgrass Research Report 2000 |