Postemergence Broadleaf Control Trial III 2002

Nick E. Christians and Luke Dant

The purpose of this study was to evaluate the effectiveness of several broadleaf herbicides, specifically for control of wild violet, but also for control of other broadleaf weeds that may be present in the plot. The study was conducted at the Iowa State University arboretum.

The experimental design was a split plot design with main plots being the control and 10 herbicide treatments as the sub-plots. Some treatments were applied as a single application of the materials (App 1) and other treatments had repeat applications made 21 days following the first application (App 2). The main plots were 10 ft x 5 ft and were split in half into 2 sub-plots measuring 5 ft x 5ft. Each treatment was replicated three times. All of the main plot treatments were applied on May 9 using a carbon dioxide backpack sprayer with #8002 flat fan TeeJet nozzles at 30-40 psi and diluted to a total spray volume of 3 gal 1000 sq. ft.. The first application was made to the entire 10 ft x 5 ft plot. The second application was made on May 30, 21 days after the first application, however, only one half of the plot was sprayed. Treatment numbers 2 and 3 only required one application; therefore, they were not sprayed a second time. The sub-plots were randomly assigned within the main plots.

Both wild violet and ground ivy damage was reported 2, 7, 14, 21 and 28 days after the first application and again 5 and 7 days after the second application (Tables 1-4). This was reported on a percent scale of 0% being no damage and 100% being dead. The percent wild violet and ground ivy cover was estimated 14, 21, 28 and 35 days after the second application based on a percent scale (0% = No weeds and 100% being complete covered by weeds).

On the 2nd day after application (5/11), there were only minor differences in weed damage on wild violets among the treatments (Table 1). The EH1349 had the least effect on weeds at that time. By 7 days after treatment (5/16), Speed Zone and Power Zone showed a clear advantage over the other treatments in weed damage. This is likely due to the presence of carfentrazone in these product, which is added to speed their activity on weeds. The effect of the second application can be seen on 6/6, when several of the treatments showed a distinct advantage over the single application alone. Power Zone at 6 pt/A and Millennium Ultra were showing the greatest effect on that date. The herbicides that provided the best overall control of wild violets on 7/3 were Speed Zone at 4.5 pt/A, Confront at 1 pt/A, and EH1349 at 4 pt/A. All materials tested significantly reduced wild violet numbers from the control.

Weed damage on ground ivy was much better with Speed Zone and Power Zone at days 7 and 14 following application. As was the case with wild violet, repeat applications showed a distinct advantage for most treatments on 6/6. All treatments significantly reduced ground ivy cover at all observation dates during the study (Table 4). There was not as great of a difference between 1 and 2 applications on the ground ivy control as was observed on the wild violet control.

Table 1. Initial damage to wild violets following herbicide application. (0 = no damage and 100=dead)

		Rate Product		Weed Phytotoxicity
	Material	(pt)/A	Initial Cover	5/11	5/16	5/23	6/4	6/6
				App 1	App 1	App 1	App 2	App 1	App 2
1	Untreated Control	NA	38	0	0	0	0	0	0
2	Speed Zone†	5.0	14	10	20	32	13	10	10
3	Power Zone†	6.0	13	15	32	27	20	18	40
4	Speed Zone	4.5	18	15	33	40	33	7	10
5	Speed Zone	5.0	34	10	30	33	37	7	25
6	Power Zone	5.0	24	15	23	17	27	5	20
7	Millennium Ultra	2.5	23	15	7	5	37	5	40
8	Confront	1.0	22	10	5	5	12	5	5
9	Trimec Classic	4.0	8	10	8	5	30	5	30
10	EH1349	4.0	6	5	5	8	15	10	27
11	NB30165	4.0‡	34	15	5	5	18	5	30
	LSD			1	1	1	10	4	4

† Single application
‡ 4.0 qt/A

Table 2. Wild Violet control by postemergence herbicides.

		% Weed Cover
	Material	6/13		6/20		6/27		7/3
		App 1	App 2	App 1	App 2	App 1	App 2	App 1	App 2
1	Untreated Control	33	27	22	22	27	27	36	36
2	Speed Zone†	17	9	18	18	5	13	17	9
3	Power Zone†	28	18	16	19	17	14	15	12
4	Speed Zone	37	6	14	3	23	3	14	4
5	Speed Zone	36	14	25	10	17	20	18	15
6	Power Zone	37	5	23	9	25	12	26	12
7	Millennium Ultra	35	16	22	9	15	7	18	9
8	Confront	26	28	10	7	14	6	13	5
9	Trimec Classic	8	19	5	10	3	6	4	8
10	EH1349	17	5	11	9	7	4	7	4
11	NB30165	34	10	21	15	20	16	21	15
	LSD	17	17	11	11	10	10	11	11

† Single application

Table 3. Initial damage to ground ivy following herbicide application.

		Rate Product	Weed Phytotoxicity
	Material	(pt)/A	5/16	5/23	6/4	6/6
			App 1	App 1	App 2	App 1	App 2
1	Untreated Control	NA	0	0	0	0	0
2	Speed Zone†	5.0	28	27	5	10	10
3	Power Zone†	6.0	35	47	5	18	40
4	Speed Zone	4.5	22	25	45	7	10
5	Speed Zone	5.0	27	28	50	7	25
6	Power Zone	5.0	25	32	45	5	20
7	Millennium Ultra	2.5	3	5	43	5	40
8	Confront	1.0	2	3	10	5	5
9	Trimec Classic	4.0	3	5	28	5	30
10	EH1349	4.0	8	8	12	10	27
11	NB30165	4.0‡	10	8	23	5	30
	LSD		1	1	13	3	3

† Single application
‡ 4.0 qt/A

Table 4. Ground ivy control by postemergence herbicides.

		% Weed Cover
	Material	6/13		6/20		6/27		7/3
		App 1	App 2	App 1	App 2	App 1	App 2	App 1	App 2
1	Untreated Control	47	47	47	47	32	32	20	23
2	Speed Zone†	3	3	6	5	4	2	1	1
3	Power Zone†	3	3	4	4	3	3	4	4
4	Speed Zone	6	1	4	1	2	1	3	0
5	Speed Zone	7	3	9	2	9	2	11	2
6	Power Zone	4	3	3	2	3	1	2	2
7	Millennium Ultra	6	2	9	1	4	1	4	0
8	Confront	7	6	8	6	3	1	2	1
9	Trimec Classic	3	2	2	2	1	1	1	1
10	EH1349	7	2	6	3	2	1	2	1
11	NB30165	6	2	4	2	3	2	3	2
	LSD	3	3	3	3	4	4	3	3

† Single application

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