potato weed control 2000

Oakes Irrigation Research Site
Carrington Research Extension Center * North Dakota State University
P.O. Box 531, Oakes, ND 58474-0531, Voice: (701) 742-2189, FAX: (701) 742-2700, email: rgreenla@ndsuext.nodak.edu

POTATO WEED CONTROL STUDY, 2000

Richard Greenland

Cooperator: DuPont

Results summary

Table 45. Herbicide treatments

Table 46. Weed control ratings, 29 June 2000

Table 47. Weed control ratings, 2 August 2000

Table 48. Weed control ratings, 22 August 2000

Table 49. Potato yield and quality

This study was designed to examine tank mix partners for Matrix herbicide. It also tests Authority, a new herbicide for potato.

MATERIALS AND METHODS

Soil: Maddock sandy loam; pH=7.4; 1.9% organic matter; soil-P, soil-K, and soil-S were very high.

Previous crop: 1999 - pumpkin and garden pea; 1998 - field corn; 1997 - broccoli and oriental vegetables.

Seedbed preparation: Disked on 29 October 1999. Multiweeded (field cultivated) on April 5.

Planting: 'Russet Burbank' potato seed pieces were placed 1 ft apart in rows 3 ft apart on April 26.

Plots: Plots were 20 ft long by 12 ft (four rows) wide. There were 4 reps.

Fertilizer: On April 4, broadcast 18 lbs N/acre and 20 lbs S/acre as 21-0-0-24. Sprayed 75 lbs N/acre on April 25. Fertigated 35 lbs N/acre as 28-0-0 on June 27 and July 14.

Irrigation: Overhead sprinkler irrigation as needed.

Pest control: See Table 45 for weed control treatments. Dragged off on May 15. Hilled on May 22. Sprayed Admire (1.3 oz/1000 ft on seed pieces as they were planted), Asana (8 oz/acre on July 19, July 26, Aug 2, and Aug 9) for Colorado potato beetle control. Sprayed Manzate (2 lbs/acre on July 7), Bravo Zn (2 pts/acre on July 19, July 26, Aug 2, Aug 9, and Aug 18), and Bravo 500 (2 qt/acre on Aug 26) for early and late blight control.

Harvest: Harvested on October 5. Yields, etc. were taken from an eight-foot section of the middle two rows from each plot.

RESULTS

A single application of Matrix controlled or suppressed foxtail and redroot pigweed, and suppressed hairy nightshade. This was poorer control than would normally be expected probably due to the Matrix being washed off the weeds by the rain immediately following application. On June 29, eastern black nightshade growth in plots receiving only a POST application of Matrix, or Lexone PRE plus Matrix POST, was much greater than in the other plots, including the check plots. The suppression of hairy nightshade and other weeds by the Matrix allowed the eastern black nightshade to grow more vigorously, and Matrix (with or without Lexone) did not control the eastern black nightshade. Lorox alone was weak on most weeds except redroot pigweed and eastern black nightshade. Lorox plus Matrix controlled all weeds except lambsquarters. The Lexone plus Matrix controlled all weeds except eastern black nightshade and was a little weak on the early control of hairy nightshade. Authority was weak on grass control, but when combined with Matrix controlled all the weeds present in the study. The addition of Lorox or Lexone to the Authority plus Matrix combination did not increase weed control. The Dual plus Lexone plus Matrix combination controlled all weeds in the study.

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Table 45. Herbicide treatments for the Oakes Irrigation Research Site 2000 potato weed control study.

Treatment number Herbicide(s) Rate
(product/acre) Application
timing¹ Comments

1 Dual II + Lexone
Matrix 2 pts + 1/3 lb
1.0 oz PRE
POST Commercial Standard

2 Lorox 1.0 lb PRE Half-rate

3 Matrix 0.5 oz POST Half-rate

4 Authority 1.5 oz PRE Half-rate

5 Authority
Matrix 1.5 oz
0.5 oz PRE
POST Half-rate
Half-rate

6 Lexone
Matrix 1/3 lb
0.5 oz PRE
POST Half-rate
Half-rate

7 Lorox
Matrix 1.0 lb
0.5 oz PRE
POST Half-rate
Half-rate

8 Lorox + Authority
Matrix 1.0 lb + 1.5 oz
0.5 oz PRE
POST Half-rate
Half-rate

9 Authority + Lexone
Matrix 1.5 oz + lb
0.5 oz PRE
POST Half-rate
Half-rate

10 Untreated

¹PRE applied on May 23, just after last hilling. No weeds present. About 5% of potatoes had leaves above the ground. POST applied on June 15. Weeds were ½ to 3 inches tall in plots receiving treatment 3 (no previous herbicide), and ¼ to 1 inch tall in the other plots. It started raining 2 to 3 minutes after I finished spraying.

Inches rainfall(R) and irrigation(I) before and after POST application on June 15:

June 1 - 0.08 R June 13 - 0.12 R June 23 - 0.13 R

June 3 - 0.07 R June 14 - 0.48 R June 24 - 0.01 R

June 4 - 0.52 R June 15 - 0.32 R June 25 - 0.59 R

June 6 - 0.06 R June 16 - 0.17 R June 26 - 0.02 R

June 10 - 0.18 R June 18 - 0.03 R June 27 - 0.50 I

June 12 - 0.50 I June 20 - 0.90 R June 29 - 0.75 I

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Table 46. Weed control ratings¹, 29 June 2000, in the potato weed control study at the Oakes Irrigation Research Site.

Treatment number² Hairy nightshade E. black nightshade Redroot pigweed Lambs- quarters Foxtail Common purslane

1 100 a³ 100 a 100 a 100 a 100 a 98 a

2 65 bc 98 a 73 a 63 c 50 b 53 bc

3 63 c 0 c 85 a 58 c 93 a 45 c

4 100 a 100 a 100 a 100 a 83 a 83 ab

5 95 ab 100 a 100 a 100 a 98 a 85 ab

6 75 abc 43 b 98 a 100 a 100 a 90 a

7 78 abc 75 a 95 a 83 b 93 a 78 abc

8 98 a 100 a 100 a 100 a 100 a 90 a

9 100 a 100 a 100 a 100 a 100 a 100 a

10 20 d 80 a 28 b 30 d 33 c 25 d

Density⁴ 2.3 0.1 2.1 1.5 1.5 4

C.V. (%) 14 23 12 6 8 20

Probability <.0001 <.0001 <.0001 <.0001 <.0001 0.0001

¹Ratings from 0 to 100: 0 = plot covered with vigorously growing weeds. 100 = no weeds in plot.

²See Table 45 for a description of treatments.

³Values in same column followed by the same letter are not significantly different (0.05 level).

⁴Weed density in weeds per square foot.

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Table 47. Weed control ratings¹, 2 August 2000, in the potato weed control study, Oakes Irrigation Research Site.

Treatment number² Hairy nightshade Redroot pigweed Lambsquarters Foxtail Witch grass

1 98 100 a³ 95 a 100 a 100 a

2 95 90 ab 58 c 60 b 70 bc

3 93 78 bc 50 c 83 a 93 ab

4 100 100 a 100 a 80 a 63 c

5 100 100 a 100 a 98 a 98 a

6 85 100 a 100 a 100 a 100 a

7 100 95 a 75 b 98 a 95 a

8 100 100 a 100 a 100 a 100 a

9 100 100 a 98 a 100 a 100 a

10 88 63 c 55 c 80 a 83 abc

Density⁴ 0.1 0.5 0.7 0.2 0.3

C.V. (%) 6 7 7 9 12

Probability 0.40 0.0005 <.0001 0.003 0.03

¹Ratings from 0 to 100: 0 = plot covered with vigorously growing weeds. 100 = no weeds in plot.

²See Table 45 for a description of treatments.

³Values in the same column followed by the same letter are not significantly different at the 0.05 level. No letters in column means there were no differences between values in that column.

⁴Weed density in weeds per square foot.

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Table 48. Weed control ratings¹, 22 August 2000, in the potato weed control study, Oakes Irrigation Research Site.

Treatment number² Hairy nightshade Redroot pigweed Lambsquarters Foxtail

1 95 ab³ 100 a 98 a 98 a

2 73 bc 88 a 73 b 63 b

3 68 cd 93 a 68 b 88 a

4 98 a 95 a 100 a 83 a

5 95 ab 98 a 93 a 90 a

6 85 abc 100 a 98 a 98 a

7 88 abc 98 a 75 b 95 a

8 100 a 100 a 100 a 95 a

9 98 a 98 a 98 a 100 a

10 53 d 55 b 38 c 60 b

Density⁴ 0.2 0.3 0.4 0.2

C.V. (%) 10 5 6 10

Probability 0.001 <.0001 <.0001 0.004

¹Ratings from 0 to 100: 0 = plot covered with vigorously growing weeds. 100 = no weeds in plot.

²See Table 45 for a description of treatments.

³Values in the same column followed by the same letter are not significantly different at the 0.05 level.

⁴Weed density in weeds per square foot.

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Table 49. Potato yield and quality in the Oakes Irrigation Research Site 2000 weed control study.

Treatment number¹ Number of tubers US #1 yield US #2 yield Total yield Hollow heart Tuber size

1000s/A ------------- cwt/acre ------------ % oz/tuber

1 108 404 56 471 50 7.1 ab²

2 113 334 74 429 15 5.9 cd

3 106 323 82 420 30 6.3 bcd

4 108 393 57 467 35 7.0 ab

5 105 377 65 460 25 7.0 ab

6 117 384 65 468 20 6.4 a-d

7 106 364 65 446 15 6.6 abc

8 107 351 72 452 25 6.7 abc

9 115 441 69 532 30 7.4 a

10 94 254 57 324 25 5.4 d

C.V. (%) 16 20 39 18 54 11

Probability 0.81 0.09 0.91 0.15 0.08 0.02

¹See Table 45 for a description of treatments.

²Values in this column followed by the same letter are not significantly different at the 0.05 level.

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Soil:	Maddock sandy loam; pH=7.4; 1.9% organic matter; soil-P, soil-K, and soil-S were very high.
Previous crop:	1999 - pumpkin and garden pea; 1998 - field corn; 1997 - broccoli and oriental vegetables.
Seedbed preparation:	Disked on 29 October 1999. Multiweeded (field cultivated) on April 5.
Planting:	'Russet Burbank' potato seed pieces were placed 1 ft apart in rows 3 ft apart on April 26.
Plots:	Plots were 20 ft long by 12 ft (four rows) wide. There were 4 reps.
Fertilizer:	On April 4, broadcast 18 lbs N/acre and 20 lbs S/acre as 21-0-0-24. Sprayed 75 lbs N/acre on April 25. Fertigated 35 lbs N/acre as 28-0-0 on June 27 and July 14.
Irrigation:	Overhead sprinkler irrigation as needed.
Pest control:	See Table 45 for weed control treatments. Dragged off on May 15. Hilled on May 22. Sprayed Admire (1.3 oz/1000 ft on seed pieces as they were planted), Asana (8 oz/acre on July 19, July 26, Aug 2, and Aug 9) for Colorado potato beetle control. Sprayed Manzate (2 lbs/acre on July 7), Bravo Zn (2 pts/acre on July 19, July 26, Aug 2, Aug 9, and Aug 18), and Bravo 500 (2 qt/acre on Aug 26) for early and late blight control.
Harvest:	Harvested on October 5. Yields, etc. were taken from an eight-foot section of the middle two rows from each plot.

Treatment number	Herbicide(s)	Rate (product/acre)	Application timing¹	Comments

1	Dual II + Lexone Matrix	2 pts + 1/3 lb 1.0 oz	PRE POST	Commercial Standard
2	Lorox	1.0 lb	PRE	Half-rate
3	Matrix	0.5 oz	POST	Half-rate
4	Authority	1.5 oz	PRE	Half-rate
5	Authority Matrix	1.5 oz 0.5 oz	PRE POST	Half-rate Half-rate
6	Lexone Matrix	1/3 lb 0.5 oz	PRE POST	Half-rate Half-rate
7	Lorox Matrix	1.0 lb 0.5 oz	PRE POST	Half-rate Half-rate
8	Lorox + Authority Matrix	1.0 lb + 1.5 oz 0.5 oz	PRE POST	Half-rate Half-rate
9	Authority + Lexone Matrix	1.5 oz + lb 0.5 oz	PRE POST	Half-rate Half-rate
10	Untreated

June 1 - 0.08 R	June 13 - 0.12 R	June 23 - 0.13 R
June 3 - 0.07 R	June 14 - 0.48 R	June 24 - 0.01 R
June 4 - 0.52 R	June 15 - 0.32 R	June 25 - 0.59 R
June 6 - 0.06 R	June 16 - 0.17 R	June 26 - 0.02 R
June 10 - 0.18 R	June 18 - 0.03 R	June 27 - 0.50 I
June 12 - 0.50 I	June 20 - 0.90 R	June 29 - 0.75 I

Treatment number²	Hairy nightshade	E. black nightshade	Redroot pigweed	Lambs- quarters	Foxtail	Common purslane

1	100 a³	100 a	100 a	100 a	100 a	98 a
2	65 bc	98 a	73 a	63 c	50 b	53 bc
3	63 c	0 c	85 a	58 c	93 a	45 c
4	100 a	100 a	100 a	100 a	83 a	83 ab
5	95 ab	100 a	100 a	100 a	98 a	85 ab
6	75 abc	43 b	98 a	100 a	100 a	90 a
7	78 abc	75 a	95 a	83 b	93 a	78 abc
8	98 a	100 a	100 a	100 a	100 a	90 a
9	100 a	100 a	100 a	100 a	100 a	100 a
10	20 d	80 a	28 b	30 d	33 c	25 d

Density⁴	2.3	0.1	2.1	1.5	1.5	4
C.V. (%)	14	23	12	6	8	20
Probability	<.0001	<.0001	<.0001	<.0001	<.0001	0.0001

Treatment number¹	Number of tubers	US #1 yield	US #2 yield	Total yield	Hollow heart	Tuber size
	1000s/A	------------- cwt/acre ------------			%	oz/tuber

1	108	404	56	471	50	7.1 ab²
2	113	334	74	429	15	5.9 cd
3	106	323	82	420	30	6.3 bcd
4	108	393	57	467	35	7.0 ab
5	105	377	65	460	25	7.0 ab
6	117	384	65	468	20	6.4 a-d
7	106	364	65	446	15	6.6 abc
8	107	351	72	452	25	6.7 abc
9	115	441	69	532	30	7.4 a
10	94	254	57	324	25	5.4 d

C.V. (%)	16	20	39	18	54	11
Probability	0.81	0.09	0.91	0.15	0.08	0.02