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

CABBAGE WEED CONTROL STUDY

Richard Greenland

Table 36. Herbicide treatments

Table 37. Weed ratings and yield data

Few herbicides are available for weed control in cabbage. In this study we examined several herbicides for possible use in cabbage. Dacthal was used on cabbage until 1998, but then its manufacture was discontinued until 2001. It is again available so we included it in the study. Lentagran, the wettable powder form of pyridate, has been labeled for post emergent use in cabbage but is no longer available. Tough is pyridate in an emulsifiable concentrate formulation which can be more injurious to cabbage but also tougher on weeds. The recommended rate for Lentagran is 2 lbs per acre. To apply the same amount of pyridate using Tough requires 24 oz per acre. We applied Lentagran at 1 or 2 lbs per acre and compared it to Tough at 12, 18, and 24 oz per acre. We also studied the herbicides Valor, Authority, Dual II Magnum, Outlook, and Stinger for use in cabbage. Dacthal, Outlook, and Dual were applied both preemergence and early post emergence. The early post emergence treatments were tried as a way to control weeds without killing the barley cover crop planted with the cabbage and to reduce cabbage injury.

MATERIALS AND METHODS

Soil:	Maddock sandy loam; pH=7.4; 2.3% organic matter; soil-P and soil-K were very high; soil-S was very low.
Previous crops:	2000 - onion and potato; 1999 - pumpkin; 1998 - field corn.
Seedbed preparation:	Disked on April 25. Multiweeded (field cultivated) three times: once on May 2 to incorporate fertilizer; and twice on May 4 to incorporate herbicide.
Planting:	Direct seeded cabbage on May 4 with a Stanhay vegetable planter modified to drill barley (1 bu/acre, 6-inch rows) between and parallel to the cabbage rows. Cabbage seeds were spaced about 7 inches apart in 16-inch rows. Plants were later thinned to 15 inches apart (about 26,000 plants/acre). Seeds were placed about ½ to ¾ inches deep into a flat, fine seedbed. Sprayed Poast + Dash (1.5 pt/acre + 1 qt/acre) on May 30 to kill the barley cover crop.
Plots:	Each plot was 6 ft wide by 17 ft long. There was a 2-ft border between plots. The study had 4 reps.
Fertilizer:	On April 19, broadcast 10 lbs N/acre and 50 lbs P₂O₅/acre as 10-50-0 and 18 lbs N/acre and 20 lbs S/acre as 21-0-0-24. Sprayed 50 lbs N/acre as 28-0-0 on May 2. Fertigated 30 lbs N/acre as 28-0-0 on July 11.
Irrigation:	Overhead sprinkler irrigation as needed.
Pest Control:	Weeds were controlled using treatments listed in Table 36. In addition, all plots were hand weeded June 27 to July 3. Sprayed Sevin (1 qt/acre on May 14 and May 24) to control flea beetle. Sprayed Asana (8 oz/acre on June 4, June 19 and July 17) and DiPel (1 lb/acre on July 5, July 9, July 25, and Aug 1) to control cabbage looper and cabbage worm.
Harvest:	A 10-foot section of the middle two rows were harvested on August 8.

RESULTS

Valor applied PRE reduced cabbage stand resulting in reduced yield, but when applied POST after Treflan PPI it controlled all weeds but lambsquarters and did not reduce cabbage yield. Dacthal controlled weeds the best when applied PRE or when applied in combination with Stinger, Tough, or Lentagran to kill the weeds that had emerged before the Dacthal was applied. Outlook and Dual had trouble controlling lambsquarters and hairy nightshade, which in turn reduced yield. Authority applied PRE gave excellent weed control but reduced stands and lowered yields. When applied early POST Authority was weak on hairy nightshade but did not reduce stand or yield. Tough did not injure cabbage more than Lentagran, even at the 24 oz rate of Tough. Weed control was less and yields were lower when only Treflan PPI and a contact POST herbicide (Tough, Lentagran, or Stinger) were applied. The best combination of herbicides was Treflan applied PPI, Dacthal applied either PRE or early POST, and Stinger, Lentagran, or Tough applied POST.

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Table 36. Herbicide treatments for the Oakes Irrigation Research Site 2001 cabbage weed control study.

Treatment Number	Herbicides	Rates (product/acre)	Time of Application¹
1	Valor	1.5 oz	PRE
2	Treflan + Dacthal	1 pt + 8 lbs	PPI + PRE
3	Authority	4 oz	PRE
4	Dual II Magnum	1 pt	PRE
5	Outlook	1 pt	PRE
6	Treflan + Dacthal	1 pt + 8 lbs	PPI + EPOST
7	Treflan + Dual II Magnum	1 pt + 1 pt	PPI + EPOST
8	Treflan + Outlook	1 pt + 1 pt	PPI + EPOST
9	Treflan + Valor	1 pt + 1.5 oz	PPI + POST
10	Treflan + Authority	1 pt + 4 oz	PPI + POST
11	Treflan + Stinger	1 pt + 1/3 pt	PPI + POST
12	Treflan + Dacthal + Stinger	1 pt + 8 lbs + 1/3 pt	PPI + EPOST + POST
13	Treflan + Lentagran	1 pt + 2.1 lbs	PPI + POST
14	Treflan + Tough	1 pt + 12 oz	PPI + POST
15	Treflan + Tough	1 pt + 18 oz	PPI + POST
16	Treflan + Tough	1 pt + 24 oz	PPI + POST
17	Treflan + Dacthal + Lentagran	1 pt + 8 lbs + 1.0 lb	PPI + EPOST + POST
18	Treflan + Dacthal + Tough	1 pt + 8 lbs + 12 oz	PPI + EPOST + POST
19	Dual II Magnum + Tough	1 pt + 12 oz	EPOST + POST
20	Outlook + Tough	1 pt + 12 oz	EPOST + POST

¹PPI is preplant incorporated (May 4); PRE is preemergence (May 10); EPOST is early post emergence -- just after cabbage emerged (May 16, there were many small weeds that had emerged); POST is when cabbage had 4 to 5 true leaves (June 8, weed sizes varied from less than 1 inch tall in plots previously treated with Dacthal to 3 to 5 inches tall in some plots treated previously only with Treflan, Dual, and/or Outlook).

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Table 37. Weed ratings and yield data for the 2001 Oakes Irrigation Research Site cabbage weed control study.

Trt¹ No.	June 27 ratings				Weeding time³	August 15 ratings			Cabbage yield	No. of heads	Head size
Trt¹ No.	CI²	Rrpw²	Colq²	Hns²	Weeding time³	Rrpw²	Hns²	Fxtl²	Cabbage yield	No. of heads	Head size
	------------------ 0 to 10⁴ -------------------				minutes	------------- 0 to 10⁴ ------------			tons/A	1000s/A	lbs/hd

1	0.5	8.0	6.8 cde⁵	10.0 a	16 ab	5.8 f	10.0 a	6.0 b	8.9 f	4.1 e	4.2 a
2	0.8	9.5	9.8 ab	9.5 ab	17 ab	9.8 ab	9.3 a-d	9.8 a	22.3 abc	18.8 ab	2.4 bcd
3	1.3	10.0	10.0 a	9.5 ab	15 ab	9.8 ab	9.8 ab	6.3 b	15.8 c-f	12.7 d	2.7 bc
4	1.4	9.6	3.4 fg	4.8 de	53 d	8.1 cde	8.5 cd	10.0 a	15.7 b-f	19.6 a	1.6 cd
5	1.4	10.0	3.4 fg	7.4 bc	34 a-d	8.8 a-d	8.8 bcd	9.0 a	17.9 b-f	19.1 ab	1.8 bcd
6	0.5	8.8	8.0 a-d	9.3 ab	23 abc	9.5 abc	9.3 a-d	10.0 a	25.7 ab	20.8 a	2.5 bcd
7	1.1	9.9	5.0 efg	5.0 cde	49 cd	9.2 a-d	8.2 d	8.7 a	16.5 b-f	18.3 abc	1.8 bcd
8	2.0	9.5	6.8 cde	5.5 cde	40 bcd	9.5 abc	8.3 d	9.0 a	11.4 ef	17.2 a-d	1.3 d
9	1.0	10.0	6.3 de	10.0 a	16 ab	9.8 ab	9.5 abc	9.5 a	21.0 a-d	17.6 a-d	2.3 bcd
10	1.4	10.0	9.4 ab	6.1 cd	35 a-d	10.0 a	10.0 a	10.0 a	19.6 a-e	20.2 a	2.1 bcd
11	2.0	9.3	5.3 ef	5.8 cd	57 d	8.3 cd	9.8 ab	8.8 a	11.0 ef	13.5 cd	1.6 cd
12	0.0	8.6	8.4 a-d	9.8 ab	10 a	9.8 abc	10.0 a	9.7 a	29.9 a	19.6 a	3.0 ab
13	1.4	9.0	6.4 cde	5.4 cde	55 d	9.1 a-d	9.1 a-d	10.0 a	17.3 b-f	19.6 a	1.7 bcd
14	1.3	9.3	6.8 cde	3.5 e	48 d	8.8 a-d	8.3 d	9.0 a	19.1 b-e	20.0 a	1.9 bcd
15	1.0	9.8	7.5 b-e	4.8 de	38 a-d	9.8 ab	9.3 a-d	9.8 a	20.7 a-d	18.8 ab	2.2 bcd
16	1.8	9.3	7.5 b-e	6.0 cd	44 cd	8.8 a-d	9.3 a-d	9.3 a	18.7 b-e	16.3 a-d	2.4 bcd
17	0.3	9.3	8.8 abc	9.3 ab	15 ab	9.5 abc	10.0 a	9.5 a	25.6 ab	18.8 ab	2.7 bc
18	0.8	9.0	9.3 ab	9.5 ab	13 a	8.5 bcd	9.8 ab	9.8 a	23.0 abc	16.3 a-d	3.0 ab
19	1.7	8.6	2.4 g	7.8 ab	50 cd	6.4 ef	9.1 a-d	9.0 a	11.7 def	13.6 bcd	1.6 cd
20	1.7	9.0	3.0 fg	9.8 ab	52 d	7.8 de	8.5 cd	9.4 a	14.0 c-f	16.4 a-d	1.6 cd

Prob.	0.15	0.14	<.0001	<.0001	0.0006	<.0001	0.004	0.012	0.004	<.0001	0.007
C.V.	78	9	25	20	52	12	8	16	35	21	37

¹See Table 36 for a list of treatments.

²Abbreviations used are: CI - Cabbage injury; Rrpw - redroot pigweed; Colq - common lambsquarters; Hns - hairy nightshade; Fxtl - foxtail species.

³On June 27 to July 3 the cabbage was hand weeded. The value given is the average time to hand weed one 6 by 17 ft plot.

⁴Ratings are from 0 to 10: 0 = no weed control or crop injury, 10 = complete weed control or all cabbage plants dead.

⁵Values in the same column followed by the same letter are not significantly different at the 0.05 level. If no letters follow values in a column then there were no significant differences between values in that column.