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

TOMATO WEED CONTROL STUDY
Richard Greenland

Tomato and nightshade belong to the solanaceae family. Because of their similarities it is difficult to control nightshade in tomato production, especially with postemergence herbicides. This study evaluated three standard herbicides (Treflan, Tillam, and Lexone) and two new herbicides (rimsulfuron and pyridate) for control of hairy and black nightshades. Rimsulfuron controls hairy nightshade in potato. Pyridate controls hairy and eastern black nightshade but may injure tomatoes. We also looked at pigweed and lambsquarters control.

Results summary

Table 62. Treatments for the 1998 tomato weed control study.

Table 63. Nightshade weed control ratings.

Table 64. Redroot pigweed and lambsquarters weed control ratings.

Table 65. Yields of tomatoes harvested on August 19.

Table 66. Yields of tomatoes harvested on August 31.

MATERIALS AND METHODS
Soil: Maddock sandy loam, Hecla sandy loam and Embden sandy loam; pH=6.8; 2.8% organic matter; soil-P was high; soil-K was very high; soil-S was very low.
Previous crops: 1997 - field corn; 1996 - pepper; 1995 - cabbage.
Seedbed preparation: Disked on 31 October 1997. Multiweeded (field cultivated) lightly on April 14. Disked on May 21. Multiweeded three times on May 26, once deep and twice shallow to incorporate herbicide treatments and smooth the seed bed.
Planting: Tuscany paste tomatoes were seeded in the greenhouse on April 13. Plants were hand transplanted to the field on May 26. Rows were spaced 8 feet apart. In-row spacing was 1.5 ft. As it was planted, each plant received one pint of fertilizer solution (1 gal 10-34-0 in 100 gal of water).
Plots: Plots were 17 ft long by 6 ft (one row) wide. Two-foot alley between plots.
Fertilizer: On April 13, broadcast 14 lbs N/acre and 70 lbs P2O5/acre as 10-50-0, 16 lbs N/acre and 19 lbs S/acre as 21-0-0-24, and 94 lbs K20/acre as 0-0-60. Side dressed 47 lbs of N/acre as urea on July 24.
Irrigation: Underground drip irrigation as needed.
Pest control: Weeds were controlled by the treatments listed in Table 62. We applied Dithane F-45 (1.6 qt/acre on July 7), Manzate (1.5 lbs/acre on July 14 and July 28) and Benlate (2 lbs/acre on July 23) for blight control. We applied Sevin (1 qt/acre on July 9 and July 23) and Asana (8 oz/acre on July 15) for insect control.
Harvest: Harvested on August 19 (tomatoes 40% red) and on September 1 (tomatoes 80% red). On each date we harvested every tomato in a 5-foot section of row.

RESULTS

Pyridate, the only herbicide to injure tomato, caused 20 to 30% crop injury as leaf burn and stunting. Tomato recovered from the leaf burn in two weeks, but remained stunted. (We used the wettable powder formulation of pyridate. The emulsifiable concentrate formulation may cause more crop injury). Pyridate controlled both hairy and eastern black nightshade when applied postemergence, but was weak on both species when applied late postemergence, possibly due to application on larger weeds. Rimsulfuron gave excellent control of hairy nightshade when applied postemergence but only fair control when applied preemergence. Rimsulfuron did not control eastern black nightshade. In fact, control of hairy nightshade by rimsulfuron allowed increased growth of eastern black nightshade. Tomato yields were highest where hairy nightshade was controlled. Eastern black nightshade, which emerged later and with lower plant density than hairy nightshade, had minimal effect on tomato yield but made harvesting very difficult. Pyridate delayed tomato maturity but did not reduce yield. Rimsulfuron controlled redroot pigweed and suppressed lambsquarters. Tillam improved control of both hairy and eastern black nightshade, but was not able to completely control them without other herbicides.

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Table 62. Treatments for the Oakes Irrigation Research Site 1998 tomato weed control study.
Treatment Number Herbicide(s) Rate Application timing
1 Treflan 1 pt PPI
2 Tillam 3 qts PPI
3 Tillam 6 qts PPI
4 Treflan + Lexone 1 pt + ½ lb PPI + PRE
5 Treflan + rimsulfuron 1 pt + oz PPI + PRE
6 Treflan + rimsulfuron 1 pt + ¾ oz PPI + PRE
7 Treflan + rimsulfuron 1 pt + oz PPI + POST1
8 Treflan + rimsulfuron 1 pt + ¾ oz PPI + POST1
9 Treflan + rimsulfuron + rimsulfuron 1 pt + oz + oz PPI + PRE + POST1
10 Treflan + Tillam + rimsulfuron 1 pt + 3 qts + oz PPI + POST1
11 Treflan + pyridate 1 pt + 0.9 lbs PPI + POST1
12 Tillam + pyridate 3 qts + 0.9 lbs PPI + POST1
13 Treflan + rimsulfuron + pyridate 1 pt + oz + 0.9 lbs PPI + PRE + POST2

PPI - May 26 (just before transplant); PRE - May 28 (right after transplant); POST1 - June 16 (weeds 0.5 to 1.5" tall); POST2 - June 30 (weeds 2 to 8" tall).

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Table 63. Nightshade control in the Oakes Irrigation Research Site 1998 tomato weed control study.
Treatment number Hairy nightshade Eastern black nightshade
June 10 June 23 July 9 July 30 June 23 July 9 July 30
---------------------------------------------- 0 to 10 ---------------------------------------------
1 4.0 2.8 1.8 0.8 8.8 8.8 9.8
2 8.8 7.5 7.0 5.0 8.3 6.8 6.8
3 8.8 8.0 8.0 5.3 9.0 7.3 6.8
4 6.3 4.8 3.0 1.3 9.3 8.8 9.0
5 7.3 6.5 5.3 3.5 8.5 7.8 6.8
6 7.5 7.3 7.0 5.3 8.3 7.3 6.8
7 4.3 8.8 9.6 9.4 8.5 7.0 5.8
8 4.0 8.8 10.0 9.9 8.0 7.3 6.3
9 7.5 9.3 10.0 9.9 7.5 5.8 5.0
10 8.3 10.0 10.0 10.0 9.3 8.5 7.0
11 4.0 9.8 9.6 9.3 10.0 10.0 9.9
12 7.5 10.0 10.0 9.8 10.0 9.4 9.8
13 6.0 5.0 7.0 4.8 8.8 9.3 9.3
LSD (0.05) 2.7 1.6 1.2 1.7 1.2 2.0 1.9
Probability§ *** *** *** *** ** ** ***

See Table 62 for treatment descriptions.

Ratings from 0 to 10 with 0 equal to no control and 10 equal to total control of weed.

§The probability that there is a difference between the values in the same column is significant at the 0.05, 0.01, or 0.001 level for *, **, or ***, respectively.

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Table 64. Redroot pigweed and lambsquarters control in the 1998 Oakes Irrigation Research Site tomato weed control study.
Treatment number Redroot pigweed rating Lambsquarters rating
June 23 July 9 July 30 June 23 July 9 July 30
------------------------------------------ 0 to 10 -----------------------------------------
1 9.5 9.0 8.9 9.5 9.3 8.5
2 9.8 8.1 8.3 9.3 7.8 6.5
3 9.3 7.5 7.5 9.3 8.3 6.8
4 10.0 9.8 10.0 9.8 10.0 9.4
5 9.8 9.9 9.9 9.5 8.9 8.8
6 10.0 10.0 10.0 9.0 8.9 8.0
7 10.0 10.0 10.0 10.0 9.5 9.1
8 10.0 10.0 9.8 9.5 8.8 8.5
9 10.0 10.0 10.0 9.8 9.1 9.4
10 10.0 10.0 9.8 10.0 9.9 9.8
11 10.0 9.6 8.5 10.0 10.0 9.5
12 10.0 9.1 7.8 10.0 9.6 9.5
13 10.0 10.0 10.0 9.8 9.5 8.5
LSD (0.05) -- 1.2 0.9 -- 1.1 1.1
Probability§ NS *** *** NS ** ***

See Table 62 for treatment descriptions.

Ratings from 0 to 10 with 0 equal to no control and 10 equal to total control of weed.

§The probability that there is a difference between the values in the same column is significant at the 0.05, 0.01, or 0.001 level for *, **, or ***, respectively.

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Table 65. Yields of tomatoes harvested August 19 in the 1998 Oakes Irrigation Research Site tomato weed control study.
Treatment number Yield Percent of total yield
red mature green total marketable total red yield mature yield
------------------------- tons/acre ------------------------- --------- % --------
1 4.5 2.8 7.2 7.9 60 95
2 7.5 10.0 17.4 18.0 45 98
3 7.8 8.0 15.8 18.0 44 87
4 4.2 3.6 7.8 8.2 53 98
5 9.8 10.4 20.2 20.6 50 99
6 8.8 13.8 22.5 24.4 40 93
7 10.8 13.9 24.7 26.6 41 94
8 7.4 13.1 20.5 21.1 36 98
9 7.6 16.3 23.9 24.8 31 96
10 10.6 22.6 33.2 33.6 33 100
11 3.2 19.5 22.7 27.0 12 84
12 3.8 24.2 28.0 31.2 13 89
13 11.3 8.3 19.5 19.6 57 100
LSD (0.05) 3.3 6.3 7.4 6.5 14 NS
Probability *** *** *** *** *** NS

See Table 62 for treatment descriptions.

The probability that there is a difference between the values in the same column is significant at the 0.05, 0.01, or 0.001 level for *, **, or ***, respectively.

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Table 66. Yields of tomatoes harvested August 31 in the 1998 Oakes Irrigation Research Site tomato weed control study.
Treatment number Yield Percent of total yield
red mature green total marketable total red yield mature yield
------------------------- tons/acre ------------------------- --------- % --------
1 5.7 0.0 e 6.2 h 6.9 93 99
2 17.5 2.5 de 20.0 d-g 22.1 88 98
3 14.3 2.7 de 17.0 fg 18.6 83 97
4 11.8 1.3 de 13.2 gh 14.0 87 98
5 13.8 1.2 de 15.0 gh 16.9 92 99
6 16.2 2.6 de 18.7 efg 21.0 87 99
7 21.7 4.9 cde 26.6 cde 28.1 84 100
8 30.2 6.5 cd 36.7 ab 39.5 82 98
9 22.1 6.3 cd 28.4 bcd 31.0 79 99
10 26.1 8.9 bc 35.1 abc 37.8 77 99
11 21.4 16.8 a 38.2 a 39.3 58 100
12 13.8 12.8 ab 26.5 cde 29.4 50 94
13 19.4 5.2 cde 24.7 def 26.9 81 97
LSD (0.05) 7.4 § § 9.8 14 NS
Probability *** *** *** *** *** NS

See Table 62 for treatment descriptions.

The probability that there is a difference between the values in the same column is significant at the 0.05, 0.01, or 0.001 level for *, **, or ***, respectively. NS means no significant differences.

§Values in each of these columns followed by the same letter are not significantly different (at the 0.05 level) from other values in the same column.

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