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, E-mail: Leonard.Besemann@ndsu.edu

New herbicides have promise for weed control in sweetcorn. There is some concern that some sweetcorn hybrids may be injured by these new herbicides. We tested the sweetcorn hybrids received for the sweetcorn performance trials for their tolerance to Aim, Callisto and Option.

The main plot was 17 ft long by 12 rows (30 ft) wide. The herbicide treatment was applied to a single row in each main plot. There was also a check row in each main plot. There were sufficient rows in each main plot so that each treated row and the check row had an untreated border row on each side. Each study had four replications.

For more details see materials and methods section in the “Sugar Enhanced” and the “Super Sweet” sweetcorn hybrid performance trials.

sh₂ sweetcorn: Aim injured sh₂ sweetcorn much more than the other treatments (Table 66). Injury by Aim was leaf necrosis or burning along with some buggy whipping of the leaves making it difficult for the new leaves to emerge. Option injury was small, light-yellow patches in the leaves. These patches were not readily visible and at about 10 feet distance could not be distinguished from the regular leaf. Callisto injury was a slight yellowing of the leaves. Injury decreased with time. At 14 DAT no injury was visible for the Option or Callisto treatments. At 30 DAT there was no visible injury to any of the sweetcorn plants from any of the herbicide treatments. Aim delayed maturity an average of about 1.5 days. Both Aim and Option lowered ear height about 1 to 2 inches. For some hybrids, such as Exotic 65 (se variety), that have low ears, this may make it harder to harvest. It should not cause harvest problems for most hybrids. None of the treatments affected the ease of ear removal from the stock, the amount of lodging, or the number of marketable ears. Option reduced sweetcorn yield, but Callisto and Aim did not. The reduction in yield with Option, even though there was no reduction in number of ears, indicates that Option must have reduced the size of the ears. This is verified in the ear measurements (Table 67) where it is seen that Option reduced the ear length. No other husk or ear traits were affected by any of the herbicides.

Table 66. Effect of Aim, Callisto, and Option on sh sweetcorn injury, maturity, number of ears and yield.

Treatment	Crop injury		Days to half-silk	Days to harvest	Ear height²	Ease of ear removal³	lodging	Marketable ears		Marketable yield
Treatment	6 DAT¹	14 DAT	Days to half-silk	Days to harvest	Ear height²	Ease of ear removal³	lodging	unhusked	husked	unhusked	husked
	----0 to 100 %---				inches	1 to 10	%	---1000s/acre---		---tons/acre---

Check	0	0	63.2 a	84.2 a	26.3 a	6.2	14.2	28.3	25.9	10.3 a	6.6 a
Aim	36 d	18 b	64.6 b	85.8 b	25.2 b	6.0	7.5	28.0	25.6	10.4 a	6.4 a
Callisto	5 b	0	63.3 a	84.3 a	25.3 ab	6.0	8.8	27.0	25.5	9.9 ab	6.4 a
Option	8 c	0	63.6 a	85.0 ab	24.4 b	5.9	10.8	26.3	23.8	9.4 b	5.8 b

Probability	<.0001	<.0001	0.009	0.03	0.015	0.4	0.47	0.15	0.17	0.02	0.03

³Indicates ease of ear removal. The higher the score, the easier it was to remove the ear.

⁴Values in the same column followed by the same letter are not significantly different at the 0.05 level. No letters = no differences

Table 67. Effect of Aim, Callisto, and Option on sh sweetcorn characteristics, maturity, number of ears and yield.

Treatment	short shank¹	Husk				Ear				Yellow intensity
Treatment	short shank¹	color²	cover³	tightness⁴	overall	length	diameter	# of rows	overall	Yellow intensity
	%	1 to 3	inches	1 to 3	1 to 10	-------inches-------			1 to 10	1 to 5

Check	92	2.0	1.3	2.0	7.1	8.1 a	1.8	16.0	8.4	2.5
Aim	88	2.0	1.9	2.0	7.3	8.2 a	1.8	15.8	8.3	2.5
Callisto	93	2.0	1.5	1.9	7.4	8.2 a	1.8	16.2	8.6	2.5
Option	89	2.0	1.6	1.9	7.3	7.9 b	1.8	15.3	8.1	2.5

Probability	0.23	0.82	0.06	0.53	0.14	0.05	0.75	0.68	0.24

⁵Values in the same column followed by the same letter are not significantly different at the 0.05 level. No letters = no differences

se sweetcorn: Aim injured se sweetcorn much more than the other treatments (Table 68). Injury by Aim was leaf necrosis or burning along with some buggy whipping of the leaves making it difficult for the new leaves to emerge. Option injury was small, light-yellow patches in the leaves. These patches were not readily visible and at about 10 feet distance could not be distinguished from the regular leaf. Callisto injury was a slight yellowing of the leaves. Injury decreased with time. At 14 DAT no injury was visible for the Callisto treatments and very little injury was visible for the Option treatments. At 30 DAT there was no visible injury to any of the sweetcorn plants from any of the herbicide treatments. Aim delayed maturity an average of about one day, but some hybrids responded differently (see Table 70). Both Aim and Option lowered ear height about 1.5 inches. For some hybrids, such as Exotic 65, that have low ears, this may make it harder to harvest. It should not cause harvest problems for most hybrids. None of the treatments affected the ease of ear removal from the stock or the amount of lodging. Aim was the only treatment to reduce the number of marketable ears. Aim and Option both reduced sweetcorn yield, but Callisto did not. The reduction in yield with Option, even though there was no reduction in number of ears, indicates that Option must have reduced the size of the ears. This is verified in the ear measurements (Table 69).

Table 68. Effect of Aim, Callisto, and Option on se sweetcorn injury, maturity, number of ears and yield.

Treatment	Crop injury		Days to half-silk	Days to harvest	Ear height²	Ease of ear removal³	lodging	Marketable ears		Marketable yield
Treatment	6 DAT¹	14 DAT	Days to half-silk	Days to harvest	Ear height²	Ease of ear removal³	lodging	unhusked	husked	unhusked	husked
	--0 to 100 %---				inches	1 to 10	%	------1000s/acre------		-----tons/acre-----

Check	0 a⁴	0	70 a	91.2 a	20.7 a	6.0	14	20.6 a	19.2 a	7.9 a	4.9 a
Aim	43 d	25 c	71 b	92.1 c	19.0 b	6.0	12	19.4 b	17.6 b	7.2 b	4.3 c
Callisto	4 b	0	70 a	91.2 a	20.3 a	6.1	13	20.9 a	19.5 a	8.1 a	5.0 a
Option	10 c	2 b	70 a	91.4 b	19.1 b	6.1	13	20.7 a	19.4 a	7.4 b	4.7 b

Probability	<.0001	<.0001	<.0001	<.0001	<.0001	0.09	0.37	0.006	<.0001	<.0001	<.0001
Interaction⁵	<.0001	<.0001	0.005	0.92	0.19	0.48	0.99	0.013	0.32	0.04	0.28

³Indicates ease of ear removal. The higher the score, the easier it was to remove the ear.

⁴Values in the same column followed by the same letter are not significantly different at the 0.05 level.

⁵When interaction between hybrid and herbicide treatment is significant, see Table 70, Table 71, Table 72 and Table 73 for hybrids

Table 69. Effect of Aim, Callisto, and Option on se sweetcorn characteristics, maturity, number of ears and yield.

Treatment	short shank¹	Husk				Ear				Yellow intensity
Treatment	short shank¹	color²	cover³	tightness⁴	overall	length	diameter	# of rows	overall	Yellow intensity
	%	1 to 3	inches	1 to 3	1 to 10	--------inches----------			1 to 10	1 to 5

Check	90 a	2.0 a	1.7	2.3	7.5	8.0 a	1.83 a	16.1 a	7.7	1.5
Aim	85 b	1.9 ab	1.8	2.3	7.4	8.0 ab	1.81 b	15.8 a	7.5	1.5
Callisto	86 b	1.9 b	1.6	2.2	7.5	8.1 a	1.84 a	16.3 a	7.6	1.5
Option	86 b	2.0 a	1.6	2.3	7.4	7.9 b	1.78 c	14.8 b	7.6	1.5

Probability	0.002	0.03	0.12	0.49	0.62	0.013	<.0001	<.0001	0.11	0.91
Interaction⁶	0	0.16	0.91	0.64	0.14	0.99	0.14	0.2	0.17	0.47

⁵Values in the same column followed by the same letter are not significantly different at the 0.05 level. Husk color did not differ

⁶Because the interaction between hybrid and herbicide treatment is significant for % short shank, see Table 72 for herbicide effects

When an ear is removed it can break off the stock just below the ear (short shank) or further down the stock leaving the ear with a long shank. All of the treatments caused a decrease in the percentage of ears that came off the stock with a short shank. Plants receiving Callisto had slightly lighter green-colored husks. None of the herbicides affected the length the husk extended beyond the end of the ear (husk cover), the tightness of the husk around the ear, or the overall appearance of the unhusked ear. Option slightly reduced the length of the ear and the number of rows of kernels. Both Option and Aim reduced the ear diameter. The color intensity of the yellow kernels of the ear was not affected by any of the treatments.

Table 70. Aim, Callisto, and Option injury to se sweetcorn and their effect on days to half-silk.

Hybrid	Seed source	Sweetcorn injury 6 DAT¹			Sweetcorn injury 14 DAT¹
Hybrid	Seed source	Aim	Callisto	Option	Aim	Callisto	Option
		----------------------------------------------- % injury -----------------------------------------------

Accord	MM	48	10	13	25	0	0
Avalon	RG	38	3	10	23	0	0
BC 0805 VP	RG	48	3	10	28	0	3
BC 1136	RG	60	5	10	43	0	3
Bon Jour	MM	35	5	10	13	0	0
Brocade	MM	48	10	10	28	0	0
Buccaneer	MM	33	3	10	18	0	3
Charisma	SW	65	8	8	45	0	3
Colonial	RG	53	5	8	30	0	3
Exotic 65	MA	38	0	10	23	0	3
Harris 1001	HR	33	5	10	15	0	0
Honey Treat	RG	33	3	10	20	0	3
Honey Select	SW	38	8	10	20	0	3
Infinite Delight II	MA	35	0	8	20	0	5
Luscious	MM	40	5	10	23	0	0
Precious Gem	MM	48	10	10	33	0	3
Providence	RG	45	0	10	20	0	3
Renaissance	HR	45	5	10	23	0	3
WH 0807	RG	30	0	10	25	0	3

Average		43	5	10	25	0	2
Probability		<.0001	NS	NS	<.0001	NS	NS
LSD (0.05)		13			7

Aim injury to sweetcorn varied with hybrid and was very severe in some cases. BC1136 and Charisma were injured most by Aim. Callisto and Option injury to sweetcorn was low and similar for all hybrids. The crop injury by Option and Callisto did not vary significantly between hybrids.

Table 71. Aim, Callisto, and Option effect on days to half-silk and percent short shank of se sweetcorn hybrids.

Hybrid	Seed source	Days to half-silk				Percent short shank
Hybrid	Seed source	Aim	Callisto	Option	Check	Aim	Callisto	Option	Check

Accord	MM	76	75	74	74	84	67	88	74
Avalon	RG	74	73	73	73	90	91	87	91
BC 0805 VP	RG	73	73	72	73	78	87	82	90
BC 1136	RG	76	73	74	73	92	93	91	94
Bon Jour	MM	68	67	67	67	99	100	98	96
Brocade	MM	73	71	70	71	65	64	53	68
Buccaneer	MM	73	72	72	72	62	49	82	86
Charisma	SW	72	70	71	70	77	92	92	90
Colonial	RG	71	69	70	70	91	91	96	99
Exotic 65	MA	65	64	65	64	96	93	80	97
Harris 1001	HR	70	69	69	70	65	78	82	92
Honey Treat	RG	68	68	68	68	91	95	83	92
Honey Select	SW	73	73	73	72	87	84	91	89
Infinite Delight II	MA	66	66	66	66	99	94	83	100
Luscious	MM	70	69	68	69	96	95	100	93
Precious Gem	MM	74	72	72	72	95	99	98	99
Providence	RG	76	74	74	75	88	91	94	88
Renaissance	HR	68	66	66	66	60	70	60	78
WH 0807	RG	70	69	70	69	95	92	89	94

Average		71	70	70	70	85	86	86	90
Probability		<.0001	<.0001	<.0001	<.0001	<.0001	<.0001	<.0001	<.0001
LSD (0.05)		2	2	1	1

Generally, those hybrids that were injured most by Aim also had the half-silk date delayed the most. Callisto and Option did not delay sweetcorn maturity. On average, the percentage of ears with short shanks was reduced by all three herbicides, but some hybrids responded differently, such as Accord where Aim and Option increased the percentage of ears with short shanks while Callisto reduced the percentage of ears with short shanks.

Hybrid	Seed source	Marketable unhusked ears				Marketable husked ears
Hybrid	Seed source	Aim	Callisto	Option	Check	Aim	Callisto	Option	Check
		----------------------------------------------- 1000's of ears per acre ---------------------------------------------

Accord	MM	16.4	16.7	18.4	17.7	13.8	17.4	14.3	16.9
Avalon	RG	20.8	18.2	23.6	20.8	19.5	19.2	18.2	19.7
BC 0805 VP	RG	19.5	21.3	18.4	19.7	20.0	18.4	21.5	18.4
BC 1136	RG	17.4	17.9	15.1	18.4	14.6	15.4	15.6	17.2
Bon Jour	MM	17.7	18.4	23.3	19.2	16.9	18.7	17.7	19.0
Brocade	MM	20.8	20.8	22.5	23.3	19.2	19.0	20.0	22.0
Buccaneer	MM	16.7	18.7	19.2	17.9	14.6	19.0	18.4	16.4
Charisma	SW	18.8	24.3	18.4	21.2	16.7	19.7	23.5	20.1
Colonial	RG	16.7	21.3	17.9	20.0	15.4	16.7	21.0	19.5
Exotic 65	MA	17.4	18.4	20.5	20.2	15.9	16.1	14.1	15.9
Harris 1001	HR	16.1	22.5	17.7	19.7	14.3	13.3	20.0	16.9
Honey Treat	RG	20.8	21.0	22.3	20.8	19.5	20.2	20.5	20.8
Honey Select	SW	25.9	22.8	21.8	20.8	18.4	17.8	18.4	17.4
Infinite Delight II	MA	22.2	23.9	20.5	25.3	18.9	20.9	22.3	23.3
Luscious	MM	19.5	20.2	21.0	19.5	19.2	19.0	19.2	18.4
Precious Gem	MM	20.0	22.3	23.8	21.0	18.7	20.5	20.8	20.2
Providence	RG	19.7	21.3	22.8	18.7	16.4	15.9	18.7	16.9
Renaissance	HR	22.3	23.3	21.5	26.1	21.5	16.9	22.5	24.9
WH 0807	RG	21.0	24.3	23.6	20.5	20.5	18.7	23.8	20.5

Average		19.4	20.9	20.7	20.6	17.6	19.5	19.4	19.2
Probability		0.0011	0.002	0.001	0.014	0.004	0	0.002	0.01

There was interaction between herbicide and hybrid treatments for the number of unhusked ears per acre but not husked ears per
acre. Note that for Honey Select, Aim increased the number of ears, but for several others, including Brocade, Charisma, Colonial,
Harris 1001, and Renaissance, Aim reduced the number of ears. Hybrids also varied in their response to Callisto and Option.
The largest percent reduction (increase) in unhusked ears for Aim, Callisto, and Option were 18 (25), 12 (19), and 19 (22), respectively.

Hybrid	Seed source	Marketable unhusked yield				Marketable husked yield
Hybrid	Seed source	Aim	Callisto	Option	Main	Aim	Callisto	Option	Main
		---------------------------------------------- tons per acre -----------------------------------------------

Accord	MM	6.5	7.3	7.5	7.6	3.5	4.1	4.6	4.7
Avalon	RG	8.2	7.7	9.1	8.6	5.1	5.2	5.7	5.5
BC 0805 VP	RG	7.9	8.7	7.1	8.0	5.1	5.7	4.8	5.0
BC 1136	RG	6.7	7.4	5.7	7.1	3.5	4.2	3.6	4.3
Bon Jour	MM	6.1	6.9	7.6	6.9	3.9	4.3	4.8	4.5
Brocade	MM	8.3	9.0	9.1	9.6	4.6	5.5	5.4	5.8
Buccaneer	MM	6.4	7.3	6.9	7.0	3.5	4.5	4.2	4.1
Charisma	SW	6.5	8.8	6.3	7.4	4.1	6.1	4.6	5.1
Colonial	RG	6.1	8.2	6.2	7.5	3.6	5.3	3.9	4.8
Exotic 65	MA	5.7	5.8	6.1	6.1	3.6	3.0	3.1	3.3
Harris 1001	HR	6.0	8.6	6.3	7.5	3.5	5.0	4.0	4.5
Honey Treat	RG	7.5	7.9	8.0	7.5	5.0	5.3	5.5	5.3
Honey Select	SW	9.1	9.1	7.9	8.2	4.3	5.0	4.2	4.5
Infinite Delight II	MA	6.9	8.1	6.3	8.3	4.4	5.4	4.1	5.6
Luscious	MM	8.0	8.3	8.3	8.0	5.4	5.6	5.5	5.2
Precious Gem	MM	7.0	8.1	8.1	7.6	4.8	5.5	5.4	5.3
Providence	RG	8.1	8.8	9.0	8.6	4.2	4.8	4.6	4.9
Renaissance	HR	7.9	8.7	7.7	9.6	4.6	4.9	4.6	5.4
WH 0807	RG	7.9	8.7	8.3	8.3	5.2	5.9	5.8	5.5

Average		7.2	8.1	7.4	7.9	4.3	5	4.7	4.9
Probability		0.0002	0.0005	<.0001	0.003	0.0002	<.0001	<.0001	0.014

There was interaction between herbicide and hybrid treatments for the unhusked yield but not husked yield. The hybrids that had yield
reductions were usually the same ones that had a reduction in number of ears.