Early season weed control in corn

Plan now for successful 2020 weed control in corn.

Uncontrolled weeds in a corn field
Uncontrolled weeds in a corn field. Photo by Erin Burns, MSU.

Given the difficult 2019 season and resulting weed seed production, weed populations could potentially be higher in 2020 compared to previous years. When considering weed control programs, keep in mind both the short range goal of controlling weeds so they are not yield limiting, and also the long range goal of weed seedbank depletion. Good control following seasons in which weed escapes were high will both preserve short term yield and have long lasting effects by diminishing the weed seedbank.

If you are in the process of making vital herbicide decisions for your corn acres, check out the Economics of Commercial Weed Control Programs in Corn from Michigan State University. Each year, the MSU weed science team asks herbicide companies to submit up to four weed control programs for the study based on soil type and weed infestation history. In 2019, 24 herbicide programs were evaluated (Table 1). Use Table 2 to compare how your current corn herbicide program fits into the broad spectrum of commercial programs available. Results in Table 2 include corn injury, weed control, program costs, corn yield and economic returns of the 24 herbicide programs evaluated.

Overall, 23 of the 24 herbicide programs tested resulted in greater than 90% control of all weeds prior to harvest. Twenty-three of the 24 herbicide programs resulted in statistically similar yield. The maximum yield in this trial was 233 bushels per acre, and yield was 83 bushels per acre in the untreated (weedy control) treatment. Weed competition in this trial resulted in a yield loss of 150 bushels per acre (64%). Twenty out of the 24 herbicide programs resulted in statistically similar gross margins. The maximum gross margin in this trial was $838.25 per acre, and the gross margin in the untreated weedy treatment was $311.91 per acre. Weed competition in this trial resulted in an economic loss of $526.34 per acre (63%).

In addition to the 2019 economics of commercial weed control programs in corn, you can also find results for soybean (non-GMO, convention till and no-till) dating back to 2004 on the MSU Weed Science website.

Further considerations

When designing herbicide programs to delay the evolution of and battle herbicide resistant weeds, the first step is to make sure your program utilizes multiple effective sites of action. The herbicide site of action refers to the location or enzyme where the herbicide acts to disrupt plant growth. Herbicide sites of action are numbered and can be found on the herbicide label or in the 2020 MSU Weed Control Guide for Field Crops. I took the treatment list for all herbicide entries in the corn commercial comparison trials from 2006-2019 and tallied the frequency of sites of action used (Table 3).

Overall site of action group numbers 5 (e.g. atrazine), 15 (e.g. Dual, Outlook, Harness) and 9 (e.g. glyphosate) were used most frequently overtime. Further, I took the treatment trade names for all herbicide entries in the corn commercial comparisons trials from 2006-2019 and created a word cloud, which is a visual representation of the treatments and highlights the frequency of the treatments included in the study overtime. When interpreting a word cloud, the treatments that are larger and are the same color were included more frequently in the corn commercial comparisons studies from 2006-2019 than those that are smaller. Not surprisingly, glyphosate (e.g., roundup) was the most frequent treatment followed by atrazine (Figure 1).

Word cloud of treatment trade names
Figure 1. Word cloud of treatments (trade names) included in MSU Economics of Commercial Weed Control Programs in Corn from 2006-2019. When interpreting a word cloud, the treatments that are larger and are the same color were included more frequently in the corn commercial comparisons studies form 2006-2019 than those that are smaller.

 

Table 1. Commercial corn herbicide programs evaluated in 2019.

Conventional

Treatments (Rate/A)

Abbreviated Form

PRE

Corvus (3.3 oz) + Harness Xtra (1.8 qt)

Corvus + HarnXtra

Acuron (3 qt)

Acuron

Roundup Ready

EPOS

Armezon PRO (16 oz) + Roundup PowerMax (16 oz) + Atrazine (1.1 lb) + NIS (0.25%) + AMS (8.5 lb)

Armezon PRO + RupPM + Atra

Degree Xtra (2 qt) + Laudis (3 oz) + Roundup PowerMax (32 oz) + AMS (8.5 lb)

DegXtra + Laud + RupPM

Capreno (3 oz) + Roundup PowerMax (22 oz) + Atrazine (1.1 lb) + AMS (8.5 lb)

Capreno + RupPM + Atra

Anthem MAXX (4 oz) + Balance Flexx (3 oz) + Atrazine (2.2 lb) + Roundup PowerMax (22 oz) + AMS (8.5 lb)

AnthM + Bal Flexx + Atra + RupPM

Warrant (3 pt) + Atrazine (0.55 lb) + Roundup PowerMax (22 oz) + AMS (8.5 lb)

Warrant + Atra + RupPM

Harness Max (64 oz) + Atrazine (1.1 lb) + Roundup PowerMax (22 oz) + AMS (8.5 lb)

HarnMax + Atra + RupPM

Halex GT (4 pt) + Atrazine (0.55 lb) + NIS (0.25%) + AMS (8.5 lb)

HalGT + Atra

PRE/POST

 

Zidua SC (3.2 oz) + Sharpen (2 oz) + Atrazine (1.1 lb) fb. Roundup PowerMax (32 oz) + AMS (8.5 lb)

Zidua SC + Sharp + Atra fb. RupPM

Zidua SC (3.2 oz) + Atrazine (1.1 lb) fb. Roundup PowerMax (32 oz) + AMS (8.5 lb)

Zidua SC + Atra fb. RupPM

Verdict (12 oz) + Atrazine (1.1 lb) fb. Roundup PowerMax (32 oz) + AMS (8.5 lb)

Verdict + Atra fb. RupPM

Balance Flexx (4 oz) fb. DiFlexx Duo (24 oz) + Roundup PowerMax (22 oz) + AMS (8.5 lb)

Bal Flexx fb. DiFlexx Duo + RupPM

SureStart II (3 pt) + Atrazine (1.65 lb) fb. Durango DMA (32 oz) + AMS (8.5 lb)

SureStart + Atra fb. Durango

Resicore (1.25 qt) + Atrazine (1.1 lb) fb. Resicore (1.25 qt) + Durango DMA (32 oz) + AMS (8.5 lb)

Resi + Atra fb. Resi + Durango

Resicore (2.5 qt) + Atrazine (1.1 lb) fb. Durango DMA (32 oz) + AMS (8.5 lb)

Resi + Atra fb. Durango

Cinch ATZ (2.1 qt) fb. Realm Q (4 oz) + Atrazine (0.55 lb) + Durango DMA (32 oz) + AMS (8.5 lb)

Cinch fb. Realm Q + Durango

Anthem MAXX (4 oz) + Balance Flexx (3 oz) + Atrazine (1.65 lb) fb. Status (4 oz) + Roundup PowerMax (22 oz) + AMS (8.5 lb)

AnthM + Bal Flexx + Atra fb. Stat + RupPM

Degree Xtra (2 qt) fb. DiFlexx (8 oz) + Roundup PowerMax (22 oz) + AMS (8.5 lb)

DegXtra fb. DiFlexx + RupPM

TripleFLEX II (1 qt) + Degree Xtra (1.5 qt) fb. Roundup PowerMax (22 oz) + AMS (8.5 lb)

TripleFLEX II + DegXtra fb. RupPM

Acuron (1.5 qt) fb. Halex GT (3.6 pt) + Atrazine (0.55 lb) + NIS (0.25%) + AMS (8.5 lb)

Acuron fb. Halex GT + Atra

Armezon PRO (16 oz) + Callisto (3 oz) + Atrazine (1.1 lb) fb. Roundup PowerMax (32 oz) + AMS (8.5 lb)

Armezon + Call + Atra fb. RupPM

Bicep II Magnum (1.3 qt) fb. Halex GT (3.6 pt) + Atrazine (0.55 lb) + NIS (0.25%) + AMS (8.5 lb)

Bicep fb. Halex GT + Atra

 

Table 2. Corn injury, weed control, program costs, corn yield, and economic returns of 24 herbicide programs in 2019.

Programs

Herbicide Treatments5

Injury 10 DAP

ANGR

CHEAL

AMAPO

AMBEL

ABUTH

All Weeds

Cost1

Yield

Economic

Return2

Prior to harvest (46 d after POST)

Conventional

 

(%)

% Control

(≥ 90%)

($/A)

(bu/A)

($/A)

PRE

 

Corvus + HarnXtra

0

95.8

100

100

99.5

100

YES

54.89

222.8*3

780.52**4

Acuron

0

100

100

100

100

100

YES

61.25

210.5*

727.94

Roundup Ready

EPOS

Armezon PRO + RupPM + Atra

0

95.3

99.5

100

100

99.5

YES

35.88

233.1*

838.25**

DegXtra + Laud + RupPM

0

99

100

100

100

100

YES

48.19

228.4*

808.31**

Capreno + RupPM + Atra

0

95.3

100

100

99.5

100

YES

35.77

217.3*

779.2**

AnthM + Bal Flexx + Atra + RupPM

0

100

100

100

100

100

YES

56.30

223.4*

781.45**

Warrant + Atra + RupPM

0

90

100

100

92.5

97.5

YES

27.77

219.3*

794.51**

HarnMax + Atra + RupPM

0

90.8

98.8

92.5

98.8

98.8

YES

50.70

221.8*

780.86**

HalGT + Atra

 

92

100

100

99.5

100

YES

40.06

226.7*

810.16**

PRE/POST

 

 

Zidua SC + Sharp + Atra fb. RupPM

0

99

99.5

100

100

100

YES

56.10

217.3*

758.68**

Zidua SC + Atra fb. RupPM

0

99

98.8

100

99

99.5

YES

43.47

210.9*

747.04

Verdict + Atra fb. RupPM

0

96

99

97

99.5

99.5

YES

47.81

222.5*

786.47**

Bal Flexx fb. DiFlexx Duo + RupPM

0

95.8

100

100

100

100

YES

55.54

224.6*

786.52**

SureStart + Atra fb. Durango

0

90

100

100

99

100

YES

60.35

218.9*

760.53**

Resi + Atra fb. Resi + Durango

0

100

100

100

100

100

YES

75.78

224.1*

770.94**

Resi + Atra fb. Durango

0

97.3

100

100

100

100

YES

69.44

221.6*

761.75**

Cinch fb. Realm Q + Durango

0

100

100

100

100

100

YES

64.66

223.6*

774.03**

AnthM + Bal Flexx + Atra fb. Stat + RupPM

0

100

100

100

100

100

YES

63.95

228*

790.96**

DegXtra fb. DiFlexx + RupPM

0

99.5

100

100

100

100

YES

54.30

218.3*

764.14**

TripleFLEX II + DegXtra fb. RupPM

0

99.5

100

100

99.5

100

YES

56.76

219.7*

767.12**

Acuron fb. Halex GT + Atra

0

100

100

100

100

100

YES

71.83

227.3*

780.55**

Armezon + Call + Atra fb. RupPM

0

93.3

100

98.8

98.3

98.8

YES

55.84

210.4*

733.07

Bicep fb. Halex GT + Atra

0

100

100

100

99.5

99.5

YES

58.36

230.5*

806.2**

Untreated

0

0

0

0

0

0

NO

0

83.2

311.91

Abbreviations: ANGR = annual grasses, mainly foxtail species, CHEAL = common lambsquarters, AMAPO = Powell amaranth, AMBEL = common ragweed, ABUTH = velvetleaf, fb. = followed by

1Herbicide costs = avg. of price lists; App. cost = $7.50/A; seeding rate = 34,600 seeds/A. Weed control costs = Herbicide $ + Additive $ + Application $

2Crop selling price = $3.75/bu (December 2019). Economic return = (Yield x Price) – Weed Control Costs

3*Not statistically different from the highest yielding 4**Not statistically different from the highest gross margins 5Many herbicide programs have long rotation restrictions to more sensitive crops, i.e., sugar beet, alfalfa, potatoes, etc. Consult Table 12 in the MSU Weed Control Guide for Field Crops (E-434) or the herbicide label for crop rotation restrictions.

Table 3. Frequency of herbicide sites of action (SOA) used in corn commercial comparisons studies from 2006-2019. Example herbicides for each site of action: 5 = atrazine, 15 = Dual, Outlook, Harness; 9 = glyphosate; 27 = Callisto, Balance Flexx, Armezon/Impact, Acuron, Laudis; 2 = Resolve, Accent Q; 4 = dicamba; 14 = Sharpen, Cadet; 10 = Liberty; 3 = Prowl H2O; 19 = Status

SOA

Frequency

5

272

15

251

9

224

27

149

2

130

4

53

14

29

10

17

3

5

19

4

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