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Weed Management In Seed Corn Production

Posted 1/20/2016
Weed management in seed corn production fields is challenging because inbred corn lines can be sensitive to various herbicides, which reduces the potential herbicide options for managing weeds.

Limited Herbicide Options for Weed Management

Weed management in seed corn production fields is challenging because inbred corn lines can be sensitive to various herbicides, which reduces the potential herbicide options for managing weeds. Additionally, seed corn does not produce a tight canopy, particularly after detasseling, allowing light to penetrate to the soil resulting in the potential for further weed flushes later in the season. Therefore, a successful weed management program includes herbicides with good soil residual characteristics. The current herbicide recommendation for seed corn producers is to use Degree Xtra® preemergence (A) followed by (fb) a postemergence (B) tankmix application of IMPACT® and Warrant® Herbicide along with ammonium sulfate (AMS) and menthylated seed oil (MSO) (Figure 1).

Additional crop-safe herbicide options in combination with Degree Xtra would be beneficial to help manage difficult weeds with different modes of action (MOA). To help determine other options, a randomized complete block trial with 3 replications of 10 different herbicide treatments, including competitive combinations, was conducted in 2015 at locations in Indiana, Iowa, and Nebraska.

Herbicide Treatments in Trial

  1. Degree Xtra fb IMPACT + Warrant Herbicide + AMS + MSO
  2. Balance® Flexx + Degree Xtra fb IMPACT + Warrant Herbicide + AMS + MSO
  3. DegreeXtrafbIMPACT+Atrazine+AMS+MSO
  4. DegreeXtrafbIMPACT+StatusHerbicide+Warrant Herbicide + Atrazine + AMS + MSO
  5. DegreeXtrafbStatusHerbicide+WarrantHerbicide+AMS + MSO
  6. TripleFLEX® II Herbicide fb IMPACT + Warrant Herbicide + AMS + MSO
  7. Lexar® EZ fb Callisto® + Atrazine + AMS + COC
  8. Corvus® + Atrazine fb Laudis® + Atrazine + AMS + MSO
  9. Corvus + Atrazine fb Capreno® + Atrazine + AMS + MSO
  10. Verdict® fb IMPACT + Atrazine + AMS + MSO

Additional Trial Guidelines

The same Monsanto seed corn inbred line was planted at each location with planting dates of May 7 (IN), May 20 (NE), and May 25 (IA). The PRE (A) applications were applied at planting and the POST (B) applications were applied at V5 corn growth stage. Crop injury evaluations were taken 2 weeks after treatment (WAT) and weed control evaluations were conducted 3 WAT (A), 3 WAT (B), and 6 WAT (B) or brown silk stage. The predominate weed species present at the locations included: common waterhemp (AMATA), velvetleaf (ABUTH), common lambsquarters (CHEAL), ivyleaf morningglory (IPOHE), green foxtail (SETVI), giant foxtail (SETFA), and yellow foxtail (SETLU).

Trial Results (Table 1)

All treatments caused some initial plant injury; however, there was no statistical difference between treatments. Plants recovered from the injuries by 6 WAT.

All treatments provided excellent broadleaf and grass control at 3 WAT (A). There were some differences in waterhemp and velvetleaf control in treatments involving Degree Xtra fb Warrant Herbicide + Status Herbicide, and TripleFLEX II Herbicide fb Warrant Herbicide and IMPACT by 3 WAT (B). Degree Xtra alone and tank mixed with Balance Flexx fb Warrant Herbicide and IMPACT provided excellent weed control compared to Corvus, Lexar EZ, and Verdict-based programs by 6 WAT (POST).

Plans are to continue this trial in 2016 to help determine additional herbicide combinations for use in seed corn production.

Table 1. Percent Crop Injury and % Weed Control

Injury (2 WAT) % Weed Control 3 WAT (A) % Weed Control 3 WAT (B) % Weed Control 6 WAT (B) (Brown Silk)
Treatment % ABUTH AMATA SETFA SETVI ABUTH AMATA CHEAL SETVI ABUTH AMATA CHEAL IPOHE
Degree Xtra® fb IMPACT®
+ Warrant® Herbicide
+ AMS
+ MSO
4.3 96.7 99.2 91 100 94.5 97.8 98.7 98.3 85* 96.7 96.7 96.3
Balance® Flexx
+ Degree Xtra fb IMPACT
+ Warrant Herbicide
+ AMS + MSO
8.7 98.3 99.2 99 100 99.5 99.5 99.5 100 96.7 98.3 98.3 96.3
Degree Xtra fb IMPACT
+ Atrazine + AMS + MSO
8.7 85* 97.5 96 100 97 98.6 97.8 98.3 98.3 98.3 98.3 94*
Degree Xtra fb IMPACT + Status® Herbicide
+ Warrant Herbicide
+ Atrazine + AMS + MSO
5.7 95 95.8 97.7 93.3 99.5 99.5 99.5 100 91.7 96.7 96.7 96.3
Degree Xtra fb Status
Herbicide + Warrant
Herbicide + AMS + MSO
9.7 93.3 95* 91 92 92* 95.3* 97 95 75* 93.3* 95* 98.7
TripleFLEX® II Herbicide
fb IMPACT + Warrant
Herbicide + AMS + MSO
7.7 100 99.2 94.5 98.3 95.3 97 95.3* 92* 90 96.7 96.7 94
Lexar® EZ fb Callisto®
+ Atrazine + AMS + COC
10.7 98.3 98.3 99 98.3 99.5 99.5 99.5 100 100 100 100 97.7
Corvus® + Atrazine
fb Laudis® + Atrazine
+ AMS + MSO
6.7 100 100 99 100 99.5 99.5 99.5 100 98.3 98.3 98.3 94.7
Corvus + Atrazine
fb Capreno® + Atrazine
9.7 100 100 99 100 99.5 99.5 99.5 100 100 100 100 98.6
Verdict® fb IMPACT
+ Atrazine + AMS + MSO
11.75 98.3 98.3 80* 98.3 98.7 97.8 98.7 98.3 98.3 98.3 98.3 97

*Statistically different (lower) at the 0.05 level of Least Significant Difference (LSD); WAT = Weeks after treatment; (A) = preemergence, (B) = postemergence; ABUTH = Velvetleaf, AMATA = Common Waterhemp, SETFA = Giant Foxtail, SETVI = Green Foxtail, CHEAL = Common Lambsquarters, IPOHE = Ivyleaf Morningglory

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