Predicting Corn Herbicide Application "Windows"

June 4, 1997 4(11):74-75

Joe Lauer and Chris Boerboom
Corn Agronomist and Weed Scientist

The cool growing season we have had so far during 1997 has slowed corn emergence and consequently changed the normal timing for some our management decisions. The decisions most influenced by the cool growing year are postemergence application of herbicides. Table 1 describes the projected last dates for application of herbicides based on the growth and development model published in the Wisconsin Crop Manager on May 22, 1997 (4(9): 58-59), the Growing Degree Units accumulated thus far, and the 30-year average for temperature at Madison, WI. In this table, postemergence herbicides have been grouped to approximate the corn growth stage. The maximum labeled growth stage for these herbicides may not exactly coincide with these corn V-stages but should be close. Keep in mind that these are only projected windows for herbicide application. These projections are subject to weather fluctuations. Also, keep in mind that there are numerous other factors that go into a herbicide application decision such as weed size at the time of application. Because of the cool temperatures this year, weed size and development may be greater than normal compared to corn. Always follow directions on the label.

Table 1. Predicted application "windows" for broadcast herbicide treatments for various 1997 corn planting dates at Arlington, WI. Predictions are based on GDU accumulation through June 3, 1997.
Corn Herbicide Planting date
growth stage (labeled max. growth stage) April 18 April 25 May 5 May 13 May 20
    Projected last date of application
~V2 Basis (V2)
Bicep Lite II (5")
Bladex 90 DF (4 leaf)
Dual II (5")
Lasso (5")
Corn stage in field is V3
Corn stage in field is V2-V3
June 7 June 10 June 12
~V3 Banvel (8" or 5 leaf)
Clarity (8")
Frontier (8")
Guardsman (8")
Marksman (8" or 5 leaf)
Scorpion (8")
Shotgun (8")
2,4-D (8")
June 5 June 7 June 11 June 14 June16
~V4 Atrazine (12")
Basis Gold (12")
Harness/Surpass (11")
Laddok (12")
Lightening (12")
Resolve (12")
June 9 June 10 June 14 June 17 June 19
~V6 Accent (20" or V6)
Beacon (20")
Exceed (20")
June 16 June 17 June 21 June 24 June 26
~V7 Hornet (24")
Liberty (24" or V7)
Stinger (24")
June 19 June 21 June 24 June 27 June 29
~V10 Resource (V10) June 29 June 30 July 3 July 6 July 7
~V12 Permit (36") July 5 July 6 July 9 July 12 July 13
Before VT Buctril
Poast Plus
July 19 July 20 July 23 July 26 July 27

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