As of June 20th, 2018, we were at 961 Growing Degree Days for Darlington.

Below are the results for Dubuque and Madison, comparing last year for the same time period, and the norm based on the 30 year average.

GDU (Growing Degree Units)

Location Date 2018 2017 Norm
Dubuque Jan 1– June 20 1130 1093 934
Madison Jan 1– June 20 947 949 897


Instead of the old saying “Knee high by the 4th of July”, this year, we’ll be seeing tassels by the 4th of July!! Earlier planting in 2018 contributed more to this, than Growing Degree Days did.

With the corn crop being further ahead this year, be on the lookout for diseases forming in corn. A foliar application of fungicide at tassel may be justified. A fungicide application made between VT and R1 have shown on average 11-14 bu. increase per acre.

When enquiring whether a fungicide application is necessary, consider the following criteria:

  1. Disease history: Low-lying fields or fields with a history of disease are more likely to respond to a fungicide.
  2. High yield history: High yield fields are more likely to show an economic response.
  3. Hybrid resistance: The lower the genetic resistance to gray leaf spot, northern corn leaf blight and anthracnose, the more potential for an economic response.
  4. Crop rotation: Corn following corn tends to harbor more disease inoculum.
  5. IPM (Integrated Pest Management) corn diseases are just starting to appear, especially in no-till corn on corn fields. Fields that already show 5-10% visible disease may have a higher risk of further development.
  6. Fertility: Low K levels and compacted soils could exacerbate disease effects on lodging and yield. If the field has poor fertility the likelihood of disease invasion is higher.

If one or more of these criteria apply to your situation, then a fungicide application may provide an economic return. Give Tom, Dan, Andrew, Mark or Kevin a call to help with making the best decision for your farm.

-Kevin Knudtson

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