Crops Bulletin
July 16, 2014 
       Issue 8        

Prepared by

Paul Kassel

Extension Field Agronomist



(712) 262-2264




Serving Clay, Buena Vista, Dickinson, Emmet, Hancock, Kossuth, Palo Alto, Pocahontas, Sac and Winnebago Counties



The U.S. Department of Agriculture (USDA) prohibits discrimination in all its programs and activities on the basis of race, color, national origin, gender, religion, age, disability, political beliefs, sexual orientation, and marital or family status. (Not all prohibited bases apply to all programs.) Many materials can be made available in alternative formats for ADA clients. To file a complaint of discrimination, write USDA, Office of Civil Rights, Room 326-W, Whitten Building, 14th and Independence Avenue, SW, Washington, DC 20250-9410 or call 202-720-5964.

Fungicide Use on Corn: The conservative approach to fungicide use on corn is usually recommended in the following situations.

  •  Corn following corn rotation.
  •  Disease susceptible hybrids.
  •  Leaf diseases - gray leaf spot, common rust, and eyespot - are present.      

However, yield benefits have been obtained from fungicide application on corn when the above factors have not been present. However, predicting this yield response without the presence of disease is more difficult. Hybrid response, weather conditions and yield potential are all factors - but are difficult to predict. However, fields that are uniform in growth and development may be good candidates for fungicide treatments if yield potential looks promising at the R1-R2 stage.


Fungicide Use on Soybean: Fungicide applications for soybean should be applied at the R3 stage (3/16 inch pod at one of the four uppermost nodes). Foliar fungal diseases of soybean are at low levels this year.   However, there is a fair amount of bacterial blight in soybeans this year.


However, fungicide applications to soybean have increased soybean yields when foliar disease levels are low. Research in northwest Iowa has shown a fairly consistent 2-3-bu/a yield benefit with fungicide applications on R3 stage soybean. A summary of studies by the Iowa Soybean Association showed a correlation with summer rainfall and yield response to fungicide application.


Weed Control on Larger Size Corn: The following is an option on corn that may still need a grass or broadleaf herbicide.  

  • Impact/Armezon is labeled for application up to 45 days pre-harvest with drop nozzles. Adequate spray coverage of weeds may be an issue. There is some concern of carryover if the 2015 crop is soybean.

Growing Degree Days (GDD): The following are GDDs from April 22 to July 15. The departure from the long-term average follows in parentheses.

  • NW crop reporting district is 1290 (-45)
  • NC crop reporting district is 1196 (-106)
  • WC crop reporting district is 1352 (-63)

Prepared by Paul Kassel, Extension Field Agronomist

Phone: (712) 262-2264, Email: