Crops Bulletin
July 3, 2012
Issue 7   


Prepared by

Paul Kassel

Extension Field Agronomist



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



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Growing Degree Days for Algona as of July 3rd  


  Plant Date         GDDs             Departure         Approx. Growth Stage


   3/28             1400             +300                  R2

   4/11             1275             +200                 VT/R1

   4/18             1225             +200                V18/VT

   4/25             1175             +175                  V18

   5/4               1100             +200                  V16

   5/9               1000             +150                  V14


This info illustrates the wide range of crop development due to the six distinct 2012 planting dates. Growth stages will vary with hybrid and hybrid maturity. Info on GDDs for other locations/dates is available on the Iowa Mesonet .


Moisture/heat stress will have a major impact on the yield potential of the early-planted corn. Later planted corn may have an advantage if temps and moisture conditions moderate. Roger Elmore and Elwynn Taylor each have articles on the effects of heat stress on corn yields in ICM News.


Current GDD accumulation has been about 27 per day. It takes 57 GDDs to produce a new leaf after the V10 stage. Therefore, corn will produce about three leaves per week with the current weather.


The normal GDD accumulations are about 700 for July and 600 for August. Hybrids in the 100 day maturity - which usually requite about 2500 GGDs to reach maturity - could reach black layer maturity by late August.


Corn Rootworm. Check fields for rootworm damage. Dig a few plants and check for rootworm scarring and feeding on the roots.


There have been a few cases where the corn rootworms have developed resistance to the YieldGard Rootworm (YGRW) trait. This has not been a widespread problem, but may occur where the YGRW trait has been used for several years in the same field.


Silk clipping may occur as corn rootworm adults emerge. Check early planted fields for damage from rootworm adults.


Prepared by Paul Kassel, Extension Field Agronomist

Phone: (712) 262-2264, Email: