Common rust seen; corn borers treated

This information was summarized from comments received from independent crop consultants and Iowa State University extension field specialists in crops located throughout the state.


Map showing field note locations

  • Low levels of common rust on inbred corn lines is present in some fields in Greene, Shelby and Crawford counties, according to Ralph von Qualen (1), ACTS, Inc., Carroll.
  • Mike Williams (2), P.M.C., reported rust on some of the seed corn lines in Carroll county. European corn borers were at high enough levels for treatment in some Monona and Woodbury county fields, but were under thresholds in fields checked in the Walnut area.
  • In fields scouted in Allamakee, Clayton and Howard counties, European corn borer numbers were as high as 3.2 borers per plant, but averaged 0.5 to 1.2 borers per plant, according to Shannon Gomes (3), Cedar Basin Crop Consulting, Waverly. Corn that is at the V7 or V8 stage generally had fairly high numbers of borers.
  • Jim Fawcett (4) noted that several farmers in Benton, Johnson and Poweshiek counties have problems with rootless corn. The nodal roots are either not developed at all or are emerging at or above the soil surface. Some of the corn is falling over and breaking off, and the problem seems to be worse in wet areas. Drought-induced K deficiency also is appearing in some corn fields, with symptoms of stunted plants and yellowing leaves.
  • European corn borers were found to be above threshold levels in some of the fields that were rescouted this past week, according to John Creswell (5). A fairly heavy infestation of true white grubs (3 or more grubs per plant) in a 20-acre field near Newton killed much of the corn.
  • Black cutworm is damaging smaller corn (at the V2 to V4 stages) in some fields in southeast Iowa, reported Jim Jensen (6). Some fields with smaller corn were affected by later flights of black cutworm moths and still need to be scouted.
  • George Cummins (7) found six corn fields in five different counties where stalk borer seriously reduced stands in the middle of the field away from borders and grass waterways. Soybean fields planted June 15-17 on untiled ground have poor stands because of seedling diseases and some were being replanted last week.

This article originally appeared on page 131 of the IC-476(18) -- July 15, 1996 issue.

Updated 05/23/2005 - 5:41am