Spider mites, dry conditions cause concern

Field Notes

Spider mites, dry conditions cause concern

These reports were received August 8 and 11 from ISU extension field specialists in crops.


  • George Cummins (1), north Iowa, reported soybean white mold in a Howard County field. This field had scattered problems with white mold last year, but the infected area is larger this year and some plants have died. He said he had not been finding many second-generation corn borer egg masses. Potato leafhopper numbers seem to be declining but are still above threshold.
  • Brian Lang (2), northeast Iowa, reported that about 1,000 acres of corn have been treated for fall armyworm within the last several weeks. Potato leafhopper continues to be a problem on alfalfa. Corn rootworm is causing some widespread lodging and goose-necking in corn, particularly in Fayette, Clayton, Allamakee, and Dubuque counties.
  • Bill Lotz (3), northeast Iowa, reported eyespot in some commercial corn fields. Several fields had damage on corn from fall armyworm. Potato leafhopper numbers continue to be above the threshold.
  • Problems with spider mites are increasing in east central Iowa, according to Jim Fawcett (4). He reported that some soybean fields have been sprayed for this pest and grasshoppers continue to be a problem. Corn is dying in areas with soil that has poor water-holding capacity and many pastures have dried up.
  • John Creswell (5), central Iowa, reported that growers are spraying for spider mites on soybean in Greene, Boone, and Guthrie counties. They also are spraying for potato leafhoppers, which continue to be a problem, and grasshoppers. He reported a very low incidence of corn or soybean disease at this time.
  • Carroll Olsen (6), southwest Iowa, reported that some fields have been treated for second-generation corn borer.
  • Mike White (7), south central Iowa, reported extremely dry conditions in Taylor, Union, and Adair counties, and the west half of Madison County. He observed some yellowing of upper trifoliolates on Roundup-Ready soybean plants 2 to 3 weeks after treatment. Potato leafhoppers are still present in high numbers in alfalfa, and spider mites are beginning to move into end-rows of a few soybean fields.
  • Jim Jensen (8), southeast Iowa, reported many grasshoppers on the edges of corn and soybean fields. He also found some stem canker of soybean. Pastures are very dry and short.

This service is funded through ISU Extension's Integrated Pest Management program.

This article originally appeared in the August 18, 1997 issue, p. 157.

Prepared by Joyce Hornstein, extension program specialist, Department of Entomology

Iowa State University, Ames, Iowa.

This information subject to a usage policy.

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Last updated 8/13/97 by John VanDyk


This article originally appeared on page 157 of the IC-478(20) -- August 18, 1997 issue.

Updated 08/17/1997 - 1:00pm