Field Notes

This information was summarized from a July 7 teleconference with ISU extension field specialists in crops. Comments also are received from independent crop consultants working throughout the state.

• Very scattered rainfall occurred over the state last week. Amounts reported were from none to more than 1 inch in the southeast.
• Corn growth stages range from V10-V14 in the northern two-thirds of the state and V10-VT (tassel) in the southern third.
• European corn borer numbers are below economic threshold for treatment in most areas. Some commercial fields are being treated.
• Mike Williams, PMC Consulting, Fremont, Neb., reports that some commercial fields in Harrison, Shelby, Pottawattamie, and Carroll counties are being sprayed for European corn borer. Rust on corn leaves also was starting to occur in some seed fields.
• Chris Clark, ABC Ag, Ida Grove, reports some fairly high numbers of European corn borer in some areas and about 1,000 acres treated. These included fields with second and third instar larvae that were above the economic threshold.
• Tom Smidt, Smidt Crop Management, Greene, reports that most fields are well below the threshold for European corn borer and only about 3 percent of commercial fields are being treated. Potato leafhoppers in alfalfa are plentiful and are being treated. Phytophthora root rot is showing up in some soybean fields and one field was sprayed for grasshoppers. Some areas had 10 inches of rain in two weeks so herbicide application was too late in some soybean fields, resulting in 18-inch velvetleaf and giant ragweed.
• Soybean fields throughout the state are beginning to bloom (R1 growth stage).
• Some possible Exceed carryover in soybean were reported, especially in the eastern third of the state.
• Potato leafhopper numbers are above threshold in many fields and are being sprayed. See pages 135-136 in this newsletter for scouting details and insecticides labeled for control. Second-crop alfalfa harvest is beginning in most areas.
• Wheat is about ready for harvest in southeast Iowa.

This article originally appeared in the July 14, 1997 issue, p. 139.