This information was summarized from a July 23 teleconference with Iowa State University extension field specialists in crops.
- Rainfall has been spotty during the past several weeks. Some areas of the state have not had rain since June 14; other areas have had localized heavy rain (up to 6 inches) and strong winds that have caused crop damage. Moisture stress in crops has become severe in some areas.
- Early-planted corn is at 50 to 60 percent silk with differences in corn development depending on planting date and moisture stress. The late-planted fields are V10 to V12. Extended diapause northern corn rootworms are in some corn-soybean rotation fields in northwestern and northern Iowa. These fields may be more prone to lodging as the pest prunes the roots. Second-generation European corn borers are flying. Corn leaf aphids were reported in several fields in southeastern and east central Iowa.
- Early-planted soybean fields are beginning pod fill. Cultivation and spraying for weeds continue in the more recently planted fields. Causes of leaf cupping and crinkling may include herbicide drift, disease, or environmental conditions. The first-generation bean leaf beetle population is present but not at high enough numbers for treatment. Spider mites also were reported, but they are generally not being treated at this time. Grasshoppers are being reported in field edges, especially in areas with reduced rainfall. In northeastern Iowa, Brian Lang reported soybean aphid in more than a dozen fields and these fields continue to be monitored.
- Second-cut alfalfa harvest is continuing and in many areas it is complete. Potato leafhoppers over threshold continue to be a problem.
This article originally appeared on pages 160-161 of the IC-486(20) -- July 30, 2001 issue.