June 4, 2007
Although corn fields that I have scouted have not had black cutworm damage above the economic threshold, Mark Carlton reports that there has been extensive cutting in some fields further south. Corn should continue to be scouted for cutworms until V5 (when five leaves have fully emerged from the whorl). The economic threshold is 2-3% of the plants cut or wilting when the cutworms are less than 3/4 inch long, or if cutworms are longer than 1 inch, the threshold is 5% of the plants cut.
I have found some corn stand losses from white grubs in the area. True white grubs have a 3-year life cycle, so feeding can continue throughout the season and stand losses are common. If replanting is justified, an insecticide seed treatment should be used to protect the replanted corn. At this late date it would likely take stands of less than about 18,000 plants per acre to justify replanting, depending on the uniformity of the surviving stand and cost of replanting. Annual white grubs usually pupate before they do enough damage to justify replanting.
grub of the Japanese beetle has been an increasing problem in corn fields in
the past few years, especially near urban areas, such as
Millipedes are being found in high numbers in some fields. Although millipedes usually do not feed on living plants, they have been known to cause stand losses in no-till corn and soybean fields under cool, wet conditions where crop residue levels are high. Although broad spectrum insecticides may kill the millipedes, a better way to manage the problem is to use residue managers to try to reduce the amount of residue left over the crop row.
recent rains have likely resulted in more losses of nitrogen in corn fields. On
Asian Soybean Rust
FOR YOUR CALENDAR
Help Celebrate ISU’s 150th Birthday With Jack Payne at the
SE Iowa Research & Demonstration Farm Spring Field Day - Crawfordsville
Doors open at 11:00 with a free health screening and displays on alternative energy, the bioeconomy, and trading carbon credits. A free lunch, courtesy of Farm Credit Services, is available at 11:30. Jack Payne, ISU Extension Vice President, will be speaking at 12:15. The farm tour begins at 1:00, where the stops include:
¨ Crop Season Review & Marketing During Volatile Times– Kevin Van Dee, Farm Superintendent & Jim Jensen, ISU Farm Management Specialist
Fungicides on Corn & Asian Soybean Rust Outlook
Daren Mueller, ISU Extension Plant Pathologist
Moving CRP to Crops – Carbon Sequestration Impacts
Mahdi Al-Kaisi, ISU Extension Agronomist - Soil Management
Bt-Rootworm Hybrid Results & Rating Corn Roots
Jon Tollefson, ISU Extension Entomologist
Earn 5 hours of CCA credits, including 2 hours in soil and water, by attending a special CCA session beginning at 9:00 a.m. followed by the afternoon field day. The morning session will include:
Crop Research in
Jim Fawcett, ISU Extension Crop Specialist
Ø Soil Bulk Density and Water Infiltration Rates with Different Tillage Systems
Mahdi Al-Kaisi, ISU Extension Agronomist – Soils
Ø Fungicides – Review of Products & Research Results in Corn & Soybeans - Daren Mueller, ISU Extension Plant Pathologist
There is a $50 registration fee ($70 after June 19). Give the Johnson County Extension Office a call or send me an e-mail note if you plan to attend. You can pay at the door.
Soybean Aphid and Bean Leaf Beetle Management Tour – August 8
techniques for the soybean aphid and bean leaf beetle will be highlighted at a
tour on the Iowa Learning farm site on the Rob Stout farm south of
If you have any questions, please feel free to contact the Iowa State University Extension Office.
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