Iowa State University Extension and Outreach

East-Central and Southeast Iowa Crop Information

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July 10, 2007

 

Iowa State University Information for Southeast Iowa

By Jim Fawcett, ISU Extension Field Agronomist
4265 Oak Crest Hill Rd. SE

Iowa City, IA 52246
319-337-2145

Covering the counties of Benton, Iowa, Johnson, Jones, Keokuk, Linn, and Washington

 

CORN

 

Fungicide Applications

 

The July 2 Issue of the ICM Newsletter provides timely information on this subject.  The Newsletter is at http://www.extension.iastate.edu/Pages/eccrops/transfer/070702ICMN.pdf as a pdf file because of a glitch on campus in getting this issue on the internet.  The July 9 issue is at http://www.extension.iastate.edu/Pages/eccrops/transfer/070709ICMN.pdf.

 

Western Bean Cutworm

 

This pest has been increasing in eastern Iowa in the past few years. Peak flights of the moths usually occur around mid-July.  The trapping network can be viewed at: http://www.ent.iastate.edu/trap/westernbeancutworm/isite. Once we see significant flights into an area, we wait about one week before scouting for egg masses.  An explanation of the scouting method is at: http://www.ipm.iastate.edu/ipm/icm/2005/7-11/wbc.html. Photos of the insect, egg masses, etc., are at the “Images” link in the upper left hand corner off of the trapping network home page given above. More information can also be found in the attached ICM Newsletter issue.

 

 

SOYBEANS

 

Bean Leaf Beetle (BLB)

 

The first 1st generation BLB are beginning to appear.  First emerging BLB are initially grey in color and have a soft shell.  As the shell hardens, they may change to other colors (red, yellow, brown).  ISU Entomologists are not very concerned with 1st generation BLB.  The larger threat is with second generation BLB after pods begin filling.  Apparently the small pods in the R3-R4 stages are not all that attractive to BLB.  Pod clipping of these small pods has been over stated.  Most small pod droppage is through “normal” pod abortion by the plant.  However, if >20% defoliation of the whole plant occurs, the pest should be controlled.  The same goes for grasshoppers (usually only along field edges) or any other chewing insect (i.e. various caterpillars, Japanese Beetles, etc.).

 

Second generation BLB will begin to show up in about 5 weeks, and tend to peak in population in early to mid-September.  As this generation populates, we monitor for threshold levels with a sweep net.  It is best to sweep in the afternoon when they tend to be most active.  The general threshold for reproductive stage soybeans is 4 per sweep in row beans and 3 per sweep in drilled beans.  More detailed threshold information can be found at:

http://www.ipm.iastate.edu/ipm/icm/1999/8-9-1999/blbeffects.html

 

An alternative method to manage the pest is to scout for 1st generation beetles in July and make the decision whether or not to spray the second generation in August, based on the numbers reached in July. This usually will result in a more timely application and help to reduce yield losses. More information on this scouting method is included in the ICM Newsletter issue that is attached.

 

Japanese Beetles

 

Japanese beetle numbers are increasing in areas where they have been a problem in past years. Continue monitoring for this pest in corn and soybeans. For more information including pictures of the beetles, see the August 19, 2002 ICM Newsletter at:

http://www.ipm.iastate.edu/ipm/icm/2002/8-19-2002/jbeetles.html

 

 

Soybean Aphid

 

Soybean aphid numbers have reached the economic threshold of 250 aphids per plant in a field that Brian Lang is monitoring in NE Iowa. Aphid numbers are also increasing in some fields of EC Iowa, but are still at very low levels (generally less than 1 or 2 per plant). Spraying too early can actually make the problem worse by killing off the beneficial insects that are helping to keep the population in check, but it is time to start weekly scouting for this pest.  A newly revised soybean aphid publication has just been released, SP 247, Soybean Aphids in Iowa – 2007.  Let me know if you would like a copy e-mailed to you (a 1 MB file).  Or you can download it from http://www.extension.iastate.edu/Pages/eccrops/transfer/07SBA.pdf.

 

 

FOR YOUR CALENDAR

 

Ag Professional Tour – July 20  9:30 a.m. to noon

NE Iowa Research Farm – Nashua

 

Emphasis on current crop and pest issues with tour of on-farm research trials. CCA credits available. 

 

 

Midwest Strip Till Conference – July 31 9 a.m. to 3:00 p.m.

Waterloo

 

Organized by Research and Extension of Iowa State University, the University of Minnesota, the University of Wisconsin, and Hawkeye Community College. Manufacturers will demonstrate equipment for strip-tillage and associated operations, including auto-guidance systems and fertilizer injectors.  Researchers, farmers, and industry representatives will present the latest information on strip-tillage related topics, including equipment selection, fertility management, and guidance technology. Participants will review information booths all day, and lunch is available on site.  This program is free and open to the public. Five Certified Crop Advisor CEUs (4.5 SW & 0.5 NM) will be available for a nominal fee.  Expo details are at: http://wrc.umn.edu/outreach/striptillageexpo/midwest/index.html

 

Soybean Aphid and Bean Leaf Beetle Management Tour – August 8

 

Management 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 West Chester on Wednesday, Aug. 8. Since first being discovered in the Midwest in 2000, soybean aphids have tended to be more of a concern in odd numbered years, so this may be more of a pest this year than last. No-till soybean plots that were planted with and without the seed treatment “Cruiser” are the focus of research conducted on this Iowa Learning Farm site. Seed applied insecticides can provide good early season bean leaf beetle control and also provide some control of soybean aphids, especially when planting is delayed as it was this spring. Also discussed at the tour will be value added crop opportunities, including “low lin” soybeans. A rain simulator will also be demonstrated at the site. A free meal, courtesy of QUALISOY (http://www.qualisoy.com/) will be available at 6:30 p.m. followed by the tour. The Iowa Learning Farm project is a unique partnership of agencies, farm and conservation groups, the general public and Iowa State University. Iowa Learning Farm project staff work to increase the adoption of residue management and conservation practices that are expected to improve water quality.

 

 

If you have any questions, please feel free to contact the Iowa State University Extension Office.

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Last Update: July 10, 2007
Contact: Jim Fawcett fawcett@iastate.edu


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