Iowa State University Extension and Outreach

East-Central and Southeast Iowa Crop Information

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July 11, 2007

 

Virgil Schmitt

Extension Field Agronomist

Muscatine County Extension

1514 Isett Avenue

Muscatine, IA 52761-4629

Phone:  (563) 263-5701

FAX:   (563) 263-5709

e-mail vschmitt@iastate.edu

www:  http://www.extension.iastate.edu/Pages/eccrops/

Covering the Iowa counties of Cedar, Clinton, Des Moines, Henry, Jackson, Louisa, Muscatine, and Scott

 

 

Integrated Crop Management Newsletter Posting Glitch

 

There is a glitch at Iowa State university preventing the July 2 and July 9 Integrated Crop Management Newsletters from being posted on the web site; it appears the problem can not be corrected until next week.  However, you can download the newsletters using the links below.

 

The July 2, 2007 issue can be downloaded from http://www.extension.iastate.edu/Pages/eccrops/transfer/070702ICMN.pdf.

 

The table of contents is:

 

Corn growth and yield formation in light of fungicide applications at tasseling

199–200

Before applying fungicides to corn: Stop! Look! Consider!

201–203

Safety, restrictions, and precautions for spraying fungicides on corn

204–205

Monitor soybean aphid populations on PIPE

206

Soybean aphid numbers increase . . . and decrease

207

Economic thresholds for western bean cutworms

208

Soybean rust update and outlook

209

Bean leaf beetle: Predicted peak first-generation dates

210–212

Iowa Learning Farm participates in Midwest Strip-Tillage Expo

213

Blooming time in Iowa

214

 

 

The July 9, 2007 issue can be downloaded from http://www.extension.iastate.edu/Pages/eccrops/transfer/070709ICMN.pdf.

 

The table of contents is:

 

Sample now for most corn nematodes

215–216

Soybean aphids exceed the economic threshold in northeast Iowa

217–218

Too early to harvest dry corn for early silage, but do consider nitrate accumulation risks

218

Weed watch: Wild parsnip and poison hemlock

219–220

Time is running out for planting an “emergency” forage crop

220

Indicators point to hay supply deficits in Iowa

221

Dicamba, stress, and distorted soybean leaves

222

July soybean disease scouting

223

July starts warm and dry

224

 

CORN

 

 

Fungicide Applications

 

The July 2 Issue of the ICM Newsletter provides excellent information on this subject.

 

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 July 2, 2007 issue of ICM Newsletter.

 

Corn Rootworms in First Year Corn – Extended Diapause of Northern Corn Rootworms?

 

I am receiving calls from and have been in two areas within my region of coverage where there is significant feeding of corn rootworms on first year corn.  Initially, it appears that they are extended diapause of northern corn rootworms.  I am encouraging the placement of emergence cages in these fields to verify that it is extended diapause of northern corn rootworms and not rotation resistant (eastern variant of) western corn rootworm (the ones that lay eggs in soybean fields).  If any of the sites turn out to be rotation resistant western corn rootworms, it will be especially important for soybean fields in those areas to be monitored for western corn rootworm beetle activity, as noted in the following item.  Stay tuned.

 

Rotation Resistant Western Corn Rootworms

 

As you know, rotation resistant western corn rootworms have been confirmed throughout the counties I cover, and levels above threshold were confirmed in the area from northeastern Muscatine County through Scott County and into Clinton County in 2006.  The Illinois and Indiana experience with this pest is that it starts out very spotty, so a cart blanc use of rootworm management in first year corn is not yet warranted.  Rather, soybean fields that will be planted to corn in 2008 should be monitored for western corn rootworm adult activity beginning in the last week of July and continuing through the first three weeks of August using the Trece Pherocon AM yellow sticky traps.  Follow the protocol developed by the University of Illinois, which can be found at http://www.ipm.uiuc.edu/fieldcrops/insects/western_corn_rootworm/wcr.pdf.  The traps can be ordered from:

 

Great Lakes IPM
10220 Church Road, NE,
Vestaburg, Michigan 48891

e-mail: glipm@nethawk.com

http://www.greatlakesipm.com/

Gemplers,
100 Countryside Drive,
PO Box 270, Belleville,
Wisconsin 53508
http://www.gemplers.com

 

 

 

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 July 2, 2007 ICM Newsletter.

 

Japanese Beetles

 

Continue monitoring for this pest in corn and soybeans in areas where they have been a problem in past years. 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.  It is at the printer now, but you can download it from http://www.extension.iastate.edu/Pages/eccrops/transfer/07SBA.pdf.

 

FOR YOUR CALENDAR

 

Midwest Strip Till Conference – July 31, 2007

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

 

 

If you have any questions, please feel free to contact the Iowa State University Extension Office.
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Last Update: July 11, 2007
Contact: Virgil Schmitt vschmitt@iastate.edu


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