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



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


The table of contents is:


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


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


Safety, restrictions, and precautions for spraying fungicides on corn


Monitor soybean aphid populations on PIPE


Soybean aphid numbers increase . . . and decrease


Economic thresholds for western bean cutworms


Soybean rust update and outlook


Bean leaf beetle: Predicted peak first-generation dates


Iowa Learning Farm participates in Midwest Strip-Tillage Expo


Blooming time in Iowa




The July 9, 2007 issue can be downloaded from


The table of contents is:


Sample now for most corn nematodes


Soybean aphids exceed the economic threshold in northeast Iowa


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


Weed watch: Wild parsnip and poison hemlock


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


Indicators point to hay supply deficits in Iowa


Dicamba, stress, and distorted soybean leaves


July soybean disease scouting


July starts warm and dry






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: 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: 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  The traps can be ordered from:


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


100 Countryside Drive,
PO Box 270, Belleville,
Wisconsin 53508






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:


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:



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




Midwest Strip Till Conference – July 31, 2007

9 a.m. to 3:00 p.m.


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:



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

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