July 10, 2007
Jim Fawcett, ISU Extension Field Agronomist
Covering the counties of Benton, Iowa, Johnson, Jones, Keokuk, Linn, and Washington
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
pest has been increasing in eastern
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 ICM Newsletter issue that is attached.
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:
aphid numbers have reached the economic threshold of 250 aphids per plant in a
FOR YOUR CALENDAR
Ag Professional Tour – July 20 9:30 a.m. to noon
NE Iowa Research Farm
Emphasis on current crop and pest issues with tour of on-farm research trials. CCA credits available.
Organized by Research
and Extension of
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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