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6/27/2011 - 7/3/2011

Western Bean Cutworm Scouting Update

By Adam Sisson, Corn and Soybean Initiative; Laura Jesse, Plant and Insect Diagnostic Clinic; and Erin Hodgson, Department of Entomology

Western bean cutworm (WBC) moths have been reported in several Iowa counties. The first moth of 2011 was captured in Hancock County, located in north central Iowa, on June 17.

Trap data by participating counties can be viewed at the North Central (NC) ipmPIPE Web page. Click on a highlighted county to see the number of recorded moths in that county. If captures occur on consecutive days and moth numbers are increasing, this is the signal to begin scouting. Tama County, located in central Iowa, experienced this on June 24, but to date there has not been any increasing trap catches in the rest of the state. The presence of adult moths in traps indicates only that scouting efforts should begin in an area.

Adult emergence can also be predicted by using a degree day (DD) model developed in Nebraska. The DD model is based on the accumulation of DDs (base 50 F) from May 1. Sources vary as to when field scouting should begin, at either 25 or 50 percent adult emergence, which are predicted at 1,319 and 1,422 DDs, respectively. The following map (Figure 1) displays the predicted dates when 25 and 50 percent adult emergence should occur based on accumulated and normal DDs.

Figure 1. Iowa climate divisions showing predicted 25 and 50 percent emergence of adult western bean cutworm moths. However, there was also a flight recorded in Tama County on the June 24.

Scouting for western bean cutworm

When scouting for WBC, examine 20 successive plants in five different areas of a field. On these plants, check for the presence of eggs or young larvae (Figures 2, 3) on the top three to four leaves. Thresholds, management options and descriptions of WBC are outlined in a previous ICM News article, Use Treatment Thresholds For Western Bean Cutworm

Figure 2. Western bean cutworm eggs

Figure 3. Western bean cutworm larvae that have just hatched


Adam Sisson is a program assistant with responsibilities with the Corn and Soybean Initiative. Sisson can be contacted by email at or by calling 515-294-5899. Laura Jesse is an entomologist with the Iowa State University Extension Plant and Insect Diagnostic Clinic; contact at or by phone 515-294-5374. Erin Hodgson is an assistant professor of entomology with extension and research responsibilities; contact at or phone 515-294-2847.

Crop Minutes: Goss's Wilt and Soybean Cyst Nematode Scouting

Alison Robertson, ISU Extension plant pathologist, found symptoms of Goss's wilt in a west central Iowa field, a field with a history of the disease. During the June 27, 2011 Crop Minute, she tells how to identify the disease and actions to take to management Goss's wilt. While there is no rescue treatment for the disease, she recommends steps to take to identify Goss's wilt and  management actions to consider.

Greg Tylka, ISU Extension nematologist, says it is time to start scouting for soybean cyst nematode. The little white females have been found on soybean roots during the latter part of June.

RUSLE2 and P Index Introductory Workshop for Writers of Manure and Nutrient Plans

By Angie Rieck-Hinz, Department of Agronomy

Livestock producers and service providers can receive training on how to use the Revised Universal Soil Loss Equation 2 (RUSLE2) and the Iowa Phosphorus Index for use in nutrient management and manure management plans at a workshop scheduled by Iowa State University Extension and the Iowa Manure Management Action Group (IMMAG), in collaboration with the Iowa USDA-Natural Resources Conservation Service.

The workshop will be held on July 26 at the Polk County Extension Office in Altoona, Iowa. The workshop starts at 8:30 a.m. and ends at 4 p.m.

This workshop is an introductory level, hands-on workshop that will provide the participant with software orientation. It will also introduce participants to the operating parameters for RUSLE2, selection of input values for RUSLE2, and developing and saving management operations for RUSLE2. In addition, real field examples will be used in the workshop to determine risk calculations of the Iowa Phosphorus Index and how to incorporate these numbers into manure and nutrient management planning requirements. Also included will be parameters for RUSLE2 and P Index calculations on snow-covered or frozen ground. Soil sampling requirements for manure management plans will also be discussed.

Many livestock producers in Iowa have manure management plans that will need to be revised in 2011 to meet the requirement to update plans every four years. The four-year plan requires new RULSE and P-Index calculations and this workshop will be a great refresher for those producers who develop their own plans or for consultants who only develop a few plans.

The cost of the workshop is $200 if registered on or prior to July 22, the late fee is $225 after July 22. The workshop fee includes handout materials, a CD with software, refreshments and lunch. Because software will be provided, participants are required to bring a MS Windows compatible laptop equipped with a CD-ROM drive and Microsoft Excel Software. Participants must have their administrator password to the computer they bring in order to install software. The workshop is limited to 30 participants.

Online registration, program information and directions to the workshop are available at



Angela Rieck-Hinz is an extension program specialist for Iowa State University Extension and is the coordinator of the Iowa Manure Management Action Group (IMMAG). Rieck-Hinz can be reached at (515) 294-9590 or by emailing

Goss’s Wilt Found in West Central Iowa

By Alison Robertson, Department of Plant Pathology and Microbiology

On June 24, we visited a grower’s field in Carroll County where we have a research study on Goss’s wilt of corn. The field has been in corn for several years and has a history of Goss’s wilt.  The field was planted May 5 and was at growth stage V6 to V7. We found plants with typical symptoms of the leaf blight (Figure 1) and also the wilting stage of the disease. This is the earliest report of Goss’s wilt in Iowa that I am aware of. It is also the first time I have seen the wilting stage of the disease in this state.

Typical lesions of Goss’ wilt were characteristic of approximately one percent of the plants in the field. Long, dark brown to grey-green lesions were evident on the edge of the leaves or along folds in the leaf. Freckles, which are diagnostic for Goss’s, were present. On some plants, only one leaf was affected, while on other plants, all leaves were affected (Figure 2). We also noticed some plants that were wilted. Closer examination of the plants revealed subtle lesions. When the stalk of the plant was cut, the vascular system of the plant was discolored orange-brown (Figure 3). In this case, infection of the plant by the bacterium was systemic. In other words, the bacterium was present in and plugging the vascular system of the plant.

There are no rescue treatments for Goss’s wilt. The disease is caused by the bacterium Clavibacter michiganenisis  subsp. nebraskaenesis. Fungicides are not effective. Management recommendations include planting resistant hybrids, rotation to a non-host crop and residue management.

Figure 1. Typical Goss’s wilt leaf lesions. Note the “freckles” in the infected tissue.  A. Robertson


Figure 2. Young corn plant with symptoms of Goss’s wilt. A. Robertson


Figure 3. Discolored vascular tissue of a young corn plant infected the bacterium that causes Goss’s wilt. W. Beck


Alison Robertson is an assistant professor in the Department of Plant Pathology and Microbiology with extension and research responsibilities; contact at or phone 515-294-6708.

This article was published originally on 7/4/2011 The information contained within the article may or may not be up to date depending on when you are accessing the information.

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