farmstead picture
Resource Homepages  
ISU Extension
Agronomy- Extension
IA State Univ.
IA Dept. of Ag
IA Crop and Pest Mngt. Newsletters
Field and Feedlot
J. Dejong
V. Schmitt
J. Holmes
J. Fawcett
B. Lang
Other States
MN Crop News
C.O.R.N. (Ohio)
Crop Watch (NE)
the Bulletin (IL)
Current topics (KS)
CAT Alert (MSU)
MN Pest Report
SW MN Pest
WI Crop Mngr
Other States
Organic Ag
Weather Data
Iowa Mesonet
MN Ag Climate
High Plains RCC
Ag Weather
AgBioWorld (for)
ETCgroup (against)
Agriculture Search Engines
Agriculture Databases

ISU Extension Logo

Northwest Iowa Extension
Crop and Pest Information
by Todd Vagts
ISU Extension Crops Specialist
Counties Served:  Carroll, Calhoun, Crawford, Ida, Monona, Pocahontas and Sac.

[Home][ISU Extension][IA State University]

Western Bean Cutworm

Northwest IA
Degree-Day and Trap Catch Information

The following chart shows the progression of accumulated degree-days (base 50) for 4 locations in central and northwest Iowa.  The chart also projects accumulated degree-days for the next 7-days according to forecasted temperatures from the "Weather Channel".

Information from the University of NE (NebGuide G98-1359-A) indicates that 25, 50 and 75 percent moth emergence occurs at 1319, 1422 and 1536 degree-days respectively.

Degree Day Accumulation

Location Aug 1 Aug 7
Ames 1713 1862
Castana 1809 1959
Kanawha 1664 1811
Sutherland 1671 1818


Scouting Recommendations from Ronald C. Seymour (Extension Educator in Adams County) and Gary Hein (Extension Entomologist Panhandle REC)
... Even though field scouting for western bean cutworm in field corn should begin when the first moths are caught, control decisions should be made shortly after the moth flight peaks. The moth flight usually peaks between July 10 and July 24. 

When scouting for western bean cutworms in corn, check 20 plants in at least five areas of each field. Look for eggs on the top surface of the upper most leaf or look for larvae in the tassel. If 8% of field corn plants, 5% of seed corn plants or 5% of popcorn plants have egg masses or larvae, consider applying an insecticide.  

Western bean cutworm moths prefer to lay eggs in corn plants that are in the late whorl stage compared to those that have completely tasseled. Pay particular attention to later planted fields or those with uneven development. Western bean cutworm eggs that hatch when corn plants are in the whorl stage of growth have a high rate of survival. The larvae are well protected in the whorl or tassel.  

If an insecticide treatment is warranted in corn fields, it should be made when 95% of the plants in a field have tasseled. This timing of the application increases the chance that the worms will be exposed to the insecticide resulting in better control.

Insecticide control options:

2005 Trap Catch Numbers

2004 Trap Catch Numbers

2003 Trap Catch Data (pdf)
West-central IA

2002 Trap Catch Data
(Excel Spreadsheet)

Click on image for graphed 2005, 2004 or 2003 data

Individual Daily Pheromone Trap Catch
2005graph     2004  graph        2003 graph


(Total) Daily Pheromone Trap Catch
2005graph       2004 graph        2003 graph

Average Daily (pheromone) Trap Catch
North vs South of Hwy 3
2005graph      2004 graph

Black-Light Trap Daily Catch
(2005, 2004, 2003 and 2002)
Updated 8-08-05

If you are in need of more pheromone, please contact me at 712-792-2364 or

I am interested to know if you find a WBC infested field.  Please contact me at 712.792.2364 or


For more information on the Western Bean Cutworm, visit the University of Nebraska website

Photos taken July 23, 2003
(click on image for larger view)

Moth Trap

How many moths? (131)

Counting Moths

WBC Egg Mass

Hatched larva

Hatching Larva

Hatched Larva

Hatched Larva

Click on images for view of Moth and Egg Mass




If you are in need of more pheromone, please contact me at 712-792-2364 or


Return to NW Iowa Crops homepage

Todd Vagts
Iowa State University Extension
Field Crops Specialist
1240 D. Heires Avenue 
Carroll, IA 51401 
Office: 712-792-2364; Cell: 712-249-6025;  Fax: 712-792-2366

For questions or comments please respond to

This page last updated on 08/08/05

Non-Discrimination and information