New Pest Forecasting Page on the Mesonet Website

May 2, 2022 1:07 PM
Blog Post

For many years, we have provided scouting alerts for key insect pests on ICM News and ICM Blog, including alfalfa weevil and stalk borer (click links for examples). We provide these updates annually since growing degree day (GDD) accumulation varies between growing seasons. Usually, these updates are prompted when benchmark GDDs have been reached in the southern Iowa counties, since heat units accumulate faster further south. This means that, up until now, we provided a static map with GDD information and a relevant scouting alert for only a small portion of the state.

Working with Daryl Herzmann, Systems Analyst with the Iowa Environmental Mesonet, we have created a webpage with maps that automatically update each day with the GDD accumulation for key pests at climate sites across Iowa. Additionally, you can select a local climate site and see the current GDD accumulation and 7- and 14-day projections. Keep in mind that sometimes weather stations report data incorrectly, so let us know if a number looks strange so we can investigate.

How do I use this page?

  1. You can get to the Pest Forecasting page 3 ways:
    1. Click on this link: Pest Forecasting Page.
    2. Go to, click on Apps, and then click on Pest Maps + Forecasting in the drop-down menu.
    3. Go to, click on Ag Weather, and look for “Pest Maps + Forecasts” on the right-hand side of the table in the “Air Temperature” or “Growing Degree Days” rows.
  2. Select pest. Use the “Select Pest” drop-down menu to select the pest you are interested in learning about.
  3. Select dates. The Start Date automatically defaults to January 1 of the current year; the End Date automatically defaults to the current date. You can select different dates if you wish. These dates only impact what is shown on the map, not site-specific forecasting.
  4. Review key GDD. Above the map, we list Key Degree Days for each pest.
    1. The Start Date tells you when to begin accumulating degree days (what to set as the start date, if applicable).
    2. Key GDDs are listed that correspond to important developmental stages or pest activity.
    3. A link to more detailed information on scouting and tracking GDDs is provided.
  5. Map. The map shows degree day accumulation across the state.
  6. Site-specific forecasting. On the right-hand side of the screen, select your local climate station. The table tells you:
    1. Current observed GDDs.
    2. Predicted GDD accumulation (and total) for the next 7 days.
    3. Predicted GDD accumulation (and total) for the next 14 days.

We hope the Pest Forecasting maps provide more utility to farmers and ag professionals in Iowa and improve scouting and pest forecasting for integrated pest management, especially in the northern portions of the state that typically have not reached benchmark GDD for pests in our ICM News alerts. For information on how GDDs are calculated for insect pests, refer to this ICM Encyclopedia article.

As you use the Pest Forecasting page, please send feedback to your local field agronomist or to the authors so we can continue to improve this service for you!


Ashley Dean Agriculture and Natural Resources Extension Specialist II

Ashley is an education extension specialist for field crop entomology at Iowa State University. She coordinates the Iowa Moth Trapping Network, the Regional Corn Rootworm Monitoring Network, and the Iowa Pest Alert Network. She also develops educational resources for field crop pests in Iowa and ...

Erin Hodgson Professor

Dr. Erin Hodgson started working in the Department of Entomology, now the Department of Plant Pathology, Entomology, and Microbiology, at Iowa State University in 2009. She is a professor with extension and research responsibilities in corn and soybeans. She has a general background in integrated...