Decorah, Iowa Pest Guide

Updated 2026-10-22 · By Kasey, Waukee, Iowa

• Winneshiek County
• Northern & Central Iowa
• 2 listed companies
• 12 sources

Decorah is the county seat and largest city of Winneshiek County and the home of Luther College. It sits in the bluffs of the Upper Iowa River, within the Driftless Area of northeastern Iowa, and is known for its Norwegian-American heritage.

This page pulls together the pest issues Decorah homeowners tend to run into, local places to get help, and how to check that a pest company holds a current Iowa license.

Decorah pest calendar

Pest timing in Iowa follows the seasons. Here is what Iowa State University (ISU) Extension describes, in roughly the order Decorah homeowners will notice it:

• Spring: ant mounds. ISU says soil-nesting ants are especially busy in wet spring weather. Raking or hosing mounds flat is usually all that is needed. ISU notes fire ants are not present in Iowa. See how to get rid of ants in Iowa.
• Summer: wasps build up. Each yellowjacket colony starts with one queen in spring and grows all summer. ISU says nests peak around Iowa State Fair time, with up to about 5,000 wasps. See wasp nest removal.
• Fall: accidental invaders. Boxelder bugs, multicolored Asian lady beetles and brown marmorated stink bugs look for winter shelter. ISU calls them generally harmless and says sealing gaps is the best defense.
• Fall and winter: mice. ISU says native deer mice and white-footed mice move indoors in fall. See mice in your Iowa home this fall.

Emerald ash borer in Winneshiek County

The state's list of officially confirmed emerald ash borer (EAB) sites, last updated at the end of 2022, includes these Winneshiek County locations: Decorah (2016). In October 2024, IDALS announced that EAB had been confirmed in all 99 Iowa counties. IDALS says an infested tree is typically killed within two to four years. Signs include canopy thinning, leafy sprouts from the trunk, S-shaped galleries under the bark, bark splitting, woodpecker damage and 1/8-inch D-shaped exit holes. If you own ash trees, get advice from a qualified tree care professional.

Local help in Decorah

• County Extension office: ISU Extension and Outreach Winneshiek County lists its office at 2316 Sweet Parkway Road, Decorah, IA 52101 (phone 563-382-2949). Extension offices are a good first stop for research-based yard, garden and pest information.
• Insect identification: the ISU Plant and Insect Diagnostic Clinic in Ames identifies insects mailed in by Iowans. Check its page for current forms and fees.
• Ticks: ISU's Medical Entomology Laboratory offers a free tick identification service by mail. It identifies the tick but does not test it for disease.
• Mosquitoes: the same ISU lab has run Iowa's mosquito surveillance program for about 50 years with state health partners, monitoring West Nile virus and mosquito numbers. Current data is on the Iowa Mosquito Surveillance website linked from its page.

Guides for Decorah homeowners

• Ant Exterminator Near Waukee: What to Expect and How to Choose a Pro
• Bed Bug Signs and What to Do in the Des Moines Metro
• Boxelder Bugs in Iowa Homes
• How to Get Rid of Ants in Iowa
• Mice in Your Iowa Home This Fall
• Wasp Nest Removal Near Waukee, Iowa

How to check a pest company's license in Decorah

Iowa requires anyone in the business of applying pesticides to another person's property to be licensed and certified by the state. To check a company:

1. Open the IDALS license lookup and choose Search By Company/License.
2. Type part of the company's name, or pick the county WINNESHIEK - 96 to see every company registered there.
3. Check that the expiration date is in the future. Expiration dates in the lookup fall on December 31.

When we searched Winneshiek County on 10/22/2026, the lookup returned 65 company records. That count includes every license type (lawn care, agriculture, golf courses and pest control) and some expired records, so narrow it down by name. A company is listed under the county of its own address, so a company that serves Decorah may be listed under a neighboring county. Our guide on choosing a licensed pest pro has a checklist of questions to ask.

Frequently asked questions

What county is Decorah in?

Decorah is in Winneshiek County, Iowa. The county matters for two things: which ISU Extension office is closest, and which county to choose in the IDALS license lookup.

Has emerald ash borer reached Decorah?

Yes. The state's confirmed-site list includes Decorah (2016) in Winneshiek County, and IDALS confirmed EAB in all 99 counties in October 2024.

How do I know a pest company in Decorah is licensed?

Search the company's name in the IDALS lookup and check that the expiration date hasn't passed. A company saying it's licensed is not the same as a current state record.

Has emerald ash borer been found in Decorah?

Yes. The state's list of confirmed sites shows Decorah in 2016. IDALS has since confirmed the beetle in all 99 Iowa counties.