Oskaloosa, Iowa Pest Guide

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

• Mahaska County
• Southern Iowa
• 4 listed companies
• 12 sources

Oskaloosa is the county seat of Mahaska County. In the late 1800s and early 1900s it was a national center of bituminous coal mining. Today it is home to William Penn University, and Lake Keomah State Park is four miles east of the city.

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

Seasonal pests around Oskaloosa

ISU Extension's seasonal guidance applies statewide, including Oskaloosa:

1. April-June: ant hills. Soil-nesting ants are most active in wet spring weather. Flattening mounds is usually enough. Ants in Iowa.
2. July-September: yellowjackets. Colonies peak around State Fair time with up to roughly 5,000 workers per nest, according to ISU. Wasp nest removal.
3. September-October: boxelder bugs, lady beetles and stink bugs. These accidental invaders gather on sunny walls and slip into gaps. ISU recommends sealing openings.
4. October onward: mice. Native mice move indoors for winter. Mice in your Iowa home this fall.

Bed bugs aren't seasonal. If you suspect them, start with our bed bug guide.

Emerald ash borer in Mahaska County

The state's list of officially confirmed emerald ash borer (EAB) sites, last updated at the end of 2022, includes these Mahaska County locations: Eddyville (2014); Rural Oskaloosa (2015). 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 Oskaloosa

• County Extension office: ISU Extension and Outreach Mahaska County lists its office at 212 North I Street, Oskaloosa, IA 52577 (phone 641-673-5841). 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 Oskaloosa 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 Oskaloosa

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 MAHASKA - 62 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 Mahaska County on 10/22/2026, the lookup returned 79 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 Oskaloosa 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 Oskaloosa in?

Oskaloosa is in Mahaska 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 Oskaloosa?

Yes. The state's confirmed-site list includes Eddyville (2014), Rural Oskaloosa (2015) in Mahaska County, and IDALS confirmed EAB in all 99 counties in October 2024.

How do I know a pest company in Oskaloosa 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.

Where is the Mahaska County Extension office?

ISU Extension and Outreach Mahaska County lists its address as 212 North I Street in Oskaloosa. Its phone number is 641-673-5841.