Quick Tips: Biting Insects and Ticks - Minnesota Department of Health


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Floods may increase insects

Standing water left by a flood can make mosquito numbers rise. Greater river flow can lead to larger numbers of black flies (biting gnats). Other insects, such as wasps, may become very aggressive.

Disease risk is low

Only a few types of mosquitoes and ticks can cause disease in people. Only a very small number of these actually carry disease.

Usually the risk of such diseases often goes down right after a flood. This risk may go up in later months or years.

The table below shows when and where diseases from tick or mosquito bites are most common in Minnesota.






West Nile virus


Western MN farm country

La Crosse encephalitis

Southeast MN wooded areas


Lyme disease

May - July

Wooded parts east-central, central, and southeastern MN

Human anaplasmosis

To protect against bites:

  • Wear insect repellent;
  • Wear long sleeve shirts and pants -- light colors reduce mosquito and black fly bites and make it easier to see ticks;
  • Avoid outdoor activity at peak mosquito feeding times (dawn and dusk);
  • Remove containers that hold water (buckets, tires, etc.) from your property.

Safe and effective insect repellent may contain:

  • Up to 30 percent DEET;
  • Picaridin, oil of lemon eucalyptus, or IR3535 can protect against mosquitoes; and
  • Permethrin can be used on clothing (not skin) to kill mosquitoes and ticks.

For best results and safety, always follow the label directions.

More Detailed Fact Sheets

Updated Monday, March 30, 2015 at 10:06AM