Mosquito Control

Mosquito populations in Iowa are determined primarily by the frequency and amount of rain that falls during the course of the spring, summer, and early fall.  Mosquitoes have a complete life cycle of four stages: Egg > Larva > Pupa > Adult.  The first three stages occur in standing water.  The eggs hatch when exposed to water; the larvae ("wrigglers") feed and grow in water; pupae ("tumblers") remain in the water while they transform to the flying adult. The life cycle typically takes up two weeks, but may take as little as a week or as long as a month.  There can be several generations of mosquitoes each summer.  “Mosquito season” generally lasts from May through September in Iowa. 

Only female mosquitoes bite and feed on the blood of humans or other animals.  Blood provides the nutrition the female needs to produce eggs to produce offspring of the next generation. 

Mosquito Management in the Home Landscape

Individual efforts to reduce the number of mosquitoes on your property may provide limited, short-term benefit. Even if you eliminate all mosquito breeding on your premises you may not see a reduction in mosquito numbers or biting activity. Mosquitoes have no respect for property lines and can fly several miles from where they developed and migrate into your backyard from adjacent areas.

Eliminate or Treat Standing Water

To reduce mosquitoes developing on your property eliminate all possible standing water sources in which mosquitoes could breed.  Eliminate and dispose of cans, tires, and other objects that could hold water.  Repair clogged rain gutters, and turn over toys, buckets, bins and other items that catch water.  Drain, fill or ditch low-lying areas that hold water for several days following a rain.

Temporary or permanent water impoundments that can't be eliminated should be inspected weekly for the presence of developing mosquito larvae. If mosquito larvae are found and cannot be physically removed, consider treating the standing water with a mosquito larvicide.  Before applying any insecticide to a body of water determine there are enough mosquito larvae present to warrant an application.  Ponds that have steep banks, are relatively free of organic matter, and have little or no vegetation extending into the edge of the pond produce very few mosquitoes compared to shallow marshy areas can serve as a breeding area for tremendous numbers of mosquitoes.

Products suggested for homeowners will contain the insect growth regulator methoprene or the bacterium specific to mosquito larvae, Bacillus thuringiensis israelensis (Bti).  When used according to label directions, these products will effectively control mosquitoes and are harmless to humans, pets, fish, and other types of wildlife.  Some insecticide cannot be applied to water containing fish or other aquatic wildlife.  Read and follow label directions. 

Mosquitoes and flooding are closely linked.  Flooding per se, does not lead to mosquitoes. It is the water that stands AFTER the flooding that creates opportunities for mosquitoes to breed. Mosquito larvae require standing, stagnant water in which to feed and grow (mosquito larvae do not live in running water). It takes 7 to 10 days of standing water for the mosquitoes to develop, which is why we see mosquitoes after the flood rather than during. It is difficult to control mosquitoes in these situations as the amount of standing water is typically extensive and cannot be effectively drained or treated.

Sprays and Fogs

Sprays and fogs applied to control mosquito adults (adulticides) are best suited for communities or large areas. Homeowner sprays and fogs are generally short-term in their effectiveness and have little benefit in reducing adult mosquitoes for an extended period of time.  Treatments you apply in your backyard may provide temporary relief from biting mosquitoes.  For a party or special event, treating mosquitoes makes sense.  As a long term strategy it is not effective.  Treatment will not last more than a day or two because of migration, so treatment should be applied the day before the event (or the morning of for a late afternoon activity).

Homeowner options for treatment include ready-to-use aerosol, fogger, garden sprayer, or hose-end applicator.   Insecticide sprays for mosquitoes should be directed to tall grass, flower beds and shrubs, underside of the deck and other areas where mosquitoes rest.  Treatment may reduce adult mosquitoes for a day or two (such as the day before a backyard picnic or family gathering). 

With all lawn and garden insecticides, the minimum re-entry interval is “after the spray has dried.”  Time required to dry depends on humidity and moisture at the time of application and may vary from minutes to hours to overnight, depending on conditions.  Check for reentry statements and other restrictions on the pesticide label and remember to read and follow label directions.

Mosquito Repellent Plants

While several plants such as scented geranium, lemon thyme, citronella grass, and "citrosa" are touted to repel mosquitoes.  These plants are ineffective as repellents.  While some of these plants contain chemicals that have been show to have some repellent properties (citronella grass produces the citronella oil used in mosquito-repelling candles, for example), these benefits are only realized when the plant is crushed to release the oils.  A plant just sitting on the patio has no effect on mosquitoes in the area.  A pile of damaged leaves sitting on a table is not terribly effective either.  The likely best way to use these plants as repellent is to crush up some leaves and rub the oil on your skin (checking to be sure you are not allergic first, of course).  This will provide some benefit, but only at a fraction of the rate as products developed and used as repellents (such as DEET). 

Use Repellents

The practical alternative for dealing with mosquitoes is to avoid outdoor activity during peak mosquito activity times (one hour before until one hour after sundown), wear light color and loose-fitting clothing, and use personal repellents for short-term protection against mosquito biting. 

Pick the repellent ingredient with a low to moderate concentration of active ingredient that best meets your needs.  Use repellent sparingly to reduce unnecessary or excessive exposure and don’t apply repellent near eyes, on lips, or on broken skin.  Apply to your face by spraying your palm and then spreading the repellent carefully.  Don’t use near food.  Wash repellent off with soap and water when it’s no longer needed.  See the CDC website for more information on repellents.


A Summary of What Works (and What Doesn't!)

Here is a list of alleged mosquito bite preventions that don’t work: 

  • Citronella candles.  (Standing directly in the smoke reduces biting by approximately 40% while dispersed smoke is of no benefit.)
  • Mosquito repellent plant.   (Little if any Citronella is released by a stationary plant; leaves would have to be crushed to release the repellent.)
  • Purple martins. (Mosquitoes are insignificant in their diet.)
  • Bats.  (Bats eat a wide and varied diet of moths, beetles, gnats, mosquitoes and others.)
  • Ultraviolet or black lights “bug zappers.” (More beneficial insects than biting pests are caught.)
  • Sonic devices, including cell phone apps and other electronic mosquito repellents that allege to produce high-pitched sounds that mosquitoes don't like.
  • Dish washing detergent in a pan of water. (while soapy water would kill any insect that gets submerged in it, a small pan of soapy water does not attract enough mosquitoes to have an effect on the population)
  • Listerine or other mouthwashes.  (some of these mouthwashes contain eucalyptol - which has some affect on mosquitoes when sprayed at a concentration of 75%.  Mouthwashes have less than 1% eucalyptol.)
  • Vitamin B, garlic, pepper and other dietary supplements.  (No research evidence of effectiveness.)

What does work?

  • Avoid outdoor activity during peak mosquito activity times: one hour before until one hour after sundown.
  • Wear light color and loose fitting clothing
  • Use personal repellents with a low to moderate concentration of active ingredient.  See the CDC website on repellents.
  • Use repellent sparingly to reduce unnecessary or excessive exposure.
  • Don’t apply repellent near eyes, on lips, or on broken skin
  • Apply to your face by spraying your palm and then spreading the repellent carefully
  • Don’t use near food
  • Wash repellent off with soap and water when it’s no longer needed.
Last reviewed:
January 2025

Links to this article are strongly encouraged, and this article may be republished without further permission if published as written and if credit is given to the author, Yard and Garden, and Iowa State University Extension and Outreach. If this article is to be used in any other manner, permission from the author is required. This article was originally published on September 1, 2016. The information contained within may not be the most current and accurate depending on when it is accessed.