Mosquitoes: A Bad Summer Buzz

Mosquitoes are both a nuisance pest and a health pest. Mosquitoes are known as the deadliest animal on earth due to the ability of some mosquitoes to transmit diseases like malaria, dengue fever, yellow fever, encephalitis, and West Nile virus (WNV). Mosquitoes feed on a variety of hosts, and the diseases they are able to transmit are specific to the type/species of mosquito.

culex mosquito JAK806
Culex mosquitoes transmit West Nile virus. (Photo: Jim Kalisch)

There are 50 species of mosquitoes in Nebraska, but only half of these feed on human blood. Male and female mosquitoes feed on plant nectar for nutrients, but the female mosquito requires a blood meal in order to produce eggs. So, if you hear that bad buzz in your ear, that’s her, and she’s out for blood.

The female mosquito lays its eggs on the surface of water, and the larval and pupal stages are aquatic. Mosquitoes breed in the smallest amount of water, which may include water collected or pooled in containers, dog bowls, planters, saucers, tires, bird baths, puddles, pools, and toys in the landscape. Adult mosquitoes are mobile and fly in from neighboring properties to bite humans and animals. They rest during the day in dark and shaded places such as flowering vegetation, tree canopies, bushes, under decks, and on structures.

Should we be worried about mosquito-borne disease in Nebraska?

In 2018, Nebraska had the highest number of human cases of WNV in the United States and the second highest number of deaths. The majority of cases occurred in eastern Nebraska. The symptoms of WNV can vary from having no symptoms at all, to flu-like symptoms and fever, to severe neurological damage, to serious fatal illness. WNV is spread by the Culex species, which are common blood feeders in the Midwest.

According to the CDC, there is no data to suggest that COVID-19 or other similar coronaviruses are spread by mosquitoes.

What can we do to reduce the number of mosquitoes and prevent mosquito bites this summer?

  • Dump standing water every five days so eggs do not have time to hatch.
  • Use EPA-approved repellents on skin. These include DEET, picaridin, oil of lemon eucalyptus, and IR3535® so adult mosquitoes cannot detect you.
  • Wear permethrin treated clothing. These are sold commercially but can also be fabricated with a DIY spray.
  • Fix and repair window and door screens to keep mosquitoes out of the home.
  • Avoid outdoor activities during peak mosquito times, such as dawn and dusk, to reduce exposure.
  • Wear light colored, loose fitting clothing because mosquitoes prefer dark colors and can bite through fabric.
  • Use an oscillating fan when sitting on an outdoor patio or deck to deter mosquitoes from landing.

Will chemical treatments to the yard by professional companies reduce mosquitoes in my landscape?

Some professional companies may have fogging, misting, and blowing equipment to apply residual insecticide (usually synthetic pyrethroids) to places where adult mosquitoes may contact and acquire a lethal dose. Chemical treatments alone will offer only a temporary relief; therefore, it is important to also focus on breeding site and harborage removal to provide long-term efficacy. Understand that the application of broad spectrum insecticides may not only reduce the mosquito population but may also harm pollinators and beneficial insects.

What can be done to bodies of water that cannot be emptied frequently?

When water cannot be dumped, Mosquito Dunks® can be dissolved in standing water such as troughs, fishponds, rain barrels, and birdbaths. Mosquito Dunks® contain the active ingredient,  Bacillus thurengiensis israelensis (Bti), a bacterium that is toxic to mosquito larvae when consumed and stops larvae from developing into biting adults. Bti is non-toxic to humans, pets, pollinators, fish, and other wildlife. They are effective immediately and can last for a month.

Why are there so many different mosquito repellents to choose from?

There are hundreds of products sold for mosquito control, but not all are equal in their ability to prevent bites. Products that have an EPA registration number on the label were evaluated against the pests listed on the label and shown to be effective and safe when applied according to the label. Products that lack an EPA registration number and marketed as “natural” may provide little to no protection at all.

Repellents work by preventing mosquitoes from detecting and biting people. Coverage on exposed skin must be thorough and can be accomplished using different application methods such as aerosol sprays, pump sprays, skin wipes, and lotions. The concentration level (which ranges from 5–100%) indicates the hours of protection before reapplication.

Insect Repellents

More tips about insect repellents:

  • Higher percentages allow for longer protection, but it’s suggested to only apply to skin the percentage needed.
  • High percentages of DEET (98%) will dissolve plastics, so be aware using around watches, cameras, sunglasses, and other plastic objects.
  • Be careful spraying aerosols near eyes and faces.
  • Use lower percentages on children, and reapply if necessary.
  • Do not apply to young children’s hands.
  • Creams and liquids can provide better application coverage.
  • Wipes are a good option when traveling because they are lightweight and not dispensed as a liquid or aerosol.
  • If also applying sunscreen, apply sunscreen first, and then insect repellent.
  • Apply to skin but not skin under clothing.

What about other devices marketed for mosquito control?

Sorry, but bracelets, citronella candles, essential oils, planting certain herbs or plants, and clip on fans do not work at preventing mosquito bites. Neither does drinking beer, installing bug zappers, eating certain foods, taking vitamin B, or using smart phone apps or plug-in ultrasonic devices.

However, Thermacell® is a battery-operated, portable device used outdoors to repel mosquitoes. It uses a butane cartridge that heats a chemical treated repellent mat that keeps mosquitoes out the area for a number of hours. The active ingredient is allethrin. From reviews, it seems to be an effective product for people who are outdoors for long periods of time, but know that it requires insecticide refills and a power source.

What about natural repellents that are plant based?

There is a misconception that natural products are “safe” when compared to long-established synthetic repellents. Natural does not equal safe. There is much to be considered when using plant-based substances as repellents, like human safety, protection from bites of the mosquito species, and environmental sustainability. Many of the “pure” essential oils are highly volatile, may cause skin irritations, and leave wearers unprotected. Essential oils have not been rigorously tested and, therefore, should be used with caution.

Insect repellents that have the active ingredient oil of lemon eucalyptus is derived from the leaves of the lemon eucalyptus tree. Its synthesized, chemical name is p-menthane-3,8-diol or PMD. It offers up to 6 hours of protection but is not recommended for children under 3 years of age. It is not the same as lemon eucalyptus essential oil, which has not been validated for safety and efficacy, and is not registered with the EPA as an insect repellent. Similarly, plants in pots or in the garden like lemon grass or citronella grass are unlikely to provide protection from mosquitoes.

In comparison to natural products, DEET has undergone stringent testing and has a good safety profile. DEET inhibits the mosquito’s response to human odor and has been used as an effective insect repellent since 1946. DEET products can be used safely on children, pregnant woman, and lactating women. As long as it is used safely (according to the label instructions) and not swallowed or rubbed into the mucous membranes, it does not cause adverse effects.

Is the permethrin clothing spray the same permethrin found in my home and garden products? 

Permethrin is a synthetic pyrethroid used as a contact insecticide and repellent against a wide variety of arthropods. It is not safe for use on skin but can be sprayed onto clothing and should be allowed to dry. It then remains effective against mosquitoes (and ticks) through multiple washings. It is a good idea to treat clothes, socks, shoes, backpacks, and other gear before outdoor activities. There are also commercial, pre-treated clothing that can be purchased that are designed to repel biting pests for up to 70 washes. Again, this is another tool in our toolbox to fight against the bite, but please continue to follow an integrated approach to preventing mosquito bites this summer.

Resources:

Jody Green
Extension Urban Entomologist at Nebraska Extension
Jody Green is the extension urban entomologist at Nebraska Extension in Douglas-Sarpy Counties. She specializes in structural, household, and health-related insect pests.
Jody Green on LinkedinJody Green on Twitter

Leave a Reply

This site uses Akismet to reduce spam. Learn how your comment data is processed.