Mosquitoes Already??

by Barbara Sanders

Even though we have had a crazy wet, cold, snowy, late Spring, the mosquitoes are out buzzing our ears and are procreating en masse. You may even be seeing their larvae wiggling in standing water.

Mosquitoes spread diseases by biting a disease-infected animal or bird and them moving to another for more food. Zika virus is spread by the Aedes species which doesn’t live in Colorado. West Nile virus spreads by the mosquitoes of the Culex species which feed from the evenings until morning. They carry the virus after feeding on infected birds. The symptoms of a bite from a mosquito with WNV for humans may be mild but it is best to consult with a health care provider. Horses, however, are in more danger and should be vaccinated by a veterinarian.

First line of defense is to remove all standing water! After every rain! Buckets, pots, saucers, bird baths. And check any other standing water frequently for the wiggling larvae.  Also, the mosquitoes like dark shrubbery. You could trim back a bit or use a spray. More on that in a bit.

There are several ways to protect ourselves from mosquito bites. Repellents come in many formulations. The synthetic repellent called deet is the most studied and used for over 40 years. The plant derived repellents containing citronella and other essential oils are as effective as deet but must be applied more often. Products containing permethrin as the active ingredient (an insecticide having some repellent properties) may be applied to clothing but not to skin. There are also devices using ultraviolet light, CO2, or an attractant. I call them “Bug zappers”, not terribly effective and they also kill a lot of beneficial insects.

Recommended products to kill the mosquitoes can be divided into two main groups: Larvicides and Adulticides. The first, Larvicides, eliminate the larvae before they emerge from the water as adults. These work on bird baths, ponds, water features, stock tanks and areas of standing water. The safest contain Bacillus thuringiensis israelensis known as Bti: Aquabac, Vectobac (which can be mixed in a sprayer), Mosquito Dunks, and Mosquito Bits (which can be broadcast). I love the dunks because they are easily found in stores and online. They are safe around pets, children, fish and birds.

Adulticides kill the adult mosquitoes. They are not very long lived but work well before an outdoor function in the evening and in the dark shrubbery where the mosquitoes will rest between bites. Look for products containing Permethrin: Safer Mosquito control, Raid Yard Guard, Ortho Outdoor Insect Fogger, and others. 

More questions may be answered by visiting the website https://extension.colostate.edu/mosquito-management/.  The website has a wealth of information as we are thawing out and are in our yards and gardens.

Barbara Sanders, Colorado Master Gardener since 1998.