Mosquito Misting Concentrates
The chemical concentrate you choose to use in your mosquito misting system plays an important role in the effectiveness of the system, the cost of operating it, and the maintenance that will be required to keep the system operating reliably for a long time. There are also safety and environmental impact factors to consider in making a choice.
What are Misting Concentrates?
Misting concentrates are highly concentrated chemical formulations designed specifically for use in mosquito misting systems. These concentrates are heavily diluted with water in the misting unit, and the pump atomizes the diluted solution through nozzles. The mist spreads through the property and, depending on the active ingredients in the concentrate, kills or repels mosquitoes and other small flying insects.
The range of chemicals suitable for this application is relatively limited, and available formulations fall into two categories: Conventional Formulations and Green/Minimum Risk Formulations. The critical difference between these two categories is how they are regulated by the US Environmental Protection Agency (EPA) for safe use.
Conventional Mosquito Misting Concentrates
Conventional formulations contain ingredients that bring them under laws requiring their registration and approval by the EPA. To use a conventional product in a mosquito misting system, its label must include directions for use in an “automated residential misting system.” Only a few concentrates currently include this language.
The active ingredients in conventional concentrates are either natural pyrethrin or permethrin. These formulations also contain a synergist, piperonyl butoxide, which makes them more effective than they would otherwise be. While natural pyrethrin is derived from flowers, it is highly refined and shouldn’t be considered as natural or organic. Permethrin is a synthetic compound that is a close chemical cousin to pyrethrin.
Natural pyrethrin and permethrin are “adulticides”, which means they are toxic to adult insects. Their “mode of action” is to disrupt an adult insect’s nervous system and they kill mosquitoes and other small flying insects on contact at very low concentrations. These compounds are destroyed very quickly by ultraviolet light and do not have a residual effect.
Effectiveness
Conventional formulations are highly effective at reducing mosquito populations and they act very quickly. According to the EPA, “permethrin is the most widely used mosquito adulticide in the U.S and its widespread use can be attributed to its low cost, high effectiveness and low incidence of pest resistance.”
Cost
Generally, conventional misting concentrates are somewhat less expensive than their Green/Minimum Risk counterparts. This is due to their higher volume, lower cost of production and the need for less frequent applications because of their relatively higher effectiveness.
Within the conventional misting concentrates category, the formulations containing permethrin as their primary active ingredient are about half the cost of formulations containing natural pyrethrin, due to its natural botanical origin and expensive production cost.
Safety
The US EPA states they do not expect risks of concerns to humans when these conventional concentrates are used in misting systems according to their label. The labels include language that says people and pets should avoid the mist. And, misting cycles should be programmed so that the units don’t mist while people are likely to be exposed. For more information, see these Active Ingredient Safety Fact Sheets.
Environmental Factors
The active ingredients in conventional misting concentrates are low in toxicity to mammals and are practically non toxic to birds. However, they are toxic to beneficial insects like butterflies and bees. This usually does not present an issue since the ingredients degrade very rapidly and the units are typically programmed to mist around dusk and dawn and not in the middle of the day when the beneficials are present and active.
The ingredients are also toxic to fish, and you’ll see language on the formulation labels that restricts their use and defines setbacks around and over bodies of water – streams, rivers, ponds, lakes. To comply with the law, you must follow the label instructions explicitly.
Other Considerations
The best conventional misting concentrates have been designed for misting. They have been formulated to disperse evenly throughout the batch tank or drum when diluted with water and remain well mixed. And, because they are water-based and contain only trace amounts of hydrocarbons, they don’t damage components in the misting system and or cause plant burn.
There are also other concentrates on the market that were originally formulated for other uses but have EPA approved misting language on the label. They usually contain more hydrocarbons and can burn plants more readily and damage some of the components in the misting system. You should avoid using these. Please see MistAway’s list of conventional formulations that we have approved for use in our systems.
“Green”/Minimum Risk Misting Concentrates
The ingredients in Green/Minimum Risk formulations come from a list of materials that the EPA considers to pose little to no risk to human health or the environment. These formulations do not require registration and are not otherwise regulated by the EPA.
Generally, these “green” formulations comprise a number of essential oils from plants. The most commonly used oils include:
- lemongrass
- wintergreen
- rosemary
- thyme
- clove
- sesame
- cedar wood
- castor beans
Other common ingredients are geraniol, itself a component of many essential oils, and sodium lauryl sulfate.
In contrast to active ingredients in conventional concentrates, where the “mode of action” is well established, how these plant oils work to either kill or repel insects is not as well studied or understood.
Lemongrass is thought to disrupt an insect’s nervous system, leading to paralysis and death, and it also masks scents that attract insects, serving as a repellent.
Wintergreen oil is known mostly for its repellent properties.
Sesame oil is thought to have synergistic effects when combined with other oils.
Sodium Lauryl Sulfate acts as a surfactant that compromises the cell membranes of insects.
Effectiveness
In misting, it is believed that these formulations control mosquitoes by repelling them from the property more than killing them, but that has not been scientifically established. Their effectiveness is more short-lived than with conventional concentrates, more variable and more influenced by environmental conditions like wind and rain.
Cost
In addition to being more costly than conventional concentrates because of their natural origin, Green formulations often require more frequent reapplication to maintain effectiveness, which also increases the relative cost of applying them.
Safety
The essential oils in green concentrates are generally regarded as safer for humans, pets and wildlife than the active ingredients in conventional concentrates. They may also be less likely to trigger allergies or other health issues associated with chemical sensitivities.
Environmental Factors
To the extent that green formulations act more to repel insects rather than kill them, there is less risk to beneficial insects, like bees and butterflies.
Other Considerations
Most of the green misting concentrates contain a significant percentage of essential oils. These oils must be “emulsified” by other inert ingredients in the formulation to prevent the oil from separating while it is in the bottle of concentrate or when it is diluted with water prior to misting.
In many of the commercially available green concentrates, the emulsification is inadequate and the oils separate, and even an energetic agitation cycle will not blend them. This characteristic makes them unfit for use in mosquito misting.
Further, many essential oils are notoriously chemically aggressive to plastics. This means the dilute mist containing these oils has the potential to damage plastic surfaces that it contacts, like lawn furniture and clear coat on a fiberglass boat. Their use also significantly increases the potential for failure of the components in the misting system. This is particularly true in the Gen 3 tankless unit, which handles the formulation in its concentrated form.
The good news is that we are seeing progress in both effectiveness and suitability for misting among green/minimum risk formulations. So, we are hopeful that green formulations will win a substantial share of the market someday.
There are a few Green/Minimum Risk concentrates that we recommend on this basis. Please see MistAway’s list of green formulations we have approved for use in our systems.