- May 6, 2016
All week you’ve been anticipating your Friday afternoon porch-party. Cold drinks, warm sunshine, and the promise of an evening of relaxation outside. Then, you hear them. The high-pitched zzzzzz hovering around your heads. Soon, people are juggling their drinks in one hand while swatting away the pesky, female, blood-suckers with the other–and, the party moves inside. As a result of new concerns about mosquito-borne illnesses many people are thinking about how to manage their yards to discourage these visitors. Read-on for our wildlife-friendly tips for reducing mosquitoes in yards.
Our yards can unknowingly be havens for breeding mosquitoes. These insects are members of Diptera, the true flies, and are principally nectar consumers. Only the females require a blood-meal as a source of protein and iron to support egg-laying.
Averaging 2-10 millimeters long, these tiny insects are not only annoying, they are responsible for transmitting diseases, like the Zika virus now known to cause neurological disorders, as well as Dengue fever, West Nile virus, various types of encephalitis, Chikungunya virus, dog heartworm, and malaria. Zika is not a new virus (it was first discovered in Africa in the 1940s). In Africa, small outbreaks, in localized areas allowed immunity to develop over time. Reactions to the virus in such places are typically minor rashes accompanied by a fever.
No one knows for sure why Zika is currently spreading so aggressively. Until now, the virus has received little attention or research. What is known, is more than 4,000 cases of a rare birth defect, microcephaly, have been reported in Brazil. This condition has been thought to be linked to mother’s exposure to Zika during gestation, however, definitive scientific research is still underway. There is a growing evidence that this outbreak is spreading much further than Brazil. According to the Center for Disease Control (map above), current active transmission is projected to impact areas in South America, Central America, Mexico and the Caribbean. In our globalized society, however, where people are constantly traveling, it is likely that Zika will be seen in many places, even those not identified in the map above.
In North America, the two non-native mosquitoes carrying Zika virus are–Aedes aegypti (Yellow fever mosquito) and Aedes albopictus (Asian tiger mosquito). These insects live only two to five weeks but can lay up to five batches of 200 eggs. Quick math: one female mosquito can lay upwards of 1000 eggs during its short life-cycle. Multiply that by the millions of mosquitoes that fly the friendly-summer-skies and it is easy to see how our yards can quickly become infested.
So, what do we do? The best bet is to understand their ecology and minimize their breeding habitat–STANDING WATER. Mosquitoes require very little water to lay their eggs. Even just a single cup of water in a plastic container, or a wet spot on a lawn lasting a single week will suffice.
Perform regular scans of your yard to make sure there is NO standing water. This includes tarps where rainwater has collected, clogged rain gutters, buckets, unmanaged birdbaths, old tires, planters, pet dishes, kiddy pools, cans or bottles. Mosquitoes need about one week to complete their lifecycle.
If you want to keep your birdbaths make sure to change the water every one to two days to disrupt the mosquito’s lifecycle. When cleaning, make sure the puddle of water dries completely so the eggs and larvae are unable to survive. If you travel for more than four days, dump your birdbath water and turn it upside-down.
If you have a rain barrel on your property, make sure it is completely covered. Or, if it is an open-top model, cover it with a fine mesh top to deter the mosquitoes from laying their eggs. The risk of rain barrels breeding mosquitoes is further reduced if they are emptied weekly to water surrounding vegetation.
Protect Yourself from Mosquito Bites
The earlier in the lifecycle you can disrupt fast-breeding mosquitoes, the better. Although it seems counter intuitive after all our talk about minimizing standing water, one habitat feature to consider installing is a small pond. The trick to using ponds to fight mosquitoes is keeping the pond a healthy, balanced ecosystem with an active predator community. Many pond-dwellers, like dragonflies, damselflies, and diving beetles are voracious mosquito hunters. Ponds do not even need to be deep to be effective. A foot of water, with emergent, submerged, and floating native vegetation will attract egg-laying dragonfly and damselflies. Adults hunt adults in the air, while larva hunt larva in the water.
The nymph stage of these insects looks like a creature out of a sci-fiction movie. Depending on the species of dragonfly they will live in ponds between two to five years before emerging and metamorphosing into adults. While minimal research has been done to quantify the effectiveness of using dragonfly nymphs to control mosquito populations in real-life conditions , we know from laboratory studies that a single dragonfly nymph can consume +/- 133 larvae in a 24 hour period.open_in_new
Ponds also provide crucial habitat for salamanders, frogs, and other amphibians which face population declines due, in part, to reduced habitat. Installing a pond is a great way to provide them with a home, while also controlling for mosquitoes. Both adult and immature amphibians will eat mosquito larvae. In the photo above, this unlucky frog is a mosquito victim, mammals are not the only source of protein treats. Those mosquitoes better watch out for that long-tongue.
There are many reasons to avoid adding non-native fish, like mosquito fish (Gambusia spp.), to a pond. As generalist consumers they will not only eat mosquito larva, but the egg and larval stages of other beneficial insects and amphibians (like frogs and dragonflies). In addition, fish produce nutrient-rich feces that can create problems for balancing the nitrogen-induced algal growth in ponds. Large patches of algae provides ideal mosquito-laying habitat.
Another addition to consider in a backyard water feature is a solar powered fountain or “waterfall”, like the one pictured above, to disturb the surface of the water. Mosquitoes need “still,” or “standing,” water surfaces for depositing their eggs. Any movement at all will discourage their laying activity.
Even with Zika concerns, broadly-applied pesticide applications are not recommended for killing unwanted pests in yards. Mosquitoes are very hard to effectively control as adults and applications often have far-reaching negative impacts, which our years of using DDT in the 1950s taught us. Amanda D. Rodewald, conservation scientist at the Lab of Ornithology, articulately reminds us of this in a recent article on the Zika scare, “…our health and well-being are inextricably linked to healthy, functioning ecosystems. We must acknowledge that rash decisions made with limited attention to the long-term are very likely to produce unintended and often undesirable outcomes.”
Instead, encourage various species of native-mosquito-consumers such as insect-eating birds, bats, damselflies, and dragonflies. Consider installing bat and nest boxes to attract resident populations. And, GET RID of any standing water.
Popular biological controls for mosquitoes include mosquito dunks. These use bacteria–Bacillus thuringiensis subsp. israelensis (Bti)–as a biological control. This bacteria is found to be lethal to mosquito larvae; but, open_in_newresearch has shown that it eventually creates a resistant population of mosquitoes. This means use of these biological controls are not an effective long-term management strategy.
Finally, how your neighbors manage their properties will influence the mosquito population on your property. Mosquitoes can travel anywhere from 300 feet to several miles depending on the species. Aedes albopictus (Asian tiger mosquito) (a species that carries Zika) will travel only 300 feet to lay its eggs. Focusing on nearby neighbors by sharing information and running local campaigns to remove areas of standing water might be an extremely effective way to minimize mosquitoes in your yard. In areas vulnerable to Zika outbreaks, this might be your best bet for protecting yourself and your community. Check-out this map to see if your community is susceptible to a Zika outbreak.
Completely eliminating mosquitoes from our properties is probably unrealistic, but with careful management decisions we can reduce populations and get back to raising our glasses at Friday afternoon parties. Incorporating some of these best-practices into your weekly yard maintenance is a good way to actively manage your risk and get back to enjoying those long summer nights.