Along with the warm climates come some unwanted guests, or should we say pests? Mosquitoes present not just an annoying aspect of spring and summer, but pose potential health risks as well. As residents and managers, how can our communities strike a balance between harmful pests and potentially harmful control solutions?
Mick Ribault, founder and president of Dragonfly Pond Works, an environmental service company in Apex North Carolina specializing in lake and pond management, working on lakes, retention ponds, wetlands, and other types of storm water, has found a safe and effective solution for managing pesky mosquitoes. "Biological control," as Ribault has termed it, uses dragonfly larvae to control mosquitoes from their earliest breeding phases, as a single dragonfly can eat several dozen to several hundred mosquitoes every day.
"Most people don't know that dragonflies are predators with an unbelievable drive for catching their prey," said Ribault. "They fly there and a half times faster, using their feet to grab the insects they are hunting." A Harvard University study ("Dragonflies: The Flying Aces of the Insect World," Science Nation, October 3, 2011) found that dragonflies were so efficient in their hunting that they caught 90 to 95 percent of the prey released into a test enclosure.
According to Ribault, recently, their flying patterns and ability to hover mid-air have been studied for drone designs. it is surprising to note, however, that dragonflies are only alive in their flying state for a short amount of time. In reality, most of their lives are actually spent in water in a larva phase. This period can range from six months to about two years.
While in larva form, dragonflies are still active predators. This is very effective because mosquitoes also breed in water, meaning that dragonfly larva can actually prey on mosquito larva.
"When we first began looking in to this control method, we researched a program out of Scarborough, Maine," said Ribault about how they developed this technique. "They had been doing it for years - essentially providing thousands of dragonfly larvae to anyone in the community with standing water and it lead to significant reduction in the mosquito population," he said.
What is the process of biological control? The process begins in a consultative fashion, where Ribault and his team make sure their client's ponds have the necessary habitat to enable the dragonfly larvae population to flourish.
The proper habitat includes beneficial plants along the shoreline. "There are three or four native plants which can be very useful - pickerel weed, aquatic irises, and rushes," Ribault said, "it's important that they are present at the water's edge for two reasons. First, they shelter dragonflies from their predators, and second, they need foliage to climb onto when they hatch." Sterile ponds, such as a maintained golf course, are not a successful environment for breeding larvae.
initially, the team may also need to get rid of invasive weeds, replace them with the beneficial plant life, remove debris, and get a habitat established as the plants root in. Because of what this process entails, in total, it takes two to three years to notice a real transformation.
"People want the quick fix but often the right solution takes longer, it's really a multi-year process," Ribault explained. "You really do not want to hire a regular mosquito spray company because a lot of the products they use are not registered by the Environmental Protection Agency (EPA) for aquatic use."
What type of maintenance is required? Once the proper environment has been put in place, clients are set up with a maintenance program that monitors existing conditions. "Sometimes, people forget that a little piece of trash in the pond is a great place for mosquitoes to breed. 'Container mosquitoes' can even find breeding areas in old tires and cups," said Ribault, " and algae can also be problematic since mosquitoes can breed right on the surface, so it will need to be removed as well."
All of these components are important to consider for successful integrated pest management. Since cost is a prominent factor, in deciding if this service is right for your property, it is important to keep in mind that it can cost a few hundred, to several thousand dollars for something more substantial, just to bring a pond up to speed. The maintenance costs can range from $150 per month to several thousand depending on the scope and size of the area.
Is the Zika Virus a factor in this process? Ribault said that his company has witnessed a steady increase in the demand for their service involving dragonfly larvae, almost three to four requests per week, which seems to correlate to the public's heightened interest in the Zika Virus.
The Zika Virus, which is a virus transmitted to humans by mosquitoes, cannot in face be passed from mosquitoes to other insects, according to the Center for Disease Control (CDC). If that were not the case, however, it appears there would still be a limited risk in the transference of the virus from dragonflies to humans, since dragonflies do not bite.
What are some other biological methods of mosquito prevention? There are a few other methods of handling mosquitoes. "Minnows and mosquito fish are also natural predators of mosquitoes, and their presence in the aquatic area can add to the success of eliminating pests. Fountain and aeration systems can be helpful in agitating the water, which creates a less hospitable place for mosquitoes to live," Ribault added, "likewise, if there is evidence of mosquito larvae in ponds and lakes, BTi, a group of bacteria that targets mosquito larvae can be added to the water.
Any other advice? Ribault, whose passion for plants and aquatic management is evident, advised that ponds usually get a bad reputation, but a lot of communities forget or neglect other areas, such as wooded locations, gutters, drains, flower pots, buckets, and kid's toys. In reality, if there is stagnant water, those places are prime breeding grounds for mosquitoes he noted.
While the process is an efficient way to control a problem, at the end of the day, Ribault is looking to create a sanctuary where communities are able to enjoy being outdoors.
*Article courtesy of CAI-SC Palmetto Communities, Issue 4, 2016