Volume 20 / April 2011

Long-Term Project Seeks To Build Guidelines for Area-Wide Asian Tiger Mosquito Control

*Originally published in Fall 2010

A long-term project to determine the best methods of controlling Aedes albopictus, the Asian tiger mosquito, is in the third of at least five years of intensive study, combining work by staff at Rutgers University’s Center for Vector Biology with field efforts by Mercer and Monmouth county mosquito control districts in New Jersey.

The project – titled “Area-Wide Management of the Asian Tiger Mosquito” – is funded through a cooperative agreement from the U.S. Department of Agriculture, according to Dr. Dina Fonseca, a Rutgers researcher who is serving as principal investigator.

Mercer County
An employee with Mercer County Mosquito Control uses a backpack sprayer to apply larvicide to a favorite habitat of Aedes albopictus – discarded tires.

“Our objective is to establish a set of operational guidelines that will enable control of the Asian tiger mosquito over a large area, beyond a single township or community,” Fonseca explained. “We are working closely with Dr. Gary Clark of the USDA’s Agricultural Research Service. The concept has been tested under similar USDA programs with plant pests such as leafy spurge. But this is the first area-wide project on mosquitoes.”

“Most Annoying Mosquito”

Fonseca said the project is designed to test the efficacy and economics of public education, source reduction, and a variety of insecticide application techniques. The project target, Ae. albopictus, is a recent arrival in New Jersey, Fonseca said. “The Asian tiger mosquito was detected here in 1995, but populations have exploded in the past five years,” she said.

“While it can be a vector of diseases, such as dengue fever and chikungunya virus and even West Nile virus, in most of our situations it’s a nuisance pest. It’s a relentless, daybiting mosquito, and it literally prevents people from being outdoors in their gardens and yards. It has become our most annoying mosquito.”

The mosquito’s larval habitats make control challenging. The pest will lay eggs above water that collects in any small container, from bottle caps to children’s toys, and tree holes. And in warm conditions, the time span from egg to larva to flying adult can be as brief as seven days.

There is good news for the people of New Jersey, however. The state has 21 mosquito control programs, most of which were formed to deal with salt marsh mosquitoes that inhabit the Atlantic coast. The districts have been in business for many decades, so the staffs have the experience and equipment to implement a full range of control techniques.

Multi-Year Project

Fonseca and her cooperators initiated the area-wide project in 2008. The objective was first to identify groups of 1,000 homes (a site) in each county with similar characteristics so they could be used as comparisons. They initially identified a dozen or so potential sites, then narrowed that group to three in each county through intensive surveillance throughout the active season. They also characterized each site for the residents’ socioeconomic and education levels.

In 2009, the project moved to conducting control in the field. In each county, one site was the control, with no project-specific mosquito control measures planned against Ae. albopictus. In the second site, residents and schoolchildren were educated and encouraged to reduce mosquito populations in their

own backyards. The third site included full intervention, with various integrated pest management  approaches undertaken to control the Asian tiger mosquito, as well as education efforts.

Ary Farajollahi, superintendent of Mercer County Mosquito Control, and Sean Healy, entomologist in Monmouth County, are in charge of the project’s mosquito control interventions.

Education Tested, Enhanced

In 2009, the education efforts focused on elementary schools serving children who live in the study sites. Working with a curriculum developed by Rutgers faculty, teachers were trained and children were engaged to learn about mosquito biology and source reduction. A door-to-door brochure distribution campaign also was implemented, a standard technique.

But the education investment fell short when it came to immediate results. “In 20 years, those students will probably be very aware of mosquito control, but the work didn’t translate into actual reductions now,” Fonseca said.

“Instead, in 2010, the education efforts relied more on ‘active’ teaching,” she explained. “For example, a group of AmeriCorps volunteers worked side-by-side with Drs. Kristen Bartlett-Healy and George Hamilton, going door-to-door engaging the residents, providing information, examples, and guidance regarding source reduction. The preliminary results so far are encouraging.”

IPM Tactics Evaluated

Similarly in 2009, Farajollahi’s and Healy’s staffs also tested an ambitious door-to-door inspection program in both Mercer and Monmouth counties.

“We went through every single home in the IPM site,” Farajollahi related. “We distributed educational material, we removed trash and debris where water collected. We also treated with larvicides where containers couldn’t be removed or emptied. Our last resource intervention was to use adulticides when Asian tiger mosquito populations exceeded our minimum threshold.”

But, in the end, door-to-door intervention “just wasn’t costeffective,” Farajollahi said.

In 2010, Farajollahi and Healy made a number of adjustments based on their project sites and previous experience.

In more densely populated Mercer County, Farajollahi’s crews did a single round of door-to-door inspections early in the season to get an “ant’s view” of the location and identify potential Asian tiger mosquito hot spots. Larvicides were applied with hand and backpack sprayers. When trap counts showed a mean of five adults per location, trucks equipped with ULV sprayers delivered adulticides.

Healy’s work in more suburban Monmouth County has been similar, but the lot size for each of the 1,000 homes is larger, so he has a much greater area to cover. That makes the work with truckmounted sprayers especially important. Both mosquito control programs are evaluating a number of novel larvicide application approaches to deal with their unique situations.

Adulticide applications provide only temporary relief against Asian tiger mosquitoes, so both counties are intensely evaluating an efficient and efficacious method of delivering a larvicide to container habitats. One such technique has been the application of VectoBac® WDG using truck-mounted and backpack sprayers within the treatment sites. The hope of the researchers is to quickly deliver a potent larvicide to larval habitats that are cryptic, numerous and mostly inaccessible.

Expansion in 2011

Fonseca said the trials will expand to the countywide level in 2011, and more experimentation will take place.

“We are starting to understand how the approaches to controlling the Asian tiger mosquito must be customized, just based on our experience in our trial sites samples,” she said. “For our guidelines to be useful on a regional or even statewide basis, there are many variables that will need careful consideration.”

One project component that will help is the economic analysis being performed by Don Shepard of Brandeis University. He is calculating costs for the various interventions, so districts will have a range for the investment each requires.

Shepard also is conducting mail and telephone surveys to ascertain how much citizens believe they currently pay for mosquito control; how much they value the service; and how much they spend on personal protection against the pests, including items such as backyard insecticides, citronella candles and other home remedies.

“At a time when our society is dealing with core issues, such as obesity, and we’re encouraging people to spend more time outside, pests such as the Asian tiger mosquito can have a negative effect on quality of life,” Fonseca said. “Our area-wide research project is designed to provide practical, adaptable guidelines that mosquito control districts can use to combat this pest.”