County gets new tool to combat mosquitoes
Traps added to monitor pests
See Something. Say Something. Many people are familiar with the national campaign to raise public awareness of indicators of terrorism and to report suspicious activities and packages to state and local enforcement. However, the Calvert County Mosquito Control Division does not want residents to be alarmed by the new specialized mosquito traps sprinkled throughout county neighborhoods.
The ominous-looking, canister-shaped trap, with wires and a battery attached, is white or black and roughly the size of a 5-gallon bucket. Each trap is labeled “Calvert County Mosquito Control (410) 535-6924.” The trap, which poses no health threat to humans, is used to monitor adult mosquito populations.
“We have an integrated pest management program in place in the county to reduce the population of mosquitoes through education, biological and insecticide applications,” said Mosquito Control Supervisor William “Bill” Clay.
The program is consistently run the same way year after year, according to Clay, stressing the Zika virus has nothing to do with how the program operates. Zika has become a prominent threat in South America and can lead to birth defects in babies born to women who have been infected with the virus.
“We haven’t changed how we run it and there will be no diversion from the normal program until Zika is found in the county,” said Clay, who acknowledged the introduction of this new trap into his arsenal of monitoring tools to detect mosquitoes that could possibly carry the virus.
Clay said the most likely scenario for Zika in Calvert County is a travel case where someone goes out of the country, contracts the disease and then comes back. To date, there are no reported cases in Calvert County. However, according to the Centers for Disease Control and Prevention, as of June 22, there were 820 cases of Zika in the United States; 819 were travel cases. The other was lab-acquired.
While there are no known mosquitoes with the Zika virus in the U.S., the new traps, called the BG-Sentinel Biogents, are specially designed to catch two varieties of mosquitoes in Calverty County that are capable of carrying the Zika: Aedes aegypti and Aedes albopictus.
“They are container breeders. They came from southeast Asia originally and breed in bamboo stalks,” said Clay. “Once they came to this country they really adapted. They came into the country in used tires [with standing water in them].”
Traditionally used for research, the new traps lure those species of mosquitoes with three different types of bait to include chemicals, such as carbon dioxide, and the emission of non-toxic substances that mimic those released from the human body. A fan pulls the mosquitoes into a collection bag once they are near the trap.
Clay’s team will set up a trap after they have done a survey of a property, at the owner’s request, where they have found a lot of breeding sites. The trap is set normally for overnight. The next day, the team collects and analyzes the mosquitoes in the trap to determine their species.
“If we catch an aegypti, we have to turn that in to the state health department for testing for the [Zika] virus. We have not caught any aegypti this year,” said Clay. Any mosquitoes identified as a possible carrier of Zika must be reported and sent to the CDC.
In addition to aegypti and albopictus, there are 58 other species of mosquitoes in Calvert County. Most mosquitoes lay their eggs on or in water, in the form of a raft containing 100 to 400 eggs. Over the course of seven to 10 days, the eggs become larvae and then pupae before becoming adult mosquitoes.
One of the biological controls used by the pest management program is the introduction of the gambusia, or mosquitofish, into standing water, such as stormwater ponds or ornamental ponds. One adult mosquitofish will eat 100 mosquito larvae and pupae a day, before they have an opportunity to turn into adult mosquitoes, reported Clay. Mosquito Control Program offers the service free of charge to residents who request the fish.
An alternative method to curtail the mosquito population is the introduction of the chemical methroprene into water. The hormone kills mosquitoes in the water as they reach adulthood.
Another trap commonly used is the New Jersey Light Trap, which uses a 25-watt lightbulb and a fan to attract mosquitoes with no bait. In partnership with communities that request pest control services, the program runs an Ultra Low Volume Program, where volunteers run the traditional trap every week, which the team also collects and inspects to also determine species.
“Species tells us where to look,” said pest management technician Sonja Gatton. “If it is albopictus, we know we are looking for a container. If its a vexan, we know that’s gotta be down in a mud puddle in the woods.”
Gatton said education is part of the inspections the team conducts and that they make a point to let the property owners know the source of the mosquitoes and how to best mitigate the problem. Physical controls used by the program include eliminating breed- ing sites by simply removing the water.
“The water goes away — the larvae die and the adults that are left in the area are looking for that container to breed in,” Clay said.
The team also sprays communities after testing is done. Testing includes setting up the non-baited light trap. The number of female mosquitoes captured dictates whether spraying should be done.
Office assistant Barbara Carlough said there are 80 communities that currently pay for mosquito spraying services at an hourly rate through an agreement.
While mosquitoes are usually a problem in the county from late April to October, Clay and Carlough work year round to control the county’s mosquito population. During peak season, up to seven additional employees are added to the staff to do field inspections, set up traps, respond and mitigate mosquito infestation complaints and drive spray trucks.
County public information officer Angela Walters shared that public messages have gone out to residents to ensure the new traps are not perceived to be suspicious packages and to discourage residents from touching or disturbing the traps if they see them.
Pest management technician Sonja Gatton inspects under a microscope a frozen mosquito collected from traps set by the Calvert County Mosquito Control Program.
BG-Sentinel Biogents is the county Mosquito Control Division’s new specialized mosquito trap. The black and white canister-shaped trap is the size of a 5-gallon bucket, and has wires and a battery attached to run a fan. Each trap has three different types of bait specifically designed to catch the two varieties of mosquitoes in Calverty County that are capable of carrying the Zika virus: Aedes aegypti and Aedes albopictus. Each trap is labeled “Calvert County Mosquito Control (410) 535-6924.”
Dozens of mosquito larvae were scooped out of a standing bucket of water. The larvae will mature to become adult mosquitoes in a matter of days.
Mosquitoes lay on a freeze plate prior to examination in the Mosquito Control Program lab area. By determining the species, the program can determine the best way to abate them.