VERO BEACH, Fla. --- At a time when the number of West Nile virus cases is setting new records, University of Florida researchers are developing an environmentally friendly way of controlling mosquitoes without pesticides.
The solution: a rugged little crustacean that wages war on mosquito larvae with an almost maniacal vengeance.
"We’re using a native organism to control mosquitoes when they breed in standing water, usually in ponds, tires and other open containers," said Jorge Rey, a professor of entomology with the University of Florida's Institute of Food and Agricultural Sciences.
"By adding tiny crustaceans called copepods to the water, we can kill mosquito larvae before they become adults that may spread West Nile and other diseases," he said. "Tests at our Florida Medical Entomology Laboratory in Vero Beach show that the copepods feed on mosquito larvae at an amazing rate, killing up to 90 percent of the larvae."
Rey said the copepod species he is testing, Macrocyclops albidus, is very aggressive toward its prey. In fact, the copepods will kill the mosquito larvae even when they are not looking for a meal.
"They will attack the larvae and maim it so it's not going to live and then drop it," he said. "We don’t know why they behave this way - it might be a reflex action or they’re just being mean."
Rey, who has been testing the copepods for almost two years in discarded tires and other containers, said they can survive year-round in any size body of fresh water. His research shows the copepods prefer young mosquito larvae, usually those not older than four days. But they will attack older larvae when the number of young larvae declines.
He said the copepod is native to Florida and common throughout the world. It poses no danger to people, animals or plants. However, they don't exist in every body of water and therefore would have to be introduced in order to be effective on a wide scale.
"Once the copepods become established, they reproduce in high numbers for effective natural or biocontrol of mosquito larvae," Rey said. "Copepods survive so well because they feed on a wide range of insect prey in the natural environment.
"Over the years, a variety of other biological control agents ranging from viruses to fish have been tried for mosquito control, but nothing seems to work as effectively as this microscopic natural predator," Rey said.
Current restrictions on pesticides, along with the growing problem of insect resistance to many chemicals, make biocontrols such as the copepod increasingly attractive, Rey said.
His research shows that the copepods are easy and inexpensive to raise and deliver to target areas. Large numbers of copepods can be reared in small plastic pools, plastic garbage cans and other inexpensive containers. The cultures do not need a lot of attention and are inexpensive to maintain. Copepods thrive in warm climates but can survive freezing temperatures for short periods. Pesticides commonly used for mosquito control do not kill the copepods.
Organisms to start the cultures can be collected in ponds and ditches and introduced into the containers with chlorine-free water. Wheat grains and Paramecium (naturally occurring microorganisms) can be used for food.
An instruction sheet for growing copepods is should be available from UF within a month. Information also can be obtained from local mosquito control offices.
He said more research is needed on ways to distribute the copepods in the environment for effective mosquito larvae control.
"Standard spray equipment can be easily modified to dispense copepods," Rey said. "Since they can withstand almost dry conditions, storage and transportation will not require large quantities of water."
He said biocontrol techniques, such as using copepods for controlling mosquito larvae, are attractive for developing countries where human resources usually are more available than money for expensive control alternatives.
