Ample Rains Send Mosquito Numbers Soaring
Rid Yard of Standing Water to Keep Populations Under Control
Jul 20, 2009
Although substantial rains subsided by mid-July, mosquitoes are reaping the benefits from wet spring and early summer periods, said Dave Smitley, professor of entomology at Michigan State University. “I’d considered last year one of the worst in my locale in the past decade, but this year has probably equaled that,’’ he said.
Rains Breed Mosquitoes
Plentiful rainfall both induced hatching and sustained larval habitats, Smitley explained.
Conditions have been ideal for broods of summer floodwater mosquitoes, which have joined the ranks of mosquito populations that hatched in spring.
Of particular nuisance is the mosquito called A. trivittatus. It is a small, aggressive insect that bites during the day and often attacks in swarms.
Floodwater mosquitoes are unique in that populations can hatch from eggs laid several years ago.
“Think of them as mosquito ‘seeds,’’’ Smitley said. “The eggs are laid in depressions that may not hold standing water every year. When we get large rain events in the summer, these habitats produce mosquitoes from the “seed bank” to add to the normal background populations.’’
Humans, Pets at Risk
Late summer is typically when populations of Culex mosquitoes begin to peak. The Culex is responsible for spreading West Nile Virus and more likely to feed on humans during this period.
Humans aren’t the only ones bothered by mosquitoes. Cats and dogs are at risk for heartworm, a parasite transmitted by the bite of an infected mosquito.
Heartworm cases are on the rise throughout the U.S., according to the American Heartworm Society. Once a pet is infected, the microscopic young heartworms mature into adult heartworms in approximately six months, damaging blood vessels and reducing the heart’s pumping ability.
Fighting Back
Reducing mosquito habitat is integral to keeping populations in check. Mosquito larvae develop in standing water, so empty children’s swimming pools, birdbaths and fountains at least once a week.
One way to kill mosquito larvae before they hatch into disease-spreading adults is to use Mosquito Dunks, a commercially available product containing a natural bacterium fatal to mosquito larvae.
Mosquito Dunks®, a registered trademark of Summit Chemical Co., kills mosquitoes for 30 days or longer, with one donut-shaped Dunk treating up to 100 square feet of water surface, the company says.
Treating the edges of the yard with outdoor foggers containing synthetic pyrethroid is another option. One drawback is that pyrethroids are not mosquito specific, so most other insects will be affected.
One of the most common forms of protection is spray-on repellents including DEET-based products, as well as products containing picaridin and lemon-eucalyptus oil derivatives.
Natural Control
Bat Conservation International recommends improving habitats for mosquito-devouring bats or even erecting a bat house.
Birds, too, have been reported to help in keeping mosquito populations in check, notably purple martins, though recent studies have questioned the validity of the claim.
Debate also continues on the effectiveness of landscaping plants, citronella candles and smoke-producing candles in keeping mosquitoes at bay. “However, research of area-wide repellants is a hot area, so expect to see more products of this type in the next few years,’’ Smitley said.
There are other options, some of which are decidedly non-toxic.
“Spending the evening on your deck or patio can also be made more tolerable with some well-placed fans,’’ Smitley said.
