Point Reyes Light - December 18, 2003
Mosquito-control district proposes annexing coast
By Ivan Gale
Marin-Sonoma Mosquito and Vector Control District has proposed expanding its boundaries into West Marin – if there is enough public concern about mosquito-borne West Nile Virus.
The district plans to mail a questionnaire to 10,000 coastal residents, asking if the Mosquito District’s services are needed.
If the responses are positive, district manager Jim Wandersheid told The Light, West Marin’s possible annexation to the district will be put to vote in November 2004, along with the question of whether voters are willing to pay $15 per year to belong. The charge would show up on a property owner’s tax bill.
Size of annexation
The Mosquito Control District currently includes 1,000 square miles in eastern Marin and Sonoma counties. In Marin, the district’s western boundary is at Woodacre.
The proposed expansion would add another 1,500 square miles of the Marin and Sonoma county coasts to the district.
Prompting the annexation proposal is the spread of West Nile virus, one of the most dangerous diseases mosquitoes can transmit.
Although the virus has yet to show up in Northern California, two human cases were reported earlier this year in Southern California. And in just the last week, three crows in the Los Angeles and San Bernardino counties were found dead from the virus.
In the US, the worst damage has been in the South. US reports of the disease grew from 62 cases in 1999 to 4,156 cases, (including 284 deaths) in 2002.
The virus was named after the West Nile region of Uganda where it was first discovered in 1937. It can cause encephalitis (an inflammation of the brain) or meningitis (inflammation of the lining of the brain and spinal cord) in humans and other animals.
Improved methods
The district’s manager acknowledges that in the past the Mosquito Control agency might have sprayed environmentally damaging pesticides, such as Malthion, into creeks, ponds, and other pools where mosquitoes breed. Today, he said, the district employs a host of "bio-rational" methods instead.
"We don’t use the harsh chemicals of yesteryear," said district manager James Wandersheid, noting that every abatement method used is also approved for organic farming.
The district manager said one popular method for controlling mosquitoes is to stock ponds and other pools of standing water with mosquito fish, which feed on mosquito larvae.
Educating residents is also a significant part of the mosquito district’s operations. District technicians often go door-to-door to inform residents about mosquito control.
Wandersheid said one problem that occurs especially in West Marin results from the fact that most homes here use septic systems. Homeowners need to completely seal off vent pipes to prevent mosquitoes from breeding in septic systems, Wandersheid said.
On occasions when district staff find mosquitoes breeding in a roadside ditch, they ask county road crews to remove whatever is obstructing the flow of water in the ditch, Wandersheid noted.
Aid from bacteria
The district sometimes sprays an encapsulated bacteria called BTI, the district manager also said. Although harmless to other creatures, BTI is deadly to mosquitoes. Mosquitoes alone carry enzymes that can break down BTI’s outer shell. Once that happens, the bacteria is released inside the mosquito, paralyzing it.
Yet another method of the district uses for mosquito control is one endorsed by the World Health Organization; it involves releasing Methoprene into standing pools where mosquito larvae grow.
The chemical mimics the insect’s natural hormones. When mosquito larvae develop and its hormone levels drop, the presence of Methoprene in the water actually halts its development, killing them before fully maturing.
Natural insecticide
A naturally occurring insecticide called Pyrethrins is also used by the district. Pyrethrins is extracted from the flowers of a plant that grows in Africa and South America.
Yet another technique the district uses in mosquito control is spreading a light-mineral oil, which creates a thin film over standing water, suffocating mosquito larvae. This method has been used for more than 20 years with no adverse affects to humans or the environment, Wandersheid said.
Wandersheid said his district also recommends to homeowners ways to control yellowjackets and rodents.