Disease-carrying mosquitoes breed beneath the streets of Sacramento
A good chef can dip a ladle into a pot, pull it up for inspection and tell you precisely how a soup is coming along.
On this late-spring morning, Randy Burkhalter stood over a catch basin, or storm drain, at Markham Way and 12th Street in Sacramento’s Land Park neighborhood, positioning a white plastic ladlelike cup affixed to the end of a long pole over the basin’s gaping mouth.
“Looks dry, you think?” he asked, pointing toward a carpet of leaves a couple of feet below.
A quick dip found liquid pay dirt, which filled the ladle he then brought above ground level for perusal. The murky water it contained was teeming with activity, a miniature neighborhood pool loaded with mosquito larvae that dived and swam around egg rafts and pupae, each egg and larva and pupa a future airborne menace, as an adult mosquito, to mammals and birds.
“You’re looking at about 400 potential mosquitoes right there,” Burkhalter, supervisor of the Sacramento-Yolo Mosquito and Vector Control District’s catch-basin program, noted. “Once West Nile [virus] hit, and they realized that these are the type of mosquitoes that are carriers of West Nile, it became very important that we take care of these catch basins. That’s how our program started.”
Since 2004, after storm drains were identified as a major trouble spot for mosquito breeding, Burkhalter and his crew of six have cataloged the region’s catch-basin locations—some 13,000 in Sacramento city center, between the American River and Sutterville Road. Problem basins are treated with larvicides, including methoprenes, hormonal treatments that prevent the pupa from developing into an adult; VectoMax, which contains bacilli that cause the stomachs of larvae to ulcerate; and, should those fail, Agnique, an oil which creates a film over water that keeps pupae from breathing.
The idea is to exterminate the mosquito in larvae and pupae stage, before they start flying, sucking blood and infecting people. If the strategy is successful, the controversial flyover spraying of pesticides to kill adult mosquitoes won’t have to occur.
To put the 400 potential mosquitoes in Burkhalter’s ladle in perspective, consider that the district considers finding just one larva for every 10 dips the threshold for taking corrective action.
“One [larva] per dip is considered pretty high,” said David Brown, the district’s manager. “Ten per dip is considered extremely high. Anything over that is off the charts. Our catch basins are off the charts.”
Before catch basins became an area of concern, the district had divided its two-county bailiwick into 26 zones, each of which is managed by a zone operator. These zone operators also manage the rural wetlands and other sources of mosquito trouble not served by the catch-basin crew.
Brown said there’s a difference in efficiency between treating those sites administered by zone operators, with a 90 to 100 percent success rate, and catch basins, which hover around 50 percent. “When we treat a site, we expect to have it [stay] treated and not have to go back to it, because we cover 2,000 square miles,” he said. “When we treat a catch basin and we come back and haven’t had that control, we’re spending an inordinate amount of time on those sites.”
The Sacramento-Yolo Mosquito and Vector Control District’s headquarters is sited on a 25-acre plot of land on Bond Road in Elk Grove, much of which is given over to more than 20 ponds where Gambusia affinis, or mosquitofish, are cultivated. The minnowlike mosquitofish are distributed by the district free to unmaintained swimming pools, the other problem area for mosquito breeding in urban areas; many of those pools sit in the backyards of homes abandoned due to foreclosure.
The agency, founded 63 years ago next month as the Sacramento-Yolo Mosquito Abatement District, is funded by property-tax revenues; it changed its name in 1990 to more accurately reflect the idea that one cannot eradicate the mosquito and the Western black-legged tick—the other primary vector, or disease-transmitting animal—population as much as contain or manage it. And in the Internet age, the district’s Web address, www.fighthebite.net, where a repository of valuable information can be found, is even easier to remember.
Inside a laboratory, three technicians peer into microscopes, examining and cataloging mosquito specimens they’ve gathered across the two counties earlier that day. Some, Culex pipiens, have been identified as carriers of West Nile virus, while others are known carriers of encephalitis (Culex tarsalis, Aedes melanimon) or malaria (Anopheles freeborni). Atop a counter, a large jar marked with a giant silhouetted mosquito sits. Inside, what looks like bulk loose-leaf tea is instead thousands of dead mosquitoes.
In another room are netted boxes where adult mosquitoes feed from chicken blood through a membrane at the boxes’ tops; here, the life cycle—egg, larva, pupa and adult—can be studied. And in another room are giant water-filled trays with larvae and pupae, which are used to study the efficacy of various agents used to keep them in check. On a table sit dozens of small dishes, each containing larvae and various concentrations of pesticides district biologists are testing.
“Our whole goal is to reduce the amount of adult mosquitoes flying,” said Brown. “Those are the bad guys. As long as they’re in the water, you’re not going to see any pathogens transmitted. But when they’re flying, that’s when bad things happen.”
That district’s monitoring of mosquito populations led, via deductive reasoning, to garden refuse. “What got us into the whole green-waste issue is that we found out that our larvacides weren’t working,” Brown said. “And they should. So we started delving into why they weren’t working as well as they should be.”
Which led to catch basins, green waste left on city streets and the claw.
A clause in Sacramento’s city charter gives residents the right to pile garden waste on street gutters, rather than place it in containers for pickup. For bicyclists, those piles represent a safety hazard when they obstruct shoulder lanes. But, according to Brown and Burkhalter, that waste—or what’s left after the tractor with the claw appendage removes the rest—gets swept or hosed into catch basins, where it clumps and allows stagnant water to pool, providing organic matter on which mosquito larvae can feed and reducing the potency of larvacides.
It comes down to dollars and cents.
“In talking with city staff, it would be less expensive if we had a containerized waste program,” Brown said, adding that what’s needed is a ballot measure to amend Sacramento’s city charter. However, that attempted fix, which Brown says should have happened “yesterday,” failed the first time at the ballot box. It may get another chance when the June 2010 primary rolls around.
But even before a measure can be placed before voters, people can make a difference by being mindful of how they dispose of green waste. Put simply, each gardener changing behavior by putting green waste in cans instead of on the street means less airborne mosquitoes, and less threat of West Nile virus infection.
Rob Fong, the Sacramento City Council member representing District 4, which includes Land Park, is on board with the move toward containerized green waste, but suggests an even better alternative. “We’d like people to use the green waste on their landscape as mulch,” he said.