http://paloaltoonline.com/print/story/print/2012/07/27/avoiding-blood-sucking-insects


Palo Alto Weekly

Real Estate - July 27, 2012

Avoiding blood-sucking insects

Mosquitos can thrive in pools, ponds or even fountains

by Helen Carefoot

Bzzzzzz. Thwack. There's nothing quite like the buzz of a mosquito to ruin a summer barbecue — or a warm night's rest.

Though 2012 has seen a decrease in mosquito activity in Palo Alto, late rains have created more possible nesting places in puddles. This excess of standing water has provided ample mosquito nesting grounds: This year so far, the Santa Clara County Vector Control District, the county sector responsible for pest control, has assisted abatement in 150 residences. Much of it occurs in foreclosed homes or in homes that have been rented out while their owners are on vacation.

Mosquito season may begin as early as January, but droughts this year after heavy rains pushed the beginning of the season back to March. Typically, the season lasts from early April to late August, with a peak in June and July.

While most folks don't take mosquitoes too seriously, last week's discovery of a squirrel with West Nile virus in Menlo Park brings the potential problem quite close to home.

Residents should take abatement measures to prevent mosquitoes from nesting in their yards, especially in sources of still water, said Russell Parman, acting district manager of the Santa Clara County Vector Control District. Close proximity to mosquito nesting grounds mean a greater chance of being bitten and possibly contracting a disease, such as West Nile virus. Timeliness is paramount in abatement because eggs become adults in about 14 days. As mosquitoes continue to lay eggs in the water source, the water becomes a more attractive venue for other mosquitoes to nest in, causing more mosquitoes to populate the same pond or fountain.

Parman advises residents to take care of any containers of standing water.

"People should empty or drain standing water of any size around the home," he said, "especially swimming pools and spas." Parman says the most common mosquito nesting grounds in Palo Alto are old catch basins and dilapidated swimming pools.

Barron Park resident Nancy Hamilton experienced abatement first hand when she discovered mosquito larvae living in her fountain. "I have a portable fountain on my deck that my dog sometimes drinks out of," she said, "I watched it carefully and saw the larvae just below the surface, which looked like thin black hairs."

After doing some research, she decided to replace the water in her fountain. Initially, Hamilton did not think it was possible for mosquito larvae to live in her fountain.

"I didn't think I would have a problem because Palo Alto water has chloromine (a chemical used to clean water), but I was wrong. The chloromine doesn't evaporate, so it doesn't take care of the problem."

Parman said Gambusia affinis, or mosquito fish, "are an extremely effective means of abatement in urban residential settings because they are environmentally friendly and able to re-populate by themselves."

Originally introduced into California as early as 1922, mosquito fish have been one of the most effective non-insecticidal and non-chemical methods of controlling mosquitoes for more than 80 years, he said. The fish live near the surface of the water source and eat the mosquito eggs resting on the surface.

A resilient species, mosquito fish are capable of surviving harsh conditions like water with low oxygen content or elevated salinity and only need to be planted once per season. In a given year, the fish may produce anywhere from 50 to 100 live-born young in three or four broods. Each fish is capable of eating more than 100 mosquito larvae daily. The fish can be placed in ponds and fountains, as well as some swimming pools.

The fish require little upkeep and can live for two to three years. The fish do not need to be fed unless the pond they inhabit is new and without vegetation; in this case, the fish can eat tropical fish flakes. Algae are beneficial for mosquito fish, but they cannot survive in ponds or fountains containing duckweed or certain types of leaves like eucalyptus, pine, oak or pittosporum.

One Barron Park resident used mosquito fish to abate her empty swimming pool after it had collected excess rainwater and was very happy with the results. "I challenge anyone to find a mosquito in that pool," she said. "They do their job and you don't have to feed them or anything."

She was also pleased with the ease of acquiring and installing the fish. "I just researched online, called the vector control agency and they set me up with them. It was really easy."

The fish are available to all Santa Clara County residents with free delivery from April through October. However, it is illegal to plant mosquito fish without a county-issued permit. Also, the fish cannot be released into the wild because they are prolific and are capable of displacing natural species. If and when mosquito fish are no longer needed or reach abundance, residents can return them to the county.

According to the Santa Clara County Vector Control District website, the two types of mosquitoes most commonly found in Palo Alto, the Culex and the Culiseta, lay "rafts," or groups of 200 to 300 eggs that float on the surface of stagnant water sources. A raft of eggs looks like a speck of soot floating atop the water and each raft is about a quarter-inch long and an eighth-inch wide.

The Culex tends to lay eggs in man-made water sources such as sewage or ponds; the Culiseta prefers warm, sheltered, foul or polluted water such as that found in neglected swimming pools or catch basins. Both mosquito varieties have been known to cluster around creeks.

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Editorial Intern Helen Carefoot can be emailed at hcarefoot@paweekly.com.

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