Playa Vista Freshwater Marsh harbored a ‘massive and unprecedented’ mosquito population this summer, but officials say it’s now under control
By Gary Walker
Playa Vista Freshwater Marsh, the 51.7-acre portion of the Ballona Wetlands southwest of Lincoln and Jefferson boulevards, has been credited with helping native birds stage a comeback in the area because of the habitat its stewards have created to attract them.
But the marsh also became a breeding ground for tens of thousands of mosquitos this summer due to a lack of routine maintenance, according to public health reports obtained by The Argonaut.
Mosquito counts at the marsh were the highest in recent history for anywhere in the Los Angeles County West Vector and Vector-Borne Disease Control District, which patrols West Los Angeles and parts of the South Bay and San Fernando Valley.
Agency Executive Director Dr. Robert Saviskas described the mosquito breeding as “massive and unprecedented” in a July 20 letter of warning issued to the Ballona Wetlands Conservancy, a consortium of nonprofit and public agencies responsible for maintaining the marsh.
“These are the highest [mosquito] counts ever recorded anywhere in the district over the last 50 years and have exposed the local residents and school children at Playa Vista Elementary School to an extremely high public health risk of contracting West Nile virus and other mosquito-borne illnesses such as Zika and dengue fever,” states the document, a second notice of intent to file a public health and safety violation that refers to an initial notice sent June 27.
“Mosquito counts have gone from a high of only 38 per night in 2015 to 14,206 per night in 2016 during the same time period due to the lack of vegetation removal and maintenance in the Playa Vista Marsh and Teal Channel,” Saviskas wrote, adding that traps placed next to and across the street from Playa Vista Elementary on July 13 had mosquito counts of 1,325 and 3,251 per night.
The Ballona Wetlands Conservancy says it has brought the situation under control by implementing a mosquito abatement plan that included lowering the water levels at the marsh and clearing vegetation throughout the entire marsh system.
“The situation has greatly improved and we are still working to comply with vector control requirements. All mosquito counts are down dramatically for the freshwater marsh and the riparian corridor,” reads a statement by the conservancy, which includes representatives of the California State Lands Commission, California Dept. of Fish and Wildlife, the nonprofit Friends of Ballona Wetlands, Playa Vista master developers Brookfield Residential and former Playa Vista developers Playa Capital.
Saviskas did not return calls to discuss the progress of abatement efforts, but according to the conservancy a mosquito count in the marsh area on Aug. 31 turned up only 20 mosquitos.
Despite Saviskas’ warnings about potential exposure to mosquito-borne illness, the July 20 notice did not state that any mosquitos in the marsh this summer tested positive for West Nile virus or any other disease.
But in June 2007, mosquitos trapped at Playa Vista Freshwater Marsh did test positive for West Nile virus — once again after breeding had spiraled out of control due to lack of routine maintenance, which resulted in a public health and safety nuisance notice, according to the document.
In 2008, the numbers of mosquitos at the marsh increased tenfold at two locations from April through May 12 due to reed and foliage growth that went unchecked. A public heath notice was issued to the conservancy that year as well.
Because of the West Nile detection nine years ago, LAUSD Board President Steve Zimmer said the district will compare notes with health officials.
“What the district has to do in this situation is find the right amount of balance in taking the proper health precautions and that we don’t restrict students in their normative school day activities,” Zimmer said.
According to a California Department of Public Health spokesperson, mosquito species detected in the marsh this summer may have increased the possibility of detecting West Nile virus but not necessarily the risk of transmitting it to humans, because not all species of wetland mosquitoes are disease vectors.
Like in 2007 and 2008, this summer’s unchecked overgrowth of reeds and bulrushes (also known as cattails) became so prolific that the weeds prevented mosquito fish, which eat mosquito larvae, from entering marsh channels.
In the July 20 notice, Saviskas wrote that the vegetation removal efforts started immediately after the first warning in June had abated only 25% of the impacted area at that time.
“The lack of maintenance over an extended period of time,” he wrote, “has created such dense growth and height (15-plus feet high in most areas …) that insecticide dispensed by the district to control the mosquitos cannot adequately penetrate the growth and get down to the water.”