Wearing plastic goggles and rubber gloves, vector control specialist Tina Smith dropped a few chemical briquettes that stunt the growth of mosquito pupae into a green backyard swimming pool in Downey. She stared into the murky water teaming with swimming mosquito pupae. “This chemical floods mosquitoes with an overdose of their own hormones,” she said as thousands of pupae floated on the surface. “They can’t develop into adults.” With the first discovery of West Nile-positive mosquitoes this week in Los Angeles County, the season for the virus has officially begun. That, along with warming temperatures and more people outdoors this holiday weekend, means it’s once again time to take up precautions, vector control and health officials said. “Memorial Day is the first weekend people are outside,” said Mark Hall, a supervisor at the Greater Los Angeles Vector Control District in Santa Fe Springs. “They’re more prone to mosquito attacks.” The discovery of mosquitoes carrying the virus came much earlier this year than last year, when positive mosquitoes were not found until July, officials said. It means that everything you might have learned last year about protecting yourself against the virus could be put to the test this weekend. For the complete story, pick up a copy of tomorrow’s Whittier Daily News. AD Quality Auto 360p 720p 1080p Top articles1/5READ MORE11 theater productions to see in Southern California this week, Dec. 27-Jan. 2165Let’s talk business.Catch up on the business news closest to you with our daily newsletter. Something went wrong. Please try again.subscribeCongratulations! You’re all set!