Biologist’s simple trap strategy can cut mosquitoes by up to 95%

A biologist says the best way to beat mosquitoes is not to spray adults in the air, but to stop them at the breeding stage. In an interview published Monday in The Washington Post, Dr. Bart Knols, who has studied mosquitoes for decades, said climate change is making mosquito season longer, hotter and more difficult, especially for people trying to sit outdoors in gardens and on balconies.

Knols said chemical spraying is often ineffective because mosquitoes quickly develop resistance. He also said it can make the problem worse by killing natural predators such as dragonflies, spiders and birds, leaving the area open for the next generation of mosquitoes. Instead, he relies on behavioral traps that exploit what mosquitoes are drawn to, namely heat, humidity and human scent.

The key example is a homemade “doom bucket,” a cheap black plastic bucket filled with water and plant material such as cut grass or dry leaves. That mixture gives off the smell of stagnant water, which female mosquitoes find ideal for laying eggs. A tablet of Bti, a natural bacterium sold in hardware and garden stores, is placed in the bottom. It kills mosquito larvae after they hatch without harming birds, pets, bees or humans. Knols said such traps initially caught 10,000 to 12,000 mosquitoes a day, then reduced local mosquito numbers by 90 to 95 percent.

He also recommends emptying standing water weekly from tarps, flowerpot saucers, forgotten children’s toys and trash-can lids, because even tiny amounts can become breeding sites. In drains or sewers that cannot be emptied, he says to add a Bti tablet. Knols emphasized that the method works best when neighbors act together, saying it takes little maintenance but can leave a neighborhood “clean and quiet for everyone.”