Homeowners use up 10 times more pesticide per acre than farmers do. But we can change what we do in our own yards.

One day last fall, deep in the middle of a devastating drought, I was walking the dog when a van bearing the logo of a mosquito-control company blew past me and parked in front of a neighbor’s house. The whole vehicle stank of chemicals, even going 40 miles an hour.

The man who emerged from the truck donned a massive backpack carrying a tank full of insecticide and proceeded to spray every bush and plant in the yard. Then he got in his truck, drove two doors down, and sprayed that yard, too, before continuing his route all around the block.

Here’s the most heartbreaking thing about the whole episode: He was spraying for mosquitoes that didn’t even exist: Last year’s extreme drought ended mosquito-breeding season long before the first freeze. Nevertheless, the mosquito vans arrived every three weeks, right on schedule, drenching the yards with poison for no reason but the schedule itself.