The Associated Press

Chemicals are routinely applied around residential landscapes to kill insect pests and troublesome weeds, but many are indiscriminate and devastate pollinators in the process.

Over the past 30-plus years, pollinator populations have crashed worldwide due to a variety of reasons, including pesticide and herbicide exposure, invasive pests and diseases, loss of habitat, loss of species and genetic diversity, and a changing climate, scientists say.

Pesticide contamination of lawns, gardens and waterways is widespread, and even at sub-lethal levels can impact pollinators’ foraging ability and hive productivity.

“Honeybees are not the most impacted of pollinators,” said Katie Buckley, pollinator coordinator with the Washington State Department of Agriculture. “Once-common butterfly and native bee species have become rare, with some on the verge of extinction.”

The rusty patched bumblebee, island marble butterfly, Taylor’s checkerspot butterfly and the familiar monarch butterfly were among those singled out by Buckley as greatly depleted.

Pesticides are over-applied by many backyard gardeners, said James Dill, a pest management specialist with University of Maine Extension.

“They don’t read the labels, or they eyeball the amounts,” Dill said. “Sometimes, if maybe an ounce is called for, they’ll use 2 ounces. They often will use a calendar spray schedule or just spray because they had a problem in the past.”

But well-informed gardeners can be a big help in reversing the pollinator declines, especially those caused by chemical poisoning.

“In general, the best defense is to avoid spraying plants that are in bloom, use pesticides that have a short half-life when possible, and use pesticides with low toxicity to bees and other beneficial insects,” Buckley said. “Whether as a farmer or a homeowner, it is critical to always read and follow the label.”