The company plans to phase out chemicals known as neonicotinoids by 2021 in eight of its products used to control garden pests and diseases.
Ortho is believed to be the first garden products brand to announce it will stop using the chemicals, said Lori Ann Burd, director of the Environmental Health Program at the Center for Biological Diversity.
Neonics and other pesticides, along with disease and declining diversity in gardens and landscapes, are among the causes of declining bee populations worldwide, a United Nations study released in February said.
About one-third of the human diet comes from insect-pollinated plants, and honeybees are responsible for 80 percent of that pollination.
Ortho will phase out neonicotinoids in three products for roses, flowers, trees and shrubs by 2017 and in other products later, said Tim Martin, the company's vice president and general manager.
The change might require gardeners to apply the reformulated products more frequently, but it will be easier to target pests while reducing the chances of hurting bees, he said.
Ortho is a division of Marysville, Ohio-based Scotts Miracle-Gro Co. The parent company reported sales of $3.02 billion last year but doesn't break out statistics for its divisions.
The severity of neonics' effects on bees appears to vary depending on the type of crops they are used on, according to a study by the U.S. Environmental Protection Agency and California's environmental agency released in January. Another study published last year says neonics might hit wild bumblebees harder than domestically raised honeybees.
Bayer CropScience and Syngenta, the top manufacturers of neonics, have said the research has exaggerated the risks and understated the benefits.
Concern about bee health is growing. The Maryland General Assembly passed a bill last week that would allow only certified applicators, farmers and veterinarians to apply pesticides containing neonics.
In March, the U.S. Fish and Wildlife Service said it would consider whether to protect two species of wild bumblebees under the Endangered Species Act amid declines in their numbers.
The environmental group Defenders of Wildlife, which asked federal officials to consider protecting the bees, said neonics were a factor in the bees' decline.
It's not yet clear what effect Ortho's decision will have on the health of the overall bee population. Neonics are used in a number of chemicals applied to food and textile crops such as corn and cotton as well as home gardens.
But May Berenbaum, a bee expert and professor of entomology at the University of Illinois, said homeowners use a significant amount of pesticides, and introducing alternatives to neonics is important.
"There are still profound problems (for bees), but this is a step toward removing one contributor to some of the problems," she said.
Berenbaum cautioned that the replacement pesticides could have their own problems. "This is not the end. This is no time for complacency," she said.
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