CULPRIT FOUND FOR HONEYBEE DEATHS IN ALMOND GROVES.

• Author: Crane, Misti
• Position: EYE ON ECOLOGY

EACH WINTER, professional beekeepers from around the nation stack hive upon hive on trucks destined for California, where February coaxes forward the sweet-smelling, pink-and-white blossoms of the Central Valley's almond trees.

Almond growers rent upwards of 1,500,000 colonies of honeybees a year, at a cost of around $300,000,000. Without the bees, there would be no almonds, and there are nowhere near enough native bees to take up the task of pollinating the trees responsible for more than 80% of the world's almonds. The trouble was, bees and larvae were dying while in California, and nobody was sure exactly why. The problem started in adults only, and beekeepers were most worried about the loss of queens.

Then, in 2014, about 80,000 colonies--around five percent of bees brought in for pollination--experienced adult bee deaths or a dead and deformed brood. Some entire colonies died.

With support from the Almond Board of California, an industry service agency, bee specialist Reed Johnson, associate professor of entomology at Ohio State University, took up the task of figuring out what was happening. Results from his earlier research had shown that some insecticides thought safe for bees were impacting larvae. Building on that, Johnson undertook a new study, published in the journal Insects, that details how combinations of insecticides and fungicides typically deemed individually "safe" for honeybees turn into lethal cocktails when mixed.

Johnson and his study coauthors were able to identify the chemicals commonly used in the almond groves during bloom because of California's robust and detailed system for tracking pesticide applications. Then, in a laboratory in Ohio, they tested combinations of these chemicals on honeybees and larvae. In the most-extreme cases, combinations decreased the survival of larvae by more than 60% when compared to a control group of larvae unexposed to fungicides and insecticides.

"Fungicides, often needed for crop protection, are routinely used during almond bloom but, in many cases, growers were also adding insecticides to the mix. Our research shows that some combinations are deadly to the bees, and the simplest thing is to just...