Yakoo752
USN
Johnson, an associate professor of entomology, and his study co-authors 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 percent 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 take the insecticide out of the equation during almond bloom,” he said.
“It just doesn’t make any sense to use an insecticide when you have 80 percent of the nation’s honeybees sitting there exposed to it.”
I was surprised – even the experts in California were surprised – that they were using insecticides during pollination,” Johnson said.
While these products were considered “bee-safe,” that was based on tests with adult bees that hadn’t looked into the impact they had on larvae.
“I think it was a situation where it wasn’t disallowed. The products were thought to be bee-safe and you’ve got to spray a fungicide during bloom anyway, so why not put an insecticide in the tank, too?”
Insecticides are fairly inexpensive, but the process of spraying is labor-intensive, so growers choosing to double up may have been looking to maximize their investment, he said.
“The thing is, growers were using these insecticides to control a damaging insect – the peach twig borer – during this period, but they have other opportunities to do that before the bees enter the almond orchards or after they are gone,” Johnson said.
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