Image credit:https://www.motherjones.com/food/2014/04/california-almond-farms-blamed-honeybee-die/
Every February in the United States, beekeepers from around the nation pack up their colonies and head to California to pollinate the Golden State’s almond trees. Almond growers pay around USD$300 million to rent these hives and without the bees, there would quite simply be no almonds.
In 2014, roughly 80,000 colonies amounting to about 5 percent of bees brought in for pollination, experienced adult bee deaths or a dead and deformed brood. Several entire colonies died.
The connection between honeybee deaths and almond trees was a mystery, but now, researchers from Ohio State University say that the answer is a combination of insecticides and fungicides. Although each ingredient has been tested and deemed individually safe for bees, using them in combination proves deadly.
Reed Johnson, an associate professor of entomology, and his co-authors identified the chemicals commonly used in the almond groves during bloom thanks to California’s highly detailed system for tracking pesticide applications. They then tested combinations of these chemicals on honeybees and larvae in their laboratory.
The possibility of a lethal combination of otherwise non-toxic chemicals had already been raised, as was originally reported in Mother Jones. The details of the combination, however, weren’t identified until the OSU group published their results in the journal Insects on 8 January 2019.
“The simplest thing,” says Johnson, “is to just take the insecticide out of the equation during almond bloom.”
This recommendation is already being put into effect and has been included in the Almond Board’s honeybee management practices. Many almond growers are rethinking their previous practices and are backing off insecticide use during almond bloom, according to Johnson.
The problem appears to have arisen because growers saw combining insecticides and fungicides as a way to ease spraying, which is a very labor-intensive process.
“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.
Johnson and his colleagues’ research will likely prove useful in studying how fungicide and pesticide combinations affect other bee-dependent crops, such as pumpkins and cucumbers.