Last week, the United States Environmental Protection Agency approved the use of a biochemical pesticide to protect managed honeybee colonies. The main ingredient of this pesticide is extracted from a familiar flower: hops.
Hop flowers have a naturally occurring compound called hops beta acid (HBA). HBAs are commonly used in beer brewing and meat preservation. They also happen to be a naturally occurring pesticide.
The natural pesticide, which uses the potassium salts from the HBAs, would kill parasitic varroa mites. Varroa mites attach themselves to honeybees, sucking out their circulatory fluid. This weakens the host bee, shortening its lifespan and making it vulnerable to a number of debilitating viruses.
If left untreated, colonies infested with varroa mites usually collapse within two to three years.
U.S. managed honeybee colonies are struggling. One survey conducted this past May found that U.S. beekeepers lost an average of 42.1 percent of their hives between April 2014 and April 2015. Some losses were as high as 62 percent.
In order to slow down that loss, scientists began looking for non-toxic ways of reducing varroa mite populations. They turned to the hop flower’s HBAs.
When the scientists wiped a solution of one percent HBA on infected honeybees, there was a 100 percent varroa mite mortality rate. The researchers also soaked cardboard strips in HBAs and placed them in infected hives. This resulted in a mite population decline that was significantly different from untreated hives.
Importantly, the HBA applications had no effect on bee mortality.
Another technique beekeepers use to fight varroa infestations is brushing bees with powdered sugar. The sugar application increases the bees’ grooming activity, which helps to dislodge mites.
However, varroa mites are not the only factor influencing honeybee decline. Scientists believe that multiple factors are contributing to these losses, though it is still unclear how some factors reduce bee populations.
One of the major culprits is synthetic pesticides. In particular, neonicotinoids are suspected to cause a great deal of damage to bee populations.
Neonicotinoids are neuro-active pesticides, meaning they affect the brains of the insects they are meant to kill. This includes honeybee workers. When worker bees come into contact with neonicotinoids, they are unable to learn and remember floral smells associated with sweet nectar rewards, which is an important skill for gathering food.
Neonicotinoids have also been linked to physiological changes in queen bees. Queen bees that were exposed to neonicotinoids had larger ovaries and stored fewer sperm, resulting in lower egg production rates.
