New research from the University of California-Davis indicates that when a mason bee is exposed to both food scarcity and pesticides, their ability to reproduce drops 57%.

This beautiful large wild bee is particularly susceptible to habitat loss and enduring pesticides, in fact when these two factors come together it produces the perfect storm for mason bees.

According to Katie Buckley, the pollinator health coordinator at Washington State Department of Agriculture, mason bees are under-appreciated pollinators that deserve protection.

The populations of wild bees, including mason bees, could seriously shrink due to widespread use of pesticides and loss of flowering plants.

Here is a 2:01-minute video by Parra Coyne explaining these research results:



US entomologists indicate this would be a big problem for farmers that rely on native bees for pollination because mason bees outperform other pollinators, even the famous honeybee, when it comes to pollinating many crops.

If mason bees are harmed, agriculture will be as well. 

Lead author of the study was Clara Stuligross, a Ph.D. candidate in ecology at UC-Davis. She and her team conducted experiments on blue orchard bees, which are a type of mason bee. They exposed the bees to a widely used neonicotinoid insecticide, imidaloprid. 

The researchers observed that the bees exposed to pesticides delayed nesting, had fewer female offspring, or nested for less time, especially those in cages with fewer wildflowers.

According to Stuligross, female mason bees are very important. They lay eggs, collect pollen and nectar and build nests. They also have longer lifespans than males, and eat more, so males are less expensive to raise.

Here is an unrelated 1:00 video by the California Farm Bureau Federation, featuring Clara Stuligross as she discusses blue orchard mason bees:




The bees in the study were stressed from limited food resources and pesticides and seemed to deliberately produce fewer females. In the bee world, biology means a fertilized egg becomes female and an unfertilized egg becomes male. The bees in the study fertilized fewer eggs, according to Stuligross.

Fewer female bees equal less plant pollination and less reproduction.

Neal Williams, a pollination ecologist and professor at UC-Davis, was the study’s co-author. He says that males don’t matter so much in the bee world. Fewer males would rarely limit population growth whereas fewer females reduces the reproductive potential of subsequent generations.

How can farmers help to protect mason bees? Researchers say there are several ways.

Plant wildflowers in pesticide-free areas, and where there is no risk of pesticide drift.  

If farmers are going to use pesticides, they should apply the pesticide AFTER bloom so the risk exposure for bees is lower.

The team suggests altering the types of pesticides used because plants absorb long-lasting “systemic” pesticides like imidacloprid, the neonicotinoid insecticide used in this study. These toxins are output through all the parts and tissues of the plant, including nectar and pollen. Systemic pesticides are dangerous to bees, according to the researchers.

Here is the UC-Davis news release about this study.

These findings were published in the journal Proceedings of the Royal Society B. 

Stuligross says the message is to be more aware of stressors to our beneficial insects, especially bees, and to do what we can to help them.