Good stewardship means protecting the environment and thoughtful consideration of a multitude of factors - including air quality, water quality, pesticide use, soil management and good agricultural practices that protect food safety.  Much has been written about almond grower stewardship.  Almond growers have received notoriety and awards for their outstanding stewardship efforts.  But little is written about grower stewardship relative to the billions of honey bees that pollinate the huge almond crop.  In particular, there are large gaps in our knowledge about how pesticides affect honey bees. 

The research gaps are starting to be addressed.  On a recent North American Beekeeping Conference agenda, 17 of approximately 100 presentations on honey bees addressed an aspect of pesticides and honey bees.  Five years ago, these presentations were not on beekeeping conference agendas.  Almond growers are contributing their share of funding this research through the Almond Board and through Project Apis m (PAm).

Several institutions are emerging in the forefront of research on pesticide and honey bees.  Pennsylvania State University (PSU), Washington State University (WSU), University of Georgia, University of Florida, and USDA-ARS laboratories in Beltsville and Tucson are among those that lead the list.  These research labs are investigating accumulation of pesticides in hives, chronic and sub-lethal effects on bees, the interaction of multiple pesticides on bees and many other factors heretofore unknown.

At PSU, researchers are screening bees, brood, honey and wax samples for pesticides.  PAm is helping fund this effort to keep fees reasonable for beekeepers and to expand the database.   USDA-ARS Beltsville reports that with low levels of the pesticide imidacloprid, higher levels of the pathogenic fungi, Nosema, were found.  USDA-ARS Tucson is looking specifically at the impact of fungicides on bee bread, the all-important bee larvae food manufactured from pollen.

EPA pesticide registration standards may evolve to insure pollinators are more fully protected.  At a recent American Honey Producers Convention, representatives from both the EPA and the California Department of Pesticide Regulation admitted that they are just now better understanding bees.  Dr. Steven Bradbury of the Office of Pesticide Programs said the registration assessments may change as they learn more about bees, including sub-lethal effects and pesticide effects on different age classes of bees.   Researchers are also suggesting synergistic effects of using pesticide combinations and toxicity of breakdown metabolites are important considerations.

Entomology graduate student Judy Wu working under Dr. Steve Sheppard at WSU has succinctly illustrated how pesticides can affect bees (see Fig. 1).  Though rare in almond applications, pesticide exposure may cause bee mortality outright.   More likely, exposure weakens hives as these chemicals piggy-back on bees back to the hive.  Either way, the result is a colony with less pollinating capability.  Dr. Eric Mussen, UC extension apiculturist reports a distinct loss of brood 17 days following exposure to a fungicide application. No doubt we’ve been living with this for years, but now are only characterizing the phenomenon.   

An integrated agricultural operation continually balances benefit vs. risk:  growers need to protect a crop that is highly sensitive to pathogens in the presence of moisture while living with a probable knock-down of some bee strength following a fungicide application.  Bees are resilient; it’s probably easier for bees to bounce back after a major stressor like a fungicide application – whereas nuts will not recover from brown rot, hull rot, anthracnose or any of the other numerous diseases.  A best management practice guideline is for growers to apply fungicides late in the day when no exposed pollen is left on the blossoms.  Another important guideline to follow is to read the pesticide labels thoroughly, particularly in reference to honey bee toxicity.  Keep in contact with your beekeeper regarding your application sprays.  Let him protect his investment while you are protecting yours.

Pesticides are probably not the primary cause of Colony Collapse Disorder (CCD), but very well may be one of the stress factors affecting a colony’s ability to survive and thrive.  Research has shown that beekeeper-applied pesticides, not grower-applied pesticides, are the most prevalent pesticide residues found in a hive.  Beekeepers must alter their practices to prevent the accumulation of miticides in hive matrices.   As continuing research unfolds, expect more attention will also be given grower-applied pesticides and the impact they have on all the various life stages of the honey bee. 

Grower management practices are becoming increasingly complicated and include more regulatory oversight.  To add to a grower’s already daunting management tasks, stewardship efforts of the future will contain more specific guidelines for the safe application of pesticides, particularly fungicides, when bees are present. 

Chris Heintz is Executive Director for Project Apis m. a non-profit bee research organization.  Should you have questions about bees, they can be answered via this column for the benefit of other Blue Diamond almond growers.   Submit your questions to This e-mail address is being protected from spam bots, you need JavaScript enabled to view it .