Risk assessments involving genetically modified as well as naturally derived microbial pest control agents (MPCAs) have focused on the inherent toxicity and pathogenicity toward non-target organisms. As part of a pesticide registration, the U.S. Environmental Protection Agency (EPA) requires testing of any MPCA to determine the risk (hazard) to non-target species, including beneficial insects. Honey bees (Apis mellifera L.) are of particular concern because of their world wide importance as supplemental pollinators of most entomophilous crops and as producers of honey and wax.

Quantifying the risk to bees of exposure to MPCAs under field conditions has not been attempted. We and other laboratories have usually tested the hazards of MPCAs to bees using artificial routes of exposure (i.e., direct spraying or mixtures of the pathogenic agent with pollen, syrup, and water) and bees contained in environmental chambers. If the pathogen being tested is a genetically altered or exotic organism, we are required to conduct the initial tests in microbial containment chambers

Plating (left) of dead bees taken from hive entrance traps. Only (right) a few bees showed any evidence of the microbial insecticide Beauveria bassiana note the ball-shaped forms near the head of this bee.

During the summer of 1995, we initiated studies aimed at providing better methods for field testing of the potential hazards posed by microbial insecticides to bees. We used a fungal insecticide Beauveria bassiana that has been registered with the EPA. The methods employed included a combination of tests proven to be useful for monitoring the effects of chronic exposures to environmental pollutants developed for field testing of microbials. We also used some new approaches, such as monitoring colony core temperatures in the brood nest.

Methods Summary

• Detailed Colony Health Records (Pre-Test)
• Ranking of Colonies by Hygienic Behavior
• Three Spray Applications to Adult Bees
• Three Replicate Colonies per Treatment
• Chalk Brood "Positive" Controls
• Heat-Killed B. bassiana "Negative" Controls
• Carrier Solvent Controls
• Healthy Colonies
• Chalk Brood Susceptible Colonies
• Varroa infested Colonies
• Assessment Endpoints
• Brood Nest Temperatures
• Brood Survival
• Adult Bee Mortality (Entrance Traps)
• Viable Fungi on Bee Cadavers
• Viable Fungi In/On Sacrificed Bees

Stefan Jaronski (Mycotech, Inc.) sprays B. bassiana on test bees

Preliminary Results

• Colony Brood Nest Temperatures Appear Sufficient to Inhibit Fungal Viability
• Viable B. bassiana Found on Only a Few Bees

Final Technical Reports and Journal Articles Presenting the Full Results of these Investigations are In Preparation.