Most people think of honey production when someone mentions bees. After all, they are one of the most beneficial insects in the world, especially the role they play in plant pollination. But what if the bees took on an additional role in the plant life cycle?
By Lisa Nowatzki
Dr. Venkat Chapara, assistant research professor and plant pathologist who works at the Langdon Research Extension Center (LREC), has answered this question. He is studying the use of bees in distributing biological agents such as fungi and bacteria right to the flowers where they are needed.
Acquiring and delivering plant pathogens by insects can happen when the pathogen adheres to insect body hairs during pollination. This mechanism has recently been exploited for crop protection by using managed pollinators (bees) as vectors or carriers of microbial biological control agents.
In other words, scientists are now using bees to deliver certain biological medicine to plants during pollination to help prevent disease.
The technique is very promising since it can provide direct delivery of biological agents to targeted areas like the blossoms and leaves of plants with little of the product being wasted, and the use of insects as carriers reduces the hazards to non-targeted organisms.
Growers are also spared significant time and money associated with conventional sprays. Effective dissemination of microbial biocontrol agents by managed pollinators like bees for management of diseases and pests has been demonstrated in several types of crops.
In Europe, the technique has been used to control fireblight in apple orchards, gray mold in strawberries and raspberries, brown rot in cherries, and sunflower head rot.
The obvious logistical question is how to give each insect a dose of the biological control agent. Though it may seem like an insurmountable problem, an ingenious dispersal method was used in some earlier studies. In practice, the solution was simple.
A dispenser of the biological agent was attached to the entrance of the hives so that the bees had to exit through the agent, picking up the powder as they went out. Then, in turn, delivering the agent to the targeted flowers of the crop being studied.
Several previous trials with different bees have proven to be effective in delivering biological agents and controlling fungi and bacteria. In South Africa, trials showed that the biological agent Eco-77 could be successfully dispersed by honey bees to prevent Botrytis in strawberries and raspberries.
Botrytis is gray mold, caused by the fungus Botrytis cinerea, and is one of the most important fruit rot diseases affecting strawberries and raspberries. Typical symptoms include a spreading brown rot and fuzzy gray mold on ripening berries. The spores are airborne and occur during periods of prolonged moisture.
The fungus infects the blossom parts of the plant and then infects the green fruit resulting in infected, mature, fuzzy fruit. Besides strawberries, raspberries are also vulnerable to this type of infection.
In 2013, a study was done to test the effectiveness of bees as vectors for microbial biological control agents. The scientists were continuing the research that had been done in greenhouses and small-acreage crops with honey bees. According to these studies, home-made wooden, Koppert, and Enviroquest dispensers had no significant effects on foraging behavior or pollen loads of the bumblebee.
After the bees walked through the dispersal area and left the hive, no difference was found in the quantity of the microbial agent Clonostachys rosea applied to the bees or blossoms, and distribution of the product in the field was not influenced by dispenser design or distance from hives.
C. rosea is a species of very destructive fungus in the family Bionectriaceae. It colonizes living plants, digests material in the soil, and is also known as a parasite of other fungi and nematodes.
The results of the study indicated that there was significantly less (10-20%) blossom infection in control plots, despite the unseasonably inclement conditions and the restricted foraging areas of the bees.
Approximately three-fold more bees exited hives without a dispenser than bees exiting hives outfitted with a biologic dispenser. However, scientists found that even though 95 percent of the initial load of the biocontrol agent was lost in the first 60 seconds of flight, C. rosea spores were recovered from blossoms at distances up to 150 meters from hives proving that microbial control agents can be used for long distance inoculation.
During the study, scientists observed bee behaviors such as foraging, pollen returns, and crop yields. From this information, scientists concluded that the added duty of vectoring does not affect pollination service. These results are consistent with those observed in prior studies.
Further examination of the collected data helped scientists concluded that the C. rosea could be effectively delivered by commercial bumble bees for the prevention of B. cinerea infection in V. angustifolium. B. cinerea is a fungus that affects many plant species, while V. angustifolium, commonly known as the wild lowbush blueberry, is a species of blueberry.
In North Dakota, as of April 1, 2018, the number of honey bee colonies for operations was at 72,000 which was a significant increase from January 1, 2018, when the number was 64,000. Though the number of colonies increased, nearly three percent of colonies were lost to diseases like varroa mites.
Since North Dakota has been the largest producer of honey in the nation for several years, outproducing every state by at least double, allowing the bees to perform double duty as pollinators and as plant inoculation vehicles seems like the next logical step in treating plant diseases without doing more harm to the environment.
Currently, honey bees are an important resource for pollination, contributing to the natural production of over 30% of the food we eat. So the next time you see a honey bee, give way because he is on his way to help pollinate and inoculate a nearby crop.