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Bumblebees become true Flying Doctors by protecting strawberries from thrips

Can bumblebees be used to suppress thrips in strawberries? According to a group of researchers, this is possible. The bumblebees can spread the entomopathogen Beauveria bassiana as a biological control agent which suppresses thrips up to 75%.

"The cultivation of strawberries within greenhouse environments is an increasingly common area of agricultural productivity, affording consistent fruit production of an otherwise highly seasonal crop. However, due to its relative novelty, few management tools have been identified, assessed, or registered to date for control of the many known pests of greenhouse-grown strawberry crops", says Peter Kevan, one of the researchers.

Apivectoring (entomovectoring) is a comparatively new technology by which biological control agents are placed into dispenser trays at the entrances of managed bee domiciles. The existing bees become dusted with the formulated agent and disperse it to flowers and other plant parts where pests (insects or fungi) are adversely affected.

This technology was originally developed in Ontario and adapted for greenhouse application through collaborations between the University of Guelph, Agriculture and Agri-Food Canada's Harrow Research and Development Centre (HRDC), and Ontario growers. Since then, a number of companies have also contributed to making it available to commercial producers around the world, including Biobest, BVT, and others. 

Saving time and money
"Apivectoring relegates the job of dispersing biological control agents to actively foraging and pollinating bees," Peter continues. "This strategy offers the advantage of saving time and money as a precision delivery technology that requires using less crop protection product and less human labor as managed bees are already used for pollination of many crops. He adds apivectoring also has the benefits of emphasizing biological control rather than chemical control, provides daily delivery, and requires less machinery and water.

"The technology improves both crop yield and quality, as proven for tomato and bell pepper production. It has also recently been adapted for soft and tender fruit protection against pathogens such as grey mold (Botrytis cinerea) in Europe, Colombia, Kenya, and the U.S", says Peter. "So, when greenhouse-grown strawberries are attacked by pests, notably by the western flower thrips (Frankliniella occidentalis), it makes sense to exploit the hundreds of trips made by Bombus impatiens bumblebees, not only to improve strawberry crop yield but to also distribute biological control products." 

Towards addressing the need for such tools, their recently conducted study evaluated the impacts of three periods of apivectoring in a commercial greenhouse strawberry production facility to determine how well the conidia of entomopathogen, Beauveria bassiana, would be disseminated for control of crop pests such as the western flower thrips, Frankliniella occidentalis. As a pollinator-vectored mycoinsecticide, this strain is registered for use against whiteflies, thrips, and aphids in greenhouse vegetables, ornamentals, and herbs.  

The experiment was conducted three times over the growing season. The first two ran for one week, while the last was conducted continuously over five weeks. 

The study was conducted at the Canadian growers of Sunrite Greenhouses and contained two different strawberry varieties, including Sanadrian and Albion. Three apivectoring bumblebee colonies with in-lid dispensers were used to disperse the microbial pest control agent. 

The results show the formulation had minimal impacts on bumblebee populations, with under 16% mortality attributed to infection by it. Through population monitoring, the researchers also found that naturally occurring thrips were being suppressed by the apivectoring biocontrol strategy, with up to 75% of Frankliniella occidentalis collected from some treatment zones testing positive for infection by B. bassiana."  

"By completing the experiments in a commercial production greenhouse, the results show that integrating apivectoring with commercial best practices can be successful. However, certain strategies should be implemented in order to maximize the crop inoculum distribution and pest management efficiency", Peter concludes.

Read the complete research here.

Charlotte E. R. Coates · Roselyne Labbé · Dana Gagnier · Andrew Laflair · Peter G. Kevan © The Author(s), under exclusive license to International Organization for Biological Control (IOBC) 2023

For more information:
Peter Kevan (e-mail)
Roselyne Labbe (e-mail)
Charlotte Coates (e-mail)