Bee-based disease prevention

Inoculating flowering plants with insect-delivered fungus can help limit disease

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Fungi that can inoculate crops against disease can be applied using insects — bumblebees, to be specific.

According to Bee Vectoring Technology (BVT) — a Canadian company with offices in the United States and Europe, and in the process of commercializing such a service — Bombus-delivered inoculants offer fruit farmers another way to augment their crop protection with an environmentally friendly biological input.

Why it matters: Biological inputs can provide disease-prevention alternatives in the face of fungicide resistance.

Observations from field trials conducted at Dalhousie, the University of Guelph, and other academic institutions also show improvements in plant health and crop quality are possible.

What is it and how does it work?

Ashish Malik.
photo: Supplied

Ashish Malik, president and chief executive officer of BVT, says his company’s bee-based inoculation service makes use of a patented “carrier formulation.”

This formulation, which helps beneficial microbes (fungal spores) stick to the bees, is mixed with those microbes as a powder. The substance is then placed at the opening of the hive where exiting bees inadvertently pick it up. Beneficial microbes are thus spread and absorbed by plants as the bees visit their flowers.

To successfully apply this technology in the field or orchard, Malik says hives must be placed at strategic points to match the bees’ foraging abilities. The extra weight the bees must carry, and how foraging behaviours change in different crops, are just two of many factors that must be considered in the calculation.

“We have to show that it’s safe to all species of bees,” says Malik.

The fungi itself is clonostachys rosea — a strain that prevents the establishment of necrotrophic (dead tissue) diseases such as mummy berry and early-season botrytis. It does this by invading the space within dead plant tissue before disease organisms can do the same (known as competitively displacing).

An inoculant powder tray within a hive. Bees then carry the powder to plant flowers.
photo: Courtesy of Bee Vectoring Technologies International

John Sutton, an Ontario-based plant pathologist and consultant working with BVT, says clonostachys rosea develops inside plant cells without producing any negative symptoms.

Sutton was also one of the original University of Guelph professors involved with isolating this fungus, which occurs naturally throughout Ontario, and revealing its capabilities in disease prevention.

While it can be applied using standard spray equipment, a method commonly used for biological control agents, Sutton says it’s only effective when coming into contact with flowers. This spurred experiments with more accurate delivery vectors.

“When spores hit the stamen they are immediately absorbed. This prevents them from being washed off,” he says. “It’s got a fairly broad range of activity. It’s certainly one of the top one or two biocontrol agents on the planet for the kinds of diseases we’re looking to control.”

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A potential (plant) health boost

Malik says years of trials in strawberries and at several academic institutions throughout Canada and the United States show the fungi and crop’s “beneficial symbiotic relationship” appears to improve growth. In some cases, this translated to higher and better-quality yields with longer shelf-life — things Malik says are of particular importance for all players in the fruit value-chain.

These trials, he adds, accounted for systems where bee vectoring has been added to standard chemical application programs, as well as those where it was a standalone method.

“We’ve never had a result where the BVT has performed worse than the current standard,” says Malik.

For David Percival, professor of whole-plant physiology and director of the wild blueberry research program at Dalhousie University, BVT has also generated some interesting results.

Research conducted under mild to moderate disease pressure conditions (in 2017) appeared to show some growth and development benefits in field tests of wild blueberries. He adds some “significant” yield increases were also seen.

Unfortunately, a late June frost in 2018, one that Percival says killed about 60 per cent of his region’s blueberry crop, prevented any meaningful comparison and replication of the previous year’s experiments.

“We saw what appear to be trends, but we really need another growing season,” he says.

Regardless, both Sutton and Percival say the opportunities posed by the technology are worth noting. This includes the ability to protect plants while encouraging pollination, something Percival says is particularly important to wild blueberry production, where huge numbers of flowers bloom in a very short window of time. He also thinks it is a great option to minimize equipment use and overall fungicide load.

Sutton adds that bee vectoring is more precise than general fungicide spray applications because bees visit flowers, directly, and basically every day. This technology could also be an answer to ongoing issues with fungicide resistance.

“I think the consistency (of application) is going to have a very big place in protecting costs,” he says.

Current limitations and price

BVT only works if the bees reach plants at flowering. If the weather is unco-operative, Malik says, the bees won’t be as effective. If no flowers are present, too, the beneficial fungi can’t be delivered. This limits current use to the time of flowering, and thus, infections like late-season botrytis cannot be effectively prevented.

In this case, Malik says a foliar fungicide application would help solve the issue and taking such action might be recommended to the farmer. Optimizing effectiveness ultimately comes from working with the farmer and working in tandem with existing crop protection systems.

Malik says the cost of using BVT is comparable to conventional application, placing it at US$300 to $400 per acre per season. However, he says the better and more abundant yields, as well as the longer product shelf life seen in trials of the technology need to be quantified.

Because no biotechnology is required for producing the product, Malik says it is suitable for conventional and certified organic production environments.

From a regulatory perspective, BVT is currently going through the approval process with the Environmental Protection Agency in the United States. Early discussions have been held with Health Canada, though no major steps have been taken in the company’s home country.

Due to a comparatively small market, Malik says Canada will be the third country in which they plan to seek regulatory approval.

He adds he and his colleague are currently investigating how to make this technology work with honeybees, as well as the potential to use bees in delivering other crop protection products. Ways to delve into non-fruit crops, like cereals, are also being explored.

About the author

Contributor

Matt is a freelance writer based between Essex County and Chatham-Kent. He is interested in all things scientific, as well as rock n' roll, hunting and history. He also works with his parents on their sixth-generation family farm.

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