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WEB EXCLUSIVE: RNA interference technology could provide new control for flea beetle

A groundbreaking new method for controlling flea beetle, the pest that causes at least $300 million in damage in North American canola every year, may hit growers’ fields early in the next decade.

RNA interference, or RNAi – a process by which RNA molecules “silence” genes targeted as threats – has already been harnessed by public and private research and development programs against several agricultural pests, including Colorado potato beetle (CPB) and corn rootworm.

According to Jim Baum, Monsanto’s insect control lead in chemistry, the use of RNAi technology against flea beetle “represents a sizable opportunity and need” for canola growers in the U.S. and Canada who have seen incomplete protection from neonicotinoid insecticides and other chemical products in recent years.

Monsanto began work on an RNAi-based product for flea beetle control several years ago, Baum says, as part of a suite of RNAi projects aimed at controlling agricultural pests, including corn rootworm and CPB.

Put simply, RNAi for flea beetle control works by “tricking” the beetle’s natural immune system to self-destruct. Beetles are fed double-stranded RNA (dsRNA) molecules that “turn down” expression of a critical gene in the flea beetle midgut, killing exposed insects within five days.

There are two possible delivery methods for RNAi-based pest control in agriculture: plants can be genetically engineered to express dsRNA in their leaves, or dsRNA can be applied externally to plants as a topical spray. Monsanto has worked with both methods; its corn rootworm product is transgenic.

But the company’s flea beetle project is currently focused on the development of a foliar insecticide that can be applied using its patented BioDirect platform.

Monsanto advanced its CPB BioDirect product to Stage 2 in 2015, and Baum says the company’s experience in RNAi for CPB control has streamlined its approach to new RNAi products.

The company has already run lab bioassays monitoring mortality in insects fed various dsRNAs, as well as seedling assays in which a set number of beetles are exposed to canola seedlings treated with dsRNA at a prescribed field rate.

Last year, Baum says, Monsanto ran successful field trials for its flea beetle RNAi project, and this year the number of trials more than doubled. (The company could not comment on the location of the field trials).

Next up, Monsanto will be analyzing effectiveness of various agronomic practices — basically, what works best in terms of rates and application timing, and how the product will work in combination with other products.

“Compared to previously approved products’ timelines, we’re being conservative with this one, recognizing that topical is a new application of the technology,” Baum says. “But if the project is successful, we’re projecting commercialization sometime on the early side of the next decade.”

Farmer and consumer outreach
Though RNAi-based insect control products won’t reach farmers’ fields for several years, they need to know what’s coming, and farmer and consumer outreach will be more important than ever for companies looking to commercialize the technology.

This is the view of Curtis Rempel, vice-president of crop production for the Canola Council of Canada.

“RNAi provides a tool or a technology that takes us outside of the traditional chemistry realm, so it has the potential for much improved environmental outcomes, but along with new technologies come a new set of regulatory and efficacy evaluations,” he says.

Just how safe is RNAi? According to Baum, RNAi has a built-in specificity that means once dsRNA is targeted to a specific insect pest, even closely related pest species are not harmed when they ingest it. “It’s hard to imagine a chemical insecticide, even Bt, that would be as specific as this RNAi product we’re talking about here,” he says.

Rempel agrees but believes farmers and consumers alike need to feel that regulators and scientists have had the opportunity to evaluate RNAi technologies in terms of environmental and societal norms.

Next year, the Canola Council hopes to include discussions around RNAi in its annual Canola Discovery Forum, and Rempel says the organization is working on developing “supporting material” to help communicate the role of RNAi in pest control to stakeholders – although he is quick to point out that communications outreach about RNAi requires the collaboration of all stakeholders.

In Rempel’s estimate, only 10 per cent of farmers are familiar with RNAi and aware of projects in the pipeline, even though they are the ones who will benefit most from its use.

But consumers shouldn’t be neglected either. After all, it’s consumers who implicitly afford farmers the “social license” to use technologies like RNAi, and they are the ones who will need to be assured of the products’ safety.

“I think we have an opportunity to do a good job of looking at the questions we’re asking, reviewing regulatory procedures and communicating these to the layperson,” Rempel says.

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August 14, 2017  By Julienne Isaacs