Multifaceted Approach For Challenging Disease Researchers Dig Into Blueberry Scorch Solutions

By Ronda Payne

Blueberry growers got a sense of just how bad scorch virus can hit the industry this summer when fields throughout the Lower Mainland and beyond started showing signs of decline from the disease.

Researchers throughout Canada have come together to explore solutions. As Eric Gerbrandt, research director with the BC Blueberry Council explains, it’s likely going to take the efforts of all those currently involved and more, to establish control for the future of the industry.

While Gerbrandt would love a silver bullet solution to prevent the spread of scorch and its economic impact, together with his fellow researchers, he understands that’s not possible. Everyone recognizes the value of the industry and is pulling together to find solutions. It’s a four-pronged approach at present.

Gerbrandt says the four avenues being explored are: Mapping the presence of the virus within fields using drone and satellite imagery; looking into plant genetic resistance to aphids; studying the taxonomy of the aphids responsible for the spread; and assessing the potential for new viruses and viral strains in the mix.

In the first avenue, satellite imagery and/ or drone camera images may help identify scorch faster. Jason Smith, chair of the BC Blueberry Council thought there was something wrong in his fields. He reached out to Jonathon McIntyre chief technology officer of i-Open Group to help him validate that hunch. McIntyre bought a cheap drone to explore the issue.

“We combined it with some open-source technologies to program the flight path, download the images, create a mosaic and then analyze the images,” McIntyre says. “We flew all his fields. We were able … to determine that there were plant health issues. Enough for him to pull his fields and order new berry plants.”

This use of open-source technology has led to opportunities. Gerbrandt is collaborating with Bing Lu, professor with SFU, on the study that brings McIntyre’s pioneering together with high-end drone and satellite work to see how technology can aid in scorch identification from a farm-to-farm level as well as a regional level.

“This is pretty preliminary,” Gerbrandt says. “It shows us the potential of what we can do. It’s not going to change the fact that we have aphids out there. But it could help us map out regional hot spots.”

Lu is bringing advanced data collection via drones and satellite imagery to the web-based open-source tool McIntyre and i-Open Group created to become an evolving data repository. Within the site, images are stored, stitched together and analyzed.

The ongoing aggregation of data is key to the tools’ efficacy. As McIntyre explains, taking public data available through the BC government and other sources of land scanning, more than 900 sources of data are used to create the initial model.

“It allows the farmers’ data to be their own,” McIntyre says.

With the images from drones, technology can identify anomalies like colour, variations, or canopy volumes that appear to be scorch hot spots in a blueberry field. Then, growers and stakeholders could be sent into the field to confirm that assumption.

“We likely will need to still go out and do

ELISA [Enzyme-Linked Immunosorbant Assay] diagnostics of each and every plant,” says Gerbrandt. “But we can make a model that allows us to take an image and show us potential issue areas.”

ELIZA can also give growers an understanding of whether they have scorch or blueberry shock virus, which can look similar initially. It’s an important differentiation as plants with shock will recover, while those with scorch will not.

Fields vary as to how many plants are infected and how much they impact adjacent plants as well as neighbouring fields. This is the random nature of the aphids that cause the spread of scorch. The severity of symptoms also varies depending upon blueberry variety, but there are currently no varieties that are resistant to the disease.

As Gerbrandt recently said, “There are no known sources of true resistance to [the virus] in blueberry plant genetic resources making long-term efforts to breed better varieties a challenging proposition.”

Scorch initially hit Elliott hard, but then spread to varieties where Elliott was a par- ent (like Liberty) and kept going into Bluecrop, Duke and beyond. Initially growers hoped Calypso wouldn’t be hit by the disease, but as Michael Dossett, breeder and geneticist with BC Berry Cultivar Inc. says, there are currently no known varieties with immunity to the disease.

This being said, Gerbrandt notes that developing varieties that are tolerant or relatively resistant of the virus are options for the breeding program underway. However, as growers know, when it comes to new varieties providing relief, that solution is a long way off given the testing that needs to be done to ensure the right traits come through in the long term.

This leaves growers in a precarious position in that they need to remove infected plants, but there may not be a benefit in replanting due to the re-infection possible from neighbouring fields. Fields that aren’t pulled, serve as reservoirs of the virus to neighbouring (and further flung) fields.

“The taxonomy of the aphids responsible for the spread [of the virus] is currently in question,” Gerbrandt says.

Researchers at ES Cronconsult and the BC Ministry of Agriculture are collection aphids to allow the ministry to identify how the aphids are related to better understand which are responsible for scorch. While this may sound simple, numerous types of aphids exist, making taxonomy essential. Finally, the fourth prong of the research is looking at novel strains of the virus. There have been reports that scorch is a “mystery virus” but the current observation is that these inconclusive test results are potentially new viral strains. Either way, it’s hard news for growers.

As Gerbrandt notes, “this research recently identified new strains, which should lead to improved diagnostics.”

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However as he further suggests, the potential for evolving interaction between viruses and viral strains, aphid populations and plant genetic responses to infection may contribute to the accelerated spread.

This leaves growers to scouting, removing of infected plants and continual control of aphids to reduce the spread of the disease. Without an obvious solution, growers need to rely on experts within the industry for guidance on best decisions in the moment.

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