Blueberries
The Elliott variety of blueberries has been hit hard by scorch virus this year, but it’s far from the only varietal that’s susceptible.
Elliott blooms later and therefore sees higher aphid concentrations during bloom, making it a likely target and host for scorch. Unfortunately, bushes can’t be sprayed for aphids during bloom due to pollination, and there are no safe varieties to switch over to, explains Michael Dossett, breeder and geneticist with BC Berry Cultivar Inc.
“There are no varieties with immunity to the disease,” he says.
The tiny aphid is the chief promoter of scorch which transfers it from one plant to another, making it possible to wipe out large acreages quickly. Rhonda Driediger, owner of Driediger Farms, has already had to remove and replant 26 of her 105 acres in blueberries.
“It’s wildfire,” she says. “It’s everywhere.”
Once infected, plants will start to look burnt – hence the name of the disease – and will gradually develop yellowed leaves which will die. Blossoms will decrease in number and in time the plant will die. No prevention is currently available, other than to spray for aphids, but this strategy is far from fail-safe.
Aphids will leave a long legacy of destruction behind them as they travel from plant to plant, creating a slow and expensive death in an invasion that farmers have no real weapons to fight.
Driediger pled the case of growers on June 4 to Lana Popham, BC’s Minister of Agriculture and Food, when the pair inspected Driediger’s fields.
“[Growers] have to remove and replace the field and this requires financial encouragement,” says Driediger. “It’s probably going to be six or eight thousand acres that will be infected.”
That could entail a loss of nearly 30 per cent of BC’s 27,000 cultivated acres.
While the Ministry of Agriculture and Food says it is aware of the increasing concerns, there have been no indications of funding for replants, which is what Driediger says the industry needs.
Carolyn Teasdale, an industry berry specialist with the ministry, continues to assist growers by staying in touch, sharing information and providing updates about strategies.
Recommendations for control are no different than they were when the disease was initially identified in BC in 2000. Growers need to control aphids, test suspect plants, and remove those that are infected.
The BC Blueberry Council has a number of scorch-specific fact sheets and a video on its website under the resources section.
Photo Government of BC | Photo Credit: Lisa Wegener, Kwantlen Polytechnical University
Scorch Damage
Symptoms on blueberry plants infected with Blueberry scorch virus. Early to late symptoms of blighting of blossoms.
Calypso is not the answer
A much anticipated and discussed variety called Calypso has been popular among growers. BC Blueberry Council research director Eric Gerbrandt says, “It may surpass Elliott to become the third most widely planted cultivar behind Duke and Bluecrop.”
There’s no wonder it’s growing in interest given that it’s a mid to late season variety, so it will have fruit for first harvest later than Bluecrop and Draper, but earlier than Liberty and much earlier than Elliott, Aurora and Last Call. It requires several picks and depending upon when it’s picked, it either stays firm for two weeks or longer in a cooler, or it may increase in firmness.
Despite the positive timing of Calypso, it does not have resistance to scorch, simply because no varieties do.
“Some varieties, such as Bluecrop, tend to tolerate it much more than others,” says Dossett. “Everyone is struggling to figure out whether replanting with blueberries right away is the best course.”
Although Calypso isn’t the answer to scorch, it does have a lot of positives in terms of its firmness. Gerbrandt notes delaying first pick may improve quality of the second pick. Second pick also improves in firmness over time in storage, perhaps beyond seven weeks.
Testing continues and Calypso may be a great option, but Gerbrandt says it has drawbacks, as do all varieties. It did not fair well during the 2021 heat dome, exceeding the damage sustained by Duke, and it may have a “mealy” texture at certain times.
These may become small concerns. With higher yields, berry size, better flavour and larger fruit than Draper, Calypso may be the next choice for berry growers.
