The pitter patter of raindrops can sound pretty in a leafy orchard, but it can also sound like a death knell to a saskatoon berry producer.
That’s because it’s the splash of a raindrop that scatters the disease E. mespili, spreading it from one leaf to many.
And in a bad year, like last year, the disease can wipe out 50 percent of the prairie crop.
“There can be devastating losses,” says Quinn Holtslag, who is co-ordinating a control program.
“For anybody who didn’t do any control (last year), there were some terrible losses: 100 percent in some cases.”
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Holtslag is teaching prairie producers how to run a simple control program that, if done right, should eliminate most of their losses.
A spray-on treatment can almost entirely control E. mespili, and Holtslag, whose recently earned PhD was based on E. mespili control, has developed a simple way for producers to figure out whether it’s time to spray.
By using a cheap but specialized thermometer that shows daily maximum and minimum temperatures, Holtslag’s system can tell producers when and when not to spray.
He’s testing the system this summer with about 100 producers and will study the results after the crop is harvested this fall.
The program’s cost of almost $105,000 is covered by federal money from the Manitoba Rural Adaptation Council, the Saskatchewan Council for Community Development and Alberta’s Agriculture and Food Council.
E. mespili has become a serious limitation to the prairie Saskatoon industry. Originally, many industry developers thought saskatoon berry bushes would be impervious to most diseases because they were native to the prairie environment and had evolved to be hardy in prairie conditions.
“We didn’t realize how severely limiting this disease would be when we started promoting the crop to producers,” Holtslag said.
However, commercial planting and farming radically increased the vulnerability of the crop.
“If you grow something in a monoculture in a localized growing region, you’ll find exactly what likes living in that environment with those plants.”
The disease was first spotted in saskatoon berry bushes at the Prairie Farm Rehabilitation Administration’s farm in Indian Head, Sask., in 1980, but is now endemic in Western Canada.
Holtslag’s control program notes daily maximum and minimum temperatures, combined with rainfall, to reveal when the disease is most likely to be a threat.
In his PhD, Holtslag established threshold levels that producers could use to decide when and if to spray, but for this year’s project he has simplified the system, giving producers a simpler yea or nay answer.
“I made it so that a producer in a relatively easy fashion can enter in data and have the model function,” Holtslag said during a recent visit to a saskatoon bush research plot in Winnipeg as he examined damaged and shrunken berries from last season dangling from flowering branches.
It had just rained that morning and with the range of temperatures that day, it was a highly vulnerable time for the plants.
However, with so many leaves on the bushes, it was also a perfect day for spraying because spraying should take place when there are lots of open green leaves to receive the treatment. The plants need about an hour to transfer the treatment throughout the plant.
Holtslag said he hopes this program doesn’t just show farmers when to spray, but also when not to. If the environmental conditions aren’t likely to make E. mespili a problem, producers shouldn’t waste the time and money on treatment.
That’s good for both producer and for consumers, he added.
