Saskatoon fungicide trials look at yield, storage

Disease control | Two chemicals that proved effective in controlling entomosporium aren’t approved in the U.S.

A new disease strategy report suggests multiple applications and modes of action are needed to suppress losses in saskatoon berries.

“Our applications, even when timing wasn’t ideal, worked well,” Sask-atchewan fruit grower Sandra Purdy told the Saskatchewan Fruit Growers Association meeting held during Crop Week in Saskatoon.

Purdy participated in one of the association’s research projects last year that started with fungicide trials on three farms.

Tough moisture conditions forced one of the growers to withdraw because he was unable to get into his orchards to spray.

“Timing of applications needed some work and that’s what we put into it,” Purdy said.

“We wanted to evaluate how systemic fungicides applied at different times during the growing season would affect the yield, quality and storage of Saskatoons.”

The trial was based on multiple applications of propiconazole (Jade-Topas) and a mix of boscalid and pyraclostrobin (Pristine). There were slight advantages in beginning with one product over another, depending on the order and timing of the products.

Applications should ideally take place at the white tip stage of blooming or after the first rain, which provides control of newly active and distributed fungal spores.

Growers say applications for Jade-Topas at this point or slightly later can injure blossoms, leading to abortion.

Pristine showed little or no damage to blossom set, they said.

The report recommended beginning with boscalid and pyraclostrobin at this early stage.

Provincial fruit specialist Forrest Scharf said growers should avoid applications during full blossom, no matter which products are used.

A second application of fungicide, in this case propiconazole, protects against infection as blossom material collects and drops off. Two more applications were then made.

Scharf said rotating the products is key to ensuring that the fungal pests don’t develop resistance.

The boscalid and pyraclostrobin combination proved effective in controlling entomosporium because of its Canadian registration for use close to harvest time.

Purdy paid for additional testing of harvested fruit from the trial and established that dramatically lower microbial counts were found on harvested material that had been treated with Pristine two weeks ahead of harvest.

“We are sure this adds to shelf life,” she said. “Shelf life is critical in getting crop to market and building those commercial food markets.”

However, the American government doesn’t recognize the boscalid and pyraclostrobin combination as a safe product for use on saskatoon berries, which are mainly produced in Canada.

In October, Purdy lost $63,000 when a truckload of her saskatoons was rejected at the U.S. border after showing it contained tiny amounts of boscalid residue.

“We are working with the authorities to get this issue dealt with, but until it is, any boscalid on berries means they can’t enter the U.S. market,” she said.

Purdy’s Prairie Berries business has invested “hundreds of thousands of dollars opening that market,” and she said it is a major issue for producers.

“This is the right product.”

Purdy said effective and sustainable pest control will put more money into farmers’ pockets through bigger crops, but she feels it is only part of the picture when it comes to improving the prairie saskatoon industry.

“It will improve overall, consistent supply, which will help the industry grow the commercial markets. We have to have a reliable supply and larger crops to gain access to those critical commercial markets,” she said.

Growers who participated in fungicide trials also saw reduced cankers in their bushes and generally healthier plants with what appears to be reduced winterkill.

The association’s project found that previous control rows that didn’t receive fungicide applications suffered from a variety of ills and some had to be removed in subsequent seasons.

Purdy’s farm received high winds and experienced huge hail losses last year, with significant damage to bushes. She will be comparing those plants to the control rows this spring.

“I’m expecting to see benefits that extend beyond just single crop yields and improved shelf life,” she said.

Purdy knows her saskatoons. With 130 acres under production, she is one of the nation’s largest growers and is heavily involved in the processing side of the business, buying other growers’ production as well.

It also means she has the most to lose when it comes to disease.

“Hundreds of growers lost their crops to disease this year. The conditions were right, or wrong, as the case might be. It was wet,” said Purdy.

Entomosporium hit growers hard. Two wetter than average years delivered the right situation to perpetuate the disease.

Rain in May often prevented growers from applying fungicide to their orchards, resulting in the loss of unprotected crops.

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