Frost Damage and ‘Uncertain’ Pollination Threaten Yakima Valley Orchards | Business

When it comes to growing and harvesting cherries, timing is everything – and over the past two seasons, extreme weather has hit at the worst times for Yakima Valley cherry growers.

A record heat wave in late June and early July damaged many cherries before they could be harvested last summer, reducing the harvest by around 20%. And in April, a two-week period of sub-zero temperatures hurt cherry blossoms and pollination in the Yakima Valley, according to growers and tree fruit experts.

“For our region, the (two-week cold snap) definitely overlapped peak cherry bloom,” said Matthew Whiting, professor of horticulture at Washington State University. “I think the impact of cold weather will be more severe on our stone fruits, especially cherries.”

Two local cherry orchard owners agreed with Whiting’s grim analysis after an average low temperature of 30.8 degrees in Yakima in April.

After a warmer than normal March, 23 out of 29 days (through April 29) recorded below normal temperatures, according to the Pendleton office of the National Weather Service. Sixteen of those days had low temperatures below zero, with record lows of 21 degrees at Yakima Airport on April 15 and 17.

“I’m in a very cold place, so I had 100% shedding,” said Greg Strutner, owner of Moon Blossom Cherries near Gleed. “The stamens of my flowers are all frozen. There is a lot of pollen, but there will be no fruit.

“The biggest problem is that it was cold for so long. Even if you had wind turbines, it made no difference,” Strutner added. “I have a full time job and only have 3 acres (of cherries), but for those who grow commercially, this is going to be devastating for a lot of people.”

Mark Barrett, owner of Barrett Orchards in northwest Yakima, said the period of cold temperatures and occasional snow from April 9 to April 23 was combated with wind turbines and sprinklers, which can have a slight cooling effect. heating even on the coldest nights.

“It’s a mixed bag,” Barrett said. “We definitely have frost damage, but we also have cherry blocks that were protected from wind and water. We just don’t know if they will be pollinated.

The cold slows down the bees

The pollination process depends on several steps occurring in the correct order, Whiting said. These include having live, compatible and available pollen; having this pollen transferred to the receptive stigmatic surfaces of the flowers (mainly by bees); and having favorable conditions for germination and pollen growth.

In general, warm conditions speed up each step of the pollination process, and the process is slower in cold weather, Whiting said.

“Our two main areas of concern are problems with fruit set – pollination – and cold temperatures which damage the floral tissues of the trees,” he said. “What is unique this year is that there have been extended periods where temperatures have not risen to the point where bees are active.”

Generally, bees hide and don’t roam among flowers if the temperature stays below 55 degrees, he said.

“This is the point above which the bees are active and come out and forage,” Whiting said. “There is some hope that the flowers that had opened and avoided major damage will still be viable, and that the bees could still plant a crop.”

An alternative to bees is the application of pollen via an electrostatic sprayer, a service provided by several commercial companies in the region.

“With this technology, the bees don’t need to carry or move the pollen,” Whiting said. “So in case of low bee activity, pollen spraying can be a good solution.”

Cherry blossoms are fading

The key is whether the last week of relatively warm April temperatures, with highs in the 60s from April 21-26, coincided with enough cherry blossoms in bloom.

Barrett said April 28 that while a few trees remained in bloom, most had turned green.

“Of all the fruit trees, cherries are the most finicky about the flower, the bees, the timing of pollination,” he said. “Some years it can take three days (for pollination), but it’s a wild weather year so I don’t know.

“Usually in a cool spring we have about seven days (for pollination). This year we had 14 days of flowering, but 10 of those 14 days were cold so the bees didn’t work.

It will take a few weeks to see how this year’s “uncertain” pollination, as Barrett called it, translates to a healthy cherry crop. Warmer weather would help, and as of April 29, when the Weather Service reports an average high of 70 degrees for Yakima, the Upper Valley still hasn’t seen an April high of 70 or higher.

WSU’s Barrett and Whiting are trying to stay optimistic.

“We are concerned about frost damage and lack of bee activity below 55 degrees, but I am still impressed with the ability of these farming systems to produce fruit and have a decent harvest despite the harsh conditions. “, Whiting said. “We’ll see how things turn out in a few weeks.”

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