Heat-damaged apples

Heat-damaged apples from the record-breaking June heat wave.

Apple growers and researchers across the Northwest say they’re concerned about fruit damage caused by the record-breaking heat wave that struck in late June.

With several weeks to go before the harvest of some varieties begins, however, it’s too early to predict the scope of the damage.

Washington growers especially are worried. The apple is the state’s highest-value crop. In 2020, according to USDA, the apple crop was worth $1.95 billion.

“This temperature event was unprecedented with both the intensity and how early it occurred,” said Lee Kalcsits, assistant professor of tree fruit physiology at Washington State University.

In scorching 100-plus-degree weather over the past week, Kalcsits has visited orchards, assessing fruit quality and heat impacts.

During the heat wave, Kalcsits said, based on infrared thermometer readings, fruit surface temperatures exceeded 140 degrees Fahrenheit in the afternoon when no sunburn protective sprays were used, and 113 to 119 degrees Fahrenheit when protective sprays were used.

“This does seem extreme but is correct,” said Kalcsits, of the extraordinarily high fruit temperatures.

The result was sunburned fruit.

Despite growers’ use of sunburn protection including netting, canopies, evaporative cooling, misting and spraying, many growers say their apples are showing sunburn browning, reducing marketability.

“The apples are sunburning big-time,” said Jesus Limon, a cherry and apple grower with orchards near Orondo and Quincy, Wash.

Limon said he’s been spraying his apples with a protective coating to limit sunburn, but the spray doesn’t seem to be very effective in such high temperatures.

Protective measures are expensive and time-consuming, so Limon, like many growers, has focused his efforts on protecting the highest-value apple varieties.

Because apples are small, Limon said it’s too early to know the percentage of damage, but he expects he’ll be able to assess the scope more accurately in a few weeks.

“I think we’ll have quite a bit of damage no matter what,” he said.

Charles Lyall, a longtime grower in Mattawa, Wash., said he’s also concerned about sunburn, especially in early-harvest apple varieties.

But, like Limon, he said it’s too early to make market or volume predictions.

“It’s a pretty big question mark right now,” he said. “You know in your gut it probably won’t be good, but you just don’t know yet.”

Lyall said he thinks the heat damage has “taken its toll” emotionally on apple growers, who have already faced many challenges over the past year.

Kalcsits, the researcher, said the recent high temperatures may reduce fruit growth rates at a key time. Later cultivars are less likely to be impacted by the heat wave, he said, while earlier varieties such as the Gala — set to be harvested in about five weeks — are likely to be impacted more.

Later varieties may not be off the hook, however, because, as Kalcsits noted, the highest summer temperatures “are usually still to come.”

“We can only hope that we don’t continue to receive 100 days later in the season as well,” he said.

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