Dry weather and prolonged high heat don’t help your onions — unless you’re a breeder field-testing new varieties for future inhospitable conditions.

Crookham Co., a major vegetable seed producer based in Caldwell, Idaho, showcased its onion varieties April 24 at nearby Wilder.

CEO George W. Crookham said tough conditions help.

“You’re always selecting the strongest,” he said.

“A year like this, with the heat, accelerates bugs and Pink Root,” said Zane Beams, Western sales manager for Seedway, a seed company. “If you have bred or selected for Pink Root resistance, the bulbs will have better resistance in the field.”

Onion variety trials in hot weather will help drive the future portfolio of seeds if those conditions occur more frequently, he said.

Heat stresses onions, which stop growing when the air temperature hits the mid-90s, said Lyndon Johnson, Crookham Co. sales development manager. “And if they show any growth, they would do it in the morning.”

With about 20 days of high temperatures over 100 degrees, this season produced fewer of the big onions for which the southwestern Idaho-southeastern Oregon growing region is known, Johnson said.

Thrips regenerate faster in high heat as their life cycle accelerates. He said mid-May to mid-July saw “quite a lot of thrips out attacking plants.”

The insect pest doesn’t like onion leaves as much when the plants mature, and at that point they “will start looking for a host and fresh green material” in other crops.

Johnson said selecting for strong root development can produce onion plants that efficiently establish themselves and begin raising a strong top structure so they can better withstand heat.

Crookham Co. onion varieties Caliber and Caldwell feature top structures with more gloss and less wax. Gloss helps heat resistance, and reduced wax makes the plant material less attractive to thrips, he said.

The company showed a handful of onion varieties with assorted characteristics. They included Epic and Defender, which are going  into the commercial lineup after several years of research and development, and grower testing.

Crookham Co. was scheduled to participate in Onion Variety Day at Oregon State University Malheur Experiment Station April 25 near Ontario.

Daytime high temperatures and nighttime lows at the station in June and July averaged their highest since 1943, OSU Malheur Research Assistant Erik Feibert said. Onions have matured at least a week early.

“It should be an interesting (OSU) trial and comparison this year between the varieties, given the stressful weather,” Feibert said.

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