Sizzling, triple-digit temperatures have stalled the growth of some pear varieties in the Rogue Valley, while hastening peach picking.

Pear trees divert energy from developing fruit to survival during the sustained 100-degree-plus heat, and usually don't make up for lost time.

"It's difficult to get much growth in this excessive heat," said Mike Naumes, president of Naumes Inc. "It's a concern because the pears were quite a ways along, and the last couple of weeks is when the fruit really grows. So heat of this magnitude really hurts."

Depending on orchard location, the scorching heat has sunburned some pears. Comice, which possess a red blush when they're picked, can turn brown on the outside when they're in excessive heat.

"They can end up in the cull line because the brown can get into the flesh," Naumes said.

Overall, the crop appears good and hasn't been touched by hail.

Naumes launched its local harvest Friday, picking Star Crimson pears, in two blocks — one off Carpenter Hill Road south of Medford and another on Suncrest Road east of Talent.

"This is a fairly normal starting time, but last year we were 10 days earlier," Naumes said.

By noon, pickers had left the orchard, with extreme heat and smoke taking their toll.

"It seems like we're getting fires more often lately than in the past," Naumes said. "It's just kind of difficult for everyone out there in that environment. Sometimes the heat holds down, but it's not happening this year."

Bartlett pear harvest is slated for Aug. 14, followed by the comice crop. Picking of Bosc, Naumes' primary local crop, begins the first week of September.

"Despite these 10 days or two weeks of hot weather, the Boscs are sizing fairly well at this point," he said. "I don't know if it's my imagination, but it seems like they got off to a better start this year, and they've got quite a bit of growing time left."

What doesn't have a lot of growing time left are the peaches at Meyer Orchard.

Even for longtime orchardist Ron Meyer, who grows 100 acres of pears and eight acres of peaches outside Talent, this is among the hottest summers in memory.

"I've seen 114 degrees twice," Meyer said. "The first time I experienced it was 65 years ago."

The good news is that he's had a plenty of irrigation water to keep up with the heat.

On the other hand, his peaches have been ripening quickly.

"The warm weather actually makes the peaches more flavorful," Meyer said.

He began harvesting the first of five varieties July 24. The peaches mature in sequence, with each variety's harvest lasting about 10 days.

"When it gets hot during peach picking, you have to be on top of the harvest," he said. "Otherwise, you get overripe fruit."

Local wine grapes are generally harvested in September and October.

Alex Levin, an assistant professor at the Southern Oregon Research and Extension Center on Hanley Road, said the heat wave came early enough not to be an extreme factor.

"If this would have happened three weeks later, it would have been bad for flavor and color development," Levin said. "When grapes are still green and the berry is hard, it can withstand the heat. Once it starts to ripen, heat can be bad."

He suggests growers bump up irrigation 20 to 25 percent on account of the heat.

"The tricky part is that most people aren't keeping the wine grapes watered," he said.

Normal watering would have to be abandoned for at least a week, he said.

"You want to control stress and relieve stress due to the high temperatures," Levin said.

He said photosynthesis continues for the vines, but the result differs.

"It's just not as efficient," Levin said. "Like people, they've got to drink a little more water and they'll be fine."

 — Reach reporter Greg Stiles at 541-776-4463 or business@mailtribune.com. Follow him on Twitter at www.twitter.com/GregMTBusiness, on Facebook at www.facebook.com/greg.stiles.31