It’s a good season for Rhagoletis indifferens — and a bad one for cherry lovers.

A “heavy pressure” season has caused cherry fruit flies to proliferate, shutting down four processors in Washington state and making “bug station” inspection employees at the California and Oregon border on Highway 101 more vigilant this summer.

The ban keeping all cherries out of California, except those that are commercially grown, inspected and certified, has been in place for 10 years, said California Department of Food and Agriculture (CDFA) Pest Exclusion Branch Chief Duane Schnabel.

But this summer, the fly infestation is bad.

“We know it’s been a bad year — we usually don’t kick any commercial growers from Washington out of the program,” Schnabel said. “And there’s three or four growers we’ve had to kick out of the system.”

Bug station blues

Employees at the inspection station at the border typically tell people to have a good day and wave them on, but for the next 10 weeks, they’ll be more cautious, asking people if they have cherries of any sort.

And it doesn’t matter whether they were purchased in a store or grown in a backyard, said Bruce Pokarney of the Oregon Department of Agriculture.

Fruit fly infestations have struck all but two Western states. The states with infestations include Oregon, Washington, Idaho, Montana, New Mexico, Utah and all but two counties in Colorado. Only California, Wyoming and Arizona are not affected.

The ban precludes taking sweet, sour, bitter, pin, black, Mahaleb and choke cherries, cherry laurel, and Japanese and Pacific plums across the border.

For example, Schnabel said, a couple came across the border last Thursday and told inspectors they’d purchased cherries at a fruit stand in Bend.

“We told them it’s likely backyard fruit (in origin), and we processed the fruit in front of them,” he said. “You crush the fruit, put it in hot water, and whatever comes out of the cherry cores we can see in the light.”

(Cherry lovers might want to stop reading about now.)

Infested cherries will divulge small larvae — worms — that die in the hot water and float to the top. Cherries can be tested at farmer’s markets, too, Schnabel said, by taking a couple cherries, crushing them and putting them in a cup of water in the sun.

“They were pretty amazed,” Schnabel said of the couple. “They’d been eating them the whole trip. Western cherry fruit larvae. Little white worms — maggots. It’s been a heavy pressure year in the Northwest. We’re seeing a lot of fruit that’s infested coming across (the border).”

This season

About 20 commercial trucks have been sent home from the border this season after shipments tested positive for the fruit fly, but that’s out of hundreds of trucks that cross California’s borders every day.

The United States is expected to produce 238 million pounds of tart cherries this season, down 23 percent from last year, according to U.S. Department of Agriculture reports. Oregon alone produced more than 79 million pounds of cherries last season.

Cherries are inspected first at the processors, and a sample is retested at border stations for verification. If the flies infest an orchard, they can devastate them for the season, Schnabel said.

That it’s challenging enough for commercial growers and processors this season, backyard tree fruits are surely worse.

“If the commercial guys are having to deal with it, we know the backyard is pretty bad,” Schnabel said. “Some years we don’t get much of anything. But backyard fruits are usually pretty heavily-laden. Every day this time of year at all our stations, we’re intercepting cherries.”

Further challenging the inspectors is that summer brings on hoards of travelers — many of them in RVs, their refrigerators filled with seasonal fruits and vegetables.

He emphasized that 99.9 percent of commercial crops are just fine.

“We’ll have cherries for 10 weeks,” Schnabel said of the summer season. “Then stone fruits. And citrus in the winter. There’ll be extra vigilance because of the pest pressure.”