WILLIAMSBURG — A mystery disease is killing apple trees in northern Michigan, and agricultural experts are searching for answers.
Area growers are concerned with an unidentified, spreading blight that has killed some varieties of McIntosh apples grown from dwarf rootstock. The malady, meanwhile, baffles researchers.
"We have quite a few dying on us," said David White, of Interwater Farm in Williamsburg.
White's McIntosh crop that was grown on dwarf rootstock is succumbing to the disease — it's affected about 20 percent of his McIntosh crop, or about three percent of his total harvest. His other apple varieties aren't affected.
But he worries that it might spread and said it's killing trees that have produced fruit for several years.
"It hurts when you put the investment in there and in 10 years you're taking it out," White said.
So far, growers and researchers are at a loss to explain the problem.
"It's one of those issues where nobody really knows what's going on," said Erwin "Duke" Elsner, agriculture extension director for Grand Traverse County.
Nikki Rothwell, head of the Northwest Michigan Horticultural Research Station in Leelanau County, said the problem is impacting McIntosh orchards throughout western Michigan and in New York state, another major apple producing state. The disease has been identified in four McIntosh varieties, she said, all with dwarf rootstock.
"We're seeing tons of decline," Rothwell said.
There's speculation the disease could be related to winter weather damage, but White said some colder sections of his orchards don't show problems.
Farmers plant trees from dwarf rootstocks because they grow smaller than standard trees, which makes it easier for pickers at harvest time. Their smaller size allows trees to be planted closer together to boost yield, and dwarf rootstock trees also produce fruit faster than standard trees.
White said a dwarf rootstock tree can produce fruit in its fourth year, while other trees can take six to eight years or more.
Steve Kalchik of SVF Inc. farm in Northport said he's also seen "scattered" attacks of the disease in his "Linda Mac" McIntosh apples.
"Some part of the orchard will have seven or eight trees in a row with it, and in other parts it's just one tree," Kalchik said.
Researchers from MSU's Extension office took a chunk of one of his dead trees and are investigating possible causes, he said.
Kalchik said the mystery disease is worrisome because McIntosh is a popular regional apple variety. Other growers have reported problems with "Pioneer Mac" varieties, he said.
"Macs are kind of our bread-and-butter apples up here," he said. "You get good tonnage and the return is pretty good."
But if farmers and researchers can't pinpoint the problem, Kalchik will be forced to pull out his afflicted trees and replace them.
"I can't afford to fight with it," he said. "When things get too bad, you have to cut your losses and start over."
Dave Alpers of Red Path Orchards in Suttons Bay said the problem is attacking his "Linda Mac" apples. It killed about 5 percent of his tree block last year, and another 5 percent this season.
"I'm very concerned about it, yeah," Alpers said. "If you keep losing 5 percent a year, it's going to affect you."
Alpers suspects the problem stems from winter damage.
"Until somebody shows me I'm wrong, that's what I think it is," he said.
