Tree fungus 'as detrimental as Dutch elm' disease affects blue spruce, including Rockford's official Christmas tree

ROCKFORD — If you peer past the ornaments and outer branches at the base of the city's official Christmas tree — a broad and bulky 40-foot-tall blue spruce — you'll find yellow and brown needles along with bare limbs more fitting for Charlie Brown's famously sad seedling than downtown's holiday centerpiece.

The tree that's the focal point of the city's Stroll on State is a victim of a widespread problem disfiguring blue spruces across the region. It suffers from a disease called Rhizosphaera needle cast — pronounced rye-zo-sphere-uh — which has drawn comparisons to the Dutch elm disease epidemic and emerald ash borer that nearly wiped out those trees in northern Illinois.

Arborists and other tree-care experts say the scourge of Rhizosphaera has surged over the past three to five years, forcing landscapers and homeowners to take down the ornamental tree known for its dense, powder-blue needles.

"I think their time has passed here," said Tim Gruner, garden curator for Anderson Japanese Gardens, the region's premier public garden. "I wouldn't plant a blue spruce anywhere in the region."

Anderson Gardens has phased out Colorado blue spruces, at times replacing them with Korean firs. But the fungal disease is present throughout the city.

"In my own neighborhood this week, actually, there were two 40- to 50-year-old blue spruces that were cut down because they were probably 60 to 70 percent dead," Gruner told the Register Star a week ago. "That's what I'm seeing — my entire neighborhood, all of the blue spruce look terrible."

The city's official Christmas tree is in the early stages of the disease, which hasn't done much to detract from the tree's beauty. Needle cast first appears on the innermost needles on the lower branches, but in severe cases branches may die as the disease spreads through the tree.

The fungus thrives in moisture and this summer saw record rainfall totals in June. Wet years such as 2017 are bad for trees and great for fungi, according to the Wisconsin Department of Natural Resources. The disease can be transmitted to healthy trees by birds, wind or rain or by humans cutting and pruning.

"To put in terms of the Christmas tree selection that we do for the city of Rockford every year, we're going to start running low on opportunities to get those bigger ones because they're probably going to be somewhat disfigured," said John Richards, president and owner of Tree Care Enterprises, which volunteers each year to harvest the city's tree. "At some point we're probably going to run out of good spruces to use."

You know the disease is present when outer needles start to turn from their bluish hue to a plum color. But by that point it's already too late. The disease has typically been present for 12 to 15 months before signs of it show, according to the University of Illinois Extension.

"With Rhizosphaera, you will lose all your inner needles, but you will have tufts of green on the edge," said Martha Smith, a certified arborist and horticulture educator with the University of Illinois Extension. "Then, when the new growth comes out the next spring, those infected needles attack the new growth and then they fall off, so you still have that tuft."

Rhizosphaera must be treated with a fungicide containing the active ingredient chlorothalonil, Smith said. It's a labor-intensive process, especially given the size of a mature spruce.

"You need to apply that when your spruce needles are just about half grown," Smith said. "Then you need to spray again when fully elongated.

"You have to do that for two years in a row and thorough coverage is important."

Some property owners choose to remove the trees and find other evergreens that serve the same purpose — they're often deployed as barriers against wind or to provide privacy. Some options are abies concolor fir, Norway spruce and balsam fir, said Jon Carlson, owner of J. Carlson Growers on Newburg Road.

"It's hard to find something that has that bright blue color," Carlson said. "In fact, there is really nothing."

Carlson said the disease is "as detrimental as Dutch elm or even the ash borer we've had the last few years." Growers like Carlson and Gruner say the time has come to stop planting blue spruce here in favor of other trees resistant to needle cast.

"They call them Colorado spruce for a reason," Carlson said. "They're probably happier in Colorado."

Kevin Haas: 815-987-1410; khaas@rrstar.com; @KevinMHaas