Many disease and insect problems start at the base of Colorado blue spruce and work their way up the tree, which suffers from environmental stresses in the Midwest.
Photo courtesy Jud Scott/vineandbranch.net
This will probably come as no surprise to property owners with Colorado blue spruce in their landscape, but the tree is in trouble.
American Nurseryman, which covers the nursery trade, posted a piece recently about an increase in the rate of decline of Colorado blue spruce (Picea pungens) in the Midwest.
The beautiful trees are popular, especially here in the lower Midwest, where we have few native conifers, said Nate Faris, a certified consulting arborist and owner of Faris Tree Consulting in Indianapolis. But because they are from the Rocky Mountains, Colorado blue spruce does not do well here. “They are stressed in our environment.”
Heavy clay soil, high humidity and summer heat are different than the cool temperatures and fast-draining soil in the higher elevations of the Rockies, their native habitat.
Signs of the most common spruce disease in Indiana, a fungus called Rhizosphaera, are yellow needles in mid to late summer and needle drop, usually from the lowest part of the tree. Another common problem is spruce spider mite. Needles develop a splotchy yellow or rusty cast. The mites start toward the center of the tree’s lower branches.
“I would say we’ve seen record levels of spruce complaints for the last three years,” said Jud Scott, a certified consulting arborists and owner of Vine and Branch Inc., in Carmel. Scott cites drought periods in 2012 and 2013, cool, wet springs, hot dry summers, radiant heat from pavement and planting areas that are too small as contributing factors.
“The most common significant problems found on samples are Rhizosphaera needle cast and spruce spider mite,” said Tom Creswell, director of the Plant and Pest Diagnostic Lab at Purdue University. “We also see stress from drought, deep planting, crowding and poorly drained sites.”
His lab has not seen an uptick in Phomopsis canker, another fungus disease, which is bad in Michigan and Illinois. It’s a harder problem to sample because it tends to affect trunks, rather than branches.
“Blue spruce is just not the right plant for many Midwestern landscapes, but even knowing all those problems, I still enjoy seeing the healthy ones,” Creswell said. “I just would never consider planting one in my own yard. Pampering my arborvitae to keep them healthy is enough work for me.”
What can the gardener do? Make sure Colorado blue spruce and all conifers are watered during drought. Spider mites can be detected by shaking a branch above a white piece of paper. If there are spots that smear, they’re likely spider mites. It’s always best to consult with a certified arborist for the best diagnosis and possible treatment.