Land Zo! – Pining Away

Mike MeyerJune 1, 2018
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Forestry specialists sleuth out the mystery of Phoenix’s dying Aleppo pines.

Take a moment to look up at the Valley’s trees and you can easily see something is amiss: Many of our towering pine trees have more brown needles than green.

From Ahwatukee to Apache Junction, our manmade landscape is dotted with these unhealthy looking trees; now city of Phoenix, and state and federal urban-forestry experts have joined forces to solve the mystery of the browning Aleppo pines.

Though not native to the area, the pines have been planted in the Valley since at least the 1930s, transplanted by homesick Midwesterners for a touch of green. City parks have used Pinus halepensis as a “workhorse’’ tree because it’s verdant year-round, can take full sun and is drought-tolerant. But now these perennial favorites are turning brown.

Experts believe it may be a bad case of Aleppo Pine Blight, a difficult-to-diagnose condition that could be caused by mildews, rust, smuts, air pollution, mites or any combination of factors.

After collecting samples from blighted trees, researchers positively identified a pine-feeding spider mite that may be the culprit, but more conclusive research is needed, says Steve McKelvie, a state forestry program specialist.

Richard Adkins, Phoenix’s forestry supervisor, advises homeowners with distressed pines to go slow with mite-killing insecticides. “Spraying will kill off the good mites as well as other beneficial insects.”

Valley pines have never experienced blight at these levels, McKelvie says.

So far, reportedly few trees have died, but if the blight continues to worsen, more may fall.

The Valley’s dry winter also could have helped trigger the browning pines. Arizona is in its 21st year of long-term drought, and dry months through this spring and a longer, hotter summer could cause even more problems for the pines. “The drought with the blight is super-stressing these trees,” McKelvie says.

To salvage the trees, the University of Arizona’s Maricopa County Cooperative Extension Office recommends homeowners water deeply to reach the pines’ absorbing roots.

And don’t go crazy with the pruning, says Rebecca Senior, a Cooperative Extension certified arborist. It could cause more stress to trees that are already stressed out.

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