Fri November 25, 2011
Garden Report

Ips Beetles Are Attacking Colorado’s Spruce Trees

If it’s not one beetle attacking Colorado trees it’s another. Most have heard about the mountain pine beetle and its assault on lodge pole pine trees – but another beetle is impacting the state’s spruce trees. KUNC gardener Tom Throgmorton has more.

Mountain Pine Beetle is getting a lot of attention.  But the Colorado state tree is being attacked.  Thousands of stately, mature Colorado spruce trees are being cut down in cities along the Front Range.  All because of a beetle less than a quarter of an inch long.

Spruce Ips Beetle is part of a group of Engraver Beetles.  All of these beetles create tunnels or galleries under the tree bark.  These tunnels destroy the flow of food killing large sections of the tree.

Ips Beetles over-winter under the bark of spruce trees.  They usually produce two generations of young each year.  One after they emerge in April and the other generation is produced in July.  If we have a mild fall a third hatching can happen in October.  Because they reproduce so quickly Ips has become a big problem.

Stressed or damaged trees are the first to be attacked by Spruce Ips Beetle.  Large, old spruce that have gotten little supplemental water are extremely susceptible.  Also trees damaged by snow and wind are attractive to the bug.

Unfortunately by the time the outward symptoms show up the most severe damage is already done.  Symptoms first show up in the top portion of a spruce.  The needles become light green to yellow.  More needles are dropped from the tree than normal.  Ultimately the damaged portion of the tree dies.  If you are unsure about your tree call a certified arborist or your local urban forestry office.

Reproducing Ips Beetles can send hundreds of young to infect other trees. Once a tree is infected the best solution is to cut down the tree.  From Fort Collins to Colorado Springs trees have been condemned and removed.

Preventative chemical sprays are difficult to apply.  The trunk of the tree needs to be soaked with the spray.  This is difficult because of the dense structure of spruce trees.  The spray needs to be timed in April and July just before new eggs are laid.  Spraying probably won’t help an already infested tree.

A healthy tree is the best defense against Spruce Ips Beetle.  Supplemental watering is essential.  Watering especially during the driest times of the year like late November.  Supplement water again in early spring if we aren’t getting our heavy, wet spring storms.  Sign your tree up for a feeding and spraying program with a licensed tree care professional. 



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