This season marks the 25th anniversary of Spruce Ips engraver beetle infesting eastern Colorado. However, there is no cause for celebration as this insect is responsible for killing thousands of spruce trees in our area. Signs of death have already appeared this winter and trees attacked in 2014 are already beginning to die. This is much earlier than usual and of great concern.
Ips beetle infestations begin at the top of the tree and work downward. Initial symptoms include a dry grayish appearance, which extends to the tree canopy, and soon after green needles will drop to the ground. When needles fall, typically small exit holes and sawdust are evident on the tree trunk. Ips kills infested trees by chewing through the water conducting tissues, while introducing a fungus that disrupts water movement throughout the tree.
There are eleven species of Ips engraver beetles in Colorado – all with a unique epidemiology. There are Ips and there are Spruce Ips. Ips that attack pines follow the typical playbook – attacking weak and severely stressed pine trees. Spruce Ips is much more aggressive, attacking tress that appear healthy.
Currently spruce trees seem unaffected, but obviously the beetles find weakened trees ripe for attack. We often point to abnormally hot dry weather for an uptick in Ips activity. But the last two years have not been abnormally hot and we’ve enjoyed better than average precipitation since 2013. What is the cause for these early signs of Spruce Ips? To be honest, we really don’t know.
We’ve had two weather events in the past year, which have defoliated many spruce – putting them under additional stress. This includes a 69 degree drop in temperature on December 4, 2012 and a 77 degree drop on November 12, 2014. Prior to the November 2014 polar vortex, Eastern Colorado weather was warm enough to support Ips beetle flights from tree to tree.
How can you prevent your spruce from coming under attack from spruce Ips? High-value spruce should be sprayed twice for bark beetles during the growing season. Many trees will benefit from fertilization encouraging tree growth. Consistent moisture is essential. Spruce trees prefer damp soils not saturated. Resist the temptation to remove live lower branches. The low branches provide shade keeping the soil cooler in the summer months. If there is bare soil under the tree, plant groundcover (vinca), or install 3 – 4 inches of mulch to help retain soil moisture.
If you believe your spruce or pine tree may be at risk a local Colorado tree service company can help.