Ask and Expert

Question from Merrilee, Salt Lake City, UT (received 5/21/20) -

Should I be treating my white fir and columnar spruce for bark beetles? We have met with two tree care companies and they've each given us detailed information of what they would propose to be done in our yard and it's conflicting. We have over 50 mature trees (firs and maples) - we care tremendously about the trees in our yard!

Thanks so much

Merilee and Doug

Answer from Ryan Davis, Arthropod Diagnostician, Utah Plant Pest Diagnostic Lab (sent 5/22/20)

Hi Merrilee,

In short, there is no reason to preventatively apply pesticides to your trees unless you have a reason to believe they are in imminent danger. Imminent danger would be:

  • spruce trees on surrounding properties have been dying (due to bark beetle (ips) attack)
  • fir trees on surrounding properties dying due to bark beetle attack or even balsam woolly adelgid attack (this would be unlikely where you are)
  • maples dying nearby (I really doubt this is happening)
  • or, your trees are very unhealthy, drought stressed and susceptible to insect and disease pressure

White Fir tree in yard

Most issues with spruce and fir in the valleys are due to drought and heat stress (which could ultimately lead to insect attack). Bark beetles that kill fir, do not kill spruce and vice-versa. The beetles that killed all of the trees up in the mountains (lodgepole pine and spruce) are two different beetles (mountain pine beetle and spruce beetle) and neither are likely to come into a residential property in the valley and kill trees. I really have not seen bark beetles killing fir trees in residential areas, though it is a possibility, I suppose. If someone is trying to push insecticide injections for bark beetles I would be very wary. There is very limited evidence that systemics work for bark beetles, and only one (emamectin benzoate: Treeage) has really shown promise.

Good Luck