Thatching Ants at Base of Large Fir Tree: No Threat to Tree Stability

Washington state homeowners have a 60-foot fir tree with thatching ants building a large mound around the roots. Concerned about root stability and storm safety.

Expert Assessment

The ant mound poses no threat to a tree this size. The root system of a 60-foot fir is extensive and deep; surface nesting does not compromise structural integrity.

Control if Desired

Use ant bait insecticide on the mound. Foraging ants carry bait back to the colony, eliminating queens and workers. Available products: Amdro, Fire Strike, Extinguish, Extinguish Plus, Distance, Green Light, Spectracide, Ferti-Lome, Advion, etc.

Important Notes

• Baits are slow-acting (weeks to months for 80–90% control)
• Do not disturb mound before baiting
• Follow label directions precisely