Ambrosia beetles (subfamilies Scolytinae and Platypodinae) are a fascinating group of wood-boring beetles that do not actually eat wood — instead, they bore tunnels into trees and wood and cultivate specialized ambrosia fungi as their food source. The fungi are carried in specialized body structures called mycangia and are inoculated into the tunnel walls, where they grow and provide nutrition for both adults and larvae. In Arizona, ambrosia beetles attack a wide range of stressed, weakened, or recently dead trees and shrubs, including fruit trees, ornamental trees, and desert-adapted species. The granulate ambrosia beetle (Xylosandrus crassiusculus) is an invasive species now present in Arizona that attacks living trees under stress. A diagnostic sign is the characteristic 'toothpick' of compacted frass that protrudes from the entry hole. Ambrosia beetle galleries stain wood with dark fungal discoloration, reducing the value of lumber. In nurseries and orchards, attacks on stressed trees can cause rapid decline and death.