CDFA Pest Prevention Plant Regulation Practice Exam

The correct answer is that Dutch elm disease is primarily spread by bark beetles. This disease, caused by the fungus *Ophiostoma ulmi*, is associated with specific species of bark beetles, particularly the European elm bark beetle (*Scolytus multistriatus*) and the native elm bark beetle (*Hylurgopinus rufipes*). As these beetles feed on the bark of infected elms, they carry the fungal spores with them. When they move to healthy elms, they introduce the fungus into the tree, which ultimately leads to the disease spreading in elm populations.

Understanding the role of bark beetles in the transmission of Dutch elm disease is crucial for effective management and prevention strategies. Other potential pathways, such as wind, water, and milled lumber, are either less significant or do not reflect the primary mechanism by which this particular disease spreads. Wind may aid in dispersing spores but does not facilitate direct infection like beetles do. Water does not play a role in the spread of this pathogen, and while milled lumber can potentially harbor the fungus, the live and active transmission associated with beetles is the primary concern. Thus, recognizing the specific role of bark beetles in the life cycle of