CDFA Pest Prevention Plant Regulation Practice Exam

Which disease requires both pear and juniper trees to complete its life cycle?

1. Ozonium root rot

2. Pear-juniper rust

3. Hawthorn-juniper rust

4. Branched broomrape

The correct answer is: Pear-juniper rust

The disease that requires both pear and juniper trees to complete its life cycle is pear-juniper rust. This is a type of rust fungus that has a complex life cycle involving multiple hosts. In this particular case, the pathogen, Gymnosporangium sabinae, thrives on juniper trees, where it produces spores that can then infect pear trees, leading to symptoms on the leaves and fruit. The interaction between these two hosts is crucial for the fungus to reproduce and spread. The cycle typically begins with the juniper trees, which bear structures that release spores in the spring. When these spores land on pear trees, they can infect them and complete the sexual reproduction phase on the pear host—ultimately producing new spores that can infect the juniper trees again. This interdependence highlights the importance of both host plants in the ecology of the disease.