CDFA Pest Prevention Plant Regulation Practice Exam

Which of the following plants must be present for the pear-juniper rust to complete its life cycle?

1. Pear trees only

2. Pear and oak trees

3. Juniper trees only

4. Pear and juniper trees

The correct answer is: Pear and juniper trees

The pear-juniper rust pathogen, known scientifically as Gymnosporangium sabinae, requires both pear trees and juniper trees to complete its life cycle. This type of rust demonstrates a complex life cycle that involves alternating hosts. During one phase, the pathogen infects pear trees and produces aeciospores, which then need to be disseminated to an appropriate juniper host to continue the life cycle. Once on juniper, the pathogen undergoes further development and produces a different type of spore called teliospores, which are crucial for the next generation of infection on pear trees. This dependency on two distinct plant hosts emphasizes the relationship between the two species in the rust's life cycle, making it essential that both pear and juniper trees are present for the pathogen to thrive and complete its reproductive cycle.