CDFA Pest Prevention Plant Regulation Practice Exam

What is required for the completion of the pear-juniper rust life cycle?

1. Pear trees only

2. Both pear and juniper trees must be present

3. Juniper trees only

4. None of the above is correct

The correct answer is: Both pear and juniper trees must be present

The life cycle of pear-juniper rust specifically requires the presence of both pear and juniper trees. This is due to the fact that the pathogen responsible for this rust, Gymnosporangium sabinae, is heteroecious, meaning it requires two different host species to complete its development and reproduction. In the first phase, the fungus overwinters on juniper trees, where it produces structures that release spores in the spring. These spores infect the leaves of pear trees, developing into galls. As the galls mature, they eventually produce more spores that return to juniper trees, completing the life cycle. Without either host, the pathogen cannot fulfill its life cycle, highlighting the dependency on both plant types for the continuation of the disease. Other choices do not account for this necessary relationship; pear trees alone or juniper trees alone would not support the full development of the rust pathogen, which is why those options are not correct. Knowing the interaction between these two species is essential for effective pest management and prevention strategies.