Pest Control Adviser (PCA) Plant Pathogens 2025 – 400 Free Practice Questions to Pass the Exam

Downy mildew of lettuce primarily affects lettuce plants, making it the direct host for the pathogen that causes this disease. The organism responsible for downy mildew, typically belonging to the genus Bremia, requires specific conditions and host availability to thrive. It has developed specialized adaptations to infect and reproduce on lettuce, making it an important disease concern in lettuce cultivation.

The disease is characterized by symptoms such as yellowing of leaves and white fungal growth on the underside of the leaves, which are easily identifiable and detrimental to lettuce crops. Understanding that downy mildew specifically targets lettuce highlights the importance of proper management practices for this crop, including crop rotation and the use of resistant varieties.

Other choices, such as tomatoes, cucumbers, and carrots, do not serve as primary hosts for downy mildew of lettuce. While these crops can be affected by other pathogens, they are not specifically susceptible to the downy mildew that primarily affects lettuce. This distinction emphasizes the specialized nature of plant pathogens and their host relationships, which is crucial for effective pest management in agriculture.