WSET Diploma D1 Practice Exam

Powdery mildew is kept in check mainly by altering the leaf microclimate, not by spraying chemicals. Opening the canopy improves air movement and sunlight penetration, which lowers the humidity and leaf wetness that help the fungus establish and spread. In a less dense, well-lit canopy, spores have fewer neighboring leaves to colonize and the leaves dry more quickly, making infection less likely. This is a cultural practice because it changes the growing environment rather than applying a treatment. The other options are chemical approaches rather than cultural adjustments, so they aren’t the typical cultural practice used for this purpose.