What condition is increased by wetting the foliage of roses?

Wetting the foliage of roses can lead to an increased incidence of disease, particularly fungal infections such as powdery mildew and black spot. When the leaves remain wet for extended periods, it creates an environment that is conducive to the development and spread of these pathogens. Fungal spores can thrive in moist conditions, and the presence of water on the foliage provides the necessary medium for these spores to germinate and infect the plant.

In contrast, while moisture retention may provide some benefits to the plant, such as aiding nutrient uptake, actively wetting the foliage does not contribute positively in that regard. Similarly, increasing the growth rate can typically occur through proper watering practices and nutrition but does not necessarily improve when foliage is intentionally wet. Pest infestations are also influenced by various factors but generally do not increase specifically due to wetting foliage alone.

Therefore, the practice of wetting rose foliage should be approached with caution and is generally discouraged, especially during cooler or humid conditions where lingering moisture can lead to disease problems.