High Tunnel Melon and Watermelon Production
Powdery mildew on cucurbit leaves.
The dry, humid and dense plant growth within a high tunnel is optimal for
development of powdery mildew. Powdery mildew (Podosphaera xanthii) is
a fungus that looks like a white mold on leaves (Figure 22). The disease appears
on the lower leaves of the vine and gradually spreads through the canopy.
The vines become weakened from leaf loss, and fruit size can be significantly
reduced. Plants should be regularly inspected, starting at fruit set for
powdery mildew. Choose resistant cultivars (Table 3). The high tunnel should
be properly vented to reduce relative humidity. Many effective fungicides
are labeled for powdery mildew control.
M173, new February 2006