 Powdery
mildew
Powdery mildew reduces yield by decreasing the
number of fruit or the length of time crops can be
harvested. The primary pathogens that cause powdery
mildew include Sphaerotheca fuliginea and
Erysiphe cichoracearum.
Symptoms:
whitish, talcum-like powdery fungal growth develops
on both leaf surfaces, petioles and stems. Symptoms
usually occur first on older leaves, on shaded lower
leaves, and on abaxial leaf surface. Older,
fruit-bearing plants are affected first. Infected
leaves usually wither and die, and plants senesce
prematurely.
Control:
disease tolerant cultivars along with fungicides are
usually used to manage powdery mildew. Management
with fungicides requires the product reach the
underside of the leaves and the lower canopy.
Systemic materials accomplish this. But strains of
powdery mildew are becoming more tolerant to these
chemicals. Resistance in fields and greenhouses has
been detected in the US, Europe and the Middle East.
Disease tolerant squash
varieties offer the best protection. |
