 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. |
