Scientific Name

Leveillula taurica

Overall Plant Symptoms

Yellow spotting of leaves progressing to leaf burn. Easily confused with other pests, especially after leaves dry.

Leaf Symptoms

Irregular shaped bright yellow spots, progressing to leaflet browning. Spores not found in all infections.

Stem Symptoms

None, however leaf burn associated with dusty or oily appearing leaf stems is caused by russet mite, not powdery mildew.

Root and Fruit Symptoms

None. Mid-season leaf loss can result in fruit sunburn.

Disease Source

Wind blown spores from infested fields or host plants.

Source Peristence

Present since 1978, over winters on several common hosts.

Favoring Conditions

Fields weakened by other problems. An effective disease model developed by UC is available to predict disease.

Critical Crop Time

Mid-season due to leaf loss and resulting sunburn potential.

Controls/Management

Dusting sulfur preventative. Registrations pending for Quadris and Rally fungicides.

Additional Notes

Symptoms often compounded by other problems.