Symptoms and Signs
Leaves infected with powdery mildew initially have small (1–2 mm), white powdery colonies. These colonies enlarge and can cover the entire leaf and stem. In severe cases, leaves become twisted and distorted.
Comments on the Disease
Foliar symptoms typically do not appear until leaves have matured. Infection and disease development are favored by dense canopies with high humidity during evening and morning, and temperatures between 55° and 90°F. Erysiphe heraclei infects various other Apiaceae crops, including celery and fennel, although it may occur as host-specific strains or isolates.
Management
During field surveys, watch for leaf distortion and yellow discoloration which are the earliest visual symptoms of powdery mildew. To reduce disease development, apply fungicide when the pathogen is first detected.
Cultural Control
Growing cilantro with drip irrigation and managing planting density to aid canopy aeration may help reduce disease development and spread.
Organically Acceptable Methods
Use cultural controls in a certified organic crop.
Treatment Decisions
Do not spray pesticide unless infection appears early in the growing season.
| Common name | Amount per acre | REI‡ | PHI‡ | |
|---|---|---|---|---|
| (Example trade name) | (hours) | (days) | ||
| Not all registered pesticides are listed. The following are ranked with the pesticides having the greatest IPM value listed first—the most effective and least likely to cause resistance are at the top of the table. When choosing a pesticide, consider information relating to the pesticide's properties and application timing, honey bees, and environmental impact. Always read the label of the product being used. | ||||
| A. | AZOXYSTROBIN (Quadris) | 12–15.5 fl oz | 4 | 0 |
| MODE-OF-ACTION GROUP NAME (NUMBER1): Quinone outside inhibitor (11) | ||||
| ‡ | Restricted entry interval (REI) is the number of hours (unless otherwise noted) from treatment until the treated area can be safely entered without protective clothing. Preharvest interval (PHI) is the number of days from treatment to harvest. In some cases, the REI exceeds the PHI. The longer of the two intervals is the minimum time that must elapse before harvest. |
| 1 | Group numbers are assigned by the Fungicide Resistance Action Committee (FRAC) according to different modes of action. Fungicides with different group numbers are suitable to alternate in a resistance management program. In California, make no more than one application of a fungicide with a mode-of-action group number associated with high resistance risk before rotating to a fungicide with a different mode-of-action group number; for other fungicides, make no more than two consecutive applications before rotating to fungicide with a different mode-of-action group number. |