Cause The fungus, Erysiphe heraclei, was reported on chervil production in California. Testing by University of California Cooperative Extension showed that strains of E. heraclei from chervil did not infect either celery or parsley. Cleistothecia were not observed.
Symptoms The main symptom is powdery white mycelium and spores on leaf and stem surfaces, leaflet twisting and bending can occur with severe infections.
Cultural control
- Prune out infected leaves or rogue infected plants to delay disease build up.
Chemical control
- Bicarbonates are registered to control powdery mildew. Thorough coverage is essential.
- Kaligreen at 2.5 to 3 lb/A on 7- to 10-day intervals. May be applied up to the day before harvest. 4-hr reentry. O
- Merivon Xemium (Group 7 + 11) at 4 to 11 fl oz/A on 7- to 14-day intervals. Do not make more than two (2) applications before alternating to a fungicide in different FRAC groups (non-Group 7 and non-Group 11). First test on a small portion of crop for phytotoxicity. Preharvest interval is 1 day. 12-hr reentry.
- Rhyme (Group 3) at 5 to 7 fl oz/A. Alternate or tank-mix with a non-Group 3 fungicide for resistance management. Preharvest interval is 7 days. 12-hr reentry.
Biological control Efficacy unknown in Oregon.
- Romeo at 0.23 to 0.68 lb/A on 7- to 10-day intervals starting prior to infection. Preharvest interval is 0 days. 4-hr reentry. O
Reference Koike, S.T., and Saenz, G.S. 2004. First report of powdery mildew caused by Erysiphe heraclei on chervil in California. Plant Disease 88:1163.