Field Identification
Fungal leaf spots with ash-gray to tan centers, reddish borders, and tiny dark fungal fruiting bodies visible with a lens—common on beet, chard, peanut, rose, and many ornamentals. Defoliation follows prolonged humid, warm spells.
Lesions often angular on veined leaves; spores spread by wind-driven rain and irrigation splash. Consecutive wet nights rapidly build epidemics.
How to Deal With It
Organic Control Methods
Copper or sulfur protectants; Bacillus-based products; neem as a supplemental rotation—apply before forecast wetting events.
Compost extracts and competitive leaf surface microbes show anecdotal help; strongest gains come from reducing leaf wetness duration.
Increase row spacing; orient rows with prevailing wind; destroy crop residue; rotate away from hosts for two years where feasible.
Drip irrigation; avoid late-day overhead watering.
Deep plow or remove infected debris in intensive beet/chard rotations; scout lower canopy first.
Let Nature Handle It
Natural Enemies
- Bacillus subtilis
- Pseudomonas spp.
- Trichoderma spp.