Cause There are several fungal leaf spots reported on oxalis in the PNW including those caused by Ramularia oxalidis, Phyllosticta guttulatae, and Septoria oxalidis. Most fungal leaf spots such as these are favored by conditions that keep leaves wet for extended periods of time.
Symptoms Circular necrotic spots on leaves of various sizes. Spots may have a brown or tan center with a dark margin. Tissue around the spot may be yellowed or chlorotic. Black fruiting bodies may be found in the center of spots.
Cultural control
- Space plants to allow for good air circulation.
- Remove and destroy infected leaves on the plant and fallen leaves.
Chemical control Not considered important enough to treat.
- Fore 80 WP at 1.5 lb/100 gal water plus a spreader-sticker may be helpful before symptoms develop. 24-hr reentry.