What’s causing brown spots on my bush beans?
I planted Jacob’s Cattle bush beans. They germinated well, but now have brown spots on some leaves. I do not see any insects on the leaves. Can you tell me what is causing the brown spots, and the best way to help the beans?
Kate Garland, Horticultural Professional
Our team agrees this appears to be ozone damage. This fact sheet does a nice job explaining the phenomenon. The good news is that they will likely recover if the ozone conditions improve. There’s not much you can do to avoid this situation.
On a slightly different note, we were just alerted to the fact that potato leafhoppers have been sighted in the region. Beans are one of their preferred crops. We recommend growing them under a lightweight row cover to avoid the damage caused by this pest.