Heat, rain make spots on peppers
Q. My peppers have spots all over the leaves and fruit. It looks like black dots. What is wrong?
Howard from Canfield
A. This is bacterial spot. Usually, it favors high temperatures and lots of rainfall. So it must have got a jumpstart back in July when we had that one week of temperatures in the 90s with lots of humidity. Then as our weather warmed and the rain kept coming, the disease flourished.
Bacterial-spot lesions start looking like water-soaked spots, but then turn yellow, and finally, brown and sunken. This disease looks like some other pepper diseases, but is unique in the way the tissue in the center of the lesion dries out and then falls out, leaving a shot-hole in the leaves of the plant.
A bacterial disease is very different when it comes to management, compared with the fungal diseases many gardeners are used to seeing. Increasing air circulation and sunlight to dry leaves will not stop a bacterial disease. Infected plants should be disposed of, away from the garden area.
The bacteria can spread through infested pepper seeds, and can last on seeds up to 10 years. It cannot survive free in the soil for long, but it can survive on plant debris. This is another good reason to do a good job cleaning up plant debris in your garden each fall.
As for saving seed from the garden (or accepting seed from others), gardeners should always use clean seed to plant to prevent bacterial diseases.
We have an OSU Extension factsheet on treating vegetable seeds with hot water or chlorine to eradicate bacterial plant pathogens. But beware— old or poor-quality seed should be tested first to be sure the treatment does not injure the seed, making it useless for planting.
Gardeners must follow the directions exactly, based on our research, to be sure the bacteria is killed.
Details can be found at go.osu.edu/bacterialspot and go.osu.edu/seedtreat.
Eric Barrett is the OSU Extension educator for agriculture and natural resources in Mahoning County. Call the hotline at the office on Mondays and Thursdays from 9 a.m. to noon to submit your questions at 330-533-5538.