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Bacteria Spot or Septoria? Help!

Tomato #3
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I'm a beginner gardener. I have three raised beds with about 12 inches deep with five tomato plants. My plants seemed fine until we started getting a lot of rain on a daily basis. Now all my plants have small dark spots on their leaves. I want to save them but don't know what to try first. Any advice is welcome.

Green Thumb
Posts: 358
Joined: Fri Mar 14, 2014 4:06 pm
Location: MD Suburbs of DC, 7a

Hi Alirae,

Putting your location and/or your profile will help with the diagnosis. If you are in the eastern part of the country it might be caused by excessive rain. That will cause yellowing of the leaves on some tomatoes. What variety of tomato is this? My grape tomato plants are exhibiting this as well. Other than the yellowing and some ugly spots and holes they are fruiting up nicely.

Posts: 13984
Joined: Tue Jan 01, 2013 8:32 am
Location: Hawaii, zone 12a 587 ft elev.

It could be alternaria canker which is a fungal problem. Large areas of the leaves between the veins are killed leading to leaf curling and death. Canker can also show up on stems and fruit. I do see spots on the stems as well. The fungus overwinters in the soil. It is important to keep picking off the lower leaves and watering at the base of the plant. The leaves should be bagged and burned. I remove the lowest foot of leaves anyway to prevent splashing and mulch helps.

Tomatoes or any of its relatives should not be planted again in this spot for three years. Alternatively you could try a tomato that is resistant, but it would still be better to change the location.

https://vegetablemdonline.ppath.cornell. ... Table.html

Septoria and bacterial spots usually show up as smaller spots and some have a halo of yellow around the spots. Your leaves have large areas of brown/black splotches and it is even on the stems. When I get bacterial speck and septoria, the stems are usually not affected and I pick off leaves early.

Taking off lower leaves of the tomato, providing good air circulation between the plants, mulching and drip watering to reduce splashing helps to control tomato diseases from starting. Once a fungal problem gets in the soil, it is best to change the location until the spore count subsides. There are soil fungicides but they are very expensive and I only used them on ornamental plants. Solarization in July-August will help kill the fungus and bacteria in the soil.

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