There are many different types of diseases that can affect tomato plants. Backyard gardeners need to be aware of these diseases, so they do not ruin your entire crop. Even if you only have a few plants, you need to know what to look for. This week I will be talking about bacterial spot and bacterial speck on tomatoes. The following information for this article came from The Ohio State University Department of Plant Pathology. Factsheets are available at https://go.osu.edu/tomato_diseases

Bacterial Leaf Spot

What to look for on the plants:

• Bacterial spot produces lesions on the entire leaf surface
• Greasy water-soaked spots on leaflets
• Older spots are dry and brown and often surrounded by yellow halos
• You will notice the spots getting bigger on the leaves
• Spots are most often seen on the entire surface of the leaves but can also be found on the stem and flower buds
• Severe infections can cause the plant to lose its leaves

What to look for on the fruit:

• Small, greasy water-soaked spots on green fruit that become slightly raised and enlarged
• Older spots are shaped irregular, light brown to black in color, and slightly sunken and have a scabby surface texture

This disease is sometimes confused with bacterial spot or bacterial canker. Bacterial leaf spot like high moisture, high humidity and warm temperatures. If bacterial leaf spot is present in your garden it can survive in the field as long as there is infected drop debris present. Consider rotating with a non-host crop before re-planting the field with tomatoes. Clean and disinfect all tools and fam equipment prior to working with new or clean plants. Good sanitation practices are critical to prevent cross contamination.  

Bacterial Speck

What to look for on the plants:

• Greasy water-soaked spots on leaflets
• Older spots are brownish black and often surrounded by yellow halos
• You will notice the spots getting bigger on the leaves
• Spot may appear on the stems
• Severe infections can cause the plant to lose its leaves

What to look for on the fruit:

• Black sunken stippling appears early on green fruit
• Spots are small and look like “pin-points” or “specks” on the fruit
• The spots can be scraped off the fruit surface with a fingernail

This disease is sometimes confused with bacterial spot, early blight. Bacterial spot like high moisture, high humidity, and cool temperatures. Just like bacterial leaf spot it can survive in the fields and the same sanitary practices should be followed to stop the spread.

This ends week one of tomato diseases. Look for next weeks article where I will be discussing Bacterial Canker and tomato pith necrosis.

Shelby Tedrow is an Agriculture and Natural Resources and 4-H Program assistant for Wayne County Extension. She can be reached at 330-264-8722
This article was previously published in The Daily Record.