How to identify tomato bacterial wilt symptoms fast

Tomato bacterial wilt symptoms begin to show after infection by Ralstonia solanacearum. Ralstonia solanacearum is a soil-borne bacterium mostly affecting crops in the tropical and subtropical regions of the world. It is a common and potentially fatal disease that affects solanaceous crops and a wide range of ornamentals.

Once established in the field, tomato bacterial wilt symptoms can be extremely difficult to control. For one, there are no chemical controls that are effective. However, cultural practices can help to reduce disease occurrence. Crop rotation and planting cover crops of non-susceptible plants (such as maize, rye, beans, and cabbage) can help to minimize pathogen populations in the soil.

Tomato bacterial wilt symptoms

In the early stages of the disease, the youngest leaves seem wilted. Plants affected by bacterial wilt typically show wilting symptoms while still green and can appear to appear suddenly. As the disease progresses, the plant’s base may develop brown cankers and root rot, and a cross-section of an infected stem may reveal brown vascular tissue discoloration.

tomato wilting
Tomato showing wilting symptoms

Plants may appear wilted in the afternoon, “recover” overnight, and then wilt again in the afternoon. This is because the plant requires less water in the morning when the humidity is high, but as the heat rises, the clogged vascular system limits water uptake, and the plant wilts. The plant eventually dies after becoming permanently wilted.

Young stems may collapse after infection or display long and narrow dark brown streaks along the stem. When you cut the cross-section of the stem, you will see the streaks of brown discoloration in the infected areas.

Bacterial ooze test

If you suspect that your tomatoes might be suffering from bacterial wilt, one sure test is the water test. First, you take an infected stem and using a clean razor blade, cut the stem. For severely infected stems, you will see a thick milky white substance coming out of the cut section of the stem. The milky white substance is bacterial colonies present in the stem.

bacterial ooze test
Tomato stem cut for bacterial ooze test

Fill a transparent glass with clean water to ensure that you have visibility.

Take the cut and dip the cut tip of the stem into the glass of water. If the wilt-causing bacteria are present in the plant, you will see white ooze flow from the stem to the bottom of the glass. The white ooze is made up of several bacterial colonies that will together form the cloudy substance you will see flowing down, through the water.

bacterial ooze test
Bacterial ooze test

Bacterial wilt thrives in hot weather of about 85 to 95 degrees Fahrenheit. High temperatures lead to symptoms showing quite early. In some cases, plants may grow without showing symptoms but the bacteria may survive in the plant and can spread to uninfected plants.

Risk factors leading to bacterial wilt infection

Cultural practices, such as using contaminated materials, and sick plants finding their way into the garden are the main sources of contamination.

While contaminated seeds may cause other tomato diseases, such as early blight, that is not the case for bacterial wilt.

Bacterial wilt thrives under a highly humid climate or late irregular watering of the plant. Also, weed presence in the farms has proven to favor the development of the disease.

Having dried contaminated plant leftovers, on the farm, poses no risk because these bacteria do not persist in a dry environment from year to year.

Managing tomato bacterial wilt

Once you spot bacterial wilt symptoms on any plant in your field, quickly remove the sick plants. When you remove these plants, put them in a plastic bag or container so that the pathogens do not spread to other plants. 

All infected plant material should be removed and destroyed. Plant only disease-free plants that have been certified. Removing sick plants is a precautionary measure. It is hard to tell just how much it reduces disease spread if the pathogen has already gotten into the soil. 

Practice crop rotation with non-susceptible plants like corn, beans, and cabbage. In this rotation, avoid using pepper, eggplant, potato, sunflower, or cosmos every three years

Consider growing all susceptible solanaceous plants (tomatoes, peppers, eggplants, and Irish potatoes) in a new garden site separate from the original. Before using in the new garden site, thoroughly hose off all soil from tiller tines and tools used in the original infested site.

Kewalo, a cultivar that is partially resistant to bacterial wilt, is a rare cultivar

In locations where bacterial wilt is abundant or widespread, the adoption of bacterial wilt-resistant rootstocks has been successful. Several bacterial wilt-resistant rootstocks for grafted tomatoes, peppers, and eggplants have recently been tested and found to be resistant to a high degree. It’s possible that grafted plants will be available.

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