Bacterial Spot Control: How to Identify and Get Rid of Bacterial Spots

Bacterial spot has the reputation of being one of the most dangerous diseases, especially in tomato. Aside from the fact that it spreads quickly, control can be quite challenging. A combination of different approaches is necessary to make sure that bacterial spot will not ruin your plants or crops. From preventive to control measures, it is critical to be wary on what methods to use to guarantee that bacterial spot will be manageable.

What is Bacterial Spot?

Bacterial spot is also known by other names, such as bacterial shot hole, bacterial leaf spot, or bacteriosis. The cause of the disease is Xanthomonas arboricola pv. Pruni. The bacterium was discovered in North America in as early as 1903. When you look under the microscope, you will see that the bacterium has a rod shape and is motile.

This disease can spread in a number of ways, but one of the most common is through infestation in its seed, as well as transplants that are already suffering from bacteria. It can affect the different parts of the plant, including twigs, leaves, and fruits. Aside from planting a seed with contamination, there are other ways by which it can multiply and spread to other hosts. Some of these ways include dew and wind. Overhead irrigation can make healthy plants susceptible to the disease if there are plants with bacterial spot nearby. Even blowing of the sand as a result of wind will spread infection. Wounds and natural openings in the plant will be ideal entry points for the bacteria. In terms of the external environment, an infection will be common in places with high moisture.

Bacterial Spot

Bacterial Spots Can Affect the Different Parts of the Plant

Identifying Bacterial Spot’s Damage

Host Plants

Among others, tomato and pepper are two of the most common host plants for bacterial spot, especially those that grow in an environment with high dew and warm climate. Aside from these, other hosts include peach, plum, prune, tart cherry, apricot, wild peach, almond, and nectarine.


The symptoms of the disease will depend on a number of factors, such as the specific host. The strain, pathotype, and race of the bacteria will also have a huge impact. Generally, below are some of the most common signs that you have to watch out for:

  • The leaves are the ones that will show the first signs of damage, specifically from their underside. There will be irregular and greasy marks. Initially, the color is dark green but after a while, it will turn either gray, purple, white, or yellow. In severe cases, bacterial spot can lead to defoliation of the host plant.
  • Damages will also be apparent on the fruit. In the case of pepper, for instance, rough circles will appear. The diameter will be about ¼ inch and it will appear like blisters. Aside from cracks, the surface will also appear rough, which is similar to tomatoes. As the fruit matures, the spots will inevitably grow larger.

Results of Infestation

Like in the case of other bacterial leaf diseases, most of the damages will be cosmetic. The physical appearance of the leaves will be unattractive. The holes in the leaves will inhibit photosynthesis, and hence, will deprive the plants of the nutrients that are essential for survival. They will grow unhealthy. Other parts of the tree will also show signs of infestation. In severe situations, the plant will end up unmarketable. Hence, this will translate to economic losses for commercial growers.

Bacterial Spot On Tomato

Tomatoes Infected by Bacterial Spots

How to Get Rid of Bacterial Spots

Natural and Organic Solutions

For the effective treatment of bacterial spot without using toxic pesticides, the following are some of the solutions that might work:

  • The reduction of economic losses due to bacterial spot is possible through choosing the right cultivars and making sure that you use the right seeds. If the seeds are already suffering from contamination, this will affect the overall growth of the seed. Purchase only from a reputable seller to have an assurance that the seeds will be disease-free.
  • Crop rotation is another solution that can prove to be promising. For instance, in the case of tomato and pepper, it will be good to rotate crops every two to three years. Plant crops that can resist or less susceptible to bacterial spot.
  • Fertilizing the soil is also a great solution, which especially works as a preventive measure. According to experts, bacterial spot is most common if the soil has low fertility. On the other hand, you should also prevent the excessive use of fertilizer. Balance the use of fertilizer to lessen the likelihood of suffering from bacterial spot.
  • Pay attention to your irrigation system as well. This is in relation to the fact that water and wind are two of the factors that will be instrumental in the spread of the disease. As much as possible, opt for drip irrigation. This will also keep the foliage dry most of the time.
  • When planting crops, it is also important to ensure proper spacing from one another. This will provide better air circulation. To add, this will also make it more difficult for the disease to spread to other plants.
  • If you see plants showing obvious signs of bacterial spot, you should uproot it as soon as possible. Leaving it on the surface will make other plants susceptible to infection. Deal with the root cause of the problem before it spreads.

Chemical Solutions

The treatment of most of the leaf diseases in a wide array of plants is possible through the use of chemicals. However, while the latter can prove to be promising, there are also drawbacks. They contain toxic ingredients. To enjoy the highest level of effectiveness, it is essential to follow the instructions from the manufacturer regarding the application of the chemicals.

Chemicals are more of a preventive treatment for bacterial spot. Right timing is vital for its success. Also, in some cases, repetitive application is necessary since rain washes down the chemicals. It will no longer be effective, which is why you should re-apply. Among others, copper sprays are some of the most common. Bonide is one of the specific brands that you might want to consider.

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