Tomato Bacterial Spots

bacterial spot tomatoes

Bacterial spot is one of the most dangerous tomato diseases in existence, since it spreads rapidly and is very difficult to control. In most cases, tomato plant become so distorted by bacterial spot that their marketability severely decreases.

Causes and Symptoms

This disease is a result of the bacteria xanthomonas campestris pv. vesicatoria, which can exist on tomato seeds as well as on specific weeds. Bacterial spot can be spread through rain, irrigation, or wet plants. Tomato plants can be infected through pores and wounds, especially in warm, moist weather.

Symptoms of bacterial spot first appear as small, greasy, and irregular marks under the tomato plant’s leaves. The spots start as a dark green, then gradually become purple and gray with black centers, possibly within a white or yellow outer circle. Bacterial spot may result in thin and cracked leaf tissue, exposing the fruit and resulting in sun-scalded output. There is also a risk that the plant might defoliate. Fruit lesions are small dark brown bumps that sink into the fruit as it grows, making it appear scabbed.

Treatments and Control

To avoid bacterial spot, cultivators should buy certified disease-free tomato seeds and use sterilized soil or a mix that is commercially rendered. If it is not possible to acquire disease-free tomato seeds, your seeds should be submerged for one minute in 1.3% sodium hypochlorite, which helps eliminate bacteria on their surface. Another option exists in submerging the seeds in 122-degree Fahrenheit water for 25 minutes. This will affect surface and inner seed bacteria, but might adversely affect the plant’s germination.

Tomato crop rotation can also be utilized each year to minimize the spread of bacterial spot. In addition, cultivators should ensure that the tomato plants do not receive too much water, as moist conditions attract the spot-causing bacteria.

In addition to the prevention methods above, copper fungicides for tomatoes will deny the growth of bacterial spot for two to four weeks. This type of fungicide is used after planting the seeds, but before transplanting plants to the field.

Copper sprays are best applied before any signs of disease are present, since this will enable them to better control it. For the most effective protection, these types of sprays should be used before and after rain, but not during. If spots are discovered, spray plants for 7 to 10 days, and for one day before transplanting them. Once in the field, spotted plants should be sprayed one week after being planted, every 5 to 7 days when the weather is rainy, and every 10 days when the weather is drier.

Comments from Other Gardeners
  • Harrison Wambua says:

    Good advice.

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