|Photo by bitkisagligi.net|
|Photo by flickrhivemind.net|
Moist weather this spring and summer has contributed to the development of bacterial diseases on tomatoes, just like it did for fireblight. The two diseases most often seen in years like this one are bacterial speck (Pseudomonas syringae pv.tomato) and bacterial spot (Xanthomonas campestris pv. vesicatoria). So far, we’ve had a couple tomato samples infected with bacteria brought to the plant clinic.
Leaf symptoms look the same for both diseases. Small water-soaked spots form and grow to about 1/8” in size with yellow halos. The centers are light brown and often tear; yellow halos are common. On more mature plants, infections are concentrated on the older foliage. Spots may also appear on the fruit pedicels.
Preventive measures are best in the course of both these diseases. Crop rotation and garden sanitation will help as the diseases can overwinter on plant debris. Unfortunately, the disease can also enter the garden on infested seed or transplants. Don’t handle or work around the plants when wet. Copper containing fungicides can be applied at the first sighting of leaf spots and can be repeated every 7 to 10 days, but may not completely stop the disease under favorable weather conditions.
For more information about tomato problems in the home garden, check out this CSU fact sheet: http://www.ext.colostate.edu/pubs/garden/02949.html.
|Photo by extension.umn.edu|