More Summer Tomato Problems -- Crop Rotation and Fertilization too!

Advice from the Help Desk of the
UC Master Gardener Program of Contra Costa County

Subject: More Summer Tomato problems  as well as Crop Rotation and Fertilization 

Client brought tomatoes from her garden with “production problems” to the Help Desk.

Response from the Help Desk: Thank you for bringing your tomato plant samples to the UC Master Gardener Program Help Desk office. You mentioned that you have been planting tomatoes in the same area for a number of years and have not had problems before this year. We found 3 different conditions in your samples that could explain why your plants are not thriving.

First, the leaves that are pale with a purplish cast on the undersides have symptoms of both nitrogen and phosphorus deficiency. Nutritional deficiency can make plants susceptible to other problems like pests and diseases. To remain healthy, tomato plants may need light applications of nitrogen every 4 weeks, and they also frequently need phosphorus. A good organic vegetable fertilizer will supply these nutrients and release them slowly. More detailed recommendations for how to fertilize tomato plants can be found here http://ipm.ucanr.edu/PMG/GARDEN/VEGES/CULTURAL/vegefertilizing.html .

Tomato Russet Mites (microscopic)
pix: UCANR

Second, your plants are infested with a microscopic pest called a tomato russet mite. Mites suck plant juices, weakening the plants. Heavy infestations can cause severe defoliation (loss of leaves). Growing tomatoes in the same
place year after year can favor a build up of this pest. The pest can also persist in petunias, morning glory, and other plants in the tomato family like potato, peppers and eggplant. We recommend that you remove the infested plants, all fallen leaves and weeds in the area, and put them in your green waste container (not in a compost pile). This will reduce the potential that russet mites will still be in your yard next year.

Additional information on the russet mites can be found here http://ipm.ucanr.edu/PMG/GARDEN/VEGES/PESTS/tomrusmite.html. 

Sulfur dusts can be used to reduce an infestation of russet mites but will not help if the pest has already killed most of the plant. If you do decide to try a treatment anyway, safety warnings applicable to the use of sulfur include wearing eye protection, long pants and long sleeves, and a hat, and avoiding contact with eyes and skin.  Additional information on sulfur is here http://ipm.ucanr.edu/TOOLS/PNAI/pnaishow.php?id=67 . 

Third, at least one of your plants has a bacterial disease, called pith necrosis, that is attacking the inside of the stems, hollowing them out. Unfortunately, this disease will kill the plant and there is no treatment for it. To prevent a re-occurrence of this disease next year, do not plant tomatoes in the same area year after year. Also, reduce stress to your plants by watering and fertilizing them adequately, but do not add excessive amounts of nitrogen (follow label directions). Finally, wait to transplant tomatoes until early May when the soil should have warmed to at least 60 degrees because colder soil favors the development of this disease.

Finally, we strongly recommend that you not plant tomatoes or other plants in the tomato family listed above in the same area more than 2 years in a row. Rotating your vegetables will help reduce the pests and diseases that you have been experiencing this year. You may also be interested in a good overall UC reference on growing tomatoes in the home garden that can be found (free) at http://ucce.ucdavis.edu/files/repositoryfiles/8159-54222.pdf

Please feel free to contact us again if you have additional problems with your garden.

Help Desk of the UC Master Gardener Program of Contra Costa County (JL)

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Note: The  UC Master Gardeners Program of Contra Costa's Help Desk is available year-round to answer your gardening questions.  Except for a few holidays, we're open every week, Monday through Thursday for walk-ins from 9:00 am to Noon at 75 Santa Barbara Road, 2d Floor, Pleasant Hill, CA  94523. We can also be reached via telephone:  (925) 646-6586, email: ccmg@ucanr.edu, or on the web at http://ccmg.ucanr.edu/Ask_Us/ MGCC Blogs can be found at http://ccmg.ucanr.edu/HortCoCo/ You can also subscribe to the Blog  (//ucanr.edu/blogs/CCMGBlog/).