Extension Master GardenerSM Volunteers of Buncombe County

tomato problem

What Can Go Wrong with Tomatoes?

What can go wrong with growing tomatoes? Almost everything! What can go right with planting tomatoes in our home gardens? Enough to keep us growing them!

Tomatoes ripening on the vine_Todd Heft_CC BY-NC 2.0_Flickr
Tomatoes ripening on the vine

What’s the problem?
Let’s face it—there are lots of challenges with homegrown tomatoes. They wilt, they spot, they crack, they dot, they blotch, they rot. Whew! The list goes on. Few vegetables—or fruits, which are what tomatoes are—are more challenging.

Helpful hints
Try following these guidelines:

  • Decide on varieties that are well-suited to our area, bred for disease resistance, and meet your eating preferences.
  • Select healthy bedding plants or start indoors from seeds 6 to 8 weeks before the expected last frost date.
  • Wait to plant until after all danger of frost has passed, usually after Mother’s Day for Buncombe County.
  • Choose a location that receives at least six hours of sun a day.
  • Plant in well-prepared soil, rich in humus, with a pH level of about 6.0 to 7.0 (find out with a soil test).
  • Maintain uniform moisture and mulch.
  • Avoid overhead watering which can promote disease.
  • Stake or cage your plants because of their vining tendencies.

What to watch for
Although there are myriad tomato problems, most are rare. Five of the most common concerns and their solutions:

  1. Bacterial spot produces small chocolate brown spots on leaves and fruit. Recommended controls are to use treated seed, apply fixed copper bactericide, avoid overhead watering, remove old plant debris, and rotate your planting area.
  2. Blossom end rot caused by calcium deficiency produces dark-brown leathery spots on the blossom end of fruit. Prevent by liming your soil (based on soil test results) and keeping your plants evenly moist—be sure to water plants during dry periods!
  3. Sunscald produces papery white areas on the side of fruit facing the sun or yellow-orange blotches at the stem end that do not ripen. Proper planting and maintenance help prevent foliage diseases that can cause leaf drop and expose fruits to too much sun.
  4. Cracks in fruit also result from an uneven moisture supply. Tomatoes may need to be watered every 2-3 days, especially in dry weather.
  5. Flea beetles produce many tiny holes in leaves. Tomatoes will tolerate a great deal of flea beetle damage, but if damage is excessive, ask about an approved pesticide.

Preventing problems
To prevent disease in future years, do not compost plant debris. Plant tomatoes in a different location at least every third year. Then, watch your tomatoes grow! If you have a bad year, don’t give up! There’s always hope for the following season.

Consider the wisdom in John Denver’s song from his 1988 album Higher Ground:

Homegrown tomatoes, homegrown tomatoes
What would life be without homegrown tomatoes?
Only two things that money can’t buy
That’s true love and homegrown tomatoes! 

Article written by Mary Alice Ramsey, Extension Master GardenerSM Volunteer.

Learn more 

Gardening in the Mountains lecture:
All Things Tomato
by Dr. Randy Gardner, Professor Emeritus, Horticultural Science, NCSU
July 19, 2018, 10 a.m. to noon
Folk Arts Center, Asheville, NC
Watch for details in early July blog announcement. 

Growing Tomatoes in the Home Garden
by NC State Extension

Late Tomato Blight Is Here
by Debbie Green, Extension Master Gardener Volunteer, July 2015

Late Tomato Blight Is Here

Late tomato blight was discovered in Buncombe County last week. This is a reprint of a post written by Debbie Green, originally published two years ago.

Tomatoes should be reaching their prime, and if you have lush green plants with ripening fruit, enjoy your harvest. If your plants aren’t looking so good however, they may have one of the many tomato diseases that sometimes thwart even the most experienced vegetable gardeners. One of the most serious of these is late tomato blight, which typically affects plants later in the growing season, but has been confirmed on plants in West Asheville as of early July this year. This disease can spread spores as far as 20 miles, so identifying the disease and destroying the affected plants may spare others’ tomatoes from developing the symptoms.

The first symptoms of late blight on tomato leaves are irregularly shaped, water-soaked lesions.
The first symptoms of late blight on tomato leaves are irregularly shaped, water-soaked lesions.

Rain and high humidity are both favorable conditions for the spread of late blight. Once your plants are infected they can’t be cured; fungicides containing copper or chlorothalonil are currently the only treatments proven effective to prevent late blight. If you spray your plants, follow label directions. Take care to cover all leaf surfaces; use eye protection and other precautions to prevent contact with the spray.

The good news is there are less devastating diseases that are not late blight, so getting a positive diagnosis is important. The first signs are irregular dark spots that look water-soaked on the newer leaves at the top of the plant, often with a lighter-colored “halo” around them. As the spots enlarge, the leaves shrivel and die. You may also see white cottony growth on the underside of the leaves. Both ripening and green fruits are also affected, with greasy looking spots that turn brown and leathery.

During humid conditions, white cottony growth of P. infestans may be visible on the underside of affected leaves.
During humid conditions, white cottony growth of P. infestans may be visible on the underside of affected leaves.

There are many images available online to help you determine if you have late blight; one of the most comprehensive series of photos is this one prepared by Dr. Meg McGrath of the Long Island Horticultural Research and Extension Center: http://www.longislandhort.cornell.edu/vegpath/photos/lateblight_tomato.htm#images. If you are unsure about the diagnosis, you can bring photos and samples of your plants to the Master Gardener Clinic at the Buncombe County Extension Office.

If you do have late blight, bag up your plant as soon as you can, but do it on a sunny day to reduce further spread of the disease. You can salvage already ripened fruit or green tomatoes that don’t show symptoms; these are safe to eat. Take care to look for affected plants other than tomatoes, especially potatoes and petunias. Weeds in the nightshade family may also show symptoms and should be removed and bagged.

Infected fruit are typically firm with spots that eventually become leathery and chocolate brown in color.
Infected fruit are typically firm with spots that eventually become leathery and chocolate brown in color.

If you lose your plants, there is always next year. There is ongoing research on less susceptible varieties and some evidence that ‘Defiant,’ ‘Mountain Merit,’ ‘Mountain Magic,’ and ‘Plum Regal’ tomato varieties are resistant to late blight. Consider planting these varieties next season if you want to increase your chances of a blight-free crop.

For more information see http://content.ces.ncsu.edu/publication/tomato-late-blight/

Contact Us

Buncombe County Extension Office
49 Mount Carmel Road
Asheville, NC 28806
Helpline 828-255-5522

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