If there is one word that strikes fear in the hearts of tomato gardeners, that word is "wilt." Imagine a long season of hard work ending in a yellow, dried up plant with no fruit. How disappointing!
To comfort frightened tomato lovers or grizzled growing veterans, let me describe the current tomato wilts. Though they are not curable, they can sometimes be prevented or their impact lessened.
"My tomato is wilting from the top down."
Tomato spotted wilt virus (TSWV) is probably the most prominent tomato disease now. It is spread by an insect called thrips.
Usually the top of the plant looks stunted or wilted, but the leaves are not limp as though they had no water. The young leaves may yellow and have red, brown or black discolorations in them. These discolorations may form a ring or circle.
The veins on the underside of leaves may thicken and turn purple. Green fruit can have raised or flat rings, semi-circles or circles on them which yellow as the fruit ripens.
Some varieties of tomato are resistant to TSWV, although they may not be completely immune. If you have a question about what variety you are looking to buy, I can talk with you about how that variety stacks up to others.
Once tomatoes get the disease, there is no control. Spraying for the thrips that spread TSWV is not effective as a curative measure.
Bag and destroy infected plants as quickly as possible early in the season to prevent spread. Late in the season, you may want to just let the infected plants finish ripening the fruit they have.
"My tomato is wilting. It looks like it is out of water."
At least three things can cause this – fusarium wilt, bacterial wilt or southern blight.
A fungus causes fusarium wilt. It blocks the water-conducting tissues in the plant. The leaves yellow and wilt, often starting at the bottom of the plant.
This disease can affect just one side or one to several branches of the plant. The plant can die early producing no fruit. If you cut into the plant, the vascular system (just under the surface of the stem) will be brown.
Fusarium wilt can survive in the soil for a long time. Do not plant tomatoes in infected areas more than once every four years. Rotate tomatoes each year. Do not plant them in the same area that you planted potatoes, eggplant or pepper last season.
Lastly, if you suspect that your crop may be infected with fusarium wilt, check the roots of the plant. Root-knot nematodes are commonly found alongside the fusarium wilt fungus and can be used as a helpful indicator of the problem.
Prevent fusarium wilt by planting resistant/tolerant varieties. Again, give me a call if you are unsure if the variety you want to grow has any type of fusarium resistance.
Bacterial wilt causes a rapid wilting and death of the plant. The plant dies so quickly it may not have time to turn yellow.
To identify bacterial wilt, cut through the stem. Bacteria wilt browns the pith, or middle, of the stem. On bad infections, the pith may be hollow.
Cut a short section of the stem and suspend it in a clear glass of water. You can often see a milky, bacterial ooze streaming out of the bottom of the cut stem.
There are no controls or resistant varieties for bacterial wilt. It also attacks peppers, potatoes and eggplant. Carefully dig out infected plants and soil and discard. Do not plant these vegetables in this area for at least four years.
Southern blight is a white mold that rots the stem at or near the soil line. The plant is stunted, wilts or dies. Look for the cottony fungus growth and the light brown BB sized fruiting structures of the fungus.
The fungus may be at or slightly above or below the soil line. You may not see the white fungus growth if the weather is dry, even though the plant may still be infected.
Bury all plant residues before planting; plant vegetables farther apart; and treat with Terraclor at planting if you have a problem with southern blight. Some people wrap the stem near the soil line with foil to slow this disease.
Tomato wilt can be devastating, but you can learn to live with it. Knowing your enemy helps to remove the fear from dealing with this disease.
If you have questions about any other diseases or issues in the garden, call Bryan County Extension at 912-653-2231 or email at firstname.lastname@example.org.