One quiet Saturday morning I was out inspecting the garden. I had noticed that several of the leaves at the top of the one of the tomato plant were missing. That morning the air was quite still but one branch was moving just a little bit. I thought, “What was going on here?”
I kept looking for whatever that was making that branch quiver ever so gently. Something was eating my tomato plant and I wanted to find out what it was. There was nothing on the tops of the branches, but soon my eye led me to a fat green caterpillar about 3 inches long, perfectly camouflaged, hanging upside down munching and crunching on my tomato leaves – a tomato hornworm.
I plucked him off, and several of his siblings, and they were history. Sometimes when you are trying to troubleshoot tomato problems or other gardening problems, you have to become a detective.
When examining plants for disease problems, the lower leaves will usually show symptoms first. Warm, wet weather is usually indicative of disease problems in tomatoes.
Septoria leaf spot and early blight usually attack the lower leaves first and both may be present at the same time. Septoria first appears as small, water-soaked spots that become circular spots about 1/8-inch in diameter.
It progresses to grayish white centers. Tiny, black specks may appear at the center. These are the fruiting fungal bodies. Spores may be spread by splashing rain. The lower leaves turn yellow, whither and fall off.
Early blight’s most obvious symptom is the premature loss of the lower leaves. Brown to black spots 1/4-inch to 1/2-inch with dark edges appears on the lower leaves. The spots merge forming a “target” appearance. The fungus may also attack the stem end of the fruit causing concentric rings and black, velvety appearance.
Fusarium wilt is another fungal disease that attacks only certain non-resistant tomato cultivars. The fungus plugs the water-conducting tissue in the stems leaving brownish streaks up and down the stem when split open. It usually appears after flowering. It progresses from the base of the stem.
Only one side of the leaf midrib, one branch or one side of the plant will first be affected. The plants die early and rarely produce fruit. Verticulum Wilt may not kill the plant, but stunts the growth and the yield is reduced.
The disease also appears on the lower leaves and progresses upward. Yellow blotches develop on the lower leaves and they will wither and drop off.
The tomato spotted wilt virus is spread by tiny insects called thrips. They live in the grass and weeds where they pick up the virus and spread it in your garden.
The tomatoes will look stunted and the younger leaves will be marked with bronze or dark spots or may have prominent purple veins. The upper foliage may become twisted and cupped as the bronze areas expand. The thrips spread the disease so rapidly that insecticides are ineffective.
Some problems such as leaf curl are caused by fluctuations in moisture condition. The tomato plant goes from very wet conditions to very dry conditions. Even out the moisture swings.
There are even more diseases which may affect tomatoes. The picture being painted appears to be very dismal, but as we know there are lots of folks who grow tomatoes successfully. How do they do it?
The first step is to purchase disease free transplants or seeds. Disease can be spread from contaminated seeds and plants. Don’t save the seeds from last year especially if you’ve had disease issues.
Bob Westerfield, vegetable specialist with UGA-Griffin, recommends selecting resistant tomato varieties. When you purchase seed or plants, the label has a code on it using abbreviations. “V” stands for verticulum wilt. “TSW” indicates resistance to tomato spotted wilt. So check out the label.
There are cultural practices as well. Plant your tomatoes in sunny locations in well-drained soil with a pH at least 6.2. Lime to the correct pH.
Fertilize according to soil test recommendation. Mulch the plants to maintain an even moisture level. Use pine bark, pine straw, newspapers and or compost. Synthetic weed barriers are also effective.
Rotate the area where you grow tomatoes from year to year. Pathogens can build up in the soil.
Remove and dispose properly the diseased plants.
Don’t water the foliage. Water the base of the plant. Damp leaves encourage disease.
Eliminate weeds around the garden area as well as in the garden.
There are good fungicides out there if used in a timely manner.
Call the office for specific recommendations.
On another note, 4-H still has Vidalia onions available for 10 pounds for $10. Stop by the office or call to reserve a bag. We are still taking applications for the upcoming Master Gardener classes starting Aug. 5.
Applications are available at the office or by emailing me at firstname.lastname@example.org.
Brian Maddy is the ANR Agent for Troup Cooperative Extension. The Troup County Extension office is located at 114 Church St. in LaGrange and may be reached at 706-883-1675, Monday through Friday, 8 a.m. to 5 p.m.