Tips on dealing with troubled tomato plants
Over the last several years my tomato plants appear to die off from the ground up. The leaves turn brown, new tomatoes stop forming, and the remaining green tomatoes slowly ripen, but grow no bigger. I was told I have a virus that kills off the plants, and the only cure is to not plant any tomatoes for four years. I used separate pots this year, away from the garden, and used new bagged soil — yet the same thing happened to the potted plants. Do you know what is happening and if I can cure this situation? Thank you.
— Bob in Bethlehem
Bob has made a good effort to control his problem.
By using clean pots and fresh soil, he has eliminated one of the most common problems — infection from soil-borne diseases. While it doesn’t eliminate them, it does limit the sources of infection. The culprits include:
Bacterial wilt: It survives in the soil for years and enters the roots through wounds from transplant, cultivation or other injury. The disease is most often seen during periods of high temperatures and high moisture. The foliage rapidly wilts but remains green and cut stems will look brown and exude small amounts of yellow ooze. Reduce chances of infection by: crop rotation, three to four years with nonsusceptible plants (not peppers, eggplants, potatoes, sunflowers, cosmos, for example); and remove and destroy infected plants (don’t compost). Early Blight: The problem winters over in the soil, on seeds and other host plants. It thrives in high humidity and temperatures. Small brown lesions first appear on older foliage and usually near the bottom of the plant. They enlarge, form concentric rings (bull’s-eye). The foliage quickly dies and there may be lesions on the stem and fruit. Plant resistant varieties, rotate crops, control weeds, mulch and space plants well apart. Trim and dispose of any infected leaves as they appear.
Late Blight: This one thrives in cool, wet weather. The spots are small, dark and may appear water-soaked. They enlarge and show white mold on the margins. Complete leaf loss may occur in as little as 14 days. The fruits exhibit shiny dark lesions. Prevention techniques include keeping the foliage dry (avoid overhead watering); allow extra space between plants, destroy any volunteer tomato, potato or other nightshade plants in the area; do not compost rotten potatoes and plant resistant cultivars.
These seem unlikely to be Bob’s culprit but there are plenty of other potential villains:
Septoria leaf spot: This problem affects the leaves and stems but does not directly attack the fruit. It thrives in cooler temperatures (mid-60s to 70s). Starting on the lower leaves, it usually occurs just as the fruit starts to set. Spots appear — beige centers with darker borders on the older leaves. Septoria leaf spot weakens the plant and reduces the size and number of fruits. While not a soil-born disease, the problem will winter over in plant debris, decaying vegetation and wild host plants.
Bacterial spot: This problem attacks green tomatoes and is most prominent in wet seasons. Spots appear on both the leaves and fruit. The spots are irregular, sometimes angular and small. They appear water-soaked on the leaves. Sometimes the area around the spots will yellow. The spot centers dry out and tear. On the fruit, the spots are raised, sometimes scabby. Bacterial spot will reduce crop yield, defoliate plants and expose fruits to sunscald (because of leaf loss). It is most common during periods of wet weather and spreads easily during heavy rainstorms. Water splashing, handling of infected plants (particularly while wet) also spread the problem. While the leaves are affected by contact with the pathogen, the fruits are infected through insect bites or other wounds to the skin surface. Protect your plants by rotating crops; avoiding overhead irrigation; clearing up all plant debris; removing and destroying any volunteer plants, pruning to improve air circulation.
■ Clear up any plant debris as it occurs and remove spent plants at the end of the season.
■ Remove leaves that become infected and discard.
■ Keep weeds under control, especially those that harbor the problem — any member of the nightshade family (datura, Jimson weed, ground cherries, for example).
■ Never compost diseased or infested plants.
■ Widely space plants, stake or cage them and consider pruning to improve air circulation around each plant.
■ Water the ground, not the leaves and water early enough in the day to be sure that any wet foliage dries before evening.
■ Rotate crops or, if using containers, use fresh soil and pots to avoid any soilborne problems.
■ Consider using a food-approved fungicide before problems appear and regularly throughout the season,
■ Select cultivars that have resistance to disease and fungal problems.
■ Mulch to decrease problems with spores splashing up on plants.
■ Do not tend wet plants.
■ Clean and disinfect tools before moving on to another plant. A simple disinfecting wipe works fine.
Note that while plant rotation and/or fresh container soil are both good preventative measures. The spores or bacteria causing the problems can be transported in by weather, weeds, animals or unsanitary conditions. So, other measures are often needed as well.
My tomato project this year has been a disaster. I started with five plants. One died before I even planted it. Three were put into large pots and were eaten by caterpillars. The remaining one, a cherry tomato, survived in a small hanging pot, but had it’s first flush of tomatoes eaten just as they ripened. I moved the plant out of range (at least from the deer, groundhogs and rabbits) and managed to harvest two handfuls so far. They were tasty but hardly worth the effort.
Thank goodness our neighbor Jack plants his tomatoes in a fenced area and tends them faithfully. He generously shares his bounty, so supplemented by purchases from local vegetable stands, we still enjoy fresh, local tomatoes. Jack has offered to grow a few of the heirloom varieties I favor in with his usual crop next year. I will probably take advantage of his kind gesture — I watched an eight-point buck munching what’s left of my hosta bed this afternoon.