What's killing my tomatoes? (picture links included)

[Robin]

[Greg & Eva Rosol]

Too much rain...not enough dry hot weather...

[Robin]

That would definitely be true. I hope that's all it is because it would mean my soil isn't harbouring anything to kill off next year's crop too.

Thanks for the response,

[Penny Morgan]

I received this small booklet with my subscription to Organic Gardening awhile back. It has 300 super tomato tips.

Tomato Disease Troubleshooting;

BACTERIAL WILT, BROWN ROT

Range: Most of the southern US, from MD to TX.

This bacterium can live in your soil for six years and may infect only a few plants at a time, leaving the others unaffected. The disease enters through the roots, causing the whole plant to wilt, beginning with the top leaves. The plant stops growing, the insides of its stems become dark brown and water soaked and the main stem near the soil line starts to decay.

Observe a long, 4-5 year rotation, and destroy infected plants promptly, Plant early in well-drained soil to avoid the disease's most encouraging conditions; young plants with wet feet. Venus and Saturn varieties are resistant.

CURLY TOP, WESTERN YELLOW BLIGHT

Range: Normally, the western US, especially arid and semiarid regions, and wherever sugar beets are grown.

This virus overwinters in perennial plants. Beet leafhopper larvae pick up the virus and transmit it to tomatoes when they mature. The new growth on infected plants will be twisted and curled. The leaves become yellow and stiff, and the flowers are malformed. The small amount of fruit produced will ripen prematurely.

In warm climates, pull the infected plants and try a second crop. Avoid planting the second crop (or next year's tomatoes) near beets. Wrap tomato plants in cheesecloth or fabric row cover, leaving the tops open, to discourage leafhoppers.

EARLY BLIGHT

Range: Most of the US, especially the New England, central, mid-Atlantic and southern states. The optimal temperature for the spread of the disease is

85 degrees.

Fungal spores, which can remain viable for more than a year, overwinter on host weeds and plant debris. Tomatoes are most susceptible to infection when they begin to set fruit. One-half inch, brown to black spots develop on lower leaves. The lesions may be round or angular in shape, with shadowy concentric rings. As these spots produce new disease spores of their own, leaves wither and die. The damage often continues until the entire plant is killed.

Full sun and ample space between plants are essential. Rotate crops and keep new plantings at least 200 feet away from previous years' plantings. Avoid early maturing varieties, which are very susceptible. You can slow the progress of the disease by picking off the bottom leaves as they brown. The plants will continue to bear, and there's nothing wrong with eating the fruit.

FUSARIUM WILT

Range: Most of US, especially the central and southern states (east of the Mississippi and south of the Ohio rivers). Hot weather (80-95 degrees) encourages infection.

The fungus overwinters in the soil and can remain there for several years. It enters tomatoes through root wounds. Lower leaves turn yellow, wilt and drop off. Just after fruit set, the entire plant may turn yellow and die. The fruit usually decays and drops. The roots appear discolored and rotted and dark streaks develop inside the lower stem and roots.

If the plant continues to produce fruit that ripens, you can eat it. But if your soil has fusarium fungus in it, it probably always will. Your best recourse is to plant resistant varieties - designated by the letter "F" after the variety name. Choose plants and seeds that are certified disease free, and plant in fertile, well-drained soil. Low potassium coupled with high nitrogen can encourage the disease.

LATE BLIGHT, BUCKEYE ROT

Range: Most severe in the eastern US during periods of cool, damp weather. Generally occurs when temps range from 60-70 degrees.

The fungus overwinters in soil that contains plant debris. Potato volunteers (or infected potato seed pieces) can spread the disease to tomatoes. In early summer, spores become windborne. The first symptoms of disease include dead, brown areas on the leaves near the base of the plant. When plants are more mature, circular or oval-shaped, greasy looking rot spots appear on the green fruit. By late summer, the plants have only a few top leaves.

As with early blight, you can slow the disease (but not much) by picking off infected leaves. And the plants will produce some fruit, which is edible.

To avoid the disease next year, don't plant tomatoes near potatoes or in soil where potatoes were grown the year before. Provide lots of air circulation and full morning sun. Stake or cage plants to keep fruit high off the ground. Wet only the root zone when watering plants.

SEPTORIA LEAF SPOT

Range: Almost everywhere tomatoes are grown. Thrives in damp weather, when temps are 60-80 degrees.

The fungus overwinters on tomato debris and weeds. At first, one-sixteenth to one-eighth inch light spots with dark margins will appear on lower leaves. The spots are smaller and more numerous than those of early blight. Later, a sprinkling of black dots appears within the spots. Affected leaves eventually wither and die.

As soon as you see these signs, break off infected leaves to keep the spores from spreading, especially during cool, wet periods. When the weather turns hotter, the disease usually is checked naturally. Space plants widely to improve air circulation. Maintain a one to two year rotation. Control host weeds (including jimsonweed, horse nettle and morning glory) and grow only varieties that are suited to your climate.

TOBACCO (TOMATO) MOSAIC VIRUS

Range: Most of the US.

The virus overwinters in weeds and soil and can be seedborne. It is readily transmitted by human activities such as suckering and tying tomato branches. Infected leaves become mottled with yellow green and dark green mosaic patterns, and they also may become wrinkled. Plants become yellow and stunted. Long dark streaks may develop on the stems, along with brown sunken rings on the fruit.

Destroy infected plants promptly. To avoid the disease next year, use certified disease free seeds and transplants. If you know the disease is present in your garden, dip your hands in a half and half mixture of milk and water when transplanting, trellising or touching tomatoes, suggests the staff at PetoSeed, a plant-breeding company in Saticoy, California.

TOMATO SPOTTED WILT

Range: Particularly serious on the West Coast, it is increasingly seen in the southern, central and eastern US.

A virus that overwinters in weeds, tomato spotted wilt is picked up by onion and other thrips and transmitted to tomatoes, especially in hot, damp weather. Bronze, ringlike spots appear on leaves, and plants become stunted. Yellow mosaic patterns may appear on leaves, and fruit may show rings of pale red, yellow or white.

You can prevent the disease by wrapping tomato cages loosely in fabric row cover to discourage feeding by thrips. Thrips are also discouraged by aluminum - surface mulch.

VERTICILLIUM WILT

Range: Most of the US, especially the northern states. Optimal temps are

70-75 degrees.

The fungus overwinters in soil and enters plants through breaks in the roots. When first affected, plants will wilt in midday, but perk up at night; each day the wilting becomes worse. Large stems near the base of the plant will show dark streaks inside. Plants usually wither and die shortly after fruit set.

As with fusarium wilt, if the plant continues to produce fruit that ripens, you can eat it. Also, as with fusarium, if your soil has verticillium, it probably always will. Grow one of the many resistant tomato varieties designated by the letter "V" after the variety name. Rotations are useful, but the benefits are limited because many plants host the fungus. Since strawberries, peppers, eggplants, and potatoes are well-known alternate hosts, do not follow these crops with tomatoes in your rotation scheme.

Hope this helps some in identifying tomato diseases.