Akin to several diseases, tomato plant diseases must be detected in the initial stage. This will result in avoiding its spread to other plants, like the eggplant, potato, and peppers that are members of the same family. In the presence of effective management practices, the disease would not be fatal.
In this disease identification, it is ascertained whether the stem, leaves, and fruit of the plant have been affected or not. Initially, the older leaves will develop dark spots with concentric rings. The nearby leaf region turns yellow. Such affected foliage perishes prematurely, thereby exposing the fruit to the sun. Wet weather intensifies the probability of an attack. The condition can be minimized by removal of the affected plants and cleaning of fallen waste. Spraying copper or sulfur necessarily prevents further propagation.
Here, the white mold is seen on the stem near the ground. Circular and dark spots are seen on the lower part of the stem. Gradually, the inner and outer stem color fades. As fungus surrounds the stem, water and nutrients are restricted from moving upwards through the stem. The plant collapses near the ground level. It has been found that using some fertilizers having ammonium and the use of extra calcium provides resistance. Crop rotation would also prove useful.
To identify this, watch for abnormally-shaped, greasy, and gray spots on the leaves. A circle of white mold encircles the spots. After some time, these spots become paper-like and dry. The stem shows black regions. Abnormally-shaped, greasy, gray, and huge spots can be seen on the fruits. In cool and wet climate, the fungus prospers.
Septoria Leaf Spot
This problem can be easily thought to be Late Blight. There are paper-like patches on the foliage that form minute and dark spots inside them. In the beginning, the older leaves get affected. Generally, copper sprays are employed to overcome the situation.
Gray Leaf Spot
Here, only the leaves are affected. On the top as well as the bottom of the leaves, tiny and dark specks are visible. These broaden and have a grayish brown hue. Finally, the centers of these specks crack and fall. The region of the leaf near these spots changes to yellow. The leaves dry and drop down. The production of the fruit is hindered. In warm and moist environment, this gray leaf spot problem becomes worse. It is binding to uproot all the affected plants and dispose the fallen garden debris.
Tomato Spotted Wilt Virus (TSWV)
The first symptom of TSWV is that the growth of the leaves in the terminal areas of the plant ceases. They become distorted and pale green. The veins of fresh leaves become thick and purple. These leaves attain a bronze color. Circular, purplish-gray, and dark spots appear on the affected leaves. Stems have purplish brown streaks. If the fruit gets infected, it exhibits ringspots and distorts. TSWV is caused by aphids and thrips. So, to control them, an insecticide, like malathion or neem would come handy. As soon as the initial symptoms are seen, the infected plants must be removed.
The distinguishing factor of this problem is that the plants droop and die quickly. The leaves do not turn yellow or develop spots. This problem is caused by soil-borne bacteria. They attack and block the food and water-carrying vessels below the outermost layer of the stem. There is no known method of treatment. The gardener must rotate crops to minimize the presence of bacterial wilt. Also, susceptible crops (potatoes, tomatoes, eggplant, peppers) should be grown in different regions of the field in consecutive years.
Timely and adequate measures are mandatory if you want to control or eliminate the various diseases related to the tomato plant.