Viruses and mycoplasmas
There are many types of viruses and mycoplasmas that can damage most vegetables. Symptoms are usually stunting, and mottled twisted leaves. There are no pesticides that can be used to kill viruses. These are often spread by aphids, thrips or leafhoppers. Reduce viruses by controlling these insects with pesticides.
Severe viruses include cucumber mosaic virus (most vegetables), zucchini yellow mosaic virus (cucumber, pumpkins, melons and zucchini), leaf roll virus and virus X and Y (potatoes), and spotted wilt virus (capsicums, lettuce and tomatoes). Big vein mycoplasma is common on lettuce in winter and does not have an insect vector. Big bud mycoplasma attacks tomatoes
Blossom end rot
Blossom end rot is not a disease. It occurs mainly in tomatoes, capsicums and watermelons as a dry rot at the end of the fruit. It is caused mainly by a shortage of water in hot weather and some varieties are more tolerant than others. Round varieties of watermelons are less affected by this rot.