Problems growing tomatoes include diseases such as crown rot and mosaic virus, as well as issues with insects. Some problems are due to poor nutrition to the plant; others are due to poor gardening practices. Hornworms and flea beetles are common insect problem on tomatoes. Many problems are alleviated through the organic gardening method of adding nutrient rich humus (compost) to the soil before planting tomatoes. Some tomato seeds are hybridized to resist common disease problems.
Leaves with purple veins and an overall purplish tint are symptoms of phosphorus deficiency. Phosphorus is not available to the plant when the soil is too cold. Tomatoes do poorly when planted early. Wait until the soil warms above 60 degrees F to put tomato plants in the ground. Once the soil warms up, phosphorus goes into the plant and the problem corrects itself.
Crown rot or Fusarium wilt is a disease evidenced by older tomato leaves turning yellow, wilting and dropping off. It is caused by a tomato fungus called Fusarium oxysporum, which attacks the plant's vascular system. The vascular system carries water through the tomato stem to the fruit and leaves. No fungicide is available for this problem, but do not plant tomatoes in the same place if this virus appears. Cucumber mosaic virus is also a common problem growing tomatoes. Symptoms are yellow mottled leaves and plants that become bushy and stunted. There are no known controls for this disease once it gets started. The plants need to be pulled up and destroyed.
Aphids and tobacco worms (hornworms) are common problems growing tomatoes. Aphids establish themselves in colonies on leaves and stems. They are small, shiny insects that eat the plant. Flea beetles leave tiny holes in the tomato leaves, which weaken the plant and encourage further disease problems. They are large green or gray-green caterpillars which chew and destroy the plant. They are voracious feeders and can strip a tomato plant bare if they are not picked off. Stink bugs cause spots and internal damage to tomatoes with their feeding practices. Damage appears on tomatoes as dark pinpricks surrounded by a light discolored area. Keep debris away from the plant base to avoid infestation by stink bugs.
Some simple fixes exist for common problems growing tomatoes. Improve garden soil by incorporating nutrient rich organic material. Healthy soil feeds plants and creates health, disease resistant plants. Pull weeds regularly and keep the garden free of waste debris from other plants. Rotate crops. Give tomato plants adequate space for good air circulation. Monitor for insects and hand pick them off plants. Check with the garden center for tomato seeds that are disease-resistant.