Tomatoes are an American diet staple, as well as the most planted food in vegetable gardens across the country. They are not difficult to grow, but they are susceptible to problems due to weather, soil conditions, improper watering, heat, sun and more. Once you know how to troubleshoot tomato problems, most of them are easy to prevent or control.
Remove diseased fruits and leaves as soon as you notice a problem. Keep plant debris cleaned up from the garden. Don't dispose of infected debris in the compost pile. You may unknowingly redistribute soil borne pathogens when you spread compost. Good garden sanitation is the best defense against many garden problems.
Check tomato foliage often. Stems and leaves should be green and spot- and insect-free. Chewed or eaten leaves accompanied by pellet-like droppings indicate tomato hornworm presence. Pick these large green caterpillars off by hand and dispose of them, or use an organic pesticide with Bacillus thuringiensis (Bt) or introduce trichogramma wasps as a biological control.
Curled or yellowed leaves may be due to wilt or virus infections. To avoid spreading disease, these plants should be destroyed, but not composted. Curled or yellow leaves may also be a symptom of aphids, which can be controlled by a strong spray of water to drown them, or by spraying neem oil. Foliar spraying should be done early to allow plenty of time for foliage to dry completely before evening.
Water the plants by drip irrigation or nonoverhead methods. Water droplets left on leaves and fruits provide favorable conditions for fungus and bacterial diseases to thrive. Some diseases brought on by overhead watering are cracked tomatoes, blossom end rot (black or brown on blossom end), bacterial speck (small black spots on leaves and fruits, often with a yellow ring around them), black mold (large black spots that may grow to cover the fruit) and tomato blights.
Provide even watering throughout the growing season. Periods of drought between periods of ample water can cause cracked tomatoes and several wilts and fungal diseases. Watering evenly also encourages good root development and larger tomatoes.
Keep your tomato plants supported so they are off the ground. Tie them to a fence or trellis, or use tomato cages or stakes for support. Fungal and bacterial diseases are usually soil borne, so don't let the stems and foliage of your plants have contact with the soil. Splash up from watering can also spread wilts and diseases. Use drip irrigation or a soaker hose for gentle watering at the soil level. Mulch helps prevent splash up.
Use lower nitrogen organic fertilizer to encourage more blossoms. If your tomato plants get too much nitrogen, they will have luxurious foliage but will not have many blooms or set many fruits. Cool temperatures can also affect fruit set and development.