• Aphids and whitefly: Blast off small infestations with a jet of water, or spray plants with soapy water, taking care to reach the undersides of the leaves. Control aphids and whiteflies by planting flowers close by to attract pest predators such as ladybugs and hoverflies. You can even purchase some pest predators to introduce into greenhouses and hoop houses.
• Spider mite: Spray the foliage thoroughly with a fine mist of water, and then cover the plant with a row cover for a few days. The shady, humid conditions will repel the mites.
• Tomato hornworm: Remove and destroy any caterpillars you find during regular inspections. Sometimes you may find hornworms covered in small white cocoons. These belong to braconid wasps, which feed on hornworms to bring them under control.
• Late blight: Avoid splashing the leaves when watering, and remove infected plants as soon as you spot the first signs of blight. Blight is uncommon on tomatoes grown under cover. There are also now some varieties described as “blight resistant.”
• Blossom end rot: Keep tomatoes evenly moist and don’t let them dry out. Feed them regularly with a liquid tomato fertilizer. Keep a careful eye on plants grown in containers, as they are especially susceptible.
• Split fruits: Keep soil consistently moist, and mulch with plenty of organic matter.
• Magnesium deficiency: Magnesium deficiency can occur if the plant is receiving too much potassium. To correct this, spray a solution of Epsom salt directly on the foliage and then begin feeding using a tomato feed containing a higher proportion of magnesium.
• Wilted plants: Plants can wilt when the soil is either too wet or too dry. Set up an irrigation system on a timer if you can’t be around to water regularly enough. Make sure containers of tomatoes have large enough drainage holes in the base and that water can drain easily. Raise containers up onto pot feet if necessary.
• Poor Fruit Set: Avoid pesticide use and make sure to open the doors of greenhouses and hoop houses to allow bees access and provide plenty of ventilation. Tapping on supports to dislodge the pollen or gently twiddling the flowers between your fingers can help improve pollination. If your climate’s very dry, raise the humidity around plants with regular damping down. Feed your plants regularly with an off-the-shelf tomato fertilizer or a homemade high-potassium liquid fertilizer such as comfrey tea.
Learn more about keeping your tomatoes healthy in this video.
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