Tomato Pests and Diseases
Tomato Pests and Diseases
August 14, 2017
In this short video, we help you troubleshoot some of the most common tomato diseases, pests, and problems in the garden!
Tomato Problems: Fix Issues Affecting Your Tomatoes
Aphids and Whitefly
Solutions: Blast off small infestations with a jet of water, or spray plants (including leaf undersides) with a soapy water solution. Plant flowers, for instance marigolds, close to your tomatoes. These will help attract aphid and whitefly predators such as ladybugs and hoverflies. If necessary you can buy these predators to introduce into enclosed environments such as a greenhouse or hoop house.
What is it? Spider mites are tiny mites that thrive in warm, dry conditions. They can quickly weaken plants. Keep an eye out for their faint webs. Take a closer look and you might see the tiny, usually red, mites.
Solutions: To avoid problems, don’t let your tomatoes dry out. If spider mites do attack, spray the plant all over with a fine mist of water. Drape the plant with a row cover for a few days to create the shady, humid conditions that the mites dislike.
What is it? The tomato hornworm is a caterpillar that chews holes in tomato fruits.
Solutions: Check your plants regularly for signs of damage, and remove and destroy any hornworms you find. You may find hornworms with little white cocoons on them. This is great news, and they belong to the larvae of braconid wasps, which feed on hornworms and help bring them under control.
See our Tomato Hornworm page for more tips.
What is it? Blight is a fatal plant disease that occurs during spells of warm, wet weather. Brown blotches show first on tomato leaves and stems, then the fruits. Eventually, the plant will wilt and collapse. Late blight also affects potatoes, which are related to tomatoes.
Solutions: Remove and destroy blight-infected plants as soon as you see signs of the disease. If your plants have suffered from blight in the past, try growing them under cover if possible – it’s rarely a problem with indoor tomatoes. When watering, take care to avoid splashing the leaves. It’s worth looking out for varieties described as ‘blight resistant’.
Learn more about avoiding blight with the right tomato.
Blossom End Rot
What is it? Blossom end rot causes sunken black patches at the blossom end of tomato fruits. It is a disease caused by dry soil conditions which results in a shortage of calcium in the plants. Plants in containers are particularly susceptible.
Solutions: Never let your soil dry out. Feed your tomatoes regularly with a liquid tomato fertilizer. Learn more about Blossom End Rot.
What is it? Tomato fruits split when they have been kept too dry, and then are watered heavily. This causes the fruits to swell faster than the skins surrounding them.
Solutions: Keep your soil evenly moist. Water regularly and mulch with plenty of organic matter to keep roots cool and moist.
What is it? Magnesium deficiency is the most common mineral deficiency in tomatoes. It often occurs as a result of high potassium levels.
Solutions: Spray a solution of Epsom salts directly onto the leaves, then start using a tomato fertilizer that contains a higher proportion of magnesium.
Wilted Tomato Plants
What is it? Plants can wilt when the soil is either too wet or too dry.
Solutions: Water generously when the weather is dry, or set up an irrigation system on a timer if you can’t be around to water by hand. Mature plants with lots of foliage may need watering twice a day. Make sure containers have generous drainage holes in the base, and raise them up onto pot feet if water doesn’t drain away easily.
Poor Fruit Set
What is it? Poor fruit set, when flowers fail to produce fruits, has a variety of causes such as poor pollination, too much heat, poor nutrition, and very dry or very humid air.
Solutions: Open greenhouse and hoop house doors every day (weather permitting) to ventilate and to allow access for pollinating insects such as bees. Pollination can be enhanced by tapping on supports to dislodge the pollen, or gently twiddle the flowers between your fingers. If your climate’s very dry, raise the humidity around plants with regular watering. And make sure to feed your plants regularly with a store-bought tomato fertilizer or a homemade high-potassium liquid fertilizer such as comfrey tea.