We love tomatoes. Unfortunately, so do many other things in the natural world, including pests and disease. As tomato season approaches, here are the culprits to watch out for.
Common Tomato Pests
Insects can wreak havoc on our gardens. Tomatoes are susceptible to a wide range of pests both in greenhouses and in the fields, but these are the most common offenders.
Aphids: Aphids pose a threat to young plants. These small insects damage foliage and weaken the plant's immune system. There are several types of aphids, including potato aphids and green peach aphids.
Tomato Fruitworms: Fruitworms larvae cause significant damage to fruit. They develop inside the fruit and their feeding results in watery insides full of larvae feces.
Hornworms: Tomato hornworms are unmistakeable. These large, green, horned caterpillars start off eating leaves but will move to the fruit once all of the leaves are stripped.
Leaf Footed Bugs and Stink Bugs: These sap-sucking insects have a distinctive shield shape. Infestations of stink bugs and leaf-footed bugs lead to fruit deformation and bud drop.
Spider Mites: Spider mite infestations can lead to defoliation and damage the leaves of tomato plants. Spider mites are no larger than the period at the end of this sentence and give leaves a silverish tint.
Leafminers: Leafminers are small flies. They lay their eggs on plants like tomatoes, and the larvae munch their way through the leaves, creating the distinctive "mining" trail that gives them their name.
Whiteflies: Whiteflies are particularly common in greenhouses. These pests suck the sap out of tomatoes, causing leaf damage, and they are also vectors for tomato diseases.
Thrips: Thrips are small, winged insects that spread tomato spotted wilt virus.
Cutworms: These larvae "cut" tomato seedlings off at the soil line, killing them, and eat low hanging fruit later on.
Tomato Pinworm: Pinworms damage fruit and foliage and infestations worsen over the course of the season.
The best pest control for tomatoes depends on the pest. There are both natural and chemical pesticides available for tomato pests, but the best way to avoid an infestation is careful crop rotation, fertile soil, and strong seedlings.
Common Tomato Diseases
Many diseases affect tomatoes. Some are treatable, others are not. As with pests, soil fertility, planting disease-resistant varieties, transplanting strong seedlings, allowing for air circulation between plants, observing proper crop rotation and employing effective pest management techniques are the best ways to prevent these diseases from damaging your tomato crop.
Tomato diseases, especially bacterial and viral, are infectious. You can prevent some spreading by containing infected plants and by observing the same disease protocol as you would for a sick child - don't touch a sick plant and then touch a healthy one.
Bacterial Wilt: Bacterial wilt is caused by a bacteria that lives in the soil. High temperatures and high moisture levels contribute to disease development, which manifests in the sudden wilt of tomato foliage.
Early Blight: Early blight is a fungal disease that first appears as small brown spots. It mostly affects older foliage and can also affect fruit, causing rot and damaging yields.
Late Blight: Late blight is more serious than early blight and is brought on by cool, wet weather. This fungus can cause complete defoliation in less than two weeks, and all infected fruit will rot.
Septoria Leaf Spot: This fungus often occurs with overhead irrigation, as it favors a high moisture content. The small, brown spots cause the leaves to yellow and drop, which reduces yields and exposes the fruit to sunscald.
Leaf Mold: Leaf mold prefers high humidity and low air circulation. The disease presents as pale green or yellowish spots that enlarge and turn yellow, killing the leaf.
Bacterial Spot: Bacterial spot causes irregular, water-soaked spots and occurs more often in wet years. It also raises scabby spots on the fruit.
Buckeye Rot: This fungus affects the fruit, resulting in brown spots that grow larger with time, causing rot. The spots may resemble those of late blight.
Anthracnose: This fungus also affects the fruit. Diseased spots may produce salmon colored fungal spores under warm and humid conditions.
Fusarium Wilt: Fusarium wilt is a fungal disease that causes the leaves to lose color as the entire plant wilts and dies. It is a warm weather disease.
Southern Blight: This fungal disease initially presents like wilt, but is accompanied by brown lesions on the stem near the soil line. As the lesions grow they result in permanent wilt of the rest of the plant.
Tomato Spotted Wilt Virus: Thrips spread TSWV, which affects plants in several ways. Growth may be stunted, leaves may have purple veins or bronze spots, fruits may yellow and die, and if the plant survives it will bear discolored fruits that fail to ripen.
Tomato Yellow Leaf Curl Virus: Whiteflies transmit TYLCV, which causes the curling of the upper leaves, blossom drop, and stunted growth.
Tobacco Mosaic Virus: A viral disease that causes the mottling of the leaves and malformed leaflets.
Sometimes it is not a pest or a disease that affects your tomatoes. Physiological disorders take their toll as well.
Blossom End Rot: Blossom end rot causes dark, rot spots on the bottom of the fruit. This is the result of a calcium deficiency in the tomato which can happen for several reasons.
Sun Scald: Fruit exposed to the direct rays of the sun in hot weather develop sun scald.
Growth Cracks: Environmental conditions like inconsistent watering cause growth cracks.
Cat Facing: Colder temperatures during fruit set cause the characteristic "cat face" deformity.
This is just a brief overview of the common pests and diseases of tomatoes. Knowing the signs of these pests and diseases helps us prevent the spread of disease and allows us to diagnose garden problems. If your garden repeatedly suffers from any of these conditions, then it is probably time to re-evaluate some of your practices to determine the cause.