Tomato Plant Diseases, Pests, & Problems: A Comprehensive Guide for UK Gardeners

Tomatoes are a staple for many allotment growers and gardeners, but they are not without their challenges. Numerous issues can befall these otherwise robust plants, from fungal diseases to pesky insects and physiological problems. But with the right knowledge, many of these problems can be prevented or mitigated.

I will run through some of the issues you may face in the UK when trying to grow tomatoes; I have encountered all of these issues over the years. If you have a problem not discussed in this article, drop me a message, and I’ll try and get back to you with a solution.

To avoid many problems, make sure you buy disease-resistent varieties in the first place – this is where I went wrong when I started growing them a few years ago.

Common Tomato Diseases

1. Late Blight

Late blight is a devastating disease that can quickly spread through a tomato crop, especially in damp, cool conditions. Symptoms include brown patches on leaves, stems, and fruits and a white fungal growth on the undersides of leaves.

source: Wikipedia


Infected plants should be removed immediately to prevent the disease from spreading.

2. Early Blight

This fungal disease usually strikes after the first fruits appear, causing dark, concentrically ringed spots on older leaves. It can lead to significant leaf loss if not controlled.

Regular fungicide applications and crop rotation can help manage early blight.

3. Fusarium and Verticillium Wilt

Both these soil-borne fungi cause yellowing and wilting of leaves, typically on one side of the plant or one branch at a time. There are no effective treatments once a plant is infected.

Prevention includes using disease-resistant varieties and proper crop rotation.

4. Blossom End Rot

This isn’t a disease but a physiological disorder caused by calcium deficiency or inconsistent watering. It presents as dark, sunken spots on the blossom end of the fruit.

Regular and consistent watering and adding calcium to the soil can prevent blossom end rot. A good tomato feed usually has added calcium.

Pests that Target Tomato Plants

1. Aphids

These small, sap-sucking insects can quickly infest tomato plants, leading to curled and yellowed leaves. Natural predators, such as ladybirds and lacewings, can control aphids. In severe cases, insecticidal soap or neem oil can be effective.

2. Tomato Hornworms

These large, green caterpillars can strip a plant of its leaves in a short time. Handpicking is an effective control measure if you have a small number of plants. Bacillus thuringiensis (Bt) is a natural bacterial disease that can control hornworms without harming beneficial insects.

3. Whiteflies

Whiteflies are tiny, winged insects that feed on the underside of leaves, leading to yellowing and leaf drop. They can also spread diseases. Control measures include reflective mulches, yellow sticky traps, and insecticidal soaps.

Other Tomato Plant Problems

1. Poor Fruit Set

Cold weather, high temperatures, or poor pollination can cause flowers to drop without setting fruit. Ensuring tomatoes have a suitable growing environment and can help overcome this issue.

2. Cracked Fruit

Rapid growth or fluctuations in temperature and moisture can cause tomatoes to crack. While it’s often just a cosmetic issue, cracks can provide an entry point for diseases. Consistent watering and using mulch to regulate soil temperature can help prevent cracking.

3. Sunscald

Sunscald appears as white, blistered patches on the fruit where it has been exposed to intense sun. It can be prevented by using a shade cloth to ensure the plant’s leaves shade the fruit.

While dealing with tomato plant diseases, pests, and problems can be challenging, it is part of the gardening journey. The knowledge you gain will help you handle these issues effectively and ensure your tomato plants thrive.