top of page

What is Tomato Blight & How Can I Fight it?

Tomato blight, also known as late blight, is a fungal disease caused by the pathogen Phytophthora infestans. It affects tomato plants and can lead to significant damage and crop loss if left untreated. Tomato blight is particularly common in areas with cool and moist conditions.

Symptoms of tomato blight typically include dark, water-soaked lesions on the leaves, stems, and fruit. The lesions may have a fuzzy or moldy appearance, especially under humid conditions. As the disease progresses, the lesions may enlarge and turn brown or black. Eventually the entire plant will look completely dead - this usually happens early to mid August and the plants will seem to go from healthy to dead within just a few days. Infected fruits can develop rot and become inedible.

To fight tomato blight, consider the following strategies:

  1. Plant resistant varieties: Select tomato varieties that are resistant to blight. These varieties are specifically bred to withstand the disease and can help reduce its impact. Here at Huron Ridge look for Mountain Majesty, Mountain Merit, and Mountain Fresh. The Mountain series of tomatoes are all late blight resistant.

  2. Crop rotation: Avoid planting tomatoes in the same location year after year. Rotate your tomato crops with other unrelated plants, as this can help disrupt the disease cycle and reduce the presence of the blight-causing pathogens in the soil.

  3. Proper spacing and pruning: Provide adequate spacing between tomato plants to improve air circulation and reduce humidity around the foliage. Prune the lower leaves to increase airflow and prevent the spread of the disease from the ground up. Mulching around the base of your plants can also help.

  4. Water management: Water the plants at ground level and try to keep the foliage dry. Avoid overhead watering, as wet foliage promotes the development and spread of fungal diseases. Consider using a drip irrigation system or a soaker hose.

  5. Fungicides: If the disease is prevalent in your area or if you have a history of blight in your garden, you can use fungicides as a preventative measure. Copper-based fungicides (which are safe to use for organic gardening) or those containing chlorothalonil are commonly used to control tomato blight. Follow the instructions on the product label for application rates and timing.

  6. Timely harvest and cleanup: Harvest ripe tomatoes promptly to prevent the disease from spreading to healthy fruits. Remove and destroy any infected plant material, including leaves, stems, and fruits. Do not compost these materials, as the spores can survive and spread.

It's important to note that prevention is key in managing tomato blight. If you have had tomato blight in your garden (or if your neighbours had) we highly recommend you start applying copper-sulphate around July 1st and every 7-10 days for the rest of the summer to prevent the start of blight as once it is evident in your crop there is little that can be done to prevent it from spreading and taking over your crop.


bottom of page