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Keep an Eye Out for These Tomato Plant Diseases

Are you growing tomato plants in your garden this year? Well, you should! The payoff of buckets and buckets of juicy, flavourful, homegrown tomatoes is well worth the effort. You can use them in so many different recipes and preserve them into sauces to last through the winter! However, if you want to ensure your tomatoes are successful, it’s crucial to be on the lookout for diseases.  

There are several issues that can pop up when growing tomatoes. Luckily, if you keep a close watch, you can usually deal with them effectively without losing your crops. Below, you’ll find our list of common tomato disease symptoms and the best ways to beat them. 


How Do I Identify a Tomato Plant Disease?

Use the following guide to identify the symptoms your tomato plants are exhibiting, and we’ll tell you what disease is causing them. Remove infected plant material with shears; disinfect the blades between every cut to prevent further spread, and throw the affected pieces in the trash, not the compost. Then, you can follow up with the appropriate fungicide or treatment. 

White, powdery coating: Powdery mildew. Treat this with copper-based fungicide. Ensure your plants have enough space between them to allow good air circulation.


Rapidly wilting plant with green leaves; cut stems reveal a slimy ooze: Bacterial wilt. You can’t cure it, so you must remove all infected plant material. Prevent it by planting disease-resistant varieties and practicing crop rotation. 


Brown circles and bullseye rings on mature foliage or fruits: Early blight. Remove infected material and use a copper-based fungicide. Prevent issues by fortifying the soil with calcium and magnesium, practicing crop rotation, and opting for disease-resistant varieties.


Dark brown or olive, soggy lesions across foliage and fruits: Late blight. Typically occurs in damp, cool weather. Remove infected material and use a copper-based fungicide. Prevent issues by ensuring your plants are spaced out to allow better air circulation, practice crop rotation, and opt for disease-resistant varieties.


Brown spots with beige centres on the leaves nearest to the ground. Severely spotted leaves turn yellow: Septoria leaf spot. Prevent its occurrence by watering the soil directly instead of watering the plant overhead. Use copper-based fungicides, practice crop rotation, and clean up any garden debris which may harbour disease spores.  

Tiny dark, scabby spots on green tomatoes; tiny dark spots on leaves surrounded by soggy brown and yellow patches: Bacterial spot. Remove infected material and use a copper-based fungicide. Prevent its occurrence by watering the soil directly instead of watering the plant overhead, practicing crop rotation, and avoiding planting peppers next to tomatoes. 


Yellowing, wilting leaves near the bottom of the plant: Verticillium wilt. Unfortunately, you can’t control this disease with fungicides, but crop rotation and planting disease-resistant varieties can prevent it. Remove damaged foliage immediately—the fruits will not be affected, but the reduction in foliage will cause slower growth and smaller yields, so you don’t need to throw out your crops if they’re showing signs of infection.

Yellowing, wilting leaves near the bottom of the plant, but only on one side of the plant: Fusarium wilt. This is similar to Verticillium wilt in terms of the damage it causes and the difficulty of treatment. Another way to determine where you’re dealing with Fusarium wilt is if you cut open the stem. It will look fine on the outside, but the inside will display a brown stripe. Raising the soil pH to 6.5–7 will help slow the spread of the disease.

Mother Nature Greenhouse - Common Tomato Diseases-blossom end rot tomato

Rotting ends on the bottom of fruits: Blossom end rot. Remove all affected fruits and toss them in the trash. This is due to calcium deficiency, and you can prevent it by enriching the soil with a calcium-fortified fertilizer or amendment.  


Pale green or yellow leaf patches, sometimes with a grey, velvety coating: Leaf mould. Prevent it with copper-based fungicide, spacing out your plants, and avoid watering overhead.


Having trouble identifying a certain tomato plant disease in British Columbia? Visit Mother Nature Garden Centre, bring in a picture of the affected plant, and we’ll help you pinpoint the problem! We have plenty of fungicides and treatments to keep your vegetable garden protected, so don’t hesitate to ask us for help in selecting the right solution.