Are coffee grounds effective against tomato blight?

Scientific studies have not demonstrated any antifungal effects of coffee grounds against the pathogens that cause tomato blight. They may make the soil slightly more acidic. Still, they will not form protective barriers on the leaves or inhibit spore germination. I have conducted controlled studies using the coffee grounds and found the same rate of infections as those in untreated plants. Concentrate on research methods which have been proven, such as resistant varieties and regulations for proper water management.

Why do coffee grounds lose to blight? They are caffeinated, which has a low antimicrobial effect in the lab, but this decays rapidly in the open. Blight spores attack leaves, not roots, thus making soil treatments ineffective. In my garden, even when used as mulch, coffee grounds resulted in an increase in humidity, making the conditions more favorable for the fungi. There are beneficial qualities, but they do not equal disease protection.

Maximize plant immunity through science-based methods. Choose tomatoes with EB/LB resistant codes, like 'Defiant PhR' or 'Mountain Magic'. Maintain consistent moisture levels with drip systems, which prevent excessive wetness in greenery. Apply copper fungicides preventively during humid periods. These techniques have diminished my garden's blight rates by 80% more than my coffee ground experiments.

If used, coffee grounds should be used wisely. Do not exceed 1/2 inch in maximum thickness as mulch, as it may compact and become uneven. Use with crushed eggshells to balance the pH out. Never put mulch around stems since moisture collects there. While they do contribute to the organic matter, efforts to control disease should be taken in advanced and proven ways for reliable protection.

Read the full article: Tomato Blight Treatment Guide: Control & Prevention