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Identifying Tomato Diseases…

Tomatoes are probably the most common variety of vegetables grown in gardens.  Weather fluctuations with temperature and moisture swing can however spawn diseases and knowing how to identify these signs will make for a healthier plant.


One example of a tomato disease that can affect tomato plants is early blight which is a fungus that over winters on harvested tomato plants from the prior season and then may spread to your new plugs in the spring with wind and moisture. Low hanging wet leaves will germinate on these fungi spores to prosper and spread.  To identify early blight, you will notice brown spots on the leaves closest to the soil grade of your garden plot when tomato plants begin to fruit.  These spots start to turn yellow and spread which will wither the leaves if your plant is infected. These brown spots will also have an outer ring around this centre spot.


Most of the damage and infected parts should only be around the lower part of the plant because of the area having the most moisture conditions.  Removing these infected leaves should help to keep the spread at bay and will add air movement around the plant and most of these tomato plants should still produce a good crop.  Determinate tomatoes after bearing fruit will complete their biological cycle vs. indeterminate tomatoes that will bear fruit until the first frost and may have this blight issue if infected for a longer production season.


Intercropping can sometimes manifest this condition because of introducing too many companion plants that may tend to crowd your variety of tomato plants.  Try and keep some space by planting your companions and other plants to prevent plant congestion and crowding.  Make sure cages and stakes can support your plants from tipping to the ground where moisture can trigger this problem and add mulch to the base to avoid rain, moisture and soil from contacting and splashing onto the plant leaves.


Remember to practice crop rotation each season to prevent soil born diseases from spreading to other plants.


  • Paul Smith