Can aerated compost teas be used on the foliage of my tomato plants to help protect against leaf spot?
I have been reading a lot about aerated compost teas and how they can be used on the foliage to help protect against things like fungus and insects. Do you agree with these type of statements? If so, could application on my tomato plants help with leaf spot?
The short answer to your question is no. There is no scientific research that indicates or supports that compost tea is effective in controlling fungus diseases or insects.
Aerated compost tea has been widely touted by gardeners as a cure for plant diseases but is largely anecdotal and not supported by peer-reviewed research. Dr. Milner, USDA, did work on strawberry fungal diseases many years ago but had very limited success. Products that are used to prevent or kill diseases or insects need to be registered as a pesticide. Compost tea is not registered.
I would suggest removing the lower foliage of the tomatoes below the first fruit cluster. This will help prevent soil fungal spores from splashing onto the leaves and continue to remove leaves as the fruit ripens. This will slow down the spread of septoria leaf spot. Here is a factsheet on Septoria Leaf Spot of Tomato.