Further to my post about blight and the use of compost tea as preventative spray I have found some more information which will explain more about it.
Compost teas work by inoculating the leaf and stem surfaces with microorganisms that serve as antagonists to invading pathogens such as Phytophthora infestans by occupying the leaf surface, making it difficult for the pathogen to get started. The beneficial bacteria also induce resistance in the plants. Additional microbes are added to the tea to enhance the antagonistic effect.
This link shows that it is not that simple to make good compost tea.
And This link is the simple version!
So as you can see, it is not as simple as it first looks, but for those of you that are interested then the following will explain further.
Click on the links for the full report.
Compost tea, applied as a foliar spray, is also reported to suppress late blight. In a German study compost teas made from either horse manure or cow manure were sprayed on potato foliage as a control measure against late blight. These teas were used either alone or with additional micro organisms added to the mix. The tea treatments were compared to three fungicides or to a water control. The compost tea alone was applied seven times per week. Compost tea with additional microbes was applied 11 times weekly. Fungicides were applied five times during the growing season. Results from the experiment can be seen HERE. As you can see, compost + microbes was equal to Ridomil MZ fungicide in reducing diseased leaf area and produced similar high yields, as did two other fungicides. Ciluan and control produced the lowest yields. Results comparing compost tea alone and compost tea with added microorganisms, compared to a water control, are shown in Table 2. The addition of microbes to the compost tea was very beneficial, bringing yields from the mixture up to double that of the tea alone or the control.
So compost tea does seem to work on the experiments done mainly on potato crops, athough potato blight is what attacks tomatoes. All I have to work out now is how to add the additional microbes!
All comments and advice very welcome on this subject.