No, it won't help with either Early ( A. solani) or Late ( P. infestans) Blight. Either one can appear early OR late in the season.

Below I've linked to the Greencure site and on the right you can see which diseasaes they claim it can help prevent and that does not include either of the two you mentioned.

It's a potassium bicarbonate product that has been most used by rose growers and if you do a Google search you'll see that many of them are saying it doesn't help with this or that either.

I'm just curious, but while Early Blight is very common, I'm wondering where you garden, in a geographic sense, that you're worried about Late Blight this coming season.

I'm not and here in the NE has been the target for LB a few years ago but much less last year and hopefully none this upcoming season. It takes a lot of variables put together to get widespread Late Blight except in the PNW where the two mating types are present so sexual spores can overwinter.

Hope that helps.

Carolyn

Here is a link that might be useful: Greencure fungicide

Carolyn last year I got early blight on my tomatoes for the first time. What should I do this year to prevent this from happening? I was thinking about trying Ortho Disease Control or is there something else I could do..
thanks in advance

THe best preventative for the two fungal foliage diseases, Early Blight and Septoria Leaf Spot in Daconil and Ortho does make a good Daconil product. Be sure to get the one with 29.6% active ingredient which is chlorothalinol.

And start on a rigorous spray schedule when you put the plants out side.

What Daconil does is to block the specific attachment sites on the leaf surface so that the those two pathogens can't attach. And Daconil is also the best we have in helping to precent Late blight as well, if you look at quite a few wesites, and that's even more important since LB can quickly become lethal while the two fungal foliage pathogens are less devastating.

Whether or not any of the foliage diseases is present in any one season is primarily due to their presence in rain droplets and they are transmitted just by air alone.

But if diseased plants shed the spores to the ground then the next year one can get what's called splashback infection from those spores that were shed to the ground when rain or irrigation splashes them back up onto the lower foliage and then the disease progresses upwards on the plants.

Carolyn

Thank you very much Carolyn, I will maintain a rigorous schedule. One more question if you have time. Should I be doing this to my butterfly bushes ? Last year I had a couple that their leaves kept turning brown.
thanks again