I don't think late blight spores get on the seeds.
If my tomatoes get late blight, I put the plant and the tomatoes into the garbage. I do not put them in my compost pile, and I do not save seeds from them.
Here on the Pacific coast, late blight happens late in the season, after the rains begin. (We do not have rain in the summer). So all my seeds are saved from healthy plants.
Here in Netherlands there is rain every week from start spring till end of summer. This is why we have blight when first fruit get red. And some people told me the blight can enter the seeds for next year. Is this treu?
ps most resistent varaties with PH2 gene are also infected.
it is impossible here to not get blights on the tomatoes. we usually have dew and fogs in the later parts of summer. all we hope for is that we can get a crop in before the plants die off completely. in the many years we've been growing tomatoes we've never lost a complete crop, but we have had some damage. still our average harvest is somewhere between 20-40lbs per plant. that works, no sprays or fussing around.
i do rotate plant but that is about all i do for trying to keep diseases and pest numbers down.
Last Edit: Jul 31, 2020 18:34:09 GMT -5 by flowerbug
For me the late blight not infecte the seeds. At a period i have throuw away the plant with the fruits infected in the compost and the next year,a lot plant was grow back without blight.
For his developpement the blight require that the leaf are humid with a t° between 11°C and 26°C. .
If you are a doubt you can past your seeds at the freezer. Try to take a tomato not too infected! There is a cut of the tomato! The blight begin by infected the peal and after the pulpit before to infected the canals wich they feed the seeds. encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcQe_nsLw7WhlEUOJbqXc6Slw-gEy3NIIYsfjd1-GuQfJQ&s For me if the,blight is really able to infected the seeds, i think that they are the last to be infected. Its possible that when the seed is at maturity the canal wich feed the seed it close and block the mushroom.
I grow tomatoes with both pH2 and pH3, so don't get visible blight. I save my own seeds, which means that untill a line stabilizes with 2 copies of each, some plants can have 1 or none of a gene. Those plants get blight on the fruits, and if they are not too bad, I keep seed so I have some control plants to compare with. Most years they are no more likely to have blight than purchased seeds with no resistance. I know that only partly answers the question:)