rainbowgardener wrote:If you are having disease issues, you would be much better off to stake or cage your tomatoes up off the soil. Lots of diseases like septoria and blight are soil borne and get transmitted through contact with the soil (even soil particles that splash up on leaves from watering).
Those of us that cage our tomatoes usually remove all the bottom leaves, just so that nothing contacts the soil.
Actually none of the common tomato foliage diseases are soil borne naturally as are the many systemic diseases, and I'm referring to:
Early Blight ( A solani), Septoria Leaf Spot, both fungal, and Bacterial Speck and Bacterial Spot.
All new infections with those are by air and embedded in rain droplets.
What can happen is if plants with those diseases shed the spores or bacteria to the soil the next year there can be splashback infection after heavy rains or too much irrigation, as was mentioned above, and thus the lower foliage becomes infected and that spreads upwards on the plants.
So as was also mentioned above, taking off the lower branches can help, but again, all NEW infections are by air and rain and sometimes by irrigation.
But there are some ways of preventing air or rain borne foliage infections as well as splashback infections.
Spraying with a good anti-fungal ASAP when the plants are put out and keeping up on a regular schedule is THE best thing that can be done.
There are no very effective sprays available to the home gardener for the bacterial ones, although you can try a copper based spray. These days some folks are concerned about build up of copper in the soil.
No treatment is 100% effective so turning the soil over deeply at the end of the season, and a tiller doesn't do the job, can help bury those agents so they have a harder time of getting near the top of the soil to cause splashback.
Mulching plants also help to prevent splashback infection as well.
I grew far too many plants and varieties each season to ever think of caging or staking, although when I lioved in certain places I did make my own CRW cages and used them and here where I am now at one place I have used a few cages.
What was easiest for me b'c of the number of plants I was growing was to sprawl them and that worked very well indeed. A farmer friend would turn under my plants in the Fall, plant winter rye, and then in the Spring turn it under again and then plow and disc and smooth off my field.
Doing that I was able to use that field for tomatoes with much less disease problems, for about 20 years without disease buildup. And I had everything else planted in that same field as well, so doing that also proected the eggplants and potatoes which share some diseases with tomatoes, all being on the genus Solanum.
Hope that helps.