Here in southern California I have had no disease or insect damage yet on my tomatoes (knock on wood). My garden is doing the best it ever did so far. I did get some damage to my TAM Jalapeno peppers where some bug punched pinholes into the peppers and laid eggs inside, turning the inside black and ruining the peppers. I didn't even have any Green Fruit Bettles this year which normally decimate my nectarines.
I use absolutely no pesticides or fungicides on my garden, except for a little snail killer I put around newly transplanted seedlings to keep the roly polys, earwigs, and slugs and snails from eating them, but I only use that when I first transplant them. I haven't fertilized my garden other than the steer, horse, or rabbit manure I put in the planting holes, or mealworm castings I sprinkle around the plants later on, except for a little ironite and zinc chelate. Before I transplant I do use chemical fertilizer when the plants are in their 4 inch pots.
I only had one tomato with BER out of hundreds I already picked. I only water once a week except when we get 100 degree days, then I might water twice a week. I have lots of bumble bees and honey bees and hummingbirds and wasps and ladybugs in my garden since I use no pesticides and have lots of plants to attract them like four O'clock, borage, lavender, rosmary, and flowering weeds.