I think the key to preventing many diseases in the vegetable garden is using organic fungicides early-before the onset of visible problems. I am using ‘Companion’ (order online) as a drench around the roots and ‘Serenade’  (get at Agua Fria Nursery only) as a foliar spray on the leaves. I had today off so I used them again. I’ve been using them about every 2 weeks.  I’m looking for less tomato loss this year and hope by keeping up on my fungicide schedule, it will help. I use this combo also on the giant pumpkins and squash and they are looking good so far also. I will cut off any suspicious leaves or branches as well as use fungicides  (see mottled leaf on bottom of picture) Of course we haven’t had any rain yet to speak of to really test them (fungal diseases love moist enviroments) so we will see…