For years now, we have grown a vegetable garden and have struggled with verticillium wilt...if that is what it is. Plants grow fine at first and then the leaves turn brown. The vegetables are of inferior quality. We have rotated the plants each year. We used steer manure for several years and for the last two years used Gordon Wells formula for fertilizer. We found a product online called Terraclean which states it will kill verticillium in the soil, but it only comes in large quantities. Is there something else we could use to kill the virus in our soil?
Verticillium would only be a problem on melon plants, potato, tomato, pepper, and strawberry. Also, the disease typically kills plants. On the dead or dying plants, did you examine the crown of the plant? Was it sunken? Did you slice through it and see if the center was brown? Were the roots brown or soggy?
If you are noticing anything with squash, corn, lettuces, broccoli, or herb plants, then the problem is something else. If it is verticillium or root rot, the problem would be worse when the soil is kept too moist for long periods of time.
Your best bet is to pick vegetable varieties that are resistant to verticillium. This handout out of University of CT has some info on the disease and on resistant varieties http://www.ct.gov/caes/lib/caes/documents/publications/fact_sheets/plant_pathology_and_ecology/verti....