I was just outside checking on the slow ripening progress of my
tomato plants and noticed something that has me concerned. There seems to be a fungus or mold at the very base of my “super fantastic” tomato plant.
Other than this issue and the slow ripening the plant seems to be
doing okay. I haven’t noticed this fungus/mold before so I don’t know
if has just appeared and is spreading rapidly or if it has been
there all along. Do you know what it is? Will it spread through
the entire plant? Will it spread to the other tomato plants and
veggies in this bed? Should I remove the entire plant?
This sounds a lot like Fusarium wilt, but it could also be Verticillium
(another fungal problem) or even walnut toxicity (do you have any black
walnut trees within 50 feet of your plants?). It might even be excessive
watering which is causing the problem.
According to The Organic Gardener’s Handbook of Natural Insect and
Disease Control edited by Barbara Ellis (Rodale, 1996), you can cut open
a stem near the soil line and look for internal discoloration.
Verticillium affects the whole plant, while Fusarium will start by
infecting individual shoots and then spread. Tomato Fusarium only affects
tomatoes, while there are numerous plants which are susceptible to
Verticillium. The best thing to do if your plant is suffering from these
fungal diseases is to destroy them, so you may want to take a sample to a
Master Gardener Clinic for diagnosis before you do anything drastic.
General resources on tomato problems:
Recognizing Tomato Problems from Colorado State University Extension.
Vegetable MD Online from Cornell University.
University of California, Davis Integrated Pest Management has
excellent pictures of the insides of the stems, for comparison.