There’s a Fungus Among Us!

I love tomatoes! I am growing over 30 tomato plants because I want a plethora of tomatoes. I crave sliced tomatoes for insalata caprese (tomatoes, mozzarella cheese, basil, balsamic vinegar/olive oil), crushed tomatoes for homemade spaghetti sauce, chopped tomatoes for salsa or rice and beans. I have to have my tomatoes! Last year, excessive rain killed all my tomato plants (along with everyone else’s around here), and I was devastated. But it was the weather. Who can control that? This is a new season, and I’ve had such excitement for my crop this year.

But now…there’s an enemy stalking my tomatoes, surreptitiously attacking the leaves and spreading its fingers of death from branch to branch. It arrived so silently, I almost missed it. But then, today….[Queue Theme from “Psycho”] the tomatoes screamed, ” There’s a fungus among us!”

Yes, my tomatoes have a dreaded fungus! Within the past couple of weeks, I started noticing brown spots on the leaves of my slicing tomatoes. (My paste tomatoes are in a separate raised bed.) Something told me that it could be a problem, but I waited. Bad move! The problem got worse – as you can see in the picture above. The lower leaves started turning yellow, and the brown “waterspots” were spreading to higher leaves. Not good!

Spots on tomato leaves ~ Septoria Leaf Spot?

Spots on tomato leaves ~ Septoria Leaf Spot?

So, I spent quite a bit of time today researching what exactly was attacking my tomatoes. I’m no expert, and I didn’t have a professional examine one of my plant leaves; but based on the pictures I looked at, it seems to be a fungus called Septoria Leaf Spot.

This fungus begins on the lower leaves and moves up the plant; it can even infect the stem. (The fruit remains unaffected; but if left untreated, the plant can die. Bye-bye fruit!) Although it can appear anytime in the season, it usually attacks early to mid-season, especially after heavy rain (or during humid weather). Well, this is Charleston, SC in May after several inches of rain a couple of weeks ago. Yep, I think I nailed the diagnosis.

Before I allowed panic to set in, I researched what to do about it. There is no “cure” for Septoria Leaf Spot or other fungal diseases, but there are ways to mitigate the chances of getting them. There are also fungicides to help prevent spreading.


There’s no guarantee your tomatoes won’t be attacked by fungus if the conditions are right – humidity, heavy rains, insect transmittal, etc. But you can do the following to give your plants the best chance of escaping it:

  • Plant tomatoes two feet apart when transplanting, so they won’t be crowded
  • Stake your plants to keep them from falling into each other.
  • Mulch heavily with pine needles or straw (not hay, which contains seeds). This will prevent soil from splashing up on the leaves when it rains or when you water. (It also helps to maintain the moisture in the soil, which tomatoes need a lot of.)
  • Do not water tomatoes from above!! Always water from beneath. Soaker hoses are great. If you don’t have a soaker system, be sure to put your nozzle on a lower setting and aim for the roots.
  • Never water at night. Watering in the morning is best. And don’t over water.
  • Prune the bottom branches of the tomato plants below the level of the first fruit cluster. This will improve circulation and keep leaves off the ground.
  • If your area is prone to fungus (like in the South), pre-treat your tomatoes with a fungicide before disease sets in.
  • Always rotate your crops. Don’t plant tomatoes or other nightshades in the same spot for at least 3 years. (Five years is better.)


If the distinctive brown “waterspots” start to appear on your tomato leaves, treat for fungus right away.

  • Carefully remove all diseased branches and leaves. Try not to touch healthy plants so you won’t spread the spores to them.
  • Treat with a foliar spray of copper fungicide, spraying all leaves (top and bottom) and stems. Repeat every 7-14 days, depending on the product instructions.

You know the proverbial saying: an ounce of prevention is worth a pound of cure? Well, I think if I had used the full ounce of prevention, I wouldn’t be seeking a cure now. I planted my tomatoes two feet apart, staked them, and always water from below. Yet, I procrastinated on pruning the bottom branches and mulching. Bad, gardener, bad!

After work today, I drove straight to the store to buy a bottle of Bonide Copper Fungicide “ready to use” for immediate application. But before I applied it, I removed all the diseased branches and leaves, as well as the lower branches. There is much more space for air circulation now (and the carrots I planted among the tomatoes can get more sunlight).

Here are the before and after pictures of my paste tomatoes:

Tomatoes unpruned

Tomatoes before pruning

Tomatoes after pruning

Tomatoes after pruning

I then used almost the entire 32 ounce bottle of fungicide on my two beds of tomatoes. Because I have to reapply every seven days, I’ll be ordering the concentrated version this weekend so I can do it more inexpensively.

Tomorrow, I’m off to Tractor Supply to get several bales of straw to mulch ALL of my beds. An ounce of prevention…and all that.


I welcome your comments. How are your tomatoes doing?


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