Grow & Tell is IPR’s biweekly gardening segment to guide you through the growing season. In each episode, I’ll walk you through gardening tasks tailored for northern Michigan’s climate and soils — whether you're working with raised beds or patio pots.
Have gardening questions you want Grow & Tell to answer? Email me at dylan.kulik@interlochen.org.
Today’s tip: How to diagnose and treat common tomato problems
Today, we’re out in the tomato hoop house tackling two common tomato issues: fungal disease and pest pressure — and what to do when they show up.
Step 1: Spotting the problem
My tomatoes looked fine a few days ago, but now I'm noticing crispy-looking, black and brown leaves. It almost looks like they were burnt. Since I don't see any telltale signs of bug pests, this seems like a fungal issue.
Bugs are a bit more obvious: Bite marks, holes, spider webs, eggs and the bugs themselves.
Don’t worry — all of this is normal. These are bugs are looking for food, and we've put food into their environment: a delicious tomato plant. But we'll spray some solutions to keep them off our plants, and save the food for us.
Step 2: For fungus, cut the water (for now)
If you've diagnosed a fungal problem, cut down your watering by a lot for a few days. Fungi like a wet environment, so if we can dry things out, we can hopefully reduce the fungal presence to zero.
(Skip this step if you're just dealing with bugs.)
Step 3: Concoct and spray your solution
For fungal disease: It'll take a few days to see if our watering trick worked. In the meantime, I’m using a foliar anti-fungal spray. Today, that’s a sulfur solution — made by mixing solution-grade elemental sulfur with water in a spray bottle.
You can get this at a garden store, just make sure the sulfur is labeled "solution grade," and follow the directions on the package for dilution.
I spray the plant from about six to eight inches away, covering both the top and underside of the leaves with a fine mist. You want full coverage of any affected leaves and stems.
Once that’s done, I let it dry and keep water levels low for a few days.
For bug pests: My go-to natural pesticide is neem oil. It’s a plant-based oil with a strong smell, a thick texture, and a mild neurotoxic effect on certain bugs: a triple threat.
Here’s my neem spray recipe:
- About 1 tablespoon neem oil
- 5–10 drops of dish soap
- Hot water to fill a 40-ounce spray bottle
(Unless you've got 50 or so tomato plants to cover, you likely won't need this much. Mix according to instructions on the neem oil you buy.)
Once you've got your ratio right, shake it thoroughly to mix it into a uniform solution.
Like with the sulfur spray, cover the top and underside of leaves, the stems, and anywhere bugs might be hiding. Neem oil works best on contact, so thorough coverage is key.
Step 4: If you see something, spray something
I’ll keep applying this neem solution and/or sulfur spray every week or every other week, as long as I see evidence of bugs or fungi. Once things calm down, I taper off but still keep an eye out.
With that, we've given our plants the best defensive barrier with foliar solutions. We're going to let them grow, and continue to come out every day and look for signs of stress.
Today's Takeaways 🍅🐛
- Wilting and crispy leaves might mean a fungal infection — reduce water and spray with sulfur.
- Neem oil is your best friend against pests.
- Spray both sides of leaves for full coverage.
Stay observant — early action makes the biggest difference.
