This year I lost two tomato plants to a mysterious disease that turned the lower plant stems black. The blackened section dies and the rest of the plant above the damaged portion dies too because it cannot get water. I went ahead and bought new tomato plants, but one of them that was planted into the same location also began to turn black.
I wasn't sure at the time what was turning my tomato stems black, but I have figured out a way to save the tomato plants from dying. The tomato plant above the damaged section is basically alive and well, so the trick is to give the upper portion an ability to obtain it's own water supply.
You will notice that, just above the damaged section, the stem is very bumpy. The tomato plant actually WANTS to grow roots to get water.
Here's what I did:
- Take a sheet of plastic and put some good quality soil in the middle.
- Tie the two corners of one side of the sheet together. Do the same with the other side. Now you have a pouch with soil inside.
- Take this soil pouch and wrap it around the stem under a leaf joint so that the soil is touching the stem. In the case of blight, this will be the good section above the black part.
- Take the loose corners of the two pouch sides and tie them together.
- Get help! Have someone hold the soil bandage up.
- Support the soil bandage. Use string or long twist ties to support the soil bandage by tying it to the leaf joint. You can also prop a piece of wood or another object under the soil bandage to hold it up. Be careful not to pull your plant over if your plant is unable to hold up the weight of the soil bandage.
Honestly, it looks like crap. It's a giant ball of soil wrapped around a stem of tomato plant.
But look at what happens after a couple weeks. Since the tomato plant wants water so badly, it starts to grow A LOT of roots really fast. They even grow out of the damaged black portions!
Once your soil bandage looks like there are lots of healthy white roots growing into it, you can cut off the stem under your soil ball. Put it down and carefully remove the plastic wrapping by cutting it open. If your plant has black stem, be sure to cut away all the black portions.
Now you can plant your rescued tomato plant into a new location.
What is the black stuff?
I looked this up and it appears to be a fungal infection called Blight or Late Blight. The spores are found in infected soil and they splash up onto the plant stems when you water your plants.
This is probably how the lower parts of the stems got affected on my plants and why I am able to save the upper portions. Infected plants can be purchased from big stores like Home Depot or Walmart, and the disease spreads easily there because the plants are in such close proximity. It's moist there, there's not much air flow, and that means good conditions for fungal infections to spread.
I suspect that some of the early tomato plants that died were infected plants. After they died, the spores sat in the soil, and they splashed up onto the new tomato plant and infected it too.
You're actually supposed to destroy infected plants. You're not even supposed to compost them. However, I don't really want to destroy my tomato plants, and I don't mind a good experiment (as you know). So this will be an interesting test to see if the newly propagated tomato plants will live and produce good fruit.
If you live near farms or areas where your infected plants could affect someone else's crop, you should probably get rid of your plants. Since mine are isolated and in the city, I don't have that issue.
Can I eat tomatoes infested with Blight?
You can eat tomatoes from blight-infected plants. It's okay. However, a really badly infested plant will produce hideous tomatoes with ugly black spots on them. I'm not sure if mine will be okay yet. We'll see.
What causes Blight? How can I avoid it?
Blight spreads easily in cold, wet weather which we had earlier in the season, but it is slowed down by hot, dry weather which we have now.
You can discourage/avoid blight in your garden by giving tomato plants a lot of breathing room. In fact, you can even trim tomato plants that have too many leaves and look overly dense. Just cut off some extra stems/leaves that look weak or don't seem to have a useful purpose. Don't get the foilage wet when you water the soil (so spores don't splash up on the stem and leaves). And ensure that leaves have a chance to fully dry out each day.
You can also avoid it by buying blight-resistant plants.
Blight can also affect potatoes. It was actually responsible for the Irish potato famine of the 1840's. So be careful if you have infected tomatos near potato plants.
Well, I hope that helps you out with your tomato growing. I love eating tomatoes fresh from my garden, and they taste so much better than store-bought ones!