Question

poor sick branches   QUESTION: Hi Mike

Just wondering if you could tell me what's wrong with my tomato?  The foliage on the lower leaves are becoming pale yellow and dry.  The stem is developing dark patches (I"ve attached a photo).  If left long enough, the branch attached to the stem becomes very weak - I can easily pull the whole branch out without resistance.  It's spreading upwards fast - please help me ID what's wrong and what I can do about it!

History:  Very wet and humid weather - sprayed thoroughly a few days ago for powdery mildew (used organic fungicide made specifically for mildew).

ANSWER: Extremely wet weather will deplete the nutrients from the soil, resulting in a yellowing of the leaves. If the roots become water-logged, it will also cause dark spots on the stems. Generally, this condition will improve as the weather becomes drier. It is important to amend the soil every spring with organic matter to improve the drainage of the soil. Clay soils are especially susceptible to retaining water and subsequently contracting root problems.

Since it is very difficult to diagnose a problem strictly off a photo, I am attaching a link that will allow you to compare the condition of your tomatoes against various photos of diseased stems and leaves common to tomato plants in general. This particular link shows disorders of the leaves, but you can click on the stem and root links to the right of the page for more photos.

http://aggie-horticulture.tamu.edu/publications/tomatoproblemsolver/leaf/

I hope this information helps. Please write again if I can ever provide assistance.

Regards,

Mike

---------- FOLLOW-UP ----------

QUESTION: Mike, thank you so much.  I do have one question; the site you linked me to didn't describe fusarium wilt, and a garden store staff had suggested I may have it and should pull the plant.  

I don't know for sure however; is there a defining symptom of FW?  For example, google searches mention 'vascular' damage; what does this mean?  Yellowing and distorting of leaves could be advanced mildew damage from what I've read from your link.  I certainly don't want to pull the plant unless I'm certain it's FW!

If it is FW; how does it spread?  I have all container tomatoes (differnet potting mixes).  Is it an airborne disease like mildew?

Thanks!

ANSWER: Wen, all I can tell you is that Fusarium wilt is a soil-borne disease that can be contracted through an infected plant from the nursery or through infected seeds from the growers. Once in the soil, it takes 2-3 years to clear. The fastest way to kill the disease is to remove all infected plants and destroy them. Do not compost them. Then cover the entire bed with black plastic and leave it on for 2-3 months. This will solarize the soil and kill of the disease.

It is also a good practice to rotate plants on a three year cycle. This prevents a soil-borne disease from infecting next year's crop. You should also purchase seed or plants that are known to be resistant to this and other diseases. Seed companies list which diseases are hybridized out of a particular variety. I only plant hybrids for this very reason.

I hope this answered your question.

Good luck.

Mike

---------- FOLLOW-UP ----------

QUESTION: Hi Mike

Following your excellent advice, I have disposed of all my diseased plants, including the stakes and cages I had used on them.  I now have two remaining questions:

1.  When will it be safe to bring in new tomatoes?  My plants were all on a balcony, and there are still other plants (e.g. capsicum, basil and other flowers) unaffected by the wilt.  Will the spores still be around to potentially infect new seedlings?

2.  Regarding the potting mix I used for the tomatoes; will I be able to re-use it to plant something completely unrelated (e.g. flowers?)

I guess I should also ask if the remaining soil will still have evil things left in it to infect my new plants too!

Thanks

Answer
Tomato diseases are relegated strictly to the nightshade family. These include tomatoes, peppers, and eggplant. Flowers and other vegetables will not be affected.

It takes 2-3 years for most diseases to be eradicated from the existing soil. If you want to plant new tomatoes, you will need to dispose of the soil from the pots, sterilize the pots with hot water and bleach, and then use new potting soil. The spores from the other pots will not infect the new plantings as long as you keep them a few feet apart.

Once again, good luck. Just make sure you choose disease resistant plants (hybrids) going forward to minimize any future problems.

Mike