Expert: Mike Mascio - 6/17/2009

Question
We live in northwest Mt. My tomato plants started out
healthy but slowly, one by one, they are getting sick. The
'disease' seems to start at the top of the plant and work
downward. The leaves curl inward. The leaves on top of the
plants are dark green, the middle lighter green and some
of the leaves on the bottom are yellow. Thinking the soil
had problems, I put them into big pots. They get lots of
southern sun. Our nights are cool but they've been covered
when needed. Thank you.

Answer
The symptoms you described lead me to believe the problem is one of two things. The most likely is that the tomatoes have contracted a disease specific to tomatoes, such as verticillium, blight, or anthracnose. The other possiblility is that they are stressed due to overwatering or excess fertilizer.

I would try and spray the plants with a copper-based fungicide. You can purchase these products at any reputable garden center. If you catch the problem early, the plants will normally recover. Even if they have not contracted a disease, the copper fungicide serves as a good preventive measure.

In regard to the latter possibility, I would suggest that in the future you mulch the plants with dried grass clipping or straw to retain moisture. Limit your watering to 1.5 inches per week. Finally, do not fertilize the plants until they begin to blossom. Excess watering will saturate the roots making it difficult for the plants to absorb oxygen and nutrients. Excess fertilizer can burn the roots resulting in the same symptoms.

I hope this answered your question. Good luck, and please write again if I can ever provide assistance.

Regards,

Mike