Friday, May 30, 2014

Yellowing Leaves

After last year's experience with the Box Car Willie tomato plant that developed Fusarium Wilt, which led to the premature death of the plant, Cindy decided to conduct an experiment by grafting a Box Car Willie plant to disease-resistant root stock.

Although the ungrafted plant produced the first green tomato, that plant was the first to start showing signs of disease in the form of yellowing leaves at the base of the plant.

A few days later, the grafted Box Car Willie plant also started showing some yellowing of the lower leaves, and so did most of the other tomatoes.

Upon closer inspection, it appeared that most of the yellowing and leaf wilt was due to powdery mildew, probably caused by the high temperatures and very dry, Santa Ana winds we had a couple of weeks ago.  Cindy had put up cloth panels to protect the plants from the sun and heat, but not much could be done to protect them from the drying wind.

She has now removed the diseased leaves and sprayed the plants with neem oil, a fungicide that should prevent the spread of the powdery mildew spores.

The disease-resistant root stock on the grafted Box Car Willie plant should help it survive this, but we're still not sure about the ungrafted plant.

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