Serving the research and extension needs
of Long Island's horticultural industries.
Vegetable Pathology contact:
Dr. Meg McGrath
3059 Sound Ave.
Riverhead, NY 11901
(631) 727-3611 (fax)
All photographs in this gallery were taken by Meg McGrath unless otherwise noted. For permission to use Meg's, please email her: firstname.lastname@example.org
Pith necrosis on tomato
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Symptoms observed in a high tunnel, June 2008. Diagnosis based on symptoms.
Leaves of affected plants were yellow and wilting.
Main stems had many adventitious roots, a common symptom for this disease.
The center of stems had brown and rotting tissue. It was hollow in severely affected stems. These are characteristic symptoms for pith necrosis.
Some fruit had brown tissue.
Pith necrosis is caused by the bacterium Pseudomonas corrugata, which is considered a weak pathogen able to attack tomato plants that are growing too fast. It occurs primarily in greenhouses with affected plants randomly distributed. Symptoms typically develop when first fruit are close to mature green. Disease incidence and severity is favored by high nitrogen fertilization, cool temperatures at night, high humidity, and plastic mulch. Nitrogen had been applied at a high rate in the high tunnel where the disease developed on Long Island.
The only strategy for managing pith necrosis is prevention by avoiding favorable conditions, in particular excessive nitrogen. Copper fungicides are not able to provide control because this soil-borne bacterial pathogen is inside the plant.
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