Plant Disease (1997) 81, 892-896

E.L. Little, S.T. Koike and R.L. Gilbertson (1997)
Bacterial leaf spot of celery in California: Etiology, epidemiology, and role of contaminated seed
Plant Disease 81 (8), 892-896
Abstract: Pseudomonas syringae pv. apii, causal agent of bacterial leaf spot (BLS) of celery, was first identified in California in 1989. By 1991, BLS was apparent in all celery-growing areas of the state. Greenhouse-produced transplants were affected most severely, and disease incidence approached 100% in some greenhouses. In this study, sources of inoculum and factors contributing to disease development were investigated in three Salinas Valley greenhouse operations during the 1991, 1992, and 1993 celery transplant seasons (January to August). Epiphytic P. syringae pv. apii was not detected on celery transplants until April or May of each year. Increased epiphytic populations preceded BLS outbreaks, and high-pressure, overhead irrigation favored bacterial infiltration and disease development. In seed-wash assays, P. syringae pv. apii was recovered from 5 of 24 commercial celery seed lots. In field tests, epiphytic P. syringae pv. apii was found on umbels of inoculated celery plants, and seeds from these plants were heavily contaminated with P. syringae pv. apii. Contaminated seed produced seedlings with large epiphytic P. syringae pv. apii populations. Hot-water treatment (50°C for 25 min) eliminated >99.9% of seed contamination. Based on these results, disease management techniques are proposed.
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Database assignments for author(s): Steven T. Koike, Robert L. Gilbertson

Research topic(s) for pests/diseases/weeds:
population dynamics/ epidemiology
transmission/dispersal of plant diseases

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Pest and/or beneficial records:

Beneficial	Pest/Disease/Weed	Crop/Product	Country	Quarant.
	Pseudomonas syringae pv. apii	Celery (Apium graveolens)	U.S.A. (SW)
	Pseudomonas syringae