Control of Umbel Blight and Seed Decay of Coriander (Pseudomonas syringae pv. coriandricola)

Abstract

Umbel blight and seed decay of coriander in Germany is mainly seed transmitted. To eradicate the pathogen from infected fruits different chemicals, hot water and dry heat treatments were investigated. For disease control a seed treatment by a combination of dry heat and sodium hypochlorite prove to be effective. In order to prevent secondary spread of the disease in the field several chemicals (oxolinic acid, flumequine, copper sulfate and copper oxychloride) were tested. All bactericides showed variable preventive effects depending on the environmental conditions. INTRODUCTION Pseudomonas syringae pv. coriandrico/a is the incitant of umbel blight and seed decay of coriander (Coriandrum sativum L.) (Toben, 1994; Toben and Rudolph, 1996). Since 1986 the disease occurs in coriander fields of a breeding company in Northern Germany. Disease symptoms appeared frequently on floral parts and fruits. These symptoms increased year by year and reduced the yield up to 80%. p. s. pv. coriandrico/a is seed transmitted. A few diseased seedlings arising from infected seed can serve as sources for contamination of nearly all plants of a coriander field. Therefore we investigated possible measures for eliminating the pathogen from seeds. In order to stop secondary spread in the field the effects of chemical sprays during flowering were also studied.