Crown rot caused by Phytophthora cactorum in Norwegian strawberry production

Abstract

Crown rot of strawberry, caused by Phytophthora cactorum, was detected for the first time in Norway in 1992. This paper reports on surveys for P. cactorum in Norwegian certified strawberry plant production and on the distribution of the pathogen in regular strawberry production. In 1996 and 1997, samples of plant material from all certified strawberry plant growers in the country were investigated by isolation on artificial growth medium and using an enzyme‐linked immunosorbent assay (ELISA). P. cactorum was not detected in any of the samples. A total of 171 isolations from plants with symptoms resembling crown rot were made from plants in a survey of the distribution of Phytophthora fragariae var. fragariae and from other samples. P. cactorum was detected at 35 different strawberry‐producing farms in 11 of the 19 counties of Norway. The fungus was most frequently isolated from cv. Korona (at 18 locations), followed by cv. Inga (at 10 locations).