Splash Dispersal ofPhytophthora cactorumfrom Infected Strawberry Fruit

Abstract

Strawberry fruits infected with P. cactorum were used to demonstrate and quantify the effects of splashing water on dispersal and distribution of inoculum. Water drops, averaging 0.026 or 0.41 cm in diameter, were dropped from various heights on infected fruits adjacent to petri plates containing selective media and positioned up to 1.2 m away. Sporangia, zoospores and mycelia were readily dispersed: as a result of water-splash from the 0.41- and 0.026-cm-diameter drops, colonies formed up to 120 and 50 cm, respectively, from the inoculum source. Numbers of colonies that developed in the plates were negatively correlated with distance from the inoculum source. A multiple regression model was used to describe number of colonies as a function of distance and water drop velocity at impact. Splash dispersal of inoculum from infected fruit to healthy, attached fruit was demonstrated with potted plants.