| A hypothetical disease cycle of leather rot of strawberry has been developed from research and observations in this study. P. cactorum can survive as oospores in mummified fruit at or immediately beneath (1 cm) the soil surface, thus serving as a source of primary inoculum. Under favorable soil conditions in the spring, oospores germinate, producing sporangia. Dispersal of sporangia and/or zoospores can occur via water splash mechanisms (rainfall or irrigation) to surrounding fruit, resulting in primary infections.;Infection occurs in the presence of free water on the fruit surface. Wetness durations as short as 1 hr between 17 and 25 C can result in high levels of infection. As temperatures increase or decrease away from the optimum temperature (('(TURN))21 C), progressively longer wetness durations are required for infection.;Formation of dispersal and/or infection units (sporangia) on infected fruit surfaces occurs in the presence of free water and is favored by temperatures between 15-25 C, with the optimum temperature ('(TURN))20 C. Sporangia can form at wetness durations of 3 hr at 15-25 C, but are produced at 12.5 and 27.5 C under wetness durations of (GREATERTHEQ) 12 and 6 hr, respectively. Longer wetness durations result in greater sporangial production at temperatures within the sporulation range. Infective propagules (sporangia, mycelia, and/or zoospores) are dispersed by splash mechanisms to nearby healty fruit, resulting in secondary infections under the proper temperature/wetness conditions.;As infected fruit mummify, oospores are formed within fruit tissue. Mummified fruit eventually fall to the soil, where the pathogen overwinters as oospores within mummified tissue, thus completing the disease cycle. |
