Cherry tomato crops were introduced in the late 1990s in the continental areas of southeast Spain. These fields had been previously cultivated with dry land crops as grapevine, olive, and cereal. After two years of cultivation, different soil-borne diseases widely appeared. The main disease observed was the root rot caused by Phytophthora parasitica, killing the plants during harvest period, concurring with the maximum demand of water from plants. The importance of the mycosis in the area together with the lack of control were the aim to first search for the inoculum sources, and then study the preservation of this oomycete in the infested soils for a long period time. Regarding the inoculum sources, no Phytophthora was found in seeds or seedlings from commercial nurseries sampled from the studied area, but the pathogen was isolated from the irrigation pools. Phytophthora parasitica was also isolated from the soils of the home gardens within the surrounded area, and even from the wheels of the tractors used in these fields. About the preservation study, a total of 92 samples from 42 different fields naturally infested with P. parasitica were analysed. All samples have been kept under laboratory conditions in sealed plastic bags. Only 20.58% of all samples preserved the oomycete for 4 years (48 months), and 18.18% for 5 years (57 months). These results can explain the rapid dissemination of the disease and its difficult control in the area.
