The powdery scab is caused by the protist Spongospora subterranea (Walk.) Lagerh f. sp. subterranea Tomlinson, which is an obligate parasite that replicates in roots and tubers of potato (Solanum tuberosum). This replication results in resistant structures which are denominated cystosori. Production of cystosori was investigated in the potato variety Diacol Capiro, which was cultivated in three types of soil (Inceptisol, Entisol, and Andisol) that were infested with cystosori. Concentration of cystosori was determined at planting (Initial), at plant senescence (Harvest), and at plant disintegration (Postharvest). The experimental design was completely randomized with two treatments and three levels each. Soil type with the levels Inceptisol, Entisol and Andisol, was one treatment; and the sampling time with the initial, harvest and postharvest, was the other. Additionally, a test of simple regression to analyze correlation of the intial and final concentration of cystosori was performed. In all types of soil, cystosori concentratio increased significantly (P<0.005) from planting to postharvest; the mean increase was 48%. There was no significant (P<0.05) difference among types of soil at any time sampling. The final concentration of cystosori (Postharvest) was significantly (P<0.005) which correalted wit the initial concentration of cystosori (Initial). These results suggest that cystosori concentration can have a substantial increase after a single potato crop cycle, and harvest residuals, such as contaminated tubers, can contribute to this increase.