A survey was performed in four locations of Semel District – as follows: Sartenk, Qesir yazdin, Sharia, and Grshin (Bawerde) – by selecting 4 greenhouses planted with cucumber plants (Cucumis sativus L.) on each location, during both growing seasons (spring and autumn) of the year 2015. The results showed that the incidence of root-knot disease increased to its maximum level (37.48%) in the autumn season and then decreased to its minimum level (34.67%) in the spring season. According to the surveyed locations, the highest disease incidence (73.05%) was recorded in Sartenk location and the lowest (13.54%) in Sharia location. Results of the interaction between the locations and seasons revealed that the highest disease incidence (80.5%) appeared in Sartenk location during the autumn growing season followed by 65.60% in the same location during the spring growing season, whereas the lowest percentage was reported in Sharia during the spring season (3.47%). Depending on the perineal patterns for species identification of Meloidogyne spp. on cucumber plants, results showed the presence of Meloidogyne javanica in all surveyed locations. Generally, in one of the greenhouses of Sartenk location, the population density of M. javanica reached its maximum level (1,762 nematodes/200 gm soil) in September 2015, while the minimum level (337.5 nematodes/200 gm soil) was recorded in May the same year.