DISTRIBUTION AND POPULATION FLUCTUATION OF ROOT-LESION NEMATODES, Pratylenchus SPP., IN IRRIGATED WHEAT AND CORN FIELDS IN MARVDASHT, FARS PROVINCE

During 2005-2007 years, totally 182 irrigated wheat and corn fields of Marvdasht and some other localities in Fars province were sampled, in order to study distribution of root-lesion nematode, Pratylenchus spp. Root-lesion nematodes of each field were identified at species level and their population densities were determined. Initial population densities of Pratylenchus species in 56 wheat fields, were determined by sampling before sowing, during November and October 2006. In addition, the population fluctuation of root lesion nematodes was studied in eight fields, during July and October 2006 and June 2007. Moreover, changes of population densities of P. neglectus and P. thornei in two wheat field were studied. The results showed that 56.6% of studied field were infested with root-lesion nematodes. P. neglectus and P. thornei were found in 39% and 14% of surveyed fields, respectively, and 3.7% of fields were infested with both species. According to the result of eight fields, sowing corn at summer and wheat at autumn increased and sugar beet, alfalfa and fallow decreased the nematode densities. During the planting season, population of root-lesion nematode increased and reached to maximum at harvest, but increasing of nematode densities happened only in roots and the nematode in soil increased at harvest.