Seasonal variation of field populations of Heterodera filipjevi, Pratylenchus thornei and P. Neglectus on winter wheat in Turkey
AbstractThe development of cereal cyst nematode Heterodera filipjevi and root lesion nematodes Pratylenchus thornei and P. neglectus was investigated under rainfed cereal conditions over three growing seasons (2002-2005) on the winter wheat cultivar Bezostaya. Juvenile emergence of H. filipjevi was recorded during the winter period from November to March. The hatching process was correlated with the lowest temperatures. Mature white females were found on roots at the beginning of May and mature cysts appeared later on. The total number of cysts and eggs in the soil had only one peak at the end of each growing season, suggesting that H. filipjevi was monocyclic. Multiplication rates were inversely correlated with initial nematode densities with ceiling levels of between 15 and 20 eggs per g of dry soil. Population densities of P. thornei and P. neglectus were low from November to March/April during the cold snow period, increased gradually to June/July and then rapidly decreased over the summer period. Numbers of nematodes were positively correlated with temperature and the multiplication rate was 0.42-3.8 for P. thornei and 0.91-2.26 for P. neglectus.