IntroductionTurkey is an important dry onion producer and the seventh leading producer after China, India, USA, Iran, Russian Federation, and Egypt with a total production of 1.8 × 10 6 t in 2012 (TÜİK, 2014). Onions are produced in many provinces of Turkey. Karaman Province, which includes terrestrial and Mediterranean mountain climate properties (Karaman Çevre ve Orman Müdürlüğü, 2007), contributes 12,657 t of dry onions or 0.0131 t/ha (2012 data;TÜİK, 2014). Onions are produced in an approximately 1000-ha area in central villages and in the Ermenek and Ayranci districts of Karaman (2012 data;TÜİK, 2014).Plant-parasitic nematodes cause 8.8%-14.6% crop losses annually and total economic yield losses of 100-157 billion US dollars worldwide (Nicol et al., 2011). Ditylenchus spp., Tylenchus spp., and Paratylenchus spp. were found most frequently and abundantly in the onion-growing areas of Karaman (Dikici and Yavuzaslanoglu, 2012). The stem and bulb nematode Ditylenchus dipsaci Kühn (Tylenchida: Anguinidae) is the most important nematode pest in a wide range of plants, including onion, garlic, hyacinth, narcissus, and tulip, particularly in temperate regions (Potter and Olthof, 1993;Tenente, 1996). Moreover, the European and Mediterranean Plant Protection Organization (EPPO) has placed D. dipsaci as no. 174 on the A2 list of phytosanitary categorization, which is distributed locally in EPPO countries, and it is regulated as a quarantine pest (EPPO, 1997).Crop losses differ depending on the initial nematode infection level in host plants. Sturhan and Brzeski (1991) reported crop losses of 60%-80% in heavily infected fields. Mennan ( 2001) reported that D. dipsaci caused a 65% yield loss in onion in the Suluova district of Amasya.
