The variegated cutworm (VCW), Peridroma saucia (Hubner, 1808) (Lepidoptera: Noctuidae), is a common polyphagous pest of many vegetable and field crops and found in many areas of the world (Rings et al., 1976 and Klein Koch and Waterhouse, 2000). VCW was first recorded in Europe in 1790 and then caused serious outbreaks in many countries throughout the Americas in 1841 (Capinera et al., 1988). The adults of these cutworms were discovered in 1967 in Turkey. At the present time, VCW is widely distributed in Turkey’s agricultural areas and it is one of the most abundant and damaging cutworm species of Turkey (Akdagcik and Ulusoy, 2007). VCW has a wide range of host plants which includes economic crops such as potato, tomato, corn, lettuce, carrot and sugar beet. VCW larvae do much damage to crops and cause considerable mortality to seedlings in the early growing season by cutting off the plant at the soil surface and feeding on the foliage of these crops (Capinera et al., 1988). Due to the high tolerance of VCW, repeated applications of conventional insecticides are widely used. Development of resistance and concerns over the destructive effects of chemicals to environmental and human safety have accelerated the development of alternative control methods for this pest (Yoshida, 2010).
Entomopathogenic nematodes (EPNs) are highly effective biological control agents against many agricultural pests particularly soil-inhabiting lepidopterous larvae because of their presence in larval stages below ground (Vashisth et al., 2013). EPNs have searching ability on hosts and the potential to survive in the soil environment. They possess free-living third-stage infective juvenile (IJ) that can survive a long time without feeding (Koppenhöfer et al., 2000). The IJs invade their hosts via natural body openings, such as the mouth, the anus and the spiracles. Once they enter to haemocoel, the mutualistic bacteria Xenorhabdus in Steinernema and Photorhabdus in Heterorhabditis are released to kill the host within 2 days (Gaugler, 2002; Griffin, et al., 2005; Kaya et al., 2006).
EPNs that infect insects have received considerable attention by scientists for their potential in the biological management of many agricultural pests (Gaugler, 1981; Gaugler and Kaya, 1990; Georgis et al., 2006; Koppenhöfer et al., 2000; Smart Jr, 1995). Many studies have been started for testing the pathogenicity of these indigenous EPN species all over the world (Ozer et al., 1995; Kepenekci, 2002; Hazir et al., 2003; Unlu et al., 2007 and Erbas et al., 2013). There are some differences known in terms of survival, pathogenicity and host range between indigenous and non-indigenous EPN species (Lacey and Georgis, 2012). Indigenous species of EPNs may be more successful in biocontrol as a consequence of compatibility to native habitats (Goudarzi et al., 2015).
The aim of this study is to evaluate the effect of four Turkish species of EPNs for the biological control of the variegated cutworm (VCW), P. saucia, under laboratory conditions.