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Öğe Antagonists and defense mechanisms of entomopathogenic nematodes and their mutualistic bacteria(Academic Press Inc Elsevier Science, 2021) Raja, Ramalingam Karthik; Arun, Alagarsamy; Touray, Mustapha; Gulsen, Sebnem Hazal; Cimen, Harun; Gulcu, Baris; Hazir, SelcukEntomopathogenic nematodes (EPNs) in the families Steinernematidae and Heterorhabditidae are effective biocontrol agents against a number of important soil insect pests and are safe to vertebrates, plants and other non-target organisms with no negative effects on the environment. They are associated with mutualistic bacteria in the genus Xenorhabdus for Steinernematidae and Photorhabdus for Heterorhabditidae and are often referred to as the nematode/bacterium complex. The natural habitat of EPNs is the soil where the third-stage infective juveniles (IJs), the only free-living stage, can infect an array of insect hosts. However, the survival of the IJs is affected by various abiotic (i.e., temperature, moisture, soil texture, soil salinity, UV light, oxygen, and pH) and biotic (i.e., natural enemies, omnivores, scavengers, competitors, and plants) factors in the soil. In this review, we summarize the impact of the biotic factors, especially natural enemies, omnivores, scavengers, and competitors against EPNs and conclude that the major predators of the IJs appear to be nematophagous fungi, mites, and collembolans. Omnivores and scavengers, particularly, mites, collembolans, ants and birds, feeding on EPNkilled insects appear to be the major mortality factors on the developing nematodes especially of insects that are 2 days or less post infection. In addition, we discuss the defense mechanisms of EPN IJs against nematophagous fungi, and the protection of the nematode-killed insects by production of the scavenger deterrent factor produced by the mutualistic bacteria against omnivores and scavengers. By understanding the interactions between EPNs and their antagonists we can improve and increase the successful use of EPNs in biological control programs.Öğe Biological Control Potential of Steinernema carpocapsae (Steinernematidae) on Monochamus galloprovincialis (Cerambycidae) Populations in Pine Logs(Kastamonu Univ, 2023) Gulcu, Baris; Baysal, Ismail; Akbulut, SuleymanAim of study: Pine wilt disease (PWD) is a serious threat to the susceptible pine forests. It is caused by Bursaphelenchus xylophilus (Nematoda: Parasitaphelenchidae) (Steiner and Buhrer 1934), Nickle 1970 and transmitted by Monochamus Dejean beetles. In the recent study, we assessed the effects of entomopathogenic nematode, Steinernema carpocapsae (Nematoda: Steinernematidae) against Monochamus galloprovincialis larvae in Anatolian black pine and Scots pine logs. Area of the study: The experiments were conducted in Duzce University, Faculty of Forestry and in a pine forest at Duzce University campus area. Material and methods: The mean number of eggs per pine logs, and the productivity of S. carpocapsae in M. galloprovincialis larvae were compared under laboratory conditions. The nematode experiments were conducted using oviposited pine logs in the field. Main results: The females of M. galloprovincialis oviposited more eggs on Scots pine compared to black pine logs. Both in black pine and in Scots pine, the survival rates of M. galloprovincialis after nematode application was significantly lower than control. Highlihts: As a result of the study, S. carpocapsae can be an efficient biological control agent of this wood-boring insect.Öğe The effect of chemical insecticides on the scavenging performance of Steinernema carpocapsae: Direct effects and exposure to insects killed by chemical insecticides(Academic Press Inc Elsevier Science, 2021) Nalinci, Esra; Karagoz, Mehmet; Gulcu, Baris; Ulug, Derya; Gulsen, Sebnem Hazal; Cimen, Harun; Hazir, SelcukEntomopathogenic nematodes are used widely in biological insect control. Entomopathogenic nematodes can infect live insects as well as dead insects (i.e., they can act as scavengers). It is important to determine compatibility of entomopathogenic nematodes with other pest management tactics such as chemical insecticides. We hypothesized that chemical insecticides have negative impact on scavenging nematodes. According to our hypothesis, we first investigated the effects of direct exposure of Steinernema carpocapsae infectivity juveniles (IJs) to three chemical insecticides, cypermethrin, spinosad or diflubenzuron in terms of nematode survival and virulence. Subsequently, using the same chemicals, we tested the effects of insecticide-killed insects on scavenger nematode penetration efficiency, time of emergence and the number of nematode progeny. Prior to our study, the impact of pesticides on scavenger nematode fitness had not been studied. Fall webworm, Hyphantria cunea, and greater wax moth, Galleria mellonella, larvae were used as host insects. The survival rate of IJs after direct exposure was 83% for cypermethrin and 93-97% for the other insecticides and control. There were no significant differences in the survival and virulence of the nematodes after 24 h exposure to insecticides. The number of nematodes that invaded the insecticide-killed host was significantly higher in cypermethrin and spinosad treated groups and live H. cunea than in the diflubenzoron treated group and freeze-killed control. However, no significant differences were observed in time of emergence. Significantly more progeny IJs emerged from Spinosadkilled insects than the freeze-killed control. In conclusion, we discovered that the fitness of scavenging IJs is not diminished by insecticides in insect cadavers. In fact, in some cases the exposure to chemical insecticides may enhance virulence.Öğe Environmental tolerance of entomopathogenic nematodes differs among nematodes arising from host cadavers versus aqueous suspension(Academic Press Inc Elsevier Science, 2020) Gulzar, Sehrish; Usman, Muhammad; Wakil, Waqas; Gulcu, Baris; Hazir, Canan; Karagoz, Mehmet; Shapiro-Ilan, David I.Environmental factors such as temperature and desiccation impact the survival and efficacy of entomopathogenic nematodes (EPNs). Most studies on environmental tolerance have focused on EPNs applied in aqueous suspension. Another approach for EPN application is via infected host cadavers. Emergence in host cadavers is also more representative of nematodes in natural populations. In prior studies, certain advantages in fitness have been observed with the cadaver application approach relative to aqueous application, yet the impact of environmental stress on these approaches requires investigation. In this study, we compared the effects of various temperatures (heat and cold) and desiccation intervals (48 and 72 hr) on the survival, virulence and reproductive capacity of Heterorhabditis bacteriophora and Steinernema glaseri when applied via cadaver versus aqueous suspension. In the heat tolerance bioassays, following exposure to 30 degrees C, 35 degrees C and 37. 5 degrees C, nematodes (from both species) in the cadaver treatments exhibited higher survival, and reproductive capacity compared with aqueous application. No survival was observed above 37.5 degrees C regardless of species or application approach. In cold tolerance, no differences were observed between the cadaver and aqueous treatments after a sequence of exposures from 10 degrees C to -2 degrees C. In desiccation assays, following exposure to 85% relative humidity for 2 or 3 days, nematodes (from both species) exhibited higher survival and reproduction in the cadaver treatment than in the aqueous treatment, whereas no differences were observed in virulence. This is the first study to find differential stress tolerance among nematodes emerged from infected host cadavers versus those applied in aqueous suspension. Our findings indicate additional advantages when using the cadaver approach for biocontrol applications, and suggest EPNs existing in natural populations may have broader environmental tolerance than those applied via aqueous suspension.
