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Abstract The present study was carried out in the agricultural areas of Northwestern Turkey with the purpose to assess the occurrence of Pasteuria spp. bacteria on plant-parasitic nematodes. The soil samples were collected from olive, cherry, peach, pear, almond, walnut, apple orchards, vineyards, vegetable, and sunflower fields, analyzed and the bacterium was detected on 30 nematode species belonging to 31 families. Nematode individuals from Rotylenchus, Helicotylenchus, Pratylenchus, Tylenchorrhynchus, and Geocenamus spp. were most frequently infected while the average height and width of the spore core and endospore ranged between 3.70-4.90 and 1.40-2.37 μm, respectively. The results indicated that Helicotylenchus digonicus, Pratylenchus thornei, P. neglectus, Geocenamus brevidens, Tylenchhorhynchus cylindricus, Rotylenchus cypriensis, Meloidogyne javanica, and M.incognita individuals were the most parasitized by the bacterium.

Abstract Background Entomopathogenic nematodes (EPNs) (Steinernematidae and Heterorhabditidae) and their symbiotic bacteria are pathogenic for a wide range of insect pests and have been used successfully as a biological control agent. Although EPNs are well studied against many agricultural insect pests, the efficacy of their symbiotic bacteria still remains unclear for many insect pests of agricultural importance. In the present study, the virulence of native EPN isolates and their cell-free supernatants of symbiotic bacteria were tested against the 3rd and 4th larval instars of Agrotis segetum (Denis & Schiffermüller) (Lepidoptera: Noctuidae) under laboratory conditions (25 ± 1 °C and R.H. 60%). Results The 4th instar larvae were more susceptible to infective juveniles (IJs) and mortalities over (95%) were achieved by all tested EPN isolates at the concentration of 100 IJs/cm2 after 72 hrs of exposure. The cell-free supernatants were more effective against the 3rd instar larvae and the highest mortalities were recorded as 42 and 60% in the contact and leaf disc bioassays, respectively. Conclusion The results indicated that the cell-free supernatants can be an ideal application for young larval stages of A. segetum. However, further studies are required to test the effectiveness of both EPNs and the cell-free supernatants of their symbiotic bacteria in field conditions.