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Background The biological diversity on planet earth is declining day by day, due to different factors such as excessive applications of pesticides. The utilization of chemical pesticides affected environment as well as microorganisms. The awareness among the peoples towards the hazards by the residual toxicity of chemical pesticides should be developed for agro-environmental sustainability. Main body Entomopathogenic nematodes (EPNs) are the bacto-helminth parasites which show classical mutualism with the genera Xenorhabdus and Photorhabdus. The nematodes along with its endosymbiotic bacteria have a biocontrol potential which could be used to reduce chemical pesticides. Applications of bioagents have been reported and resulted in considerable reduction in pathogens. Furthermore, these bioagents are biodegradable, eco-friendly and easy to apply for protection of crops against diverse pathogenic organism. The nematode-bacterium complexes are effective against huge range of bacteria, fungi, nematodes and insects that are harmful to the crops. Along with biocontrol potential, the endosymbionts produce diverse secondary metabolic compounds, exoenzymes and toxic compounds that show antibiotic, antimycotic, nematicidal, miticidal and anticancerous properties. Conclusion The present review deals with the diversity of endosymbiotic microbes from EPNs and their role in biocontrol for the agro-environmental sustainability.

Background Entomopathogens such as nematodes, bacteria and fungi are well recognized for their biocontrol potential. This study was carried out to examine the insecticidal properties of the Heterorhabditis bacteriophora Poinar, Beauveria bassiana Balsamo-Crivelli, Bacillus thuringiensis Berliner, individually and in combination against 3rd instar larvae of Spodoptera litura Fabricius (Noctuidae: Lepidoptera) under controlled laboratory and greenhouse conditions at Eternal University, Baru Sahib, Sirmaur, Himachal Pradesh. Results The results demonstrated that the combined applications of the tested entomopathogens resulted in 100% insect mortality under the laboratory conditions. Among the individual concentrations, applications of 200 IJs/ml were noticed highly virulent with (98%) mortality, followed by B. thuringiensis (96%) and then by B. bassiana (92%). However, single treatments were also evaluated that further showed a highest mortality in the target pest by H. bacteriophora, followed by B. thuringiensis. Among the combined treatments by H. bacteriophora plus B. thuringiensis (200 IJs + 1 × 1012 CFU/cm2) more effective caused (100%) mortality were noticed in the laboratory and (28%) under the greenhouse conditions than H. bacteriophora plus B. bassiana (200 IJs + 1 × 1010 conidia/cm2) that caused (100%) mortality and (34%) damage under both, laboratory and greenhouse conditions. Conclusion Laboratory bioassay and greenhouse evaluation tests demonstrated that the combined sprayed treatments showed reliable and fast synergism. This study could be recommended to the farmers to control the pest.

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