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Three entomopathogenic nematode populations were isolatedfrom agricultural fields in the Anantnag district of Jammuand Kashmir (India). Sequences of multiple gene regionsand phenotypic features show that they are conspecific andrepresent a novel species. Molecular and morphological featuresprovided evidence for placing the new species into the “Kushidai”clade. Within this clade, analysis of sequence data of the internaltranscribed spacer (ITS) gene, the D2D3 region of the 28S rRNAgene, the mitochondrial cytochrome oxidase I (mtCOI) gene, andthe mitochondrial 12S (mt12S) gene depicted the novel speciesas a distinctive entity closely related to Steinernema akhursti, S.kushidai, and S. populi. Phylogenetic analyses also show thatthe new species is a sister species to S. akhursti, and thesetwo species are closely related to S. kushidai and S. populi.Additionally, the new species does not mate or produce fertileprogeny with any of the closely related species, reinforcing itsuniqueness from a biological species concept standpoint. Thenew species is further characterized by the third-stage infectivejuveniles with almost straight bodies (0.7–0.8 mm length), poorlydeveloped stoma and pharynx, and conoid-elongate tail (49–66 μm) with hyaline posterior part. Adult females are characterizedby short and conoid tails bearing a short mucron in the firstgeneration and long conoid tails with thin mucron in the secondgeneration. Adult males have ventrally curved spicules in bothgenerations. Moreover, the first-generation male has rounded manubrium, fusiform gubernaculum, conoid and slightly ventrallycurved tails with minute mucron, and the second generationhas rhomboid manubrium anteriorly ventrad bent, and tails withlong and robust mucron. The morphological, morphometrical,molecular, and phylogenetic analyses support the newspecies status of this nematode, which is hereby describedas Steinernema anantnagense n. sp. The bacterial symbiontassociated with S. anantnagense n. sp. represents a novelspecies, closely related to Xenorhabdus japonica. These findingsshed light on the diversity of entomopathogenic nematodes andtheir symbiotic bacteria, providing valuable information for futurestudies in this field.&nbsp

Background The complex including entomopathogenic nematodes (EPNs) of the genera Steinernema and Heterorhabditis and their mutualistic partner, i.e., Xenorhabdus and Photorhabdus bacteria, respectively possesses many attributes of ideal biological control agents against numerous insect pests as a third partner. Despite authenic opportunities for their practical use as biocontrol agents globally, they are challenged by major impediments especially their cost and reliability. Main body This review article presents major attributes of EPNs to familiarize growers and stakeholders with their careful application. As relatively high EPN costs and frequently low efficacy are still hindering them from reaching broader biopesticide markets, this is to review the latest findings on EPN strain/species enhancement, improvement of production, formulation and application technology, and achieving biological control of insects from the standpoint of facing these challenges. The conditions and practices that affected the use of EPNs for integrated pest management (IPM) are identified. Besides, efforts have been made to address such practices in various ways that grasp their effective approaches, identify research priority areas, and allow refined techniques. Additionally, sampling factors responsible for obtaining more EPN isolates with differential pathogenicity and better adaptation to control specific pest(s) are discussed. Conclusion Specific improvements of EPN production, formulation, and application technology are reviewed which may help in their broader use. Other diverse factors that optimize EPNs to constitute a cost-effective, value-added approach to IPM are also demonstrated.

The native isolates of entomopathogenic nematodes (EPNs) Heterorhabditis bacteriophora MK256358, H. bacteriophora MK263023, H. bacteriophora MK256378 and Steinernema cholashanense MK128155 were tested in laboratory for their virulence and reproductive potential against 4th instar larvae of Oriental armyworm, Mythimna separata Walker (Lepidoptera: Noctuidae), the serious pest of rice in Kashmir valley. All the EPN isolates were highly effective against 4th instar larvae of M. separata. Insect mortalities reached 100% within 24-48 hours at nematode concentrations of 200 infective juveniles (IJs)/larva. The trend was similar at lower concentrations of IJs, but more time was required. The best performance was shown by H. bacteriophora MK256358 and S. cholashanense MH128155 followed by H. bacteriophora MK256378 and H. bacteriophora MK263023 in terms of killing and reproductive potential. The values obtained for lethal concentration (LC50) and lethal time (LT50) of the tested EPN isolates differed significantly. Our results demonstrate the potential of the native EPN isolates against M. separata but before recommendation multi-location field trials need to be conducted to confirm their validity at farm level.

Plant-parasitic nematodes are one of the biological constraints responsible for lowering the production and quality of stone fruit. They cause severe losses to stone fruits all over the world. These nematodes are soilborne microscopic organisms that attack plant roots. They puncture plant roots with the help of their stylet and remove cell contents, and as a result, the capacity of such damaged roots to uptake water and nutrients is drastically reduced. The symptoms exhibited by the affected plants include retarded growth, wilting, and predisposition to infection by other pathogens. The major nematodes of stone fruits are root-knot nematode (Meloidogyne spp.), root-lesion nematode (Pratylenchus spp.), ring nematode (Criconemella spp.), dagger nematodes (Xiphinema spp.), spiral nematode (Helicotylenchus spp.), and pin nematode (Paratylenchus spp.). The growth of peach can be suppressed by 5000 Criconemella xenoplax/100 g soil. Similarly, Pratylenchus vulnus can suppress the yield of peach by 16%. In cherry and plum, the damage threshold limit for Pratylenchus penetrans is 80/100 g soil and 320/100 g soil, respectively. Besides, nematodes such as Xiphinema sp. and Longidorus sp. are reported to transmit cherry leaf roll virus. Nematodes also aggravate the disease in the presence of other microorganisms. Meloidogyne javanica is reported to increase the incidence of crown gall of peach roots caused by bacterium Agrobacterium tumefaciens. Therefore, strategic management practices are advised to be adopted to overcome the menace of these tiny microorganisms. These include physical, cultural, biological, and chemical methods. However, the integration of all these methods has been found to yield better results in comparison to any individual practice.

Four strains of Steinernema feltiae were isolated from agricultural fields in Anantnag district, the hilly areas of Pir Panjal region of Jammu and Kashmir Union territory of India. Phylogenetic analysis of the Internal Transcribed Spacer rDNA sequences revealed that three isolates belong to the well defined ‘Himalayan clade’ of S. feltiae, whereas one isolate belongs to the cosmopolitan group of haplotypes of this species. Morphometric data for one of these Himalayan isolates are provided and the phylogeography of S. feltiae is discussed. Finally, analysis of the GenBank records has shown that S. feltiae is ubiquitous in most geographical regions of the globe.

Entomopathogenic nematodes Steinernema and Heterorhabditis are excellent biocontrol agents of crop insect pests. These beneficial nematodes decrease the reliance on synthetic pesticides and assist in maintaining a desirable ecological balance. They adapt to a wide range of behavioural strategies, and their degree of efficacy varies with species and the ecological niche where nematode-insect interactions take place. Occurrence and distribution of entomopathogenic nematodes are related to certain insect groups that are considered their suitable hosts. Soil texture and presence of a host affect the nematode’s direction of movement. The specific behaviours and cues used by infective juveniles of different nematode species vary while searching and finding the hosts. The process of infection is governed by several factors such as host recognition behaviour, acceptance behaviour and infection behaviour. Cues such as feces or cuticle associated with living insects affect a nematode’s foraging behaviour which varies with respect to nematode species. Therefore, correct selection of nematode species is of foremost importance in the insect pest management strategies. Apart from nematodes’ habitat preference and infection behaviour, survival strategy and reproductive behaviour are other important parameters that need attention.

Nematodes parasites on grapevines are serious concern for viticulturists because nematodes divert nutrients from normal vine growth to supply their own needs, which in turn results in lack of vine vigour and reduced crop yield. They are widely distributed throughout the grape growing areas of the world. Xiphinema americanum is found in 85% of western Oregon, 10% areas of California, 12.5% areas of southern Spain and three-quarters of the vineyards in France. Similarly, Meloidogyne arenaria, M. incognita, and M. javanica are serious problem of most grapevine growing areas in California, the Mediterranean Basin and South Africa; M. hapla in Southern Australia; M. ethiopica in Chile and M. chitwoodi in California. This chapter reviews diversity, distribution, economic losses and management of nematodes parasitic on grapevines. The worldwide annual loss due to plant parasitic nematodes on grapes is 12.5%. In Australia, yield loss due to root-knot nematode Meloidogyne spp. has been estimated at 7% while in California it is 20%. The nematodes have diverse nature of attack. Meloidogyne are sedentary endoparasites that form galls on grapevine roots; Pratylenchus are migratory endoparasites which cause lesion on roots; Tylenchulus semipenetrans are semi-endoparasites that attack the roots and their young females can be observed in groups clinging to rootlets. Criconemoides, Tylenchorhynchus feed ectoparasitically on roots. Other nematodes such as Xiphinema spp., Longidorus spp. and Trichodorus spp., besides feeding ectoparasitically on roots, also act as vector, transmitting the viruses to plants. The synergistic effects of nematode and virus cause drastic reduction in fruit set, which may go up to 80% and may even lead to death of the grape vines. Crop rotation, soil solarization, soil amendments, application of chemicals, use of certified root stocks and planting of nematode resistant root stocks are some management practices which need to be included in an effective manner in integrated nematode management of grapevines.

Plant parasitic nematodes such as Pratylenchus, Meloidogyne, Paratylenchus, Criconemoides and Heliocotylenchus represent a worldwide concern for pome, stone and nut fruit growers. This chapter contains lists of nematodes in apple, peach, pear, plum, cherry, almond, apricot, walnut, pecan and walnut. Nematodes have various attack strategies, feeding ectoparasitically and endoparasitically causing necrosis and galls on the roots, stunted plant growth, varying degree of chlorosis, wilting of foliage and sometimes death of the plants. Other parasitic nematodes such as Xiphinema, Longidorus, Trichodorus and Paratrichodorus are also vectors of transmission of viruses to plants. The plant roots weakened and damaged by nematodes are easy prey to many types of pathogenic fungi and bacteria which invade the roots and accelerate root decay. The negative effects on plant growth decrease yields and plant growth. Annual yield loss of 13.54% has been estimated to world’s major horticultural crops due to damage caused by plant parasitic nematodes. Studies reveal a 16% yield suppression of peach due to single nematode species Pratylenchus vulnus. Growth suppression of apple can be caused by 15 Pratylenchus penetrans/100 g soil, 30/100 g for pear, 80/100 g for cherry and 320/100 g for plum. Similarly 5,000 and 4,200 Criconemella xenoplax/100 g soil can suppress the growth of peach and walnut, respectively. The great loss of some fruits are due to increased rates of tree mortality due to disease complex such as cherry decline and peach tree short life syndrome where stress caused by nematode parasitism results in an increase in susceptibility of the tree to other pathogens. This ultimately leads to a reduction in agricultural sustainability. Nematode management therefore becomes a priority for the security of food supply. Hot water treatment of planting materials, soil manipulation, use of certified planting materials, dipping the planting materials in systemic chemicals having nematicidal properties, pre and post planting treatment of nurseries with nematicides, soil fumigation, soil treatment with chemical nematicides, application of oil seed cakes in tree basins, use of bioagents and of course, the identification of nematode resistant rootstocks/cultivars are some of the management strategies which need to be applied in an effective manner for their inclusion in integrated nematode management programme.

The high cost of chemical pesticides, its adverse effect on the environment and development of resistance against chemicals in the host demand an alternative approach for crop pests management, which should be ecofriendly and cost-effective. Entomopathogenic nematodes belonging to genera Steinernema and Heterorhabditis together with their symbiotic bacteria Xenorhabdus and Photorhabdus, respectively, and slug-parasitic nematodes Phasmarhabditis with its symbiotic bacteria Moraxella have been considered as promising biocontrol agents for the management of crop insect pests and slugs. These nematodes have short life cycle, wide host range, and can resist under unfavourable conditions and environmental extremes. Survival and pathogenicity of these nematodes vary from 5°C to 35°C. They can be mass produced under both in vivo and in vitro conditions. With the realization of these attributes among these bioagents there is a need to search out an ideal formulation and proper application technology to include them in pest management programme.