Nanotechnology is emerging as an innovative and sustainable agricultural approach that minimizes environmental impacts by developing nanostructured materials to promote plant growth and combat plant-parasitic nematodes (PPNs). Plant-based nanoparticles (NPs) are attracting increasing attention as they are more environmentally friendly, economical and biocompatible compared to traditional chemical and physical synthesis methods. The ability of plants to reduce and stabilize metal ions and form NPs of specific size and morphology through their biochemical content offers great advantages for agricultural applications. Phytochemicals produced by plants enable the biological synthesis of metal and metal oxide NPs by acting as reducing agents and coating agents in NP synthesis. The effects of plant-based NPs in nematode control are based on mechanisms such as the disruption of the nematode cuticle, induction of oxidative stress and interference with parasite metabolism. Several plant species have been investigated for the synthesis of metal and metal oxide nanoparticles such as silver (Ag-NPs), nickel oxide (NiO-NPs), zinc oxide (ZnO-NPs), copper oxide (CuO-NPs) and iron (Fe-NPs). These biologically synthesized NPs show potent biological activity against important PPNs such as Meloidogyne spp., Pratylenchus spp. and Heterodera spp. The integration of plant-derived NPs into agricultural systems has significant potential for plant growth promotion, nematode suppression and soil health improvement. This review highlights their role in reducing environmental impact in agricultural applications by examining the sustainable synthesis processes of plant-based NPs.

The black cutworm, Agrotis ipsilon (Hufnagel) (Lepidoptera: Noctuidae) is considered to be one of the serious polyphagous pests that spend a large part of its life in the soil environment, where many microorganisms live including entomopathogenic nematodes (EPNs) (Rhabditida: Steinernematidae and Heterorhabditidae). EPNs have been long used for suppressing the soil-dwelling insects like cutworms and are successful biological control agent against A. ipsilon larvae. In the present study, the efficacy of local EPNs isolates against the fourth larval instar of A. ipsilon was evaluated at different concentrations (10, 25, 50, 100 IJs/larva/Petri dish and 25, 50, 100 IJs/cm² soil) in two different experiment environments including filter papers in Petri dishes and soil in plastic containers under laboratory conditions at 25 ± 1 °C. Larval mortalities of A. ipsilon were recorded first, second, third, and fourth day post inoculation where the mortality rates increased by increasing the concentrations. The maximum mortality rate (100%) was reached within 2 days after inoculation, inoculating the Heterorhabditis bacteriophora FLH-4-H and H. indica 216-H isolates at concentrations of 50 and 100 IJs/cm², in the plastic container experiment. The highest mortality rate (90%) was obtained by Steinernema carpocapsae E76-S isolate at a concentration of 100 IJs/larva/Petri on the fourth day after inoculation, in the Petri dish experiment. The lethal concentration values (LC₅₀ and LC₉₀₎ of the A. ipsilon larval population were 52 IJs and 129 IJs, respectively, for S. feltiae E76-S isolate in the Petri dish tests. In the plastic container experiment, the lowest LC₅₀ and LC₉₀ values found to be 17 IJs and 23 IJs, respectively, for H. bacteriophora FLH-4-H isolate. The results showed that all indigenous EPN isolates had good potentials in the management of A. ipsilon.

The codling moth, Cydia pomonella (L.) (Lepidoptera: Tortricidae), is one of the major pests in pome fruit production worldwide. Heavy treatment of the larvae of C. pomonella with insecticides triggered the development of resistance to many groups of insecticides. In addition, the increasing concern about the adverse effects of synthetic insecticides on human health and the environment has led to the development of sustainable and eco-friendly control practices for C. pomonella. The entomopathogenic nematodes (EPNs) (Steinernema and Heterorhabditis spp.) and their endosymbionts (Xenorhabdus and Photorhabdus spp.) represent a newly emerging approach to controlling a wide range of insect pests. In the present study, field surveys were conducted in apple orchards to isolate and identify EPNs and their endosymbionts and evaluate their insecticidal efficacy on the larvae of C. pomonella. EPNs were isolated from 12 of 100 soil samples (12%). Seven samples were identified as Steinernema feltiae (Filipjev, 1934) (Rhabditida: Steinernematidae), whereas five samples were assigned to Heterorhabditis bacteriophora (Poinar, 1976) (Rhabditida: Heterorhabditidae). The pathogenicity of the EPN species/isolates was screened on the last instar larvae of G. mellonella. The two most pathogenic isolates from each EPN species were tested against fifth instar larvae of C. pomonella under controlled conditions. The maximum mortality (100%) was achieved by all EPN species/isolates at a concentration of 100 IJs/larva 96 h after treatment. The endosymbionts of selected H. bacteriophora and S. feltiae species were identified as Photorhabdus luminescens subsp. kayaii and Xenorhabdus bovienii, respectively. The mortality rates ranged between 25 and 62% when the fifth larval instar larvae of C. pomonella were exposed to the treatment of cell-free supernatants of symbiotic bacteria. In essence, the present survey indicated that EPNs and their symbiotic bacteria have good potential for biological control of C. pomonella.

A survey for naturally occurring entomopathogenic nematodes (EPNs) was conducted in various agricultural fields in central Turkey, Nevsehir, between 2015 and 2016 years. EPNs were recovered from 20 of 112 soil samples (17.9%). Seventeen isolates were identified as Steinernema feltiae (Rhabditida: Steinernematidae). One was unknown Steinernema sp. (Rhabditida: Steinernematidae), and two were Heterorhabditis bacteriophora (Rhabditida: Heterorhabditidae). The most common species was S. feltiae, which was recovered from 5 out of 8 sites. The pathogenicity of these isolates was evaluated on the last larval instar of Galleria mellonella L. (Lepidoptera: Pyralidae) at different concentrations (25, 50, 100 IJs) in the laboratory at 25 ± 1 °C. Maximum mortality rate (87%) was achieved from the H. bacteriophora AVB-15 isolate at the lowest concentration after 48 h post-inoculation, while the only isolate that caused maximum mortality of (100%) at the concentration of 50 IJs/ml, 24 h post-inoculation was S. feltiae DDKB-17 isolate. All isolates showed high pathogenicity on G. mellonella last instar ranging from 63 to 100% at the concentration of 100 IJs/ml, 48 h post-inoculation. The present survey revealed that these EPNs are commonly present at Nevsehir, and they might have a good potential in biological control of insect pests.