Use of Plant Material in the Management of Plant Parasitic Nematodes

Abstract

Use of synthetic chemicals creates significant environmental dangers, which is a significant global issue. As a result, researchers have looked into plant materials and taken on the challenge of finding more environmentally friendly alternatives. As organic soil amendments, dried leaves, seed powders and cakes, tree fibers, and green manures all possess nematicidal qualities. It is permitted to combine them with other cultural techniques as an organic soil addition. They might be extracted chemically using acetone, methanol, or ethanol, or they could be prepared as aqueous extracts, root extracts, or exudates for use as extracts. They were used as a soil drench, a root dip, and as a foliar application. The plant materials have a significant impact on altering the soil’s ecosystem, and if properly developed, they could result in the long-awaited ecological alternatives to synthetic nematicides. It would be cheap for the resource-strapped subsistence farmer to control plant parasitic nematodes by utilizing botanical nematicides.

1. Introduction

Nematodes are basic animals often only containing 1000 cells or less [1]. Nematodes throughout or part of their life cycle are worm-shaped, also called vermiform, even though some species become enlarged and rounded in later life stages [2]. According to Lambert and Bekal [1], a nematode’s basic body structure is a tube inside of a tube. Their outer skin, or cuticle, is produced by the inner hypodermis. The muscles can only move dorsally and ventrally since they are longitudinally linked to the nematode’s hypodermis. An inner tube, the alimentary canal, and fluid that applies pressure to the body wall to preserve shape and permit movement are all inside the nematode. A hollow mouth spear known as a stylet is located at the head of a plant parasitic worm (Figure 1). According to Sato et al. [4], the worm uses this stylet to puncture plant cells, absorb food, and create proteins and metabolites that aid the nematode in parasitizing the plant. The stylet is connected to the pharynx, which is subsequently connected to the intestinal ends, by the rectum in the case of the female nematode and the cloaca in the case of the male. According to Lambert and Bekal [1], three to five salivary glands that are connected to the pharynx produce secretions that may be discharged from the stylet and aid the nematode in invading and parasitizing plants.

Figure 1.

A typical nematode structure (Source: [3]).

Plant parasitic nematodes pose a severe threat to crop yield globally [5, 6]. Nicol et al. [7] predicted that they might lead to yearly losses of up to 25%, or more than 80 billion US dollars. The primary cause of these losses is an endoparasitic worm that is notoriously difficult to control and that resides and feeds inside the root tissue [4]. The Solanaceae family (potato, tomato, and pepper), Gramineae (rice, wheat, and maize), Malvaceae (cotton, okra), and Fabaceae (soybean, cowpea), among others, are among the host plants that plant parasitic nematodes feed on [4].

Because of the significant nematode population decline and yield gain brought about by the use of chemical nematicides, plant parasitic nematode control/management (Figure 2) has relied extensively on them for decades [8, 9]. Chemical nematicides are the most efficient and quickly acting nematode management techniques, but they are also dangerous to the environment and people’s health [10]. Nematicides, like methyl bromide, are poisonous if swallowed or absorbed through skin contact [11]. A central nervous system depression and allergic disease may result from repeated exposure to chemical nematicides [12]. Additionally, they are relatively pricey for many small farmers. Alternative management strategies for plant parasitic nematodes that do not harm the environment have received a lot of attention from researchers [13]. This chapter focuses on environmentally acceptable management solutions for plant parasitic nematodes employing plant material (powder and extracts) and testing the effectiveness of various treatment techniques (bare-root dip, soil soaking, and amendment).

Figure 2.

The stages in nematode assessment and management.

2. Use of plant extract in control plant parasitic nematode

Ononuju and Nzenwa [14] investigated the impact of cold and hot aqueous extracts of five plant specimens (Luffa cylindrica, Momordica charantia, Euphorbia hirta, Desmodium scorpiurus, and Stachytarpheta cayennensis), the wood ash of Gmelina arborea, a synthetic insecticide (Karate-Lambda cyahalothrin), and untreated tap water (control) on the egg hatchability as well as control of Meloidogyne spp. in cowpea (Vigna unguiculata (L.) Walp in the laboratory and greenhouse. The ability of nematode eggs to hatch was significantly decreased by L. cylindrica hot water extract (HWE) and M. charantia cold water extract (CWE), according to laboratory results. According to greenhouse results, the cold water extract (CWE) of S. cayennensis, the HWE of L. cylindrica, and the HWE of E. hirta all considerably increased cowpea yield. The populations of nematodes in the soil, on the roots, and in the galls on the roots were reduced by the aqueous extracts. The outcome of G. arborea extracts and synthesized Karate-Lambda-cyhalothrin did not differ noticeably. Umar and Mohammed [15] described the impact of water hyacinth leaf extracts on Meloidogyne incognita juvenile mortality in a laboratory setting. Young M. incognita were exposed to the leaf’s crude extract and diluted extracts for 120 h. Juvenile mortality was 100% in the crude extracts. Additionally, they noted that as exposure time increased, juvenile mortality did as well. In order to suppress M. incognita on soybeans, Umar and Aji [16] investigated the effects of two organic amendments, namely bitter leaf (BL) and cashew seed kernel (CSK). Plants were infected at the base with 1000 juvenile M. incognita 3 weeks after germination. Each plant’s base soil was mixed with a bag of each of the two amendments separately 2 weeks following germination. The study’s findings showed that treated plants outperformed the untreated control in terms of growth indices and nematode control. In comparison to bitter leaf, the CSK (cashew seed kernel) amendment proved more effective against nematodes. The studies further indicated that both amendments could be used in the nematode control. According to Liman et al. [17], nematode population on tomato seedlings treated with leaf extract from the mahogany plant was considerably lower than on untreated tomato seedlings. They also stated that there are noticeable differences between the extracts’ effects on the test organism at different concentrations. The results showed that the severity of galling plant height and root length in tomatoes exposed to various leaf extract concentrations differed significantly.

In the laboratory and the screenhouse, Adenike and Atolani [18] investigated the effectiveness of the Lawsonia inermis L. cypress shrub in the management of root-knot nematodes of the genus Meloidogyne spp. The quantity of nematode eggs that hatched in the laboratory was dramatically lowered by L. inermis aqueous extracts. In comparison to 11.7% of the eggs treated with a 25% crude extract of L. inermis (L.), 92% of the control eggs that were not treated hatched. As much as 98.4% of the L. inermis (L.) in 100% crude concentration perished within 2 days of the experiment. The amount of nematodes found in the soil and roots of the screenhouse plant was significantly reduced by 15% aqueous crude concentration. Additionally, compared to the untreated control plants, all treated plants galled less.

Olabiyi [19] asserts that a number of plant extracts exhibit nematodal and pathogenic effects on the greenhouse and field pest tomato root-knot nematode. Root-knot nematode eggs were put into tomato seedlings, cv. DT69/257, which were being grown in soil that had been steam-sterilized in the screenhouse at concentrations of 5000, 10,000, 15,000, 20,000, and 25,000. At inocula levels of 15,000, 20,000, and 25,000 eggs of M. incognita, the number of leaves, plant height, fruit output, and root galls were all significantly decreased. Field-planted tomato seedlings were treated with aqueous extracts of marigold, nitta, and basil in four different concentrations: 25,000, 500,000, 750,000, and 100,000 ppm (parts per million)/plant. Whole aqueous plant root extracts were used in the trials, and they resulted in a decrease in the number of root-knot nematodes in the soil as well as an increase in plant height, plant leaves, and fruit yield when compared to the control. The aqueous root extracts’ ability to effectively control root-knot nematodes was shown by the treated plots’ much fewer root galls.

The effectiveness of aqueous ginger extracts against the root-knot nematode Meloidogyne javanica was investigated by Amer-Zareen et al. [20]. Higher extract concentrations (100%) in in vitro investigations inhibited root-knot egg hatching which led to juvenile death. In a 25% concentration, Pasteuria endospore adhesion was stronger. Plant growth was enhanced and disease severity was reduced when Pratylenchus penetrans and plant extracts were administered simultaneously. The bacterial antagonist parasitized 72% of the females in the 25% extract plus P. penetrans treatment, and each juvenile had nine bacterium spores attached to its nematode cuticle.

According to Dos et al. [21], an ethanolic rhizome extract of Artemisia vulgaris suppressed the host plant infectivity, mortality, hatching, and galling of the root-knot nematode Megadora. Both of the extract’s effects were dose-dependent, with 2.35 mg/ml of the extract reducing egg hatching by 50% and 55.67 mg/ml of the extract raising second-stage juvenile mortality by 50% after 12 h of exposure. An exposed host, Phaseolus vulgaris and Becanta trepar, shows a dose-dependent reduction in nematode infectivity (50% inhibition at 6.28 h). When applied directly to the soil, the extract reduced root-galling on a susceptible host in a dose-dependent manner (50% inhibition at 32.36 mg/ml). While maintained in the dark at 25°C for 15 days, the extract did not lose its activity.

Pavaraj et al. [22] evaluated the efficacy of a bionematicide called goat weed leaf extract against the black gram (Vigna mungo)-infested root-knot nematode, Meloidogyne incognita. The study also looked at the root gall index to determine the nematode population density. The total protein, lipid, and carbohydrate contents of the experimental plants treated with varied concentrations (2 to 10 ppm) of Ageratum conyzoides leaves were also tested after 40 days of treatment (DAT). Because the extract significantly reduced the virulence of the root-knot nematode, it is advisable to utilize it as a bionematicide going forward.

In vitro nematicidal effects of ethanol extracts from the following plant species were reported by Slomp et al. [23]: Apocynaceae species include Mandevilla velutina (Mart.) Woodson and Tithonia diversifolia (Hemsl.); Zeyheria montana Mart. (Bignoniaceae); Lippia alba (Mill.) N.E. Brown (Verbenaceae); Tabernaemontana catharinensis A. DC.; Croton antisyphiliticus Mart. (Euphorbiaceae); and Serjana erecta Radlk. (Sapindaceae). The experiment made use of the plant parasitic nematodes such as Pratylenchus zeae and Pratylenchus jaehni. The findings showed that the studied extracts had considerable nematicidal activity, particularly those that Eclipta alba had shown (DL50 (ppm) values = 304.08; 55.32 for P. zeae and DL50 (ppm) = 1000; 212.82 for P. jaehni, across periods of 12 and 24 h, respectively). T. catharinensis had shown (DL50 (ppm) values of 215.26; 60.04 for P. zeae and 825.44; 376.60 for P. jaehni, across periods of 12 and 24 h, respectively). Z. montana had shown (DL50 (ppm) values = 166.43; 34.08 for P. zeae and DL50 (ppm) = 1000, 427.34 for P. jaehni, across periods of 12 and 24 hours, respectively) and S. erecta showed (DL50 (ppm) values = 178.74; 74.12-P. zeae and DL50 (ppm) = 689.24; 249.50-P. jaehni, across periods of 12 and 24 h, respectively). These results show that the evaluated plant demonstrated significant nematicidal effects, which have significant economic or environmental ramifications and may aid in the extension of agricultural activities around the world.

Under greenhouse and field circumstances, the suppression of the root-knot nematode M. incognita was studied by Kamal et al. [24] using plant extracts of eucalyptus (Eucalyptus camaldulensis), marigold, garlic, and neem as well as essential oils. After 24–48 h of exposure, an in vitro investigation of plant materials demonstrates a nematicidal effect on young worms. The largest percentage of nematode deaths was obtained by the neem extract (65.4%), followed by essential oils (64.4%), marigold extract (60.5%), and garlic and eucalyptus extracts (38.7–39.5%). Neem extracts and essential oil treatments were more effective than other methods at reducing M. incognita populations in soil and the root gall index in screenhouse and outdoor settings. Neem and essential oil treatments provided the tomato plant with the most outstanding protection toward root-knot nematode in a field experiment, 44.2 and 32.6%, respectively.

In 2008, Khan et al. assessed the efficiency of ethanolic extracts of Azadirachta indica, Tagetes erecta, Withania somnifera, and Eucalyptus citriodora against nematodes associated with papaya (Carica papaya). The fresh shoot weight of papaya seedlings grown in pots was significantly increased, according to their research, when plant extracts were used. The fresh root weight was mainly unaltered compared to the control. The amount of incognita juveniles, the root-knot index, and the number of egg masses per root were all considerably reduced by all treatments. The three main nematode species associated with papaya, M. incognita, Helicotylenchus multicinctus, and Hoplolaimus indicus, all significantly lowered their population densities in the field. The most impacted species by Withania and Tagetes species were M. incognita, H. multicinctus, and H. indicus. The treatments, in this order: Withania somnifera > carbofuran > A. indica > T. erecta > E. citriodora, enhanced the papaya yield.

Olabiyi et al. [25] discovered that using aqueous leaf extracts of Nicotinia tabacum, Hyptis suaveolens, and C. papaya at 50 and 100% led to higher growth and yield of tomatoes in comparison to the control using only distilled water. The results also demonstrate that the plant height, number of leaves, root weight, number of fruits, and fruit weight were better at a range of 406 cm, 223, 52, 151, and 534 g, respectively. The control plants were in the following numerical order: 21.3 cm, 11.2, 15.4, 6.5, and 24.5 g. In the control trial, tomato plants were severely galled by Meloidogyne species, which led to thick roots. Additionally, the root gall index and the number of soil nematodes were significantly decreased by the leaf extracts.

Meloidogyne incognita egg masses or larvae were subjected to different concentrations of neem leaf (fresh and dry), groundnut leaf, Borrelia sp., and garlic bulb, according to Agbenin et al. [26]. The findings demonstrated that compounds from garlic bulbs and neem leaves killed larval stages and prevented egg masses from hatching. Neem and garlic bulb extracts were compared in the screenhouse using weekly applications of 25 ml from each pot at 20% concentrations. In the screenhouse, each pot was infused with 2000 M. incognita larvae and 2 kg of pasteurized soil. These extracts significantly reduced tomato root-knot nematode infection indices, as compared to the control. But garlic extract held more promise than neem leaf extract for the in vivo control of tomato root-knot infection. Using crushed bark extracts from the E. camaldulensis, G. arborea, and Cassia siamea, Yusuf [27] demonstrated that they might affect the root-knot nematode’s larval egg hatch. He discovered that exposure to these extracts varied in their ability to suppress hatching. As the concentration of the water-soluble bark extracts rises, egg hatch inhibition rises as well. Eighty-nine percent of the larvae hatched much more frequently at the control (distilled water).

In an ultisol solution treated with aqueous leaf extracts of bitter leaf (Vernonia amygdalina L.) and mango (Mangifera indica L.), the tomato cultivar Roma VF responded to M. javanica Treub. infestation, according to a screenhouse experiment conducted by Ogwulumba et al. [28]. There were three different leaf extract concentrations used: 150, 300, and 450 g/l. The results demonstrated that the two leaf extracts considerably altered each of the evaluated parameters. The extracts showed a strong nematotoxic effect on the nematode by reducing the number of galled roots and the galled index as well as increasing the fruit weight at the application rate of 450 g/l.

Susan and Noweer [29] investigated the effects of five aqueous extracts on the root-knot nematode (incognita), including neem seeds (A. indica), marigold leaves (T. erecta), pyrethrum leaves (Chrysanthemum cinerariaefolium), basil leaves (Ocimum basilicum), and chinaberry leaves (Melia azedarach). All of the materials under investigation affected the survival of the nematode juveniles, depending on the material’s properties and concentration. In comparison to Oxamyl 24% L and the untreated control, the majority of the investigated compounds considerably reduced the second-stage juveniles of M. incognita in the soil and roots of eggplant (Solanum melongena L.) cv. Baladi in field settings. The type and amount of the investigated chemicals had an impact on how much nematodes decreased. The majority of examined substances also resulted in a discernible rise in fruit weight per plant.

According to studies by Saad et al. [30], Khalil [31], Saad et al. [32], and Khan et al. [33], azadirachtin (Achook® 0.15% EC and Nimbecidine® 0.03% EC) showed strong activity against M. incognita in tomato plants. Gall, egg masses, and juveniles were reduced by 69.31 and 64.48%, 62.25 and 40.37%.The root-knot nematode, M. incognita, on tomato plant was investigated on neem leaves and seeds by the potato cyst nematode (Globodera rostochiensis). According to Lynn et al. [34], root-knot nematode (M. incognita) on cucumber is significantly suppressed by neem-based formulations and azadirachtin. Neem extracts showed a 38–50% reduction in nematode count [30]. Additionally, investigations on the root-knot worm M. incognita showed that the use of dry neem leaves enhanced the weight of fruit per plant of eggplant by 19% [33]. Different dosages of the Eriobotrya japonica extract, according to Sultana et al. [35], were successful in preventing M. incognita and Cephalobus litoralis infections. After 48 h at 1% concentration, the crude extract demonstrated a 90% and ethyl acetate fraction 97% mortality rate against M. incognita species, as well as 81 and 50% against C. litoralis species.

Izuogu et al. [36] found that root-knot nematodes in maize can be effectively controlled by leaf extracts from Moringa oleifera and Jatropha curcas. Plants treated with M. oleifera perform better in terms of growth parameters than plants treated with J. curcas (P > 0.05), while untreated control plants experienced the least growth. A. indica and Eucalyptus spp. seeds were used as aqueous extracts at concentrations of 25, 50, and 100% to control the activity of M. javanica. All seed extracts killed M. javanica eggs, and second-stage juvenile mortality increased with increasing extract concentration. Liu et al. [37] investigated the impact of a Dryopteris crassirhizoma chloroform extract on the ultramicroscopic structures of M. incognita. It was shown that the extract significantly damaged the ultrastructure of the worm and clearly damaged the nematode’s external and internal structures. According to Jada et al. [38], an ethylacetate extract of Detarium microcarpum Guill. and Perr. bark had an impact on the root-knot nematode M. javanica. The findings show that the juvenile mortality rate for M. javanica was substantially greater at 100% concentration of the ethylacetate extract, with 90 juvenile deaths at 72 h, than at 80% concentration, with 87 juvenile deaths at 72 h. The lowest number of juveniles was found at 0% ethylacetate extract concentration, where one juvenile died after 24 h. Izuogu et al. [39] demonstrated the efficacy of aqueous leaf extracts of Cassia occidentalis and Cymbopogon citratus at 25, 50, 75, and 100%, while 0% served as the control in the management of the okra nematode. It was determined that the treated plants, especially those that received 50% level and above, performed significantly better (P = 0.05) than the control in terms of growth, yield, soil nematode population, root weight, and root gall indices.

Alstonia boonei de Wild and Bridelia ferruginea Benth. are two plants whose leaves were examined for nematicidal activity by Fabiyi [40]. With a 75% concentration being the most active, all fractions examined were significantly beneficial in increasing juvenile mortality. With longer exposure times came an increase in mortality. With a percentage mortality of 48.62%, fractions from Alstonia boonei were substantially (P = 0.05) more toxic to M. incognita juveniles than the reference standard carbofuran, which had a mortality rate of 48.89%. Egg hatching was significantly reduced when using the fractions compared to carbofuran’s crude extracts. In vitro tests were conducted by Tiyagi et al. [41] to determine the effects of water extracts from Chromolaena odorata, Tithonia diversifolia, T. erecta, and Occimum gratissimum leaves at 6.6, 10.0, 13.3, 16.6, and 20% W/V (percent weight/volume) on eggs and second-stage juveniles of incognita. Egg hatch was strongly suppressed by water extracts of T. erecta by 90.5% compared to O. gratissimum, which generated the lowest egg inhibition of 70.72%. Tagetes erecta also caused 100% juvenile mortality within 24 h of exposure, next to Tagetes diversifolia (59%), C. odorata (50%), and O. gratissimum (26.5%) with the minimal concentration.

Aji et al. [42] looked at the effects of several garlic extracts, lemongrass, onion, tridax, and distilled water as control and the results revealed that garlic extract at the crude concentration at 72% h gave the best result (86.68%) followed by its diluted forms. The findings also indicated that nematode mortality increased with exposure time and concentration. The toxic effect of wild sunflower, Tithonia diversifolia, was evaluated against the root-knot nematode, M. incognita, on eggplant Solanuum melogena. T. diversifolia aqueous extract was applied at 0, 25, 50 75, and 100% concentrations, while carbofuran was applied at 0, 2500, 5000, 7500, and 1000 ppm. According to the experiment’s findings, T. diversifolia aqueous extract and carbofuran solution significantly decreased the pace at which nematodes multiply and caused root damage. When compared to the control, this results in higher growth and yield [43].

3. Experimental plants used in the control of plant parasitic nematode

3.1 Calotropis procera

Calotropis procera is a member of the Apocynaceae family. The leaves of this untamed shrub, which can reach a height of 1–3 m, are 10–13 cm in width by 17–19 cm in length. It is an established medicinal herb that can be found all across the tropics of Asia and Africa [44]. According to Mother Herbs [45], gigantic swallow wort, often known as milkweed, plays a significant impact in enhancing soil fertility and soil water retention capacity. The root bark is a laxative, febrifuge, anthelmintic, depurative, and expectorant. The root’s powder is effective against asthma, bronchitis, and dyspepsia and encourages gastric secretions. The dried whole plant is an excellent tonic, expectorant, depurative, and anthelmintic. In India, the root bark is used to cure leprosy, chronic eczema, and elephantiasis. In addition, paralysis, swellings, arthralgia, and intermittent fever can all be treated with leaves. Flowers are effective in the treatment of tumors, inflammations, catarrh, anorexia, and asthma.

3.2 Cassia obtusifolia

According to Brunken et al. [46], the plant Cassia obtusifolia L., also known as “sickle pod,” is a member of the Fabaceae subfamily Caesalpinioideae. Senna obtusifolia, a legume in the genus Senna, is another name for it. All of tropical Africa, with the exception of Madagascar, is home to the plant. The species name obtusifolia is derived from Latin and means blunt leaf, an accurate description of the shape of the leaves, while the genus name “Cassia” came from Greek and signifies an aromatic plant. According to Harvey [47], it is also known as fetid senna or arsenic weed. This plant is grown in home gardens for this purpose in a number of nations, including Senegal, Ghana, Cameroon, and Ethiopia. The young, fragile leaves of this plant are occasionally consumed as vegetables in Africa and worldwide. According to Dirar [48], the plant’s green leaves are fermented in Sudan to create the high-protein food item known as “kawal,” which is consumed by many as a meat alternative. It is also utilized as a hedge, green manure, medicinal herb, and fuel wood.

3.3 Coffee senna

Coffee senna (Senna occidentalis (Linn)) is a member of the Caesalpinioideae subfamily of the Leguminosae family. According to the Greenhouse [49], it is also known as stink wood, smelling pee, Nigerian senna, and Negro coffee. According to Yadava and Satnami [50], this shrub’s roots can help prevent ringworm infections. It is used to treat snake bites and as a diuretic. The plant is bitter, laxative, expectorant, anti-inflammatory, antimalarial, and analgesic, according to Mother Herbs [45]. It is used to decrease blood pressure, and bronchitis is treated with a floral infusion and an asthmatic beverage made from the seeds that tastes like coffee.

3.4 Sesamum indicum

Sesamum indicum Linn belongs to the Pedaliaceae family. It is a yearly erect herb that is glandular-pubescent and branches from the base. The leaves are alternate or lower appositive and frequently profoundly three lobed [51]. It is cultivated to produce seeds with a high oil content. Most of the world’s sesame is grown in tropical, subtropical, and southern temperate countries, as well as in Africa, China, India, and South America. Tropical regions, sandy soil that drains well, and hot, muggy weather are the conditions that the plant grows best in. An excellent source of cooking oil is sesame seeds. Sesame seeds can be used in bread stock, crackers, salad, cooking oil, sesame cakes, wine, and brandy. Young leaves are edible in stews, dried stems are burnable as fuel, and the ash is used to manufacture soap. It is used in confectionery to make sesame seed buns and chips and acts as an insecticide, bactericide, and antifungal synergist for pyrethrum insecticides. Lecithin and lignin give it antioxidant properties and prevent the formation of cholesterol. Sesame oil is used in the pharmaceutical industry to treat nasal mucosa, dryness, impaired vision, vertigo, anxiety, headaches, and sleeplessness. The myristic acid in seeds makes them valuable in the production of medicines that fight cancer. It is also used in the production of biodiesel, a viable alternative to the diesel fuel [52].

3.5 Waltheria indica

A flowering plant that belongs to the mallow family, Malvaceae, is called Waltheria indica L. This plant’s common names include lazy morning velvet leaves and it is pantropical in distribution. It is a short-lived subshrub that can grow up to 2 m tall and has a 2-cm stem diameter. The majority of its habitat is dry, disturbed, and well drained. According to Zongo et al. [53], in Africa, South America, and Hawaii, the herb is often used in traditional medicine, notably to relieve pain, inflammation, asthma, erectile dysfunction, bladder problems, diarrhea, dysentery, conjunctivitis, wounds, and abscesses.

4. Methods of application of the plant extract

4.1 Bare-root dip

Root dipping is the process of coating plant roots with a special solution called root dip, protecting them from pests and diseases, and/or promoting root growth. When used as a root dip to treat M. incognita, plant extracts of clove, chili, neem, and onion were found to be beneficial [54]. Chili was found to be the most effective plant extract when treating root-knot nematodes. Leaf and pod extracts of C. procera and Thevetia peruviana were used as bare-root dip treatments to suppress the phytonematodes M. incognita and Rotylenchulus reniformis infecting tomato and eggplant. On the treated plants, there were noticeable decreases in the growth of root knots brought on by M. incognita and nematode multiplication caused by R. reniformis. At various concentrations of leaf extract and dip intensities, M. incognita second-stage juvenile larval penetration was likewise impacted. According to Siddiqui and Alam [55], bare-root dipping of tomato and eggplant in leaf extracts of margosa/neem and a related species Persian lilac/bakain significantly reduced root-knot nematode larvae penetration and the ensuing root-galling and population growth of the reniform nematode. The root-dip therapy helped plants grow while masking the harmful nematode effects. Root-galling and the reniform nematode population gradually decreased along with an increase in extract content and dip time. Abbas et al. [56] looked at the efficacy of several application tactics, such as soil drench and root dip in biological remedy (azadirachtin) and synthetic chemicals (Cartap, Virtako), on M. incognita. The findings showed that both the treated and untreated root portions of Cartap were more effective than Virtako at reducing egg masses. The quantity of egg masses was dramatically decreased in the treated (45.7, 58.2) and untreated (93.7, 80.7) root portions, respectively, by cure and azadirachtin. When compared to the root-dip approach, the nematode reproduction parameters for soil drench were much lower for all compounds. Jada and Zirafilla [57] used seedling root dips at four different concentrations and four different exposures to determine whether shea butter (Vitellaria paradoxa) bark extracts are effective against M. javanica infection of tomatoes. The results of the experiment at Loko and Mayo Belwa locations showed that the root-dip method with 60% concentration at 60-min exposure in shea butter bark extracts produced the highest number of flowers/plant, the lowest nematode population in 100 g of soil, and the lowest nematode population in 10 g of roots/plant. They came to the conclusion that root dipping of bark extracts from V. paradoxa might control M. javanica in the field.

Compared to T. peruviana, leaf extracts from C. procera caused a relatively stronger suppression of nematode proliferation. Increases in leaf extract content and dip duration resulted in greater reduction in illness incidence [41]. To cure cowpea (Vigna unguiculata (L.,) Walp) cultivar pusa komal and okra (Abelmoschus esculentus (L.) Moench) infected with Rotylenchulus reniformis, bare-root dip treatments of Murraya koenigii (L.) Spreng. and Vitex negundo L. leaf extract were utilized. R. reniformis nematode multiplication on the experimental plants was significantly reduced. Comparatively more nematode proliferation inhibition was induced by Murraya leaf extracts than Vitex. There has been an improvement in plant growth. With an increase in leaf extract content and longer root-dip times, root-dip treatment effectiveness improved in terms of plant weight and decreased disease incidence [58]. On tomato, chili, and brinjal, three natural remedies based on neem oil and pongamia oil (NOPO) were investigated for effectiveness against the root-knot worm M. incognita. No. 60 EC (c), No. 60 EC (A), and NOPO 60 EC(c) are the formulations in question. The mixture was evaluated as a root dip for seedlings. The control was outperformed by each of the tree formulations No. 60 EC(c) formulation was shown to be the most effective at reducing the nematode population on tomato, chili, and garden eggs when compared to the other two formulations [59]. When used in three different ways: foliar spray, root dip, and pseudostem injection, the two avermectin chemicals, such as abamectin and emamectin benzoate, have the ability to control plant parasitic nematodes. Radopholus similis on banana and M. incognita on tomato were the subjects of research. Any of the nematodes tested did not respond well to foliar application of either avermectin or emamectin benzoate to tomato or banana. The effectiveness of banana and tomato root dips in preventing the growth of M. incognita in tomatoes as well as R. similis in bananas was only average. The common chemical nematicide fenamiphos was not as effective in controlling M. javanica and R. similis as avermectin injections (1 ml) into banana pseudostems [60]. With the help of corm pairing/hot water root dip, Tithonia diversifolia leaf mulch, and a combination of Tithonia and hot water root dip, researchers examined the impact of some cultural practices on the population and control of plant parasitic nematode infestation as well as the impact of these practices on some growth and yield attributes of plantain cv. Agbagba. The untreated plantlets served as the control. According to the findings, M. incognita, H. multicinctus, and R. similis had the lowest population of plant parasitic nematodes in plots treated with hot water root dip and Tithonia mulch. Tithonia plants’ height, leaf count, and sucker production were significantly boosted by a hot water root-dip treatment. According to Nwanguma et al. [61], plantains treated with hot water root dip and Tithonia mulch displayed early flowering and fruiting as well as a noticeable increase in bunch weight.

4.2 Soil drenching

It is the process by which chemicals that are water soluble are injected into the soil and then absorbed systemically by plant components after flooding the roots. It is very useful in combating plant parasitic nematode, fungi, and certain diseases as well as delivering nutrients to the roots [62]. In order to achieve the desired result with soil drenching, the soil should be moist but not saturated [63].

The effectiveness of plant products, which include; neem oil, extract of Nicotiana tabacum, Veratrum album, and neem Azal; potato cyst nematode (G. rostochiensis) population density and growth, were both detected in response to drenches. All of the formulations that were tested increased plant growth and yield while reducing nematode reproduction. Neem oil combined with extracts of N. tabacum and V. album at 0.5 and 1.0%, as well as neem Azal at 0.3% (and neem oil at 0.3%), were the most successful in lowering the feared incidence by 78% [64]. Hosta (Host asp) and ferns (Matteuccia pensylvanica) infested by Aphelenchoides fragariae were successfully controlled by hot water drenching 300 days after treatment (DAT). As compared to the control (25°C), hot water drenching at 70 and 90°C reduced A. fragariae in the soil but not in the leaves. Plants bathed in 90°C water had fewer nematode-infected leaves per plant than plants treated with 25 and 70°C water. The host’s development parameters were not negatively impacted by hot water treatments. When compared to the control at 150 DAT, boiling water (100°C) sprayed once every month for three consecutive months (April, May, and June) significantly decreased the number of infected leaves and the degree of infection in hosta leaves but not in fern fronds. Similar to how the population of A. fragariae was reduced in hosta leaves by 67%, fern fronds by 50%, and soil by 61–98% over a control period of 150 DAT by boiling water (100°C). Despite having no effect on fern growth, a boiling water drench decreased the size and quantity of hosta leaves by 49 and 22%, respectively, in comparison to the untreated control [65, 66]. The soil was exposed to seven different H₂O₂ concentrations (1, 10, 100, 250, 500, 750, and 1000 mM) at different times (24 h before and 24 h after the inoculation time). All hydrogen peroxide (H₂O₂) treatments markedly reduced the worms’ egg/g fresh root reproduction rate in comparison to the untreated control. The nematode reproduction was least impacted at 10 mM H₂O₂. Exogenous injection of H₂O₂ may affect nematode reproduction directly as well as indirectly through its ability to cause tomato plants to become resistant to nematode infection [67]. A greenhouse soil bacteria mixture of Lactobacillus farraginis, Bacillus cereus, and Bacillus thuringiensis strains with antinematode activity was tested for its effectiveness on the root-knot nematode. In order to compare two control groups of M. incognita, the soil was either doused with sterile distilled water or treated with the broad-spectrum carbamate insecticide carbofuran. The results show that the bacterial mixture can successfully control the roots against nematode.

In order to assess the development of second-stage juveniles (J2) of M. javanica on the roots of sensitive tomato cv., Javed et al. [68] utilized neem formulations applied as soil drenching. Tiny-Tim was investigated in a supervised environment. Beginning 7 days after transplant, three different neem preparations—neem cake, aza 5 mg, and aza 10 mg—were soaked in water at the rate of 10 ml per pot, with 4% ethanol-treated plants serving as a control for comparison. The results revealed that the roots of tomato plants were equally permeable to J2, but substantially less so than those of water control plants after being treated in three different neem formulations and ethanol. More effectively than water control, three neem treatments—including aza (5 mg) and aza (10 mg)—halted the development of J2. On the roots of plants treated with aza (10 mg), less J2 were able to develop into immature females than on the roots of ethanol control plants. The plants treated with all three neem formulations and ethanol showed decreased root gall formation when compared to the water control. Aza was found to work best at 10 mg for preventing root nematode infection. Piliostigma thonningii leaf aqueous extracts were applied by drenching around eggplants in a field that had been infected with M. javanica. The results revealed that the crude extract-treated eggplants had the tallest plants, the most fruits per plant, the highest yield, and the lowest galling indices and final nematode populations [69].

4.3 Soil amendment

According to Davis and Whiting [70], a soil amendment is any material that is supplemented to a soil to improve its physical properties, such as water retention permeability, water infiltration, drainage, aeration, and structure. The goal is to give the roots a better habitat. Three halophytic plant species, including Tamarindus indica, Suaeda fruticosa, and Salsola imricata, were investigated for their ability to control the M. javanica infection that affects okra (Abelmoschus esculentus (L.) Moench cv. Arka anamika) and eggplant (Solanum melongena L. cv. Black beauty). When incorporated into soil at concentrations of 0.3, 0.5, and 1% (W/W), halophytes significantly decreased hatching and, consequently, mortality of second-stage juvenile in vitro. They also significantly increased the growth of eggplant and okra, and at higher concentrations (0.5 and 1%) they were able to control root-knot nematode infection [71]. Studies examining the effects of different soil amendments, including grass, ash, and rice husk, on M. javanica infestation on Roma tomato (Lycopersicon esculentum), revealed notable variations among the amendments in terms of height, days to 50% flowering, leaf number, fruit per plant, and galls per root per plant. The soil should be treated with organic matter (poultry droppings, grass ash, and rice husk (RH) ash) at the rate of 10 to 20 t ha⁻¹ for the greatest growth, performance, and management of the tomato root-knot nematode [28]. The nematicidal efficacy of the leaves of four medicinal plants—Azadiractha indica A. juss, Calotropis procera (Ait) R. Br., Datura stramonium L., and Tagetes erecta L.—was examined for the purpose of controlling M. incognita. In comparison to the untreated, all leaf amendments at various dosages considerably enhanced the plant growth characteristics of okra and decreased root-knot infection [72]. Three organic wastes were employed to control the root-knot nematode (Meloidogyne spp.) on tomato: sawdust (SD), rice husk (RH), and trash dump (RD). In total, 15, 30, and 45 tons of organic garbage was spread over each acre. As the control, Furadan (3G) was administered at rates of 16, 32, and 64 kg/ha to unaltered plots. According to the findings of the study [73], the RD treatment considerably increased tomato output by 17–100% for RD, 13–84% for SD, and 21–63% for RH.

On the development of potted mung plants and the root-knot worm M. incognita, the effects of urea application and soil treatment with nimin (a neem-based product) and neem, castor, and rocket-salad oils as well as soil amendments with urea coatings in varying concentrations of nimin and oil of neem, castor, and rocket salad at 0.02, 0.04, and 0.06 grams per pot improved plant growth and increased chlorophyll content of mung leaves at 1% treated with urea coated with nimin rather than neem oil, castor oil, and rocket salad. This was accomplished by significantly slowing the growth of the root-knot nematode. According to Wani and Yaqub [74], urea-altered soil performs better than soil amended with lesser amounts. According to Parihar et al. [75], an organic amendment has an antagonistic effect on the root-knot nematode (M. javanica) that infects bottle gourds. Before inoculating bottle gourds with second-stage juvenile root-knot nematodes, Datura stramonium leaves were mixed with the soil. When compared to other plant species or organic additives like Argemone mexicana, Lantana camara, Parthenium hyterophrus, W. somnifera, and others, the stramonium-treated soil (100 g) leavers were found to be most effective at decreasing the reproductive potential of the nematode and increasing chlorophyll content and plant growth.

Numerous plant species’ essential oils and extracts have demonstrated promising nematicidal efficacy against nematodes that parasitize plants. For instance, nematode mortality in extracts from Tagetes spp. and M. azedarach aerial portions was considerable [76, 77]. Other plants with essential oils that contain nematicidal properties include thyme (Thymus vulgaris), garlic (Allium sativum), and oregano (Origanum vulgare) [78, 79]. Garlic aqueous extracts significantly decreased the quantity of M. incognita juveniles in a research by Mokbel et al. [80]. These natural nematicides provide prospective substitutions for synthetic chemical nematicides, lowering dangers to human health and environmental contamination.

Green manures and composted plant matter are examples of plant-based supplements that can indirectly enhance soil health and control nematode numbers. According to Borges et al. [81], these additions improve the soil microbial community by encouraging the activity of beneficial species such nematophagous fungus, bacteria, and predatory nematodes that eat plant parasitic nematodes. According to Riga et al. [82], compost application led to a decrease in the number of root-knot nematodes. Argemone mexicana L. (Papaveraceae) was studied for its allelochemical and nematicidal potential, and Shaukat et al. [83] found that the polar nature of the toxins was indicated by the fact that an ethanol-soluble extract of the leaf material caused more juvenile mortality of M. javanica than either ethyl acetate or hexane extracts did. A. mexicana decomposing tissues in soil at 50 g kg1 were extremely harmful and caused 80% plant mortality in tomato plants. Plant development was improved at 10 g kg1, however it was significantly slowed down at 30 g kg1. When A. mexicana was allowed to disintegrate in the soil, M. javanica population densities in the rhizosphere and in roots, as well as gall formation, were considerably reduced by 10, 30, or 50 g kg1.

Additionally, some green manures alter the nutritional balance of the soil, which has a detrimental effect on nematode populations. For instance, imbalances in the carbon-to-nitrogen (C/N) ratio can be brought on by significant amounts of carbonaceous additives like rice bran, wheat straw, or sawdust. This causes nitrogen to become immobilized, which restricts the amount of nitrogen available to nematodes and hence lowers their number. Desaeger et al. [84] study showed that carbonaceous amendments have a suppressive effect on M. incognita. Glucosinolates and thiophenes, which have potent nematicidal effects, have been demonstrated to be released by certain plants, such as mustard (Brassica spp.) and marigold (Tagetes spp.) [85, 86]. Neem (A. indica) and castor (Ricinus communis) plants have also demonstrated inhibitory effects on nematode reproduction [87, 88].

In contrast to the control treatment, which saw an increase in nematode population, Kago et al. [89] observed that Brassica tissue treatments at 1908 g and 5292 g and the other treatments inhibited nematode population throughout the third season. The effectiveness of the treatments was evident in seasons two and three due to the sharp decline in nematode numbers. The study also showed that soils supplemented with Brassica tissue contained much more nutrients than the other treatments, with high amounts of calcium, potassium, nitrogen, and phosphorus as well as organic carbon being discovered in soils amended with Brassica tissue in comparison to the other treatments.

In comparison to the control, M. incognita race 1 and M. javanica populations in tomato plants, root gall populations in olive plants, and final nematode populations were all reduced when composted dry cork was added to the potting mixture at varied ratios [90]. Many soil’s physical, chemical, and biological features depend on the amount and quality of organic matter, which is why replenishing organic matter has become an important part of soil health management programs, according to Widmer et al. [91]. They highlighted that the diversity and abundance of free-living and parasitic nematodes are impacted by the addition of organic matter to the soil, rotation crops, cover crops, green manure, and other sources of organic matter. They continued by stating that appropriate organic materials should be used in soil management plans in order to enhance the chemical, physical, and biological characteristics of the soil, as well as to reduce plant parasitic nematodes and soilborne illnesses.

Biofumigation is also a form of soil amendment that involves incorporating plant materials, particularly those from the Brassicaceae family, into the soil to release volatile compounds that exhibit nematicidal activity against various plant parasitic nematodes, including Meloidogyne spp. (root-knot nematodes) and Heterodera spp. (cyst nematodes). Cruciferous plants, such as mustard (Brassica juncea), oilseed radish (Raphanus sativus), and Ethiopian mustard (Brassica carinata), are rich in glucosinolates, which are converted into isothiocyanates upon tissue disruption. These isothiocyanates can significantly lower nematode populations due to their potent nematotoxic effects [92, 93, 94]. Sunhemp considerably reduced root-knot nematode populations in okra crops, according to Wilhelm et al.’s [95] research. Brassica juncea (Indian mustard) greatly reduced root-knot nematode populations in okra crops, according to a study by Ntalli et al. [96]. Ghosh et al. [97] found that the usage of mustard cake (Brassica spp.) significantly reduced the number of root-knot nematodes in eggplant crops. Additionally, marigold intercropping reduced root-knot nematode populations in tomato crops by 70% [98]. The nematicidal activity of neem (A. indica) extracts against Meloidogyne spp. was demonstrated by Castagnone-Sereno et al. [99], demonstrating that neem contains azadirachtin, which inhibits the worms’ ability to molt and hinders their growth and reproduction. Neem is also believed to contain the compound azadirachtin, which has strong nematocidal activity against a number of nematode species [100].

Buena et al. [101] examined the biofumigant impact of pepper crop residues for regulating M. incognita populations in the laboratory by adding 0, 5, 10, and 20 g of pepper crop residue to 500 g of nematode-infested soil. After 20 days at 25°C, pepper crop residues significantly reduced M. incognita populations and root gall indices in susceptible tomato cv. Marmande while also increasing soil potassium (K), nitrogen (N), and organic carbon (C). The efficiency of biofumigation using pepper crop residues along with fresh animal manures (with and without plastic cover), methyl bromide, and a control was evaluated using root gall indices on a pepper crop. Subtreatments for grafted and nongrafted susceptible peppers were used in all treatments, except the control. According to this finding, biofumigation using pepper crop wastes is an effective nonchemical method for managing M. incognita populations, especially when used in conjunction with plastic cover, nitrogen-rich organic matter, and grafting on resistant pepper. On grafted plants, biofumigation using pepper crop residues and plastic cover, and methyl bromide treatment, with equal effects, root gall indices were lower and yields were higher. Das and Bahera [102] carried out a pot culture study to ascertain the effect of two biofumigants, cabbage and cauliflower leaves, on the population of plant parasitic nematodes infecting okra. In comparison to the untreated control, the experiment reduced the number of root-knot nematodes (40.7%), lance nematodes (40.8–80.1%), spiral nematodes (49.1–79.7%), and stunt nematodes (40.8–81.3%) while improving plant growth parameters, such as shoot length (23.3–54.6%), root length (14.1–46.5%), fresh shoot weight (28.4–81.9%), and fresh root weight (22–38%). With regard to reduction in nematode population and improvement in plant growth metrics, it was discovered that the leaves of both cabbage and cauliflower were comparable.

5. Discussion

Nematode problems are difficult to identify early enough, as the nematode keeps building up in the field over time. Epidemics are frequently the result of this, which calls for prompt and efficient control measures. Nematicides are useful as supplemental therapies or as the last resort when conventional forms of control are ineffective, particularly in high priced crops [103]. The demand for natural pesticides has been driven by the need for a better but faster alternative, and the knowledge that is currently available indicates that plants have great potential as a source of natural pesticides [104].

A significant issue with the usage of synthetic nematicides, in addition to their toxicity to mammals, was their recent finding in groundwater [105]. These terrifying environmental risks are an excellent cause to oppose environmentalists’ use of them, which increases enthusiasm for greater ecological ways of control. In this aspect, using organic soil amendment has showed potential. However, there are numerous considerations against using organic soil additives on a wide basis. The two main ones are the slow activities and the bulky materials that must be used in huge numbers [106]. These should not be seen as obstacles to the advancement of this promising strategy; instead, technologies should be created to lessen these pressing issues and enhance the strategy’s appeal. For instance, the cheaper price and more widespread availability of amendments compensate for their poorer efficacy as compared to synthesized nematicides. Furthermore, small farmers or horticulturists with low financial means who have access to locally produced wastes will benefit most from the utilization of organic matter [107].

There is a chance that as a result of these treatments, hitherto undiscovered antagonists of plant parasitic nematodes could become more prevalent and reduce nematode populations. Plant extracts and organic soil amendments would have an impact on the intricate soil ecosystem. In their native environment, plant parasitic nematodes are attacked by a variety of soil organisms, including fungi, bacteria, protozoa, other nematodes, and invertebrates [108]. However, nothing is known about how they behave in the field. A number of bacteria and fungi tested for the treatment of specific plant parasitic nematodes showed promise. An additional advantage that calls for more research is the liming effect of plant extracts, such as those from Acalypha wilkesiana [109].

6. Conclusion

In conclusion, the idea of biological nematicides is highly appropriate and their development should be promoted because there is a need for the creation of novel compounds that would be environmentally friendly. Additionally, nematologists need to develop a more systematic approach to biocontrol and have a better grasp of the ecology of soil microbes. Additionally, details are required regarding the kind of impact the treatments would have on the composition of the soil community. The development of better control measures might benefit from knowledge of how nematodes and their natural enemies interact in their natural habitat. By better understanding how to employ organic material to manage plant parasitic nematodes, this information will prevent this intriguing idea from being abandoned on dubious reasons. We must allow the concept enough time to develop and produce a compelling answer. In the long term, it might even prove to be a more superior and efficient choice than synthetic nematicides. An appealing solution to the environmental issues caused by the use of synthetic nematicides is the use of organic resources, either as soil amendments or in the form of extracts.

The utilization of organic materials as extracts seems to give a good biological alternative to synthetic nematicides, if properly developed. More field testing needs to be carried out to evaluate the usefulness of these materials in practical situations.