The root-knot nematode, Meloidogyne incognita, poses a significant economic threat as an endoparasite for various vegetables, including cabbage. Utilizing botanicals is an essential aspect of green technology to combat root-knot nematode infection. This study investigates the efficacy of four botanicals (Oxalis corniculata, Ricinus communis, Lantana camara, and Pluchea lanceolata) as emerging phyto-nematicides against M. incognita using both in vitro experiments (J2 mortality after 24, 36 and 48 hours exposure to 3000, 2000, 1000, 500, and 0 mg/L of the four botanicals and then determination egg hatching of M. incognita after 3 and 5 days incubation with various concentrations of the selected botanicals) and pot experiments. In the in vitro study, different extracts from the leaves of botanicals were applied to the second juvenile stage (J2) of M. incognita. The highest mortality of J2 and reduction in egg hatching for O. corniculata extract (89.96 and 86.79%), while the lowest effects (9.01 and 11.50 %) were observed for P. lanceolata extract. The extract of O. corniculata caused complete damage to the morphology of J2 via rupturing the cuticle of posterior, middle, and interior portion. In the pot experiment, M. incognita adversely affected growth shoot length (51.37%), root length (55.10%), fresh head weight (63.14%), and dry head weight (61.79%) by down-regulation of biochemical and epidermal traits compared to un-inoculated plants. However, the soils amended with botanicals especially O. corniculata recorded highest retardation of M. incognita infestation in cabbage roots, hence improved the growth and yield compared to the infected plants. The most beneficial effect denoted by O. corniculata at 100 g/pot on the infected cabbage plants associated with improving carotenoids (83%), chorophyll (117%), and nitrate reductase activity (79%) compared to stressed plants only. Also, O. corniculata at 100 g/pot maximally increased the number of stomata (130%), lengths (87%), and width (141%) of stomatal pore infected cabbage plants compared to the infected plants. These findings recommended the importance of O. corniculata as an eco-friendly organic phyto-nematicide that effectively restrict the damaging impacts of M. incognita on cabbage and may be other crops.

Although plant damages caused by phytoparasitic nematodes has been known at world level since the second half of the 19th century, the most effective methods for their management were discovered only in the past century. At first, plant parasitic nematodes (PPN) were controlled by the same products used against insect pests (carbon disulfide, chloropicrin, methyl bromide), but since 1940, with the discovery of the nematicide activity of the soil fumigant DD (dichlopropane-dichloropropene), chemical nematicides played a pivotal role in increasing the yield of many agricultural crops. In the second half of the past century and especially during its last two decades, the high demand from the farmers for chemical products having immediate nematicidial activity stimulated the interest of many chemical companies in patenting and marketing an increasing number of new chemical products. They were both fumigants (methyl bromide, chloropicrin, dibromoethane, bromochloropropane, dichloroethane, dichloropropane, dichloropropene, dazomet, metam sodium, metam potassium, methyl isothiocyanate, dimethyldisulfide) and non-fumigants (aldicarb, abamectin, benfuracarb, cadusaphos, carbosulfan, carbofuran, benfuracarb, fosthiazate, fluopyram, fenamiphos, ethoprophos, oxamyl, iprodione, thionazin). In the meantime, awareness increased about the negative impact of plant protection products were having on the environment and the need to regulate their approval and use in the European Union (EU). This resulted in a number of EU decrees adopted by all member States to restrict the marketing and use of these products. This led to a drastic reduction in p.a. nematicides on the market, which are already in limited numbers compared to fungicides and insecticides. In this phase of transition towards eco-sustainable agriculture, as alternative products are not yet available for all crops and for all the different species of parasitic nematodes, agricultural operators are having considerable difficulties. The future of the market for synthetic nematicides is not promising. Today, only a handful of active ingredients (dazomet, metam sodium, metam potassiium fenamiphos, fosthiazate, fluopyran, abamectin) are registered in EU. However, studies are underway to search for less polluting products, such as plant extracts, volatile organic compounds, and nano-formulations. The use of these products should be integrated with the implementation of appropriate crop systems, the use of cover crops, soil amendments, rigorous sanitation practices, and resistant planting material, obtained both by conventional and modern technique, for a sustainable control of PPN.