Nicholus M. Mnyambo

This study investigated the synthesis of green nanoparticles (NPs) from Lantana camara (NPlc) and Tabernaemontana elegans (NPte) using Aloe vera as a reducing and stabilizing agent. It further assessed the impact of the synthesized nanoparticles on Meloidogyne incognita juvenile hatch and mortality. Nanoparticles were synthesized by combining plant extracts and A. vera gel in five volume ratios (100:0, 25:75, 50:50, 75:25, and 0:100 v/v). The physical characteristics of the nanoparticles were analyzed using UV-Vis spectroscopy, transmission electron microscopy (TEM), and selected area electron diffraction (SAED). The results confirmed the polycrystalline structure and morphological diversity (cubic, triangular, platelet, and irregular forms) of the nanoparticles, with composition ratios significantly influencing their structural properties. All concentrations with Aloe gel produced nano-scale (A. vera extract ratio was found to be 50:50, accompanied by small nanoparticles exhibiting a highly defined ring pattern and well-developed polycrystalline structures. In bioassays, different concentrations of NPlc and NPte significantly (P ≤ 0.05) inhibited M. incognita juvenile hatch and increased juvenile mortality. The lowest juvenile hatch rates (6.9–7%) and highest inhibition levels (72–74%) were recorded at the 50:50 plant extract to A. vera ratio. Hatch inhibition and mortality were time-dependent, with minimal effects observed at 24 hours and the highest (79%) responses at 72 hours of exposure. These findings demonstrate that green-synthesized nanoparticles can be produced from L. camara and T. elegans , which possess strong nematicidal potential and may serve as sustainable, eco-friendly alternatives to conventional chemical nematicides.

Root-knot nematodes (Meloidogyne incognita (Kofold and White) Chitwood) are among the most damaging pests affecting tomato (Solanum lycopersicum L.) production globally, leading to significant yield losses. Conventional control using synthetic nematicides is increasingly constrained due to environmental, health, and regulatory concerns, highlighting the need for safe and sustainable alternatives. This study evaluated the nematicidal potential of Morus alba L. (mulberry) leaf extracts and their effects on tomato growth parameters under controlled experimental conditions. Phytochemical screening revealed the presence of flavonoids, saponins, phenols, glycosides, tannins, and terpenoids, indicating strong bioactivity. Treatments consisted of varying extract application rates (5–25 g/plant) applied either before or after nematode inoculation. Results showed that application of mulberry extracts significantly (P less than 0.05) reduced nematode population densities and improved plant growth compared to untreated controls. The 15 g treatment applied before nematode inoculation produced the most pronounced suppression of nematode juveniles and eggs, coupled with enhanced root and stem growth. These effects are attributed to the phytochemical constituents of the extract, which may interfere with nematode metabolism and reproduction while promoting plant vigour. The findings suggest that M. alba extracts possess promising nematicidal potential and can be developed as eco-friendly biocontrol agents for sustainable tomato production.

Meloidogyne incognita, a widespread and damaging plant parasite, reduces crop yields. Chemical treatments are common but pose health and environmental risks, leading to a search for safer alternatives. Plant extracts with secondary metabolites, like those from Maerua angolensis and Tabernaemontana elegans, show promise for nematode control, though their efficacies vary. This study aimed to investigate how the timing of applying T. elegans and M. angolensis extracts influenced the population densities of M. incognita and the growth of tomato (Solanum lycopersicon L.) plants. The experiment was a factorial design with two plant extracts applied at 5 g per plant and three different timings of application relative to nematode inoculation. Additionally, the experiment included positive (chemical standard (Nemacur^® 10 GR)) and negative (plants inoculated with nematodes only) controls, alongside naturally grown plants. The results indicate that applying plant extracts before the nematode inoculation or simultaneously with the inoculation reduced the total nematode populations as effectively as the Nemacur positive control. Plants treated with extracts showed improved growth variables compared with those treated with Nemacur^® and the natural growing conditions. In conclusion, applying plant extracts before or simultaneously with nematode inoculation effectively suppressed the nematodes and enhanced the plant growth variables. These findings suggest that such plant extracts could be adopted as part of integrated nematode management strategies in agricultural settings.