Green synthesis of silver nanoparticles (AgNPs) from plant extracts is simple, fast and environmentally friendly. In this study, an aqueous extract of fresh leaves from Larrea tridentata was evaluated as a possible source of reducing and stabilizing agents to obtain AgNPs. The synthesized nanoparticles were characterized by X-ray diffraction, revealing the metallic nature of Ag nanoparticles. Transmission electron microscopy (TEM) studies showed spherical nanoparticles with sizes below 28 nm. Furthermore, its bactericidal effect against Clavibacter michiganensis subsp. michiganensis (Cmm) infection in tomato plants was determined. Forty-two days after inoculation with Cmm, the disease incidence in plants with AgNPs did not exceed 20% at 50 mg L −1 , and it also reduced disease severity by 36%, which correlates with the inhibition of bacterial growth in the tissue (up to 95%). The physiological analysis also showed the growth-promoting effect of AgNPs in diseased plants, increasing shoot length (22.1%) and root dry weight (25.73%) compared with the pathogenic control. Congruently, AgNPs increased enzyme activity for CAT, APX, POD, and total phenol and flavonoid concentrations in the leaves. Slower symptom development and reduction in bacterial growth in AgNPs-treated plants could be due to this bactericidal activity and the induction of an antioxidative protection system.

The insecticidal and repellent effect of essential oil isolated from fresh leaves of Porophyllum linaria on maize weevil was evaluated, as well as the effect on the grain germination after treated. In total, 28 constituents were identified by gas chromatography coupled with mass spectrometry accounting for 99.86% of whole essential oil. The main majority compounds were β-myrcene (41.94%), D-limonene (20.29%), and estragole (20.03%). Contact toxicity significantly increased with dose and time after treatment. With the 800 ppm (highest concentration), the mortality (%) obtained for the tenth and fifteenth day was 43 and 82%, respectively, whereas with 50 ppm (lowest concentration) 30% mortality was obtained at the end of the experiment (fifteenth day). At 15 d (end of the experiment), the LC50 y LC90 were obtained with values of 329.01 ± 44.35 y 1058.86 ± 117.76 ppm, respectively. For a concentration of 800 ppm, a selection index of zero was obtained, indicating the preference of the pest to the untreated maize (control). The maize grains germination test showed a significant reduction both in the length of hypocotyl and radicle of maize grain. So, in the highest dose, the hypocotyl and radicle length was 1.40 ± 0.34 and 9.14 ± 0.55 cm, respectively, whereas the control group registered 3.28 ± 0.39 and 13.02 ± 0.97 cm, respectively. This finding is promising since as it could result in the identification of botanical substances capable of suppressing maize weevil, Sitophilus zeamais development.

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In the current research, our work measured the effect of silver nanoparticles (AgNP) synthesized from Larrea tridentata (Sessé and Moc. ex DC.) on the mycelial growth and morphological changes in mycelia from different phytopathogenic and beneficial fungi. The assessment was conducted in Petri dishes, with Potato-Dextrose-Agar (PDA) as the culture medium; the AgNP concentrations used were 0, 60, 90, and 120 ppm. Alternaria solani and Botrytis cinerea showed the maximum growth inhibition at 60 ppm (70.76% and 51.75%). Likewise, Macrophomina spp. required 120 ppm of AgNP to achieve 65.43%, while Fusarium oxisporum was less susceptible, reaching an inhibition of 39.04% at the same concentration. The effect of silver nanoparticles was inconspicuous in Pestalotia spp., Colletotrichum gloesporoides, Phytophthora cinnamomi, Beauveria bassiana, Metarhizium anisopliae, and Trichoderma viridae fungi. The changes observed in the morphology of the fungi treated with nanoparticles were loss of definition, turgidity, and constriction sites that cause aggregations of mycelium, dispersion of spores, and reduced mycelium growth. AgNP could be a sustainable alternative to managing diseases caused by Alternaria solani and Macrophomina spp.