The synthesis of metal oxide nanoparticles with the use of plant extract is a promising alternative to the conventional chemical method. This work aimed to synthesize zinc oxide nanoparticles (ZnONPs) using plant extract of chamomile flower (Matricaria chamomilla L.), olive leave (Olea europaea) and red tomato fruit (Lycopersicon esculentum M.). The synthesized ZnONPs were characterized by UV–Visible spectroscopy, Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), transmission electron microscopy (TEM) and scanning electron microscopy (SEM) with EDS profile. The XRD studies confirmed the presence of pure crystalline shapes of ZnO nanoparticles. The ZnONPs synthesized by Olea europaea had the least size range of 40.5 to 124.0 nm as revealed by the SEM observation while XRD revealed a dominant average size of 48.2 nm in the sample which is similar to the size distribution analysis obtained from TEM. The antibacterial effect of ZnONPs synthesized by Olea europaea on Xanthomonas oryzae pv. oryzae (Xoo) strain GZ 0003 had an inhibition zone of 2.2 cm at 16.0 µg/ml which was significantly different from ZnONPs synthesized by Matricaria chamomilla and Lycopersicon esculentum. Also, the bacterial growth, biofilm formation, swimming motility and bacterial cell membrane of Xoo strain GZ 0003 were significantly affected by ZnO nanoparticle. Overall, zinc oxide nanoparticles are promising biocontrol agents that can be used to combat bacterial leaf blight diseases of rice.

The biosynthesis of silver nanoparticles (AgNPs) through the use of endophytic bacteria is a safe replacement for the chemical method. The study aimed to synthesize AgNPs using endophytic bacterium Bacillus siamensis strain C1, which was isolated from the medicinal plant Coriandrum sativum. The synthesized AgNPs with the size of 25 to 50 nm were further confirmed and characterized by UV-visible spectroscopy, Fourier transform infrared spectroscopy, X-ray diffraction, transmission electron microscopy and scanning electron microscopy with EDS profile. The synthesized AgNPs at 20 μg mL⁻¹ showed a strong antibacterial effect against the pathogen of rice bacterial leaf blight and bacterial brown stripe, while an inhibition zone of 17.3 and 16.0 mm was observed for Xanthomonas oryzae pv. oryzae (Xoo) strain LND0005 and Acidovorax oryzae (Ao) strain RS-1, respectively. Furthermore, the synthesized AgNPs significantly inhibited bacterial growth, biofilm formation and swimming motility of Xoo strain LND0005 and Ao strain RS-1. In addition, the synthesized AgNPs significantly increased root length, shoot length, fresh weight and dry weight of rice seedlings compared to the control. Overall, this study suggests that AgNPs have the potential to protect rice plants from bacterial infection and plant growth promotion.

Recently, the use of herbs in the agriculture and food industry has increased significantly. In particular, Rosmarinus officinalis L. extracts have been reported to have strong antibacterial properties, which depend on their chemical composition. The present study displayed a biological method for synthesis of magnesium oxide (MgO) nano-flowers. The nano-flowers are developed without using any catalyst agent. Aqueous Rosemary extract was used to synthesize MgO nano-flowers (MgONFs) in stirring conditions and temperature at 70°C for 4 h. The mixture solution was checked by UV-Vis spectrum to confirm the presence of nanoparticles. The MgO nano-flowers powder was further characterized in this study by the X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and Fourier transform infrared spectroscopy. In addition, bacteriological tests indicated that MgO nano-flowers significantly inhibited bacterial growth, biofilm formation, and motility of Xanthomonas oryzae pv. oryzae, which is the causal agent of bacterial blight disease in rice. The electronic microscopic observation showed that bacterial cell death may be mainly due to destroy of cell integrity, resulting in leakage of intracellular content. As recommended, the use of Rosemary extract is an effective and green way to produce the MgO nano-flowers, which can be widely used in agricultural fields to suppress bacterial infection.

Mosquitoes act as key vector for transmission of devastating parasites and pathogens which affect millions of people globally. In this research, the green synthesis of silver nanoparticles of Cassia fistula fruit pulp as an innovative and operative tool against vector mosquitoes is presented. Silver nanoparticles were characterized by a series of techniques including Fourier transform infrared spectroscopy, Transmission Electron Microscope and confirmed by Scanning Electron Microscope, UV-Vis spectrophotometry and X-ray diffraction. Silver nanoparticles were highly effective against the larvae (I–IV instar) and pupae of Aedes albopictus and Culex pipiens pallens after 24, 48 and 72 h of treatment. Ae. albopictus had LC50 values ranging from 8.3 mg/L (I instar) to 17.3 mg/L (pupae) and LC50 ranging from 1.1 mg/L (I instar) to 19.0 mg/L (pupae) against Cx. pipiens pallens. The systemic effect of AgNPs was further assessed in the fourth instar larvae of Ae. albopictus and Cx. pipiens pallens by measuring the levels of total proteins and activity of two important marker enzymes: Acetylcholinesterase and α- and β-carboxylesterase. Overall, the findings of the study suggest that the use of Cassia fistula-fruit pulp extract mediated synthesis of silver nanoparticles can be used for controlling vector mosquitoes. This is the first report on the mosquito larvicidal and pupicidal activity of AgNPs synthesized by Cassia fistula fruit pulp and its possible mechanism of action.

Bacterial leaf blight caused by Xanthomonas oryzae pv. oryzae (Xoo) is one of the most devastating diseases, resulting in significant yield losses in rice. The extensive use of chemical antibacterial agents has led to an increase the environmental toxicity. Nanotechnology products are being developed as a promising alternative to control plant disease with low environmental impact. In the present study, we investigated the antibacterial activity of biosynthesized chitosan nanoparticles (CSNPs) and zinc oxide nanoparticles (ZnONPs) against rice pathogen Xoo. The formation of CSNPs and ZnONPs in the reaction mixture was confirmed by using UV-vis spectroscopy at 300–550 nm. Moreover, CSNPs and ZnONPs with strong antibacterial activity against Xoo were further characterized by scanning and transmission electron microscopy, Fourier-transform infrared spectroscopy, and X-ray diffraction. Compared with the corresponding chitosan and ZnO alone, CSNPs and ZnONPs showed greater inhibition in the growth of Xoo, which may be mainly attributed to the reduction in biofilm formation and swimming, cell membrane damage, reactive oxygen species production, and apoptosis of bacterial cells. Overall, this study revealed that the two biosynthesized nanoparticles, particularly CSNPs, are a promising alternative to control rice bacterial disease.

Termites are eusocial arthropod decomposers, and improve soil fertility, crop yield, and also are used by humans for their benefits across the world. However, some species of termites are becoming a threat to the farming community as they are directly and indirectly causing major losses to the agricultural system. It is estimated that termites cost the global economy more than 40 billion USD annually, and considerable research has been done on their management. In this review, we present the available information related to sustainable and integrated termite management practices (ITM). Furthermore, we insist that the better management of this menace can be possible through: (i) improving traditional methods to keep termites away from crops; (ii) improving agricultural practices to maintain plants with more vigor and less susceptible to termite attack; and (iii) integration of available techniques to reduce termite infestation in crops and surroundings. The application of an effective combination of traditional practices with recently developed approaches is the best option for agricultural growers. Moreover, keeping in mind the beneficial nature of this pest, more innovative efforts for its management, particularly using rapidly emerging technology (e.g., RNA interference), are needed.