Tailoring Ca-Based Nanoparticles by Polyol Process for Use as Nematicidals and pH Adjusters in Agriculture

The remarkable progress in nanotechnology has extended the application of inorganic nanoparticles (NPs) in the agriculture sector, as both economically sustainable and environmentally sound alternatives. Root knot nematodes are undoubtedly a foremost problem of agriculture, and research strives to develop effective materials to tackle this issue. Herein, the microwave-assisted selective polyol synthesis of different compositions of Ca-based NPs, Ca(OH)2, Ca(OH)2/CaCO3, and CaCO3 is reported and the products were evaluated as nematicides and pH adjusters. Two precursors (CaCl2 and Ca(NO3)2) and three polyols (1,2-propylene glycol (PG), tetraethylene glycol (TEG), polyethylene glycol (PEG 8000)) that differ in their redox potential have been utilized to provide selectivity over composition. On the basis of the utilized polyols, NPs are produced as inorganic/organic hybrid formulations with a biocompatible organic coating that provides increased colloidal stability and controlled release of active components. Characterization of NPs has been carried out by XRD, TGA, FTIR, TEM, and pH-metry. Each composition exhibited different pH changing ability, an essential feature for agrochemical applications. The in vitro nematicidal activity of Ca(OH)2, Ca(OH)2/CaCO3, and CaCO3NPs was evaluated on second stage juveniles (J2) of two Meloidogyne species (Meloidogyne incognita and Meloidogyne javanica) based on nematode paralysis experiments. Results unveiled nematicidal activity for all evaluated Ca-based NPs, while Ca(OH)2 and CaCO3 NPs appeared to be the most and the least effective ones, respectively. The nematicidal effect appears to be boosted by the release of [OH]- anions, as indicated by pH-metric measurements, displaying the crucial role of [OH]- anions in their nematicidal activity

Bio-pesticides: Harmful or harmless to ammonia oxidizing microorganisms? The case of a Paecilomyces lilacinus-based nematicide

Bio-pesticides are considered as low-risk compounds, a belief mainly based on their natural origin rather than on experimental evidence. Thus there is a need to explore the ecotoxicity of bio-pesticides and mostly their impact on soil microbes which is largely unknown. The effect of Quillajia saponaria plant extract (QLAgri (R)) and Paecilomyces lilacinus strain 251 (PL251, BIOACT (R)) on the microbial community was investigated comparatively to the synthetic nematicides oxamyl and fluensulfone. Particular attention was given to potential effects on ammonia-oxidizing bacteria (AOB) and archaea (AOA). No effect of QLAgri (R), oxamyl and fluensulfone on the soil microbial community and AOB/AOA was observed. In contrast BIOACT (R) stimulated the growth of copiotrophic Gram negative bacteria and fungi as determined by phospholipid fatty acids (PLFA) analysis. Terminal restriction fragments length polymorphism (TRFLP) and qPCR analysis of the amoA gene showed a significant time-dependent inhibitory effect of BIOACT (R) on the abundance of AOB/AOA up to 20 days post application. Further qPCR analysis indicated that PL251 did not proliferate in soil. These results suggested the establishment of complex interactions between BIOACT (R) and AOB/AOA which were further explored. In a follow-up study BIOACT (R) and its co-formulants, glucose (78%) and skimmed milk powder (6%), both induced a transient inhibitory effect on potential nitrification and abundance of AOB/AOA, whereas no effect was seen when PL251 spores were used. Overall, our data suggest that the transient effect of BIOACT (R) on nitrifiers was the result of a competitive exclusion by copiotrophic microorganisms feeding on co-formulants rather than a direct toxicity effect. (C) 2013 Elsevier Ltd. All rights reserved

Nematicidal Activity of Mint Aqueous Extracts against the Root-Knot Nematode Meloidogyne incognita

The nematicidal activity and chemical characterization of aqueous extracts and essential oils of three mint species, namely, Mentha × piperita, Mentha spicata, and Mentha pulegium, were investigated. The phytochemical analysis of the essential oils was performed by means of GC-MS, whereas the aqueous extracts were analyzed by LC-MS. The most abundant terpenes were isomenthone, menthone, menthol, pulegone, and carvone, and the water extracts yielded mainly chlorogenic acid, salvianolic acid B, luteolin-7-O-rutinoside, and rosmarinic acid. The water extracts exhibited significant nematicidal activity against Meloidogyne incognita, and the EC50/72h values were calculated at 1005, 745, and 300 mg/L for M. × piperita, M. pulegium, and M. spicata, respectively. Only the essential oil from M. spicata showed a nematicidal activity with an EC50/72h of 358 mg/L. Interestingly, menthofuran and carvone showed EC50/48h values of 127 and 730 mg/L, respectively. On the other hand, salicylic acid, isolated in the aqueous extracts, exhibited EC50 values at 24 and 48 h of 298 ± 92 and 288 ± 79 mg/L, respectively