Rapid sequential detection of Al3+ and glyphosate using an "Off-On-Off" fluorescent probe based on salicylate modified layered double hydroxides.

A fluorescent probe based on salicylate modified layered double hydroxide (LDH-SA) is presented, enabling the swift sequential detection of Al3+, fosetyl-Al and glyphosate in aqueous environment. The probe was synthesized using a simple co-precipitation procedure, and its properties and synthesis conditions were thoroughly characterized and optimized. A unique "off-on-off" fluorescent response was observed when the probe sequentially interacted with Al3+ and glyphosate, and the detection method based on this phenomenon was established. The limits of detection for Al3+ and glyphosate were determined as 0.03 µmol/L and 0.03 mg/L, respectively, with rapid detection periods of one minute and four minutes. The LDH-SA/Al3+ complex requires Al3+ to generate a chelation-gathered fluorescence effect, which is the mechanism by which it quenches LDH-SA. This is possible due to the inhibition of excited-state intramolecular proton transfer and photoinduced electron transfer processes within LDH-SA after incorporating Al3+. Upon interaction with glyphosate, competitive complexation between glyphosate and Al3+ is initiated, which leads to a recovery of the fluorescence spectrum of LDH-SA and demonstrating the "off-on-off" behavior. An "INHIBIT" logic gate system was devised utilizing the response, indicating potential applications in fluorescence-based devices. Such a rapid, sequential detection capacity is impressive. It attests to the utility of LDH-SA as a probe for Al3+ or glyphosate, and suggests promise for applications in pollutant analysis or environmental monitoring applications.

Method validation, dissipation and residue status of fluopicolide and fosetyl-aluminium in citrus using a rapid extraction method coupled with ultra-performance liquid chromatography-tandem mass spectrometry.

The dissipation and residue status of a combination of fluopicolide and fosetyl-aluminium (fosetyl-Al) in citrus were evaluated in an experimental field. An efficient and sensitive liquid chromatography-tandem mass spectrometry, with rapid extraction, was carried out according to the SANTE guidelines. During the method validation, the recovery was within the range of 106.1-117.5, 94.4-115 and 85.4-109.5%, for fluopicolide, its metabolite 2,6-dichlorobenzamide and fosetyl-Al, respectively, with a relative standard deviation (RSD) of 0.3-10.6%. As a result, accuracy and precision at the spiking concentrations of 0.01, 0.05 and 0.10 mg/kg in citrus were within the acceptable range of 70-120% with an RSD of 20%. The amount of the deposits of fluopicolide, 2,6-dichlorobenzamide and fosetyl-Al was less than the limit of quantification (LOQ) at 0.01 mg/kg at 0 day, adhering to the application in standard [1.77 + 2.66 g of active ingredient (a.i.)/L] and double (3.54 + 5.32 g a.i./L) doses. The present study proposes that the utilisation of fluopicolide and fosetyl-Al in citrus and the soil may not pose a health or environmental hazard provided that good agricultural practices are followed.

Effects of Magnesium, Pyrophosphate and Phosphonates on Pyrophosphorolytic Reaction of UDP-Glucose Pyrophosphorylase.

UDP-glucose pyrophosphorylase (UGPase) carries a freely reversible reaction, using glucose-1-P and UTP to produce UDP-glucose (UDPG) and pyrophosphate (PPi), with UDPG being essential for glycosylation reactions in all organisms including, e.g., synthesis of sucrose, cellulose and glycoproteins. In the present study, we found that free magnesium (Mg2+) had profound effects on the reverse reaction of purified barley UGPase, and was absolutely required for its activity, with an apparent Km of 0.13 mM. More detailed analyses with varied concentrations of MgPPi allowed us to conclude that it is the MgPPi complex which serves as true substrate for UGPase in its reverse reaction, with an apparent Km of 0.06 mM. Free PPi was an inhibitor in this reaction. Given the key role of PPi in the UGPase reaction, we have also tested possible effects of phosphonates, which are analogs of PPi and phosphate (Pi). Clodronate and etidronate (PPi analogs) had little or no effect on UGPase activity, whereas fosetyl-Al (Pi analog), a known fungicide, acted as effective near-competitive inhibitor versus PPi, with Ki of 0.15 mM. The data are discussed with respect to the role of magnesium in the UGPase reaction and elucidating the use of inhibitors in studies on cellular function of UGPase and related enzymes.

The use of phosphonates in agriculture. Chemical, biological properties and legislative issues.

The Phosphorus (III) derivatives, named Phosphonates, include congeners with properties as fungicides that are effective in controlling Oomycetes. Examples are organic compounds like Fosetyl-Al [Aluminium tris-(ethylphosphonate)] and salts formed with the anion of phosphonic acid [(OH)2HPO] and Potassium, Sodium and Ammonium cations. According to IUPAC, the correct nomenclature for these compounds is "phosphonates", but in common language and scientific literature they are often named "phosphites", creating ambiguity. The European legislation restricts the use of phosphonates, with the ban for application in organic agriculture. However, phosphonate residues were detected in some organic products due to their addition to fertilizers allowed in organic agriculture. The legitimacy of this addition is controversial, as it is not evident if phosphonates have also a nutritional role in addition to their fungicidal properties. The new European Directive EU 1009/2019 resolves the problem by banning the phosphonates addition to fertilizers and placing a limit of 0.5% by mass for unintentional addition. However, an official method is not available for phosphonates determination in fertilizers and approval by the European Committee for Standardization (CEN) is necessary in a short time. This review presents an overview about the chemical, biological, analytical and legislative aspects of phosphonates and aims at providing: clarity on the correct nomenclature to avoid misunderstandings; the evaluation of phosphonates properties with the absence of a nutritional role, justifying the ban on adding to fertilizers; a summary of analytical techniques that could be considered by CEN to complete the analytical background for the agricultural use of phosphonates.

The Effect of Applied Salinity and Water Stress on Chemical Suppression of Phytophthora ramorum from Soilborne Inoculum in Rhododendron.

A serious concern for nurseries is the potential for Phytophthora ramorum and other Phytophthora species to colonize roots without inducing aboveground symptoms in plants that then serve as cryptic reservoirs of inoculum. Episodic abiotic stresses that reduce plant water potential can compromise the host resistance to trigger disease development from root and crown infections during many Phytophthora-plant interactions. We conducted a series of experiments with root-inoculated Rhododendron plants in a potting soil mix to assess the influence of excess salt or water deficit on ramorum blight development and the potential for these abiotic stresses to affect the efficacy of oomycete-suppressive chemical soil treatments. During growth chamber trials, P. ramorum colonized roots of both nonsalt-treated and salt-treated plants. However, salt treatment offset the benefit realized from soil treatment with mefanoxam (Subdue Maxx) and mandipropamid (Micora), as evidenced by the enhanced pathogen colonization of roots. A 3-week episode of water stress imposed after chemical treatment but before inoculation eliminated protection against P. ramorum root colonization conferred by fosetyl-Al (Aliette). At an outdoor experimental nursery, foliar symptoms were apparent in 23% of root-inoculated plants during two trials and absent during one trial. However, the majority of inoculated plants in all trials had colonized roots with little or no aboveground symptoms. A single application of Subdue Maxx or Aliette reduced root colonization by P. ramorum in Rhododendron plants. Although salt stress did not enhance ramorum blight symptom expression at the nursery, salt partially offset protection from P. ramorum root colonization obtained by Subdue Maxx.

Quantification of fosetyl-aluminium/phosphonic acid and other highly polar residues in pomegranates using Quick Polar Pesticides method involving liquid chromatography-tandem mass spectrometry measurement.

Interest in the quantification of highly polar substances in crops has noticeably increased in the last five years. This study was designed to assess quantification of six polar residues, chlorate, ethephon, fosetly-aluminium (fosetyl-Al), glyphosate, phosphonic acid and perchlorate. A total of 2513 pomegranate samples intended for export from Turkey were analysed using the Quick Polar Pesticides (QuPPe) method. The method was in-house validated with very good performance results. The limits of quantification (LOQs) for residues were much lower than the respective EU Maximum Residue Levels (MRLs). Phosphonic acid was detected in 38.5% of pomegranate samples at quantifiable concentrations, calculated as fosetyl-Al. The concentrations ranged between 0.005 and 12.9 mg kg-1. The 20% of pomegranate samples showed fosetyl-Al levels above the EU MRL of 2 mg kg-1. Other polar residues were not detected in any pomegranate samples. This is the first report about highly polar pesticides in pomegranates cultivated in Turkey.

Phosphonic acid: a long-standing and versatile crop protectant.

Phosphonic acid-based fungicides, also referred to as phosphonates, have been used extensively as crop protectants in horticulture since the late 1970s, and more recently in native ecosystems and forestry. Discovering that phosphonates are effective against foliar and soilborne oomycete diseases, such as those caused by species of Phytophthora, Pythium and Plasmopara, was a significant breakthrough, especially for soilborne pathogens that are notoriously difficult to manage. Phosphonates have played an important role in protection of forests and sensitive natural ecosystems, under threat from these pathogens. Since introduction, their increased application in management of non-oomycete diseases, along with other functionalities, demonstrates their versatility in agriculture and more broadly. Continued use of phosphonic acid crop protectants will be underpinned by demonstrated efficacy and safety, and a better understanding of specific interactions within the plant, pathogen and environment. © 2020 Society of Chemical Industry.

Sonication-Assisted Production of Fosetyl-Al Nanocrystals: Investigation of Human Toxicity and In Vitro Antibacterial Efficacy against Xylella Fastidiosa.

Recently, there is a growing demand in sustainable phytopathogens control research. Nanotechnology provides several tools such as new pesticides formulations, antibacterial nanomaterials and smart delivery systems. Metal nano-oxides and different biopolymers have been exploited in order to develop nanopesticides which can offer a targeted solution minimizing side effects on environment and human health. This work proposed a nanotechnological approach to obtain a new formulation of systemic fungicide fosetyl-Al employing ultrasonication assisted production of water dispersible nanocrystals. Moreover, chitosan was applicated as a coating agent aiming a synergistic antimicrobial effect between biopolymer and fungicide. Fosetyl-Al nanocrystals have been characterized by morphological and physical-chemical analysis. Nanotoxicological investigation was carried out on human keratinocytes cells through cells viability test and ultrastructural analysis. In vitro planktonic growth, biofilm production and agar dilution assays have been conducted on two Xylella fastidiosa subspecies. Fosetyl-Al nanocrystals resulted very stable over time and less toxic respect to conventional formulation. Finally, chitosan-based fosetyl-Al nanocrystals showed an interesting antibacterial activity against Xylella fastidiosa subsp. pauca and Xylella fastidiosa subsp. fastidiosa.

Effect of white mustard cover crop residue, soil chemical fumigation and Trichoderma spp. root treatment on black-foot disease control in grapevine.

BACKGROUND: Black-foot disease is one of the main soilborne fungal diseases affecting grapevine production worldwide. Two field experiments were established to evaluate the effect of white mustard cover crop residue amendment and chemical fumigation with propamocarb + fosetyl-Al combined with Trichoderma spp. root treatment on the viability of black-foot inoculum in soil and fungal infection in grafted plants and grapevine seedlings used as bait plants. RESULTS: A total of 876 black-foot pathogen isolates were collected from grafted plants and grapevine seedlings used as bait plants in both fields. White mustard biofumigation reduced inoculum of Dactylonectria torresensis and the incidence and severity of black-foot of grapevine, but no added benefit was obtained when biofumigation was used with Trichoderma spp. root treatments. The effect of white mustard residues and chemical fumigation on populations of D. torresensis propagules in soil was inconsistent, possibly because of varying pretreatment inoculum levels. CONCLUSION: Biofumigation with white mustard plants has potential for improving control of black-foot disease in grapevines. This control strategy can reduce soil inoculum levels and protect young plants from infection, providing grape growers and nursery propagators with more tools for developing integrated and sustainable control systems. © 2018 Society of Chemical Industry.

Peer review of the pesticide risk assessment of the active substance fosetyl.

The conclusions of EFSA following the peer review of the initial risk assessments carried out by the competent authorities of the rapporteur Member State France and co-rapporteur Member State Estonia for the pesticide active substance fosetyl are reported. The context of the peer review was that required by Commission Implementing Regulation (EU) No 844/2012. The conclusions were reached on the basis of the evaluation of the representative uses of fosetyl as a fungicide on grapes, citrus and pome fruits. The reliable end points, appropriate for use in regulatory risk assessment, are presented. Missing information identified as being required by the regulatory framework is listed. Concerns are identified.