Search

BACKGROUND Organic pest management eschews synthetic pesticides and insecticide resistance is rarely studied in organically managed systems. Spinosad is a biologically based insecticide used widely by both organic and conventional growers. Colorado potato beetle, Leptinotarsa decemlineata, is infamous for its ability to evolve resistance to insecticides. Spinosad resistance was surveyed in conventionally managed fields in eastern New York in 2006. In response to grower reports of spinosad failure on two organic farms in 2009, resistance to spinosad was assayed in both conventionally and organically managed fields the following year, and growers were surveyed for their prior spinosad use. RESULTS In 2006, spinosad resistance measured as median lethal dose (LD50 ) varied 9.8-fold among the eight conventional fields sampled and a laboratory susceptible strain. In 2010, the resistance ratios of LD50 values relative to a laboratory susceptible strain ranged from 17.5 to 40.6 in conventionally managed fields, and from 128.7 to 5750.3 in organically managed fields, a dramatic increase from 2006 with higher resistance ratios in organically managed fields. Organic growers reported much heavier use of spinosad in the years prior to 2010. CONCLUSION This is the first report of high-level resistance to spinosad in Coleopterans. Selection strength due to number of years used and number of applications per season appear to have been the primary factors driving the evolution of resistance to spinosad, highlighting the need for resistance management in organic production, where fewer alternative active ingredients for resistance management are available. © 2021 Society of Chemical Industry.

To reduce high-level radiotoxic waste generated by nuclear power plants, highly selective separation agents for minor actinides are mandatory. The mixed N,O-donor ligand N,N,N',N'-tetrakis[(6-carboxypyridin-2-yl)methyl]ethylenediamine (H4TPAEN; 1) has shown good performance as a masking agent in Am3+/Eu3+ separation studies. Adjustments on the pyridyl backbone to raise the hydrophilicity led to a decrease in selectivity and a decrease in M3+-Nam interactions. An enhanced basicity of the pyridyl N-donors was given as a cause. In this work, we examine whether a decrease in O-donor basicity can promote the M3+-Nam interactions. Therefore, we replace the deprotonated "charged" carboxylic acid groups of TPAEN4- by neutral amide groups and introduce N,N,N',N'-tetrakis[(6-N″,N''-diethylcarbamoylpyridin-2-yl)methyl]ethylenediamine (TPAMEN; 2) as a new ligand. TPAMEN was crystallized with Eu(OTf)3 and Eu(NO3)3·6H2O to form positively charged 1:1 [Eu(TPAMEN)]3+ complexes in the solid state. Alterations in the M-O/N bond distances are compared to [Eu(TPAEN)]- and investigated by DFT calculations to expose the differences in charge/energy density distributions at europium(III) and the donor functionalities of the TPAEN4- and TPAMEN. On the basis of estimations of the bond orders, atomic charges spin populations, and density of states in the Eu and potential Am and Cm complexes, the specific contributions of the donor-metal interaction are analyzed. The prediction of complex formation energy differences for the [M(TPAEN)]- and [M(TPAMEN)]3+ (M3+ = Eu3+, Am3+) complexes provide an outlook on the potential performance of TPAMEN in Am3+/Eu3+ separation.

Structural investigations of three actinide(IV) 4-phosphoryl 1H-pyrazol-5-olate complexes (An = Th(IV), U(IV), Np(IV)) and their cerium(IV) analogue display the same metal coordination in the solid state. The mononuclear complexes show the metal centre in a square antiprismatic coordination geometry composed by the two O-donor atoms of four deprotonated ligands. Detailed solid state analysis of the U(IV) complex shows that dependent on the solvent used altered arrangements are observable, resulting in a change in the coordination polyhedron of the U(IV) metal centre to bi-capped trigonal prismatic. Further, single crystal analyses of the La(III) and Ce(III) complexes show that the ligand can also act as a neutral ligand by protonation of the pyrazolyl moiety. All complexes were comprehensively characterized by NMR, IR and Raman spectroscopy. A single resonance in each of the 31P NMR spectra for the La(III), Ce(III), Ce(IV), Th(IV) and Np(IV) complex indicates the formation of highly symmetric complex species in solution. Extended X-ray absorption fine structure (EXAFS) investigations provide evidence for the same local structure of the U(IV) and Np(IV) complex in toluene solution, confirming the observations made in the solid state.

Two N,N′-bis(3-alkoxy-2-hydroxybenzyl)cyclohexane-1,2-diamine proligands, H2L1 (R = OCH3) and H2L2 (R = OC2H5), and five heterodinuclear ZnII/LnIII complexes, [Zn(L)(µ-CH3COO)Ln(NO3)2], containing [L1]2– and Gd3+, Tb3+, Er3+, or Yb3+ and [L2]2– and Yb3+ have been synthesised and structurally characterised. The complexes are isostructural and crystallise in the P21/n monoclinic space group. Zinc(ii) is coordinated by the inner N2O2 donor set of the ligand and an oxygen of the bridging acetate anion; the lanthanide(iii) ions possess an O9 coordination environment involving the interaction with the ligand’s outer O4 donor set, two bidentate nitrate ions, and the bridging acetate.