Photolysis of the novel meta-diamide insecticide broflanilide in solutions: Kinetics, degradation pathway, DFT calculation and ecotoxicity assessment.

Broflanilide, as a novel meta-diamide insecticide, presents high bioactivity against agricultural pests. However, there was limited report regarding the photolysis fate of broflanilide. In this study, the photodegradation kinetics and influence factors of broflanilide, including different solvents, pH, iron, S2O82- and SO32- were investigated under UV condition, and the reaction mechanism and transformation pathway were explored. The reaction rates (k) showed solvent-specificity in ultrapure water (0.015 min-1), ethyl acetate (0.051 min-1), methanol (0.084 min-1) and acetonitrile (0.193 min-1), correspondingly. The photolysis of broflanilide was slowest in the acid condition (pH = 4.0) compared with that in the neutral (pH = 7.0) and alkaline (pH = 9.0) conditions. The iron (Fe2+ and Fe3+) presented significant inhibition on the photodegradation due to the light shielding effect. Additionally, the UV/peroxydisulfate (S2O82-) and UV/sulfite (SO32-) technologies could effectively accelerate the photodegradation of broflanilide, which has the potential for rapid treatment of pesticides in the aqueous environment. Six transformation products (TPs) were detected in water, peroxydisulfate and sulfite solutions, and the possible transformation pathways, including dehalogenation, cyclization, N-dealkylation, oxidation, reduction and hydrolysis, were proposed. Importantly, the reaction mechanism was explained through the analysis of molecular electrostatic potential and molecular orbitals. The predicted toxicity of the TPs indicated that several highly toxic TPs need to pay more attention in future risk assessments. This study provides a new perspective for evaluating the ecological fate and risks of pesticides.

The Cost of Resistance to Diamide Insecticide Varies With the Host Plant in Spodoptera frugiperda (Lepidoptera: Noctuidae).

Fitness costs associated with insect resistance to insecticides can be exploited to implement resistance management programs. However, most of these studies are restricted to evaluating biological traits on artificial diets. Here, we investigated the fitness cost associated with chlorantraniliprole in Spodoptera frugiperda (J.E. Smith) feeding on corn, soybean, and cotton plants. We used a near-isogenic strain of S. frugiperda resistant to chlorantraniliprole (Iso-RR), a susceptible strain (SS), and heterozygotes strains (H1 and H2) to evaluate several biological and population growth parameters. Larval survival of the Iso-RR strain was on average 90% on corn, 65% on soybean, and 57% on cotton plants. Development time of the larval stage also differed among host plants, Iso-RR strain took on average 14, 17, and 26 days to reach the pupal stage on corn, soybean, and cotton plants respectively. Net reproductive rate, intrinsic rate of population increase, and finite rate of population increase were higher for Iso-RR strain feeding on corn plants than other host plants. The relative fitness, based on the intrinsic rate of population increase, of S. frugiperda resistant strain on corn, soybean, and cotton plants were 1.04, 0.85, and 0.88, respectively. Therefore, no fitness cost was observed for S. frugiperda feeding on corn plants, but a significant fitness cost was observed when this pest fed on soybean and cotton plants. We showed that the food source influences the fitness cost of S. frugiperda resistant to diamide. Such information may help to implement resistance management strategies based on each crop.

Residue and distribution of drip irrigation and spray application of two diamide pesticides in corn and dietary risk assessment for different consumer groups.

BACKGROUND: As the use of diamide insecticides on corn continues to increase, there is growing concern about their residue levels on corn and dietary risks to populations. In this study, the distribution, dispersion and transfer efficiency of two diamide insecticides (tetrachlorantraniliprole (TCAP) and cyantraniliprole (CNAP)) in different parts of corn and soil were investigated in a 1-year field trial in Guangzhou and Lanzhou using two different application methods - spray and drip irrigation, respectively - and the dietary risk of the insecticides to different consumer populations was assessed under the two application methods. RESULTS: The results showed that drip irrigation had a longer persistence period than spraying, and there was a hysteresis in the absorption distribution of the agent in different parts of corn, which was gradually transferred to the leaves after absorption from the roots. The average TE1 (transfer efficiency) and TE2 were 0.230-0.261 and 1.749-1.851 for TCAP and 0.168-0.187 and 2.363-2.815 for CNAP, respectively. At corn harvest, both TCAP and CNAP were below detectable levels in soil and corn. For different consumer populations, hazard quotients ranged from 0.001 to 0.066 for TCAP and from 0.003 to 0.568 for CNAP - both well below 100%. CONCLUSION: This study indicates that TCAP and CNAP applied by spray or drip irrigation are safe for long-term risk of human intake and also provides guidance for the use of both insecticides in agricultural production to control corn pests, especially in arid and semi-arid areas. © 2022 Society of Chemical Industry.

Degradation of anthranilic diamide insecticide tetrachlorantraniliprole in water: Kinetics, degradation pathways, product identification and toxicity assessment.

In the present study, aqueous behavior and fate of diamide insecticide tetrachlorantraniliprole (TCTP) were investigated under laboratory-controlled conditions. Half-lives of TCTP photolysis in natural water and pH buffers were 1.4-2.8 h, comparing with those of 1.2-231 d for hydrolysis. Both processes were highly influenced by pH with respect to degradation kinetics and routes. The hydrolysis rate of TCTP was accelerated by elevated temperatures. The presence of nitrate enhanced TCTP photolysis while fulvic acid exhibited suppression, with the extent of both effects as a function of concentration. Four degradation products were identified using a variety of spectroscopic approaches. Key reactions involved in the degradation pathways include intramolecular substitution and cyclization. There was a reduction in the acute toxicity of all four products to Daphnia magna by comparison with TCTP, whereas they were still classified as category 1 or 2 hazardous substances to the aquatic environment according to the Globally Harmonized System of Classification and Labelling of Chemicals (GHS) standards.

Resistance and fitness costs in diamondback moths after selection using broflanilide, a novel meta-diamide insecticide.

The diamondback moth (DBM) Plutella xylostella (L.) (Lepidoptera: Plutellidae) is an insect pest found around the world that feeds on cruciferous crops. The DBM has become resistant to most insecticides in current use in the field. Broflanilide is a novel meta-diamide insecticide that binds to a new site on the γ-aminobutyric acid receptor and very efficiently protects against most pests in the order Lepidoptera, including DBM. In this study, the resistance of a laboratory-bred susceptible strain of DBM to broflanilide and the fitness costs posed by broflanilide to the DBM were evaluated. The DBM had no obvious resistance to broflanilide after 10 generations of selection. The realized heritability h2 was 0.033, suggesting a low risk of resistance developing in this strain. The F10 generation had no cross-resistance to the insecticides abamectin and endosulfan (which target the γ-aminobutyric acid receptor) and chlorantraniliprole (which targets a non-γ-aminobutyric acid receptor). The specific activities of important detoxification enzymes (cytochrome P450 monooxygenase, esterase, and glutathione S-transferase) were not obviously altered. However, the larval stage was prolonged and the adult stage was shortened significantly in F11 generation than the F0 generation. The total preoviposition period TPOP significantly prolonged 1.90 d in F11 generation. The fitness value Rf (0.93) was lower for the F11 generation than the F0 generation. The results indicated that long-term exposure to broflanilide exerts clear fitness costs in the DBM. This information will be useful in identifying reasonable broflanilide application guidelines for managing broflanilide resistance in the DBM.

Resistance Risk Assessment of the Ryanoid Anthranilic Diamide Insecticide Cyantraniliprole in Aphis gossypii Glover.

Cyantraniliprole targets the ryanodine receptor and shows cross-spectrum activity against a broad range of chewing and sucking pests. In this study, a cyantraniliprole-resistant cotton aphid strain (CyR) developed resistance 17.30-fold higher than that of a susceptible (SS) strain. Bioassay results indicated that CyR developed increased cross-resistance to cyfluthrin, α-cypermethrin, imidacloprid, and acephate. In CyR, piperonyl butoxide synergistically increased the toxicity of cyantraniliprole, α-cypermethrin, and cyfluthrin. The cytochrome P450 activities in the CyR strain were significantly higher than those in the SS strain. The mRNA expression of CYP6CY7, CYP6CY12, CYP6CY21, CYP6CZ1, CYP6DA1, and CYP6DC1 in the CYP3 clade, and CYP380C6, CYP380C12, CYP380C44, CYP4CJ1, and CYP4CJ5 in the CYP4 clade, was significantly higher in CyR than in SS. The depletion of the most abundant CYP380C6 transcript by RNAi also significantly increased the sensitivity of CyR to cyantraniliprole. Transgenic expression of CYP380C6, CYP6CY7, CYP6CY21, and CYP4CJ1 in Drosophila melanogaster suggested that the expression of CYP380C6 and CYP4CJ1 was sufficient to confer cyantraniliprole resistance, with CYP380C6 being the most effective, and that CYP380C6, CYP6CY7, and CYP6CY21 were related to α-cypermethrin cross-resistance. These results indicate the involvement of P450 genes in cyantraniliprole resistance and pyrethroid cross-resistance and provide an overall view of the metabolic factors involved in resistance development.

Cascade annulation of malonic diamides: a concise synthesis of polycyclic pyrroloindolines.

A concise synthesis of polycyclic pyrroloindolines from simple malonic diamides via an intramolecular oxidative coupling/condensative cyclization cascade process is reported. The reaction provides an efficient method to construct polycyclic pyrroloindolines in good to excellent yields, which should be useful in the synthesis of natural products and pharmaceutical molecules.

Assessment of chronological lifespan dependent molecular damages in yeast lacking mitochondrial antioxidant genes.

The free radical theory of aging states that oxidative damage to biomolecules causes aging and that antioxidants neutralize free radicals and thus decelerate aging. Mitochondria produce most of the reactive oxygen species, but at the same time have many antioxidant enzymes providing protection from these oxidants. Expecting that cells without mitochondrial antioxidant genes would accumulate higher levels of oxidative damage and, therefore, will have a shorter lifespan, we analyzed oxidative damages to biomolecules in young and chronologically aged mutants lacking the mitochondrial antioxidant genes: GRX2, CCP1, SOD1, GLO4, TRR2, TRX3, CCS1, SOD2, GRX5, and PRX1. Among these mutants, ccp1Δ, trx3Δ, grx5Δ, prx1Δ, mutants were sensitive to diamide, and ccs1Δ and sod2Δ were sensitive to both diamide and menadione. Most of the mutants were less viable in stationary phase. Chronologically aged cells produced higher amount of superoxide radical and accumulated higher levels of oxidative damages. Even though our results support the findings that old cells harbor higher amount of molecular damages, no significant difference was observed between wild type and mutant cells in terms of their damage content.