Role of climate change variables (standing water and rainfall) on dissipation of chlorantraniliprole from a simulated rice ecosystem

Effects of anthranilic diamide insecticides on metamorphosis in the common toad Rhinella arenarum (Hensel, 1867) at concentrations found in aquatic environments

Anthranilic diamides (AD) are a modern class of insecticides used as alternatives to pyrethroids and neonicotinoids, particularly against lepidopteran pests. Despite their widespread use and presence in surface waters, little is known regarding their effects on amphibians. The aim of this study was to examine the effects of environmentally-relevant concentrations of AD insecticides chlorantraniliprole (CHLO) and cyantraniliprole (CYAN) on metamorphosis of the toad Rhinella arenarum. Tadpoles were exposed to CHLO or CYAN at concentrations ranging from 5 and 5000 µg/L from stage 27 until metamorphosis completion. Both insecticides produced a non-monotonic acceleration of the time required for individuals to progress through development and a decrease in the proportion of individuals completing metamorphosis, although a delay in metamorphosis was also observed at 5 µg/L of CHLO. Snout-vent length and body weight of metamorphosed toads were not markedly affected by either insecticide. CHLO was more toxic than CYAN, with a lowest observed effect concentration (LOEC) for CHLO on time to metamorphosis defined as 5 µg/L compared to 5000 µg/L for CYAN. The LOEC for reduced metamorphic success defined as 50 µg/L for CHLO compared to 500 µg/L for CYAN. As most effects occurred after stage 39, when metamorphosis depends upon thyroid hormones, it is conceivable that that AD insecticides act as endocrine disruptors. These findings suggest that contamination of surface waters with CHLO and CYAN may disrupt amphibian development in the wild and warrant further research to investigate the possibility of endocrine-disruption by ADs.

Fate of pesticides in agricultural runoff treatment systems: Occurrence, impacts and technological progress

The levels of pesticides in air, water, and soil are gradually increasing due to its inappropriate management. In particular, agricultural runoff inflicts the damages on the ecosystem and human health at massive scale. Present study summarizes 70 studies in which investigations on removal or treatment of pesticides/insecticides/herbicides are reported. A bibliometric analysis was also done to understand the recent research trends through the analysis of 2218 publications. The specific objectives of this study are as follows: i) to inventorize the characteristics details of agriculture runoff and analyzing the occurrence and impacts of pesticides, ii) analyzing the role and interaction of pesticides in different environmental segments, iii) investigating the fate of pesticides in agriculture runoff treatment systems, iv) summarizing the experiences and findings of most commonly technology deployed for pesticides remediation in agriculture runoff including target pesticide(s), specifications, configuration of technological intervention. Among the reported technologies for pesticide treatment in agriculture runoff, constructed wetland was at the top followed by algal or photobioreactor. Among various advanced oxidation processes, photo Fenton method is mainly used for pesticides remediation such as triazine, methyl parathion, fenuron and diuron. Algal bioreactors are extensively used for a wide range of pesticides treatment including 2,4-Dichlorophenoxyacetic acid, 2-methyl-4-chlorophenoxyacetic acid, alachlor, diuron, chlorpyrifos, endosulfan, and imidacloprid; especially at lower hydraulic retention time of 2-6 h. This study highlights that hybrid approaches can offers potential opportunities for effective removal of pesticides in a more viable manner.

Uptake, Translocation, and Terminal Residue of Chlorantraniliprole and Difenoconazole in Rice: Effect of the Mixed-Application with Adjuvant

Plant oil adjuvants are widely used to improve the utilization rate of pesticides. In this study, the uptake, translocation, and terminal residue of chlorantraniliprole and difenoconazole spraying with plant oil adjuvant in rice (Oryza sativa L.) were evaluated. After being mixed with the tank-mixed plant oil adjuvant, the cuticular wax of rice leaf was destroyed, which decreased the hydrophobicity of the rice leaf and facilitated the wetting, spreading, and penetration of pesticides onto the rice leaf. Additionally, the adjuvant promoted the translocation of difenoconazole from leaves to stems, but had little effect on the translocation of difenoconazole from leaves to roots, while inhibiting chlorantraniliprole translocation. Although adjuvant increased the initial deposition of chlorantraniliprole and difenoconazole on rice, the terminal residue was not significantly affected. The findings can promote the safe use of chlorantraniliprole and difenoconazole in rice production, especially when used with plant oil adjuvants. In the future, studies on more rice cultivars will be necessary to determine the generality of the conclusions.

Multi-biomarkers approach to assess the toxicity of novel insecticide (Voliam flexi®) on Clarias gariepinus: From behavior to immunotoxicity

This study was conducted to determine for the first time the immunological, histopathological, histochemical, and ultrastructural changes; hematological and biochemical alterations; and poikilocytosis induced in Clarias gariepinus by Voliam flexi® 40% WG (thiamethoxam + chlorantraniliprole). Beside control fish, juvenile C. gariepinus were subjected to three sublethal concentrations of Voliam flexi® (43.5, 87.5, and 175 mg/L) for 15 days. Voliam flexi® induced immunotoxic impairments in C. gariepinus, such as a decrease in some immunity variables (lysozyme and phagocyte activity, immunoglobulin concentration, and nitro blue tetrazolium level). It also caused an extreme increase in the levels of primary cytokines (interleukin-1β and IL-6), compared with the control. The toxic effects of Voliam flexi® increased gradually with the increasing concentrations tested. Histological examination of the liver demonstrated necrosis, vacuolated hepatocytes (fatty deposition), melanomacrophage centers, foci of inflammatory cells, congested and dilated blood sinusoids, hepatic degeneration, fibrosis increment (Sirius Red stain), and glycogen depletion, as well as cytopathological alterations. We conclude that the toxic effects of Voliam flexi® must be restricted or prevented by using control mechanisms in aquatic systems.

Residue dynamics and bio-efficacy of triflumezopyrim against Nilaparvata lugens and non-targeted effect on natural enemies in a rice ecosystem

Triflumezopyrim (TMP), a mesoionic insecticide, is commonly used for controlling planthoppers in rice. However, the relationship between the TMP residue and toxicity against brown planthoppers (BPHs) has not been studied in detail. We are reporting the dissipation of TMP from rice plant and soil under field conditions. The median lethal dose and median lethal concentration were 0.036 ng per insect and 0.525 mg L-1, respectively. TMP at recommended dose (25 g a.i. ha-1) recorded 1.25 live BPH per hill as against 25.5 per hill in control at 14 days after treatment. TMP was considered to be harmless to the natural enemies, namely, Cyrtorhinus lividipennis and Lycosa pseudoannulata in the rice ecosystem. The residue of TMP from rice plant and soil was estimated using the QuEChERS method using three different doses (12.5, 25, and 50 g a.i. ha-1). The limit of quantitation (LOQ) of TMP in plant and soil was 5 µg kg-1 and 1 µg kg-1, respectively. The maximum content of TMP in soil was less than 1% that of plant content on day 1. The dissipation pattern of TMP both from plant and soil was better explained by the first-order double-exponential decay model (FODED) as compared to the first-order kinetic model. Overall, the half-lives of TMP were ranged from 2.21 to 3.02 days in plant tissues and 3.78 to 4.79 days in soil as per the FODED model. Based on the persistence and toxicity of TMP, we could conclude that TMP will be effective against BPH up to 7-10 days after application. Triflumezopyrim with reasonable persistence and high efficacy could be recommended as an alternate pesticide in BPH management in rice.

Assessing Potential Environmental Impacts of Pesticide Usage in Paddy Ecosystems: A Case Study in the Deduru Oya River Basin, Sri Lanka

Rice paddies are unique ecosystems that provide rich wetland habitat. Their enduring existence across vast stretches of land has led them to evolve into unique systems serving a diverse assemblage of organisms and sustaining a staple grain for many people. With food demand rising, agricultural intensification through agrochemical application is a common practice used to boost food production in developing countries, including Sri Lanka. The aim of the present study was to assess the concentration of pesticide residues in water in rice ecosystems and discover their potential impacts on both environmental health and the most common fauna groups across a cropping year in Sri Lanka. A total of 270 water samples from waters associated with paddy fields within a watershed were analyzed for 20 commonly used pesticides; in addition, local farm holders were surveyed to assess pesticide usage details in three selected paddy tracts. We then used the Cornell University environmental impact quotient (EIQ) calculator and the ECOTOX Knowledgebase to determine the exposure risk associated with individual pesticides relative to their application rates and aquatic concentrations. Survey results demonstrate that several pesticides were overapplied at rates 1.2-11 times the recommended application, and the EIQ demonstrated high environmental risk of two of the agrochemicals detected, 2-methyl-4-chlorophenoxyacetic and diazinon. Fish, amphibians, insects, and beetles were found to have a wide range of potential adverse outcomes from exposure to diazinon, captan, thiamethoxam, and chlorantraniliprole. To balance the trade-offs between food security and ecosystem sustainability, the present study recommends that adoption of quantifiable environmental health indicators be considered as part of the national policy regulating pesticide use. Environ Toxicol Chem 2022;41:343-355. © 2021 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.