Concentrations Of Insecticides Research Articles

Exposure to low-concentration fipronil impairs survival, behavior, midgut morphology and physiology of Aedes aegypti larvae

The Aedes aegypti mosquito is a vector for various arboviruses, including dengue and yellow fever. Insecticides, such as pyrethroids and organophosphates, are widely used to manage and control these insects. However, mosquitoes have developed resistance to these chemicals. Therefore, this study aimed to investigate the effects of the commercial formulation of fipronil (Tuit® Florestal; 80% purity) on the survival, behavior, morphology, and proteins related to signaling pathways of the midgut in A. aegypti larvae under controlled laboratory conditions. Significant reductions in immature survival were observed in all concentrations of fipronil tested. Low insecticide concentration (0.5 ppb) led to decreased locomotor activity in the larvae and caused disorganization of the epithelial tissue in the midgut. Moreover, exposure to the insecticide decreased the activity of detoxifying enzymes such as catalase, superoxide dismutase, and glutathione-S-transferase. On the other hand, the insecticide increased protein oxidation and nitric oxide levels. The detection of LC3, caspase-3, and JNK proteins, related to autophagy and apoptosis, increased after exposure. However, there was a decrease in the positive cells for ERK 1/2. Furthermore, the treatment with fipronil decreased the number of positive cells for the proteins FMRF, Prospero, PH3, Wg, Armadillo, Notch, and Delta, which are related to cell proliferation and differentiation. These findings demonstrate that even at low concentrations, fipronil exerts larvicidal effects on A. aegypti by affecting behavior and enzymatic detoxification, inducing protein oxidation, free radical generation, midgut damage and cell death, and inhibiting cell proliferation and differentiation. Thus, this insecticide may represent a viable alternative for controlling the spread of this vector.

Physical durability and insecticidal activity of long-lasting insecticidal nets in Cruzeiro do Sul, Brazil

Vector control is one of the principal strategies used for reducing malaria transmission. Long-lasting insecticidal bed nets (LLINs) are a key tool used to protect populations at risk of malaria, since they provide both physical and chemical barriers to prevent human-vector contact. This study aimed to assess the physical durability and insecticidal efficacy of LLINs distributed in Cruzeiro do Sul (CZS), Brazil, after 4 years of use. A total of 3000 LLINs (PermaNet 2.0) were distributed in high malaria risk areas of CZS in 2007. After 4 years of use, 27 ‘rectangular’ LLINs and 28 ‘conical’ LLINs were randomly selected for analysis. The evaluation of physical integrity was based on counting the number of holes and measuring their size and location on the nets. Insecticidal efficacy was evaluated by cone bioassays, and the amount of residual insecticide remaining on the surface of the LLINs was estimated using a colorimetric method. After 4 years of use, physical damage was highly prevalent on the rectangular LLINs, with a total of 473 holes detected across the 27 nets. The upper portion of the side panels sustained the greatest damage in rectangular LLINs. The overall mosquito mortality by cone bioassay was < 80% in 25/27 rectangular LLINs, with panel A (at the end of the rectangular bednet) presenting the highest mortality (54%). The overall mean insecticide concentration was 0.5 µg/sample, with the bednet roof containing the highest average concentration (0.61 µg/sample). On the conical LLINs, 547 holes were detected, with the bottom areas sustaining the greatest damage. The cone bioassay mortality was < 80% in 26/28 of the conical LLINs. The mean insecticide concentration was 0.3 µg/sample. After 4 years of use, the insecticidal efficacy of the LLINs was diminished to below acceptable thresholds.

Transgenerational effect of a tea saponin–matrine mixture promotes fecundity and alters associated bacteria in the fall armyworm Spodoptera frugiperda

The fall armyworm Spodoptera frugiperda is a one of the most invasive and damaging pests that causes serious economic losses in several crops. Botanical insecticides such as tea saponin and matrine, as environmentally acceptable biopesticides, are widely used for controlling pests. Insecticide stress affects both individuals and the associated bacteria in insects. However, it remains unclear that if sublethal effects and bacteria are the drivers for the adaptive mechanisms of insecticides in fall armyworm. We examined the effectiveness of a 10:1 v/v mixture of biological insecticides against the fall armyworm and the impacts of several biological parameters and demographic variables of the armyworm targeting two generations at primary exposure. Moreover, the influence of the insecticide mixture on the associated bacteria of the fall armyworm was assessed via 16 S rRNA sequencing. The results showed that the mixture was highly toxic to fall armyworms, and the fecundity of the initially exposed generation (F0) significantly decreased; however, there was no significant effect on longevity. The larval duration, the total pre-reproductive period, longevity, fecundity, and mean generation time of the fall armyworm in the F1 significantly increased; yet the intrinsic and finite rates of the increase and the net reproductive rate remained fairly constant. Additionally, the population of associated bacteria was affected in both generations, with an increase in the microbial diversity within the fall armyworm compared to that of the F0 generation. Also, an increase in abundance of several genera of bacteria, including Acinetobacter, Serratia, Enterococcus, and Pseudomonas, was noted following treatment with the insecticide mixture. These results broaden our understanding of the impact of sublethal insecticide concentrations on the fall armyworm and its associated bacterial community.

Effects of sublethal fipronil insecticide concentrations on fitness and abundance profile of endosymbiont microbial species Nilaparvata lugens

Abstract. Awaluddin, Dadang, Anwar R, Giyanto. 2024. Effects of sublethal fipronil insecticide concentrations on fitness and abundance profile of endosymbiont microbial species Nilaparvata lugens. Biodiversitas 25: 998-1006. Fipronil is a widely used active ingredient for controlling Nilaparvata lugens Stal. (Hemiptera: Delphacidae), but the effect exerted on fitness ratio and composition of endosymbiont microbes remain unknown. Therefore, this study aimed to investigate effects of insecticide by assessing fitness ratio and bacterial composition of endosymbionts in N. lugens before and after applying sublethal fipronil concentrations. A pair of LC15-equivalent fipronil-treated imago were introduced into treatment pots planted with rice 30 days after transplanting. Additionally, N. lugens endosymbionts were identified using full-length primers 27F and 1492R targeting the 16S rRNA gene. The results showed that fipronil application increased the total number of nymphs and fitness ratio of N. lugens in both IR64 and ciherang rice varieties. Similar observations were obtained with erythromycin application, although the differences were not statistically significant compared to the control. Fipronil application tended to cause an insignificant increase in the percentage of hatched eggs, while samples lacking this treatment contained abundant quantities of an endosymbiont, Acinetobacter soli. After applying insecticide, a significant alteration occurred in the composition of endosymbionts, with a substantial increase in Delftia acidovorans and D. lacustris, which both contributed to the enhanced fitness and tolerance of N. lugens to fipronil. These results showed the intricate interactions between bacteria and insects, as well as the mechanisms underlying insecticide resistance, thereby providing valuable insights for the development of new pest management strategies.

Ecological consequences when organisms avoid a contaminated environment: A study evaluating the toxicity of fipronil

The ability of aquatic organisms to sense the surrounding environment chemically and interpret these signals correctly is crucial to their survival and ecological niche. This study applied the Heterogenous Multi-Habitat Assay System - HeMHAS to evaluate the avoidance potential of Daphnia magna to detect fipronil-contaminated habitats in a connected landscape after a short (48 h), previous, forced exposure to an environmentally relevant concentration of the same insecticide. The swimming of daphnids was also analyzed by recording the total distance covered. D. magna preferred areas with less contamination, although the effect of fipronil on their swimming ability (a decrease) was observed for all the concentrations tested. The application of non-forced multi-compartment exposure methodologies is a recent trend and is ecologically relevant as it is based on how contamination can really produce changes in an organism's habitat selection. Finally, we consider the importance of more non-forced exposure approaches where Stress Ecology can be aggregated to improve systemic understanding of the risk that contaminants pose to aquatic ecosystems from a broader landscape perspective.

Demographic analysis of the biological parameters of Spodoptera frugiperda after sublethal exposure to insecticides

Spodoptera frugiperda (JE Smith) is one of the most destructive pests, causing serious yield losses of corn on all continents except Europe. Low-lethal concentrations of insecticides may affect not only the survival rate but also the demographic parameters of a pest. To understand the effect of low-lethal concentrations of insecticides on S. frugiperda, the developmental parameters after low-lethal concentrations treatment by three different modes of action pesticides tetrachlorantraniliprole, spinetoram, and lufenuron were analyzed. For F0 generation, the pupal length and weight of FAW after insecticide treatment were significantly longer and heavier than that of control. For the F1 generation, the adult longevity and egg hatching rate after spinetoram and lufenuron treated was significantly shorter and lower than that of the control. While no significant effect was observed for the intrinsic rate of increase (r), finite rate of increase (λ), and mean generation time (T) of S. frugiperda, the net reproductive rate (R0) significant decreased after the spinetoram and lufenuron treatment. Results showed tetrachlorantraniliprole, spinetoram, and lufenuron negatively affect larval survival rate, but spinetoram and lufenuron caused early maturity, and all three insecticide treatments increased egg reproduction. The results of this study suggest that low-lethal concentration exposure to insecticides negatively impacts the life table parameters of S. frugiperda, and those three insecticides from different modes of action cannot cause FAW resurgence and can be recommended as insecticides to control FAW. Those results will be helpful for researchers working on S. frugiperda management using chemical pesticides in an integrated pest management program.

Lethal Concentration and Lethal Time Botanical Insecticide Tuba Root Extract Against Spodoptera frugiperda J. E. Smith Larvae

Utilization of botanical insecticides is an option to control environmentally friendly Spodoptera frugiperda pests. The purpose of this study was to determine the lethal concentration (LC) and lethal time (LT) of botanical insecticides on the third instar larvae of S. frugiperda in the laboratory. The experiment was conducted at the Applied Entomology Laboratory, Faculty of Agriculture, Gadjah Mada University, Yogyakarta, over a period of 3 months, from September to November 2022. The concentration treatments used were 0, 2, 4, and 8 ml/L of water. The experiment was designed using a completely randomized design (CRD) with 4 treatments and 5 replications. Larval mortality data was processed using probit analysis in order to determine the value of Lethal Concentration (LC50 and LC95) and Lethal Time 50 (LT50). The results showed that the tuba root powder extract concentration showed LC50 and LC95 namely 0.07% equivalent to 0.7 ml/L of water and 1.53% equivalent to 15.3 ml/L of water. Meanwhile the concentration of 8 ml/L of water extract of tuba root flour causes LT50 of S. frugiperda larvae causing time to tend to be faster at 1.86 days or 44,64 hours after application. Botanical insecticides of the tuba root extract concentration show high efficacy against S. frugiperda larvae so that they can be recommended as a component for integrated pest management (IPM).

Effect of washing method on the reduction of insecticide residues and quality characteristics of sweet cherry fruits

Sweet cherry trees were sprayed with 5 insecticides (acetamiprid, dimethoate, lambda-cyhalothrin, malathion, tau-fluvalinate) at the recommended field doses in this study. Fruits were harvested after the pre-harvested interval for each pesticide completed and then they were immersed into tap water and three different washing solutions (with three different concentrations) for 3 minutes (at 20ºC). Insecticide concentrations were detected with a multi-residual analysis method using LC-MS/MS in Bursa Uludağ University in 2022. Following the treatments, changes in the quality characteristics of fruits were also investigated by quality (colour, texture and fruit cracking rate, water-soluble dry matter) and sensory analysis (fruit and stem colour, firmness, appearance, general acceptability). The results revealed that washing method with tap water during 3 min decreased insecticide residue level by 7-45% depending on insecticide active compound. Higher reduction rates were observed by washing with citric acid (10%), sodium bicarbonate (2.5%) and sodium hydroxide (0.5%). But significant reductions were detected only in lambda-cyhalothrin and malathion residues when compared with the newly harvested fruit samples. Processing factors (PF) of all washing methods were generally lower than 1 except for three treatments. PF values showed variations depending on the type of washing solution and the active compound of insecticides. Although washing with citric acid (10%), sodium bicarbonate (2.5%) and sodium hydroxide (0.5%) solutions caused reduction in residue levels, their negative effects on the quality and sensory characteristics of the fruits cannot be ruled out.

Pyriproxyfen Contamination in Daphnia magna: Identifying Early Warning Biomarkers.

Pyriproxyfen is an insecticide currently employed in numerous countries for the management of agricultural and indoor pests. Several studies indicate that this insecticide has been detected in multiple rivers, with concentrations reaching as high as 99.59 ng/L in the Júcar River in Spain. Therefore, the determination of some biochemical and genetic effects of this insecticide on aquatic organisms could serve as an early warning mechanism to identify potential disruptions in various biomarkers. Based on this, Daphnia magna organisms were exposed to pyriproxyfen sublethal concentrations for 21 days. Some biochemical parameters, including cholesterol, triglycerides, glucose, lactate, and LDH activity, were determined. Additionally, some genetic biomarkers associated with oxidative stress, heat shock proteins, lipid metabolism, hemoglobin, metallothioneins, and vitellogenin synthesis were evaluated in daphnids exposed to the insecticide for 21 days. LDH activity increased significantly in those daphnids exposed to the highest insecticide concentration (14.02 µg/L), while cholesterol levels decreased significantly. In contrast, glucose, total proteins, and triglycerides remained unaffected in D. magna exposed to pyriproxyfen. On the other hand, exposure to the insecticide led to notable alterations in gene expression among individuals. Specifically, genes associated with lipid metabolism and reproduction exhibited a significant reduction in gene expression. Fabd expression was decreased by approximately 20% in exposed daphnids, while vtg expression was suppressed as much as 80% when compared to control values. Furthermore, it was observed that the hgb1 and hgb2 genes, associated with hemoglobin synthesis, exhibited significant overexpression. Notably, the dysfunction observed in both hemoglobin genes was linked to an increase in pigmentation in Daphnia magna during the course of the experiment. These alterations in gene expression could serve as effective indicators of early contamination even at low pesticide concentrations.

Effectiveness of pyriproxyfen-pyrethroid and chlorfenapyr-pyrethroid long-lasting insecticidal nets (LLINs) compared with pyrethroid-only LLINs for malaria control in the third year post-distribution: a secondary analysis of a cluster-randomised controlled trial in Benin

Malaria continues to kill approximately 650 000 people each year. There is evidence that some second-generation insecticide-treated nets, which combine insecticide formulations with different modes of action, are protective against malaria while the nets are new; however, evidence for their impact over 3 years is scarce. In this study, we report the third-year results of a cluster-randomised controlled trial assessing the long-term effectiveness of dual-active ingredient long-lasting insecticidal nets (LLINs). This is a secondary analysis of a cluster-randomised controlled trial, carried out between May 23, 2019, and April 30, 2023, in southern Benin. Restricted randomisation was used to assign 60 clusters (villages or groups of villages with a minimum of 100 households) to the three study groups (1:1:1) to evaluate the efficacy of pyriproxyfen-pyrethroid LLINs and chlorfenapyr-pyrethroid LLINs compared with pyrethroid-only LLINs (reference) against malaria transmission. The study staff and communities were masked to the group allocation. The primary outcome was malaria incidence measured over the third year after LLIN distribution, in a cohort of children aged 6 months to 9 years at the time of enrolment, in the intention-to-treat population. Here, we present the data of the third year post-LLIN distribution. The trial was registered with ClinicalTrials.gov, NCT03931473. Study net use declined over the 3 years and was consistently lowest in the pyriproxyfen-pyrethroid LLIN group (at 36 months: 889 [39·4%] of 2257 participants vs 1278 [52·2%] of 2450 participants for the chlorfenapyr-pyrethroid LLIN group and 1400 [57·6%] of 2430 participants for the pyrethroid-only LLIN group). The cohort of children for the third year of follow-up (600 per group) were enrolled between April 9 and 30, 2022. Mean malaria incidence during the third year after distribution was 1·19 cases per child-year (95% CI 1·09-1·29) in the pyrethroid-only LLIN reference group, 1·21 cases per child-year (1·12-1·31) in the pyriproxyfen-pyrethroid LLIN group (hazard ratio [HR] 1·02, 95% CI 0·71-1·44; p=0·92), and 0·96 cases per child-year (0·88-1·05) in the chlorfenapyr-pyrethroid LLIN group (HR 0·80, 0·56-1·17; p=0·25). No adverse events related to study nets were reported by participants. During the third year, as was also observed during the first 2 years, the pyriproxyfen-pyrethroid LLIN group did not have superior protection against malaria cases compared with the standard LLIN group. In the third year, people living in the chlorfenapyr-pyrethroid LLIN group no longer benefited from greater protection against malaria cases and infections than those living in the pyrethroid-only LLIN group. This was probably influenced by lower study net use than previous years and the declining concentration of partner insecticides in the nets. UNITAID, The Global Fund. For the French translation of the abstract see Supplementary Materials section.

Learning, memory, and sensory perception are impaired by exposure to the organophosphate, ethion, and the insect growth regulator, hexaflumuron, in honey bees (Apis mellifera L.)

Insecticides are a major tool for controlling pest species. Their widespread use results in damage to non-targeted insects, with honey bees particularly at risk. During foraging, honey bees learn and remember floral characteristics that are associated with food. As insect pollinators, honey bees inadvertently contact chemicals which can have multiple negative impacts. The toxicity of two insecticides from different classes, ethion (47.79 mg a.i.L−1) and hexaflumuron (500 mg a.i.L−1), on learning, memory, and sensory perception were evaluated. We found that oral exposure to ethion had adverse effects on learned proboscis extension toward reward-associated odors and colors. In addition, we showed reduced sucrose consumption and sucrose responsiveness after exposure. Hexaflumuron also impaired olfactory learning and memory and decreased responsiveness to sucrose and water. Exposure to sub-lethal concentration of the cholinergic organophosphate insecticide, ethion (47.79 mg a.i.L−1), and the field-recommended concentration of hexaflumuron (500 mg a.i.L−1), significantly impaired behavior involved in foraging. Our results suggest that several behavioral characteristics of honey bees be evaluated when testing an insecticide rather than relying on just one behavioral measure.

Olfactory Learning Behavior and Mortality of the Honey Bee Apis mellifera jemenitica in Response to Pyrethroid Insecticide (Deltamethrin).

Honey bees are constantly threatened due to the wide use of pesticides. This study presents the effects of deltamethrin on the mortality, olfactory learning, and memory formation of the native Saudi bee Apis mellifera jemenitica. Topical and oral application of realistic field and serial dilutions of deltamethrin (250, 125, 62.5, and 25 ppm) caused significant mortality at 4, 12, 24, and 48 h posttreatment. Bee mortality increased with the increasing concentration of insecticide at all tested posttreatment times. Highest mortality was observed at 24 h and 48 h after both exposure routes. Food consumption gradually decreased with increasing concentration of deltamethrin during oral exposure. The LC50 of deltamethrin was determined at 12, 24, and 48 h for topical (86.28 ppm, 36.16 ppm, and 29.19 ppm, respectively) and oral (35.77 ppm, 32.53 ppm, and 30.78 ppm, respectively) exposure. Oral exposure led to significantly higher bee mortality than topical exposure of deltamethrin at 4 h and 12 h, but both exposure routes were equally toxic to bees at 24 h and 48 h. The sublethal concentrations (LC10, LC20, and LC30) of deltamethrin significantly impaired the learning during conditioning trials, as well as the memory formation of bees at 2, 12, and 24 h after topical and oral exposure. Thus, deltamethrin inhibits learning, and bees were unable to memorize the learned task.

Metabolic Resistance Mechanisms Evident in Generations of Anopheles gambiae (Kisumu) Adults Exposed to Sub-lethal Concentrations of Permethrin Insecticide

Background: Anopheles gambiae mosquitoes are one of the best-known of the genus Anopheles because of their predominant role in transmitting the most dangerous malaria parasite species (to humans), Plasmodium falciparum. Unfortunately, An. gambiae mosquitoes have grown resistant to the most popular and widely used insecticides, particularly Permethrin, spreading across Africa. The current study sought to determine the lowest Permethrin concentrations that could be a selection pressure for metabolic resistance development in the renowned adult An. gambiae (Kisumu) mosquito population. Methods: Established, insectary-reared, and fully susceptible strains of Kisumu populations were reared, and exposed for mortality assay and Lowest Sub-lethal Concentrations (LSLCs) determination at the adult stage. Various exposure concentrations were achieved by slightly modifying the Centre for Disease Control (CDC) protocol. Adult Kisumu mosquitoes exposed to the same LSLC over generations were compared with unexposed control populations by way of resistance status and correlating levels of esterase, monooxygenase, and Glutathione-S -transferases (GST) metabolic enzymes. Information obtained was analysed using SPSS 16.0 and Analysis of Variance at P=0.05 with the aid of Graph-Pad prism 8. Results: The LSLCs of Permethrin with mortality rates not significantly (P&gt; 0.05) different from control Kisumu strains (0.00) were 0.2μg (0.00) and 0.4μg (0.00) per CDC bottle, i.e., LSLC 1 and LSLC 2 respectively. The LSLC 1 exposure lasted five generations (f0-f4), during which resistance statuses were consistently below 1.00±0.82 (4.0%) after 1 hour. There was no significant difference (P&gt;0.05) in the levels of esterase across generations, while monooxygenase and GST levels were significantly up-regulated (P&lt;0.05) in subsequent generations of LSLC 1-treated mosquitoes. However, there was a consistent and progressive increase in GST level with advancing generations. Conclusion: It may be concluded that the P450 monooxygenase enzyme mechanism is a prelude to the overexpression of the GST enzyme. Hence, if the development of the GST resistance enzyme can be inhibited or stopped in An. gambiae mosquito vector populations, multiple resistance and cross-resistance mechanisms in malaria vectors could be effectively regulated.

Comparative evaluation of sublethal doses of different insecticides on the ovipositional behavior of whitefly (Bemisia tabaci) in Brinjal

The world's worst invading insect is the whitefly, Bemisia tabaci Gennadius (Hemiptera: Aleyrodidae). For B. tabaci's thorough field control, research on the sublethal impacts of popular insecticides is crucial. We examined the effects of sublethal insecticide concentrations on whiteflies' predilection for oviposition on treated plants of brinjal (Solanum melongena L. cv. Hisar Shyamal) using a multiple-choice test during the 2019 and 2020 growing seasons. The insecticide efficacy was evaluated on the basis of the oviposition preference of B. tabaci on brinjal plants that were raised in pots and repeatedly treated with a distinct dosage of insecticides. The biochemical changes of treated brinjal leaves were also examined in this research, along with their connection to oviposition tendency. The findings showed that whiteflies favored fenpropathrin 30 % EC and deltamethrin 2.8 % EC treated plants for oviposition over diafenthiuron 50 % WP and thiamethoxam 25 % WG. In comparison to untreated control plants, most eggs were deposited on sublethal doses of fenpropathrin 30 % EC treated plants at 50 g a.i./ha and deltamethrin 2.8 % EC at 7.5 g a.i./ha. The findings of biochemical tests showed that with the exception of lesser dosages of fenpropathrin (30 % EC) as well as deltamethrin (2.8 % EC), all insecticidal treatments reduced total sugar and amino acids. Additionally, all the pesticides reduced the overall phenol level and significantly altered the crude protein content. The treated brinjal plant with deltamethrin 2.8 % EC and fenpropathrin 30 % EC attracted whiteflies for oviposition because it provides an improved site for them in terms of nourishment.

EFIKASI EKSTRAK SERAI WANGI DAN DAUN SIRSAK DALAM MENGENDALIKAN SERANGAN ULAT GRAYAK (Spodoptera litura J.E. Smith) PADA BUDIDAYA SAWI HIJAU

Efficacy of Lemongrass and Soursop Leaf Extracts for Controlling ArmywOrm (Spodoptera litura J.E. Smith) Infestation in Green Mustard Cultivation]. Employing vegetable insecticide as a primary measure for controlling armyworms (Spodoptera litura) represents an environmentally friendly strategy to enhance yield. This research, conducted between December and February 2021 at the Plant Protection Laboratory and Plant Protection Gauze House, Faculty of Agriculture, Bengkulu University, aimed to determine the effective concentration of vegetable insecticides for managing armyworms infestation in green mustard. A randomized complete design (CRD) with six treatments and five replications was employed for the efficacy test. The treatments comprised: control, lemongrass extract, soursop leaf extract, lemongrass and soursop leaves extracts in a 1:1 ratio, lemongrass and soursop leaves extracts in a 1:2 ratio, and lemongrass and soursop leaves extracts in a 2:1 ratio. The results demonstrated that both lemongrass and soursop leaf extracts, either individually or in combination, effectively controlled S. litura larvae. Notably, an 8% concentration of citronella extract exhibited the highest mortality rate at 60%, with soursop leaves achieving 53.3%. In combination extracts, lemongrass and soursop leaves extracts in 1:1 and 2:1 ratio resulted in a 43.4% larvae control, while the ratio of lemongrass 1:2 to soursop leaves achieved a 36.6% larvae control. Overall, the research underscores the potential of vegetable insecticides, specifically lemongrass and soursop leaf extracts, as viable components of integrated pest management strategies to maintain crop yield in green mustard cultivation.

Effects of bifenthrin on microcrustaceans grazing behavior on a phytoplankton assemblage dominated by Cyanobacteria.

Insecticides are widely used for pest control and frequently reach aquatic systems, imposing a risk to the biota. In this work, the effect of environmental concentrations of bifenthrin on the grazing capacity of Simocephalus vetulus (Cladocera) and Argyrodiaptomus falcifer (Copepoda) on phytoplankton was evaluated. Fifteen microcrustacean individuals and a natural phytoplankton assemblage dominated by Cyanobacteria were exposed during 46 h to three concentrations of bifenthrin (C0 0 μg L-1, C1 0.02 μg L-1, and C2 0.05 μg L-1). A significant decrease in both microcrustaceans grazing rates on total phytoplankton was observed in C2 compared to C0 and C1. The filtration rate (ml ind-1 h-1) of S. vetulus decreased significantly for the cyanobacteria Anabaenopsis arnoldii, Dolichospermum circinale, and Glaucospira sp. in C2 compared to C0 and C1. The ingestion rate (org ind-1 h-1) of A. falcifer decreased significantly in C1 and C2 compared to C0 only for A. arnoldii. Regarding phytoplankton morphological groups, the filtration rate of S. vetulus decreased in C1 and C2 compared to C0 for Colonies and Coenobiums in C2 concerning C0 and C1 for Filaments and in C2 compared to C0 for Silicified. For A. falcifer, the ingestion rate was reduced in C2 compared to C0 for Silicified, Flagellated, and Sessile. The results showed that bifenthrin affected both microcrustaceans grazing capacity on phytoplankton, especially at the highest insecticide concentration.

Spinosad‐infused biodegradable hydrogel beads as a potential organic approach for argentine ant, Linepithema humile (Mayr) (hymenoptera: Formicidae), management in California citrus orchards

AbstractArgentine ant, Linepithema humile (Mayr), disrupts biological control services in California citrus orchards, leading to economically damaging densities of honeydew‐producing hemipteran pests. With the elimination of chlorpyrifos, the sole registered insecticide for L. humile control in California citrus, the development of effective alternatives is necessary. One alternative is aqueous sugar baits laced with minute concentrations (0.0001%) of insecticide. Field trials were conducted to assess the efficacy of spinosad and thiamethoxam‐infused alginate hydrogel beads (HGBs) for L. humile control. Thiamethoxam‐infused HGBs have previously shown high efficacy against L. humile in citrus. Spinosad is approved for organic use, while thiamethoxam, a neonicotinoid, along with other neonicotinoid insecticides, might soon face deregistration in California, underscoring the need for alternative insecticide chemistries for ant control. Therefore, this study aimed to optimize spinosad‐loaded HGBs by identifying efficacious concentrations, application rates, and deployment frequency, and to compare with thiamethoxam‐infused HGBs, the standard reference treatment. Results showed that spinosad‐infused HGBs significantly reduced high‐density L. humile populations in citrus orchards. Notably, the highest spinosad concentration tested (0.01%) demonstrated comparable control to both 0.0001% and 0.01% thiamethoxam concentrations. A tri‐weekly application schedule for spinosad‐infused HGBs provided best control. Trees treated with 125 or 250 g of hydrogels infused with 0.01% spinosad at weeks 0, 3, and 6 displayed significantly reduced ant activities compared to plots treated solely during weeks 0 and 6, as well as control plots lacking HGB applications. Spinosad‐infused HGBs may offer an effective alternative to thiamethoxam‐infused HGBs for control of L. humile in California citrus orchards.

Revealing the Extent of Pesticide Runoff to the Surface Water in Agricultural Watersheds

Pesticides are beneficial in protecting crops from pests and improving agricultural productivity; however, concerns on pesticide pollution in water have increased due to their indiscriminate use and lack of adequate regulations. Many studies have focused on the risks of pesticides considering the limited number and types of pesticide residues in crops and soils, and duration, and very few have focused on surface water throughout the year. Therefore, this study comprehensively identified 308 pesticides in surface water samples collected monthly over one year in the Saemangeum Basin, Korea. Both targeted and non-targeted analyses were used to identify 171 and 24 pesticides, respectively. Results highlight the extensive extent of pesticide contamination. Among the quantified pesticides, bromobutide and pretilachlor consistently exhibited high concentrations and risk levels, as indicated by their elevated risk quotient (RQ) values. Seasonal variations in pesticide concentrations revealed distinct patterns with intensified herbicide use during summer and increased insecticide concentrations during autumn. This study highlights the presence, distribution, and associated ecological risks of pesticides in surface waters, emphasizing the necessity of comprehensive monitoring and regulatory measures to protect aquatic ecosystems. The high RQ values identified for specific pesticides underscore the urgent need to implement effective strategies to mitigate these environmental risks.

Pesticides in a temperate coastal lagoon in southwest Europe (Ria de Aveiro, Portugal) – Risk assessment and acute assays with Artemia and Daphnia

The Ria de Aveiro lagoon has been considered one of the most important Southern European long-term monitoring sites (LTER-site) concerning climate change and anthropogenic pollution. Nevertheless, studies concerning pesticide contamination herein are few and mostly outdated. Here, 56 pesticides dissolved in the aqueous phase (DAP) and suspended particulate matter (SPM) were examined to fill the knowledge gap, considering the hydrophobic nature of most evaluated compounds. Water samples were taken seasonally from eight sites, and both DAP and SPM fractions were analysed by gas-chromatography-mass spectrometry. The annual average concentrations of fungicides, herbicides and insecticides were ≈57 ng/L, ≈409 ng/L and ≈1058 ng/L in DAP and ≈7 μg/g, ≈28 μg/g and ≈67 μg/g in SPM. These pesticides and the excessive phosphate concentrations suggest that the lagoon's water quality may be hazardous to biota and humans. Invertebrates were identified as the most threatened trophic level using deterministic risk assessment, with chlorpyriphos and chlorfenvinphos being the primary culprits. Acute experiments with Artemia and Daphnia supported the suppositions.

Sublethal doses of insecticide reduce thermal tolerance of a stingless bee and are not avoided in a resource choice test.

Insecticides and climate change are among the multiple stressors that bees face, but little is known about their synergistic effects, especially for non-Apis bee species. In laboratory experiments, we tested whether the stingless bee Tetragonula hockingsi avoids insecticide in sucrose solutions and how T. hockingsi responds to insecticide and heat stress combined. We found that T. hockingsi neither preferred nor avoided sucrose solutions with either low (2.5 × 10-4 ng µl-1 imidacloprid or 1.0 × 10-4 ng µl-1 fipronil) or high (2.5 × 10-3 ng µl-1 imidacloprid or 1.0 × 10-3 ng µl-1 fipronil) insecticide concentrations when offered alongside sucrose without insecticide. In our combined stress experiment, the smallest dose of imidacloprid (7.5 × 10-4 ng) did not significantly affect thermal tolerance (CTmax). However, CTmax significantly reduced by 0.8°C (±0.16 SE) and by 0.5°C (±0.16 SE) when bees were fed as little as 7.5 × 10-3 ng of imidacloprid or 3.0 × 10-4 ng of fipronil, respectively, and as much as 1.5°C (±0.16 SE) and 1.2°C (±0.16 SE) when bees were fed 7.5 × 10-2 ng of imidacloprid or 3.0 × 10-2 ng of fipronil, respectively. Predictions of temperature increase, and increased insecticide use in the tropics suggest that T. hockingsi will be at increased risk of the effects of both stressors in the future.