Systemic Insecticides Research Articles

The impact of imidacloprid and its metabolites on long-term neurodevelopmental and neurodegenerative disorders in a Zebrafish model

This research aimed to assess the impact of lower dose, longer duration exposure of imidacloprid (IMI) on neurodevelopmental and neurodegenerative disorders in comparison to acute exposure within an in vivo zebrafish model. Sensitive, selective, accurate and efficient liquid chromatography tandem mass spectrometry (LC-MS/MS) methods were developed to quantitate bioaccumulation of IMI and its primary metabolites, as well as changes in neurotransmitter concentrations following IMI exposure. This study also assessed liver damage in response to imidacloprid administration as a measure of acute and chronic toxicity in a zebrafish larval model. Introduction: IMI [1-(6-chloro-3-pyridylmethyl)-N-nitroimidazolidin-2-ylideneamine] is a systemic neonicotinoid insecticide belonging to the chloronicotinyl nitroguanidine chemical family produced to replace the organophosphorus pesticides in commercial agriculture (Crosby EB et al. Neurotoxicol Teratol [Internet]. 2015;49:81–90) (Kumar A et al, Egypt J Forensic Sci [Internet]. 2013;3(4):123–6). The extensive use of these pesticides increases the risk to biodiversity of freshwater aquatic surroundings due to their potential bioaccumulation and toxicity (Muazzam B et al, J Water Supply Res Technol-AQUA. 2019;68(8):718–30). While pesticide usage has economic benefits in large-scale agriculture, exposure can lead to detrimental effects on humans. Researchers studying the effect of IMI on human nicotinic receptors (α4β2) have reported that IMI may have more substantial side effects on humans than originally anticipated (Li P et al, J Neurosci Res. 2011;89(8):1295–301). Zebrafish larvae were exposed to IMI at 4 and 5 days post fertilisation to determine the no observed adverse effect level (NOAEL) of IMI. Behavioural activity tracking of the zebrafish larvae was monitored using Daniovision software. Oil red O was used to stain for fatty liver accumulation (steatosis) which is indicative of hepatotoxicity following IMI exposure. After this, adult zebrafish were exposed to the NOAEL concentration for 21 days. Key endpoints included developmental effects, behaviour indicative of neuropathology, neurodegeneration and possible bioaccumulation in the adult zebrafish tissues (brain and liver). Neurotransmitter concentrations were measured in the adult zebrafish brain tissue at the end of the treatment period to evaluate changes in neurotransmitter signalling and potential neurodevelopmental effects using a LC-MS/MS method. Bioaccumulation of IMI and its metabolites in zebrafish brain and liver was evaluated using LC-MS/MS. The NOAEL of IMI in zebrafish larvae was determined to be 2.5 μg/L. Hepatotoxicity in the form of steatosis was observed in larvae subsequent to a 5-day treatment period. Adult zebrafish were exposed to the NOAEL IMI concentration for 21 days. No significant behavioural abnormalities were observed in the adult zebrafish during the treatment period. The calibration curve for the neurotransmitters fits a quadratic (weighted 1/C) regression over the concentration range of 3.906–1000 ng/mL, 7.813–1000 ng/mL, 15.625–1000 ng/mL and 31.250–1000 ng/mL for acetylcholine, serotonin, gamma-aminobutyric acid and dopamine, respectively. The calibration curve for IMI and its metabolites fits a quadratic (weighted 1/C) regression over the concentration range of 0.098–12.5 ng/mL, 0.195–12.5 ng/mL, 0.391–12.5 ng/mL and 0.781–12.5 ng/mL for desnitro-imidacloprid, imidacloprid, imidacloprid-urea and 5-hydro-imidacloprid, respectively. Robust LC-MS/MS methods were developed for the quantitation of IMI, desnitro-imidacloprid, imidacloprid-urea and 5-hydro-imidacloprid, as well as serotonin, dopamine, acetylcholine and gamma-aminobutyric acid neurotransmitters in 200 μl zebrafish brain and liver homogenate. These methods were used to observe changes in neurotransmitter signalling in response to low-level, long-term exposure to imidacloprid, even in the absence of behavioural changes. Furthermore, together with the evaluation of bioaccumulation of imidacloprid and its metabolites in the brain and liver of zebrafish, this study provides indications of impact on human health following chronic neonicotinoid exposure.

Sustainable alternative for removing pesticides in water: Nanomodified activated carbon produced from yeast residue biomass

The systemic insecticide thiamethoxam (TMX) has been frequently used with the need to intensify agricultural activities and food production. Given the pollution concern, biosorption emerges as an efficient and low-cost treatment. Thus, this work proposes to use the environmentally friendly activated carbon magnetic nanocomposite (YAC-NP) produced with yeast residues from the sugar-alcohol industry for the sorption of TMX in water. YAC-NP and its precursors (NP and YAC) were characterized by X-ray (XRD) and Fourier Transform Infrared (FTIR) spectroscopies to investigate their morphology and interaction with TMX. The Boehm titration informed the predominance of acidic character to YAC by the presence of carboxylic, lactone, and phenolic groups. The YAC-NP pH at the point of zero charge (pHPZC) was 6.05, and the best conditions for TMX sorption by YAC-NP occurred at the 2–7 pH range and 30 min of contact time. Sorption tests were performed using batch procedures at increasing concentrations of TMX (5–100 mg/L) and 1 g/L adsorbent dose. The experimental adsorption capacities (Qexp) for YAC, NP, and YAC-NP were 31.52 ± 1.69, 2.42 ± 0.54, and 12.50 ± 0.33 mg/g, respectively. TMX contents were determined by Ultraviolet–visible Spectroscopy (UV/Vis). The pseudo-2nd-order kinetic equation best fit the experimental data (r2 = 0.9996). Among the eight isotherm models applied to the experimental data, Hill, D-R, Temkin, Toth, and R–P were the models that best described the sorption process. YAC-NP reusability in TMX removal was assessed, and a decrease from 71.87 to 0.69% was observed after 10 adsorption cycles.

Effects of chronic exposure to the new insecticide sulfoxaflor in combination with a SDHI fungicide in a solitary bee

The recent EU ban of the three most widely used neonicotinoids (imidacloprid, thiamethoxam and clothianidin) to all outdoors applications has stimulated the introduction of new insecticides into the market. Sulfoxaflor is a new systemic insecticide that, like neonicotinoids, acts as a modulator of nicotinic acetylcholine receptors. In agro-environments, bees can be exposed to this compound via contaminated pollen and nectar for long periods of time. Therefore, it is important to assess the potential effects of chronic exposure to sulfoxaflor, alone and in combination with fungicides, on pollinators. In this study, we tested the effects of chronic exposure to two field concentrations of sulfoxaflor (20 and 100 ppb) alone and in combination with four concentrations of the fungicide fluxapyroxad (7500, 15,000, 30,000 and 60,000 ppb) on syrup consumption and longevity in females of the solitary bee Osmia bicornis L. Exposure to 20 ppb of sulfoxaflor, alone and in combination with the fungicide, stimulated syrup consumption, but did not affect longevity. In contrast, syrup consumption decreased in bees exposed to 100 ppb, all of which died after 2–6 days of exposure. We found no evidence of synergism between the two compounds at any of the two sulfoxaflor concentrations tested. Comparison of our findings with the literature, confirms that O. bicornis is more sensitive to sulfoxaflor than honey bees. Our results highlight the need to include different bee species in risk assessment schemes.

Reduction in residual cyantraniliprole levels in spinach after various washing and blanching methods.

Pesticides are used to protect crops from pests and diseases. However, as many pesticides are toxic to humans, it is necessary to assess methods that can remove pesticide residues from agricultural products before human consumption. Spinach is consumed immediately after a relatively simple washing and heating process in the Republic of Korea. Cyantraniliprole is used as a systemic insecticide during spinach cultivation, which means it might remain in the crop after processing. Consequently, it is important to assess whether residues can be reduced to levels that are harmless to the human body after processing. This study investigated lowering the residual cyantraniliprole levels in spinach after washing and blanching. The amount of cyantraniliprole residue in the spinach samples sprayed with cyantraniliprole during cultivation was analyzed using ultrahigh-performance liquid chromatography-tandem mass spectrometry (UHPLC–MS/MS). The time of each washing and blanching method was set at 1, 3, and 5 min. The residual levels of cyantraniliprole decreased by 15.1–54.6% and 60.1–93.5% based on the washing and blanching methods employed. The most effective washing method to lower residual cyantraniliprole levels was steeping with a neutral detergent, resulting in cyantraniliprole reduction by 42.9–54.6%. When spinach was blanched after steeping washing with a neutral detergent, the largest removal rates of 77.9 and 91.2% were observed after 1 and 3 min of blanching, respectively. Blanching for 5 min after steeping and running washing exhibited the highest reduction rate of 93.5%. Therefore, a considerable amount of cyantraniliprole residue in spinach could be removed by washing or blanching. Based on the results of this study, blanching after steeping washing can be implemented as an effective method of lowering pesticide concentrations in spinach and other crops, thereby reducing their potential toxicity to humans upon consumption.

Toxicity of Formulated Systemic Insecticides Used in Apple Orchard Pest Management Programs to the Honey Bee (Apis mellifera (L.))

Honey bees (Apis mellifera) are one of the most important pollinating species of flowering plants. Recently, populations of honey bees have been declining due to a combination of factors, including the widespread use of agricultural pesticides. Laboratory studies were conducted to determine the acute oral toxicity of different formulated pesticides to honey bee adults. In particular, we assessed the acute oral toxicity of two neonicotinoids (acetamiprid, Assail 30SG and thiamethoxam, Actara 25WDG) and two other systemic insecticide products (sulfoxaflor, Closer 2SC and flupyradifurone, Sivanto 200SL), all of which are generally used in pest management programs in commercial apple orchards in the Eastern United States. Honey bees were fed a range of doses of each pesticide in order to create a response curve, and LC50, LC90, and LD50 values were determined. The pesticide formulation containing flupyradifurone as the active ingredient was found to be the least toxic to honey bees followed by the formulations containing sulfoxaflor and acetamiprid. The toxicity values obtained in this study differ from other studies testing only technical active ingredient compounds, suggesting the need to evaluate formulated products while conducting ecotoxicological risk assessment.

Persistence of cyantraniliprole in sandy loam soil and effect of organic manure amendment

The persistence of cyantraniliprole, a new systemic insecticide of the class anthracitic diamide, was studied under the laboratory conditions in sandy loam soil and the soil amended with farmyard manure (0.5%), after spiking at 1, 2 and 4 ?g kg-1 levels in three different soil moisture regimes viz. air dry, field capacity level and also in saturated conditions. Degradation was comparatively faster in saturated than at field capacity and air dry condition. There was an increase in the persistence with increase in the spiking concentration. The persistence of cyantraniliprole was dependent on soil moisture condition, organic matter content and concentration of cyantraniliprole used.

Management of Sucking Pests of early Season Cotton by Application of different Seed and Soil Insecticides in Pakistan

Cotton is cash crop of Pakistan and sucking insect pests are serious issue especially in early cotton season. To cope with the issue, a field experiment was conducted to investigate the post emergence effectiveness of two seed and two soil applied insecticides on populations’ development of sucking insect pests in cotton. The seed applied insecticides i.e. Imidacloprid (Confidor 70 WS) and Thiamethoxam (Actara 70 WS) were applied to the seed before sowing. Two granular insecticides i.e. Aldicarb (Temik 10 G) and Carbaryl (Sevin 10 D) were applied in furrows with a modified applicator that was calibrated to deliver the desired rate. The results showed that all the tested insecticides were very effective in controlling the targeted sucking insect pests i.e. thrips, whiteflies and jassids as compared to untreated cotton. Conversely, the seed applied insecticides i.e. Imidacloprid and Thiamethoxam showed more effectiveness compared to soil applied granular insecticides i.e. Aldicarb and Carbaryl in reducing sucking pests’ populations. Such systemic insecticides applied as treated seed can be present in sufficient quantity in germinating plants leading to toxicity to pests, and helpful for safety of natural enemies. The population trends of the three principal sucking insect pests namely thrip, whitefly and jassid were varied significantly over the study months thereby indicating that the population build up was favoured by certain factors. Consequently, the use of seed applied insecticides can be a major component to put into practice in the integrated pest management technology of cotton.

Phylogenomic and functional characterization of an evolutionary conserved cytochrome P450-based insecticide detoxification mechanism in bees

The regulatory process for assessing the risks of pesticides to bees relies heavily on the use of the honeybee, Apis mellifera, as a model for other bee species. However, the validity of using A. mellifera as a surrogate for other Apis and non-Apis bees in pesticide risk assessment has been questioned. Related to this line of research, recent work on A. mellifera has shown that specific P450 enzymes belonging to the CYP9Q subfamily act as critically important determinants of insecticide sensitivity in this species by efficiently detoxifying certain insecticide chemotypes. However, the extent to which the presence of functional orthologs of these enzymes is conserved across the diversity of bees is unclear. Here we used a phylogenomic approach to identify > 100 putative CYP9Q functional orthologs across 75 bee species encompassing all major bee families. Functional analysis of 26 P450s from 20 representative bee species revealed that P450-mediated detoxification of certain systemic insecticides, including the neonicotinoid thiacloprid and the butenolide flupyradifurone, is conserved across all major bee pollinator families. However, our analyses also reveal that CYP9Q-related genes are not universal to all bee species, with some Megachilidae species lacking such genes. Thus, our results reveal an evolutionary conserved capacity to metabolize certain insecticides across all major bee families while identifying a small number of bee species where this function may have been lost. Furthermore, they illustrate the potential of a toxicogenomic approach to inform pesticide risk assessment for nonmanaged bee species by predicting the capability of bee pollinator species to break down synthetic insecticides.

Effectiveness of Flonicamid 50 wg against Bemisia tabaci (Genn.) under greenhouse conditions in Tunisia.

Flonicamid is a systemic insecticide that acts as a feed blocker with potential use against whiteflies in an IPM program. The efficacy of flonicamid against populations of Bemisia tabaci in geothermal greenhouses in southern Tunisia. Flonicamid was tested in irrigation and foliar spraying on a greenhouse tomato crop. The use of the insecticide in irrigation or foliar spraying showed significant insecticidal activity on eggs, larvae and adults of B. tabaci. They are comparable to those caused by the reference insecticide confidor and different from those of the control on the different stages of development of B. tabaci. It is advisable to use flonicamid in an integrated pest management program in a heated greenhouse.

The endoplasmic reticulum-mitochondrial crosstalk is involved in the mitigation mechanism of eucalyptol on imidacloprid toxicity in Ctenopharyngodon idellus kidney cells

Imidacloprid (IMI), a systemic neonicotinoid insecticide widely used in agriculture, resulting in persistence in aquatic environments that threaten the survival of organisms. Eucalyptol (EUC), a monoterpenoid found in plants, can be applied to medicine, food, and aquaculture. However, the potential protective effects of EUC on cell damage under neonicotinoid pesticide toxicity, and the role of ER stress and its mediated apoptosis and necroptosis in it, remain unclear. Therefore, we treated Ctenopharyngodon idellus kidney (CIK) cells with 20 mg/L IMI and 20 μM EUC for 48 h. The results showed that IMI exposure caused a higher GRP78 levels, activated ATF6, PERK-eIF2α and IRE1-XBP1 pathways, led to the decline of ATPase activities and ATP content, induced the expression of cytokine (TNF-α, IL-1β, IL-6 and INF-γ), triggered BCL2/BAX-mediated apoptosis and RIP1/RIP3/MLKL-dependent necroptosis in the CIK cell line. Surprisingly, EUC had an effect against IMI-induced cytotoxicity, showing that it effectively mitigated the above-mentioned IMI-exposure-induced changes. Taken together, these results suggested that EUC could alleviated IMI-induced cell death and dysimmunity by recovering ER stress/mitochondria imbalance. These results partly explained the mechanism of biological threat on fish under IMI exposure and the potential application value of EUC in aquaculture.

Exposure to the novel insecticide flupyradifurone impairs bumblebee feeding motivation, learning, and memory retention

Bees are vital pollinators of crops and wildflowers and as such, wild bee declines threaten food security and functioning ecosystems. One driver of bee declines is the use of systemic insecticides, such as commonly used neonicotinoids. However, rising pest resistance to neonicotinoids, and restrictions on their use in the EU, has increased the demand for replacement insecticides to control crop pests. Flupyradifurone is a novel systemic insecticide that is thought to be relatively ‘bee safe’ although it can be present in the nectar and pollen of bee-attractive crops. Bumblebees rely on learning to forage efficiently, and thus detriments to learning performance may have downstream consequences on their ability to forage. While neonicotinoids negatively influence bumblebee learning and memory, whether this is also the case for their replacements is unclear. Here, we exposed bumblebees (Bombus impatiens) to an acute, field-realistic dose of flupyradifurone before training them to learn either an olfactory or colour association. We found that flupyradifurone impaired bumblebees' learning and memory performance in both olfactory and visual modalities. Flupyradifurone-treated bees were also less motivated to feed. Given the similarity between the detriments to cognition found here and those previously reported for neonicotinoids, this implies that these insecticides may have similar sub-lethal effects on bees. Restrictions on neonicotinoid use are therefore unlikely to benefit bees if novel insecticides like flupyradifurone are used as an alternative, highlighting that current agrochemical risk assessments are not protecting bees from the unwanted consequences of pesticide use. Sub-lethal assessments on non-Apis bees should be made mandatory in agrochemical regulation to ensure that novel insecticides are indeed ‘bee safe’.

The pest control and pollinator protection dilemma: The case of thiamethoxam prophylactic applications in squash crops

A major challenge in sustainable agriculture is finding solutions to manage crop-damaging pests such as herbivores while protecting beneficial organisms such as pollinators. Squash is a highly pollinator-dependent crop that is also attractive to herbivores like the striped cucumber beetle. While synthetic insecticides can provide control of insect pests, they can also affect non-target organisms such as pollinators. Thus, growers need to balance pest management with pollinator protection to ensure optimal yield. Thiamethoxam is a commonly used systemic insecticide that translocates throughout plants, leaving residues in nectar and pollen. The aim of this study was to evaluate whether there are uses of this insecticide that provides efficient pest control while minimizing pesticide pollinator exposure. Specifically, we tested how different prophylactic application methods (seed treatments, in-furrow applications, and early foliar sprays) of commercially available thiamethoxam products impact pest control, bee visitation, yield, and pesticide residues in flowers of squash crops. We found that among the different methods of thiamethoxam application, in-furrow application best prevented defoliation and resulted in the highest fruit weight and number. However, it also produced the most frequent and highest concentrations of thiamethoxam in nectar and pollen, reaching lethal levels for squash bees. Our study provides evidence that under current application methods, thiamethoxam does not provide a sustainable solution for squash growers and further research is required on more efficient pesticide delivery methods, as well as non-pesticide pest control measurements.

Neuroprotective Effect of N-acetylcysteine Against Monocrotophos-Induced Oxidative Stress in Different Brain Regions of Rats.

Monocrotophos (MCP) is systemic organophosphate insecticide used against crop pests. It is reported to cause mammalian toxicity through both acute and chronic exposure. In the present study, we have shown the protective role of N-acetylcysteine (NAC) against MCP-induced oxidative stress in frontal cortex, corpus striatum and hippocampus brain regions of rats. Male Albino Wistar rats were divided into control, NAC-treated, MCP and NAC + MCP-treated groups. An oral dose of MCP (0.9mg/kg b.wt) and NAC (200mg/kg b.wt) was administered for 28days. Results showed an increase in lipid peroxidation (LPO) and protein oxidation followed by decreased antioxidant enzymes after 28days of MCP exposure. Histopathological analysis showed that monocrotophos exposure caused neurodegenerative changes as evident by neurons with dystrophic changes in the form of shrunken hyperchromatic nuclei in all the regions of the rat brain. N-acetylcysteine supplementation to MCP-treated rats showed a reduction in oxidative stress and ameliorated cellular alterations in all of the three regions. The results of the study indicate that N-acetylcysteine offers neuroprotection by improving antioxidant response and decreasing oxidative stress in different regions of the rat brain.

Effectiveness of insecticides against pests of white cabbage grown using seedling technology

Among the two methods of growing white cabbage, the seedling technology is more widely used in North-Western Russia. Watering seedlings in cassettes with a systemic formulation of neonicotinoid insecticide Actara, WDG (250 g/kg thiamethoxam) prior to planting has been developed to protect white cabbage from early spring pests: flea beetles of the genus of Phyllotreta and the cabbage root fly. This approach is widely used by commercial growers and its efficacy requires monitoring under current conditions because of a possibility of resistance development. Testing Actara, WDG in 2019 and 2021 at the experimental field of All-Russian Institute of Plant Protection didn’t show any significant decrease of biological effectiveness of seedling treatment. Testing biological effectiveness of systemic insecticides belonging to the chemical class of carbamates Lannate, WSP (250 g/kg metomil) and the new class isoxazolines isocycloseram was carried out in parallel. Biological effectiveness of the latter insecticide was higher compared to Actara against the flea beetles and the cabbage root fly during a 21-day period. In addition, plant infestation with diamondback moth decreased. Efficacy indices of Lannate were significantly lower. Isocycloseram shows a good potential for inclusion into the Index of Registered Formulations of the Russian Federation to protect cabbage against a complex of insect pests. Having an additional active ingredient available to farmers will be begenicial for developing rotation schemes to combat pest resistance.

Potential Use of Chitosan-TiO2 Nanocomposites for the Electroanalytical Detection of Imidacloprid.

The detection of toxic insecticides is a major scientific and technological challenge. In this regard, imidacloprid is a neonicotinoid that is a systemic insecticide that can accumulate in agricultural products and affect human health. This work aims to study the properties of chitosan–TiO2 nanocomposites in which nanoparticles with high surface area serve as molecular recognition sites for electroanalytical imidacloprid detection. We show that the best sensitivity to imidacloprid was obtained using a modified electrode with a chitosan–TiO2 nanocomposite with a 40 wt.% of TiO2 nanoparticles. By using a three-phase effective permittivity model which includes chitosan, TiO2, an interface layer between nanoparticles and a matrix, we showed that nanocomposites with 40 wt.% of TiO2 the interface volume fraction reaches a maximum. At higher nanoparticle concentration, the sensitivity of the sensor decreases due to the decreasing of the interface volume fraction, agglomeration of nanoparticles and a decrease in their effective surface area. The methodology presented can be helpful in the design and optimization of polymer-based nanocomposites for a variety of applications.

Field mixtures of currently used pesticides in agricultural soil pose a risk to soil invertebrates

Massive use of pesticides in conventional agriculture leads to accumulation in soil of complex mixtures, triggering questions about their potential ecotoxicological risk. This study assessed cropland soils containing pesticide mixtures sampled from conventional and organic farming systems at La Cage and Mons, France. The conventional agricultural field soils contained more pesticide residues (11 and 17 versus 3 and 11, respectively) and at higher concentrations than soils from organic fields (mean 6.6 and 10.5 versus 0.2 and 0.6 μg kg−1, respectively), including systemic insecticides belonging to neonicotinoids, carbamate herbicides and broad-spectrum fungicides mostly from the azole family. A risk quotient (RQi) approach evaluated the toxicity of the pesticide mixtures in soil, assuming concentration addition. Based on measured concentrations, both conventional agricultural soils posed high risks to soil invertebrates, especially due to the presence of epoxiconazole and imidacloprid, whereas soils under organic farming showed negligible to medium risk. To confirm the outcome of the risk assessment, toxicity of the soils was determined in bioassays following standardized test guidelines with seven representative non-target invertebrates: earthworms (Eisenia andrei, Lumbricus rubellus, Aporrectodea caliginosa), enchytraeids (Enchytraeus crypticus), Collembola (Folsomia candida), oribatid mites (Oppia nitens), and snails (Cantareus aspersus). Collembola and enchytraeid survival and reproduction and land snail growth were significantly lower in soils from conventional compared to organic agriculture. The earthworms displayed different responses: L. rubellus showed higher mortality on soils from conventional agriculture and large body mass loss in all field soils, E. andrei showed considerable mass loss and strongly reduced reproduction, and A. caliginosa showed significantly reduced acetylcholinesterase activity in soils from conventional agriculture. The oribatid mites did not show consistent differences between organic and conventional farming soils. These results highlight that conventional agricultural practices pose a high risk for soil invertebrates and may threaten soil functionality, likely due to additive or synergistic “cocktail effects”.

Impact of insecticide programs on pests, the predatory mite Phytoseiulus persimilis, and staked tomato profitability.

Various insecticides are available to manage diverse pest complexes in commercial vegetable production, but knowledge gaps exist regarding their overall performance in pest suppression, profitability, and compatibility with biological control. We conducted trials in staked tomatoes in western North Carolina in 2017-2018 to compare how different insecticide programs managed key pests and their interactions with Phytoseiulus persimilis Athias-Henriot, a predator of the twospotted spider mite (TSSM, Tetranychus urticae Koch). Treatments compared no insecticides to broad-spectrum ('hard') foliar applications, selective ('soft') foliar applications, and to chemigation of selective systemic insecticides. Treatment efficacy was based on pest control, net profitability, and Environmental Impact Quotient (EIQ) ratings comparing environmental and human health risks. All programs similarly suppressed aphids, while flower thrips and flea beetle populations were low and unaffected by program. Only the 'hard' foliar program suppressed TSSM (including P. persimilis), which quickly rebounded. This program inhibited biological control, and eventual TSSM suppression was likely caused by P. persimilis immigrating from nearby plots. All programs were generally equivalent in reducing fruit damage. Net profits were similar among insecticide programs, which were significantly greater than in untreated plots. Yield and profit trends were similar both years, but impacted by record flooding in 2018. Safer and more selective chemigation and 'soft' foliar programs were as effective and economical as the 'hard' foliar program, while also conserving biological control. These results support existing research demonstrating that improved insecticide use can be integrated with biological control for more profitable and environmentally sustainable vegetable production. © 2022 Society of Chemical Industry.

Effects of systemic insecticides against emerald ash borer on ash seed resources

Emerald ash borer (EAB), Agrilus planipennsis, is an invasive insect that was accidentally introduced to North America from Asia. It continues to spread rapidly across North America and is responsible for the death of tens of millions of ash trees (Fraxinus spp.). All North American species of ash are susceptible to EAB infestation threatening the ash resource and diversity. Measures such as systemic insecticide treatments in urban forests and collection of ash seeds provide a means of conserving genetic resources. Understanding the effect these insecticides could have on ash seed viability is therefore important to informing conservation efforts. Another potential concern for effective conservation of ash seeds is the ash seed weevil (Lignyodes spp.) whose larvae develop in and feed on ash seeds. However, the effect of EAB insecticides on weevil infestation levels in ash seeds has not been investigated to date. Our study investigated the effect of two systemic insecticide treatments, azadirachtin and emamectin benzoate, on levels of ash seed weevil infestation, seed germination ability, and seed germination time of seeds collected from boulevard trees of green ash (F. pennsylvanica Marsh.) in cities in Minnesota from 2017 to 2019. Weevil infestation levels were similar between untreated and treated trees in 2017 and 2018. In 2019, the weevil prevalence in untreated trees was on average 17% and 30% higher than in azadirachtin and emamectin benzoate-treated trees respectively. Weevil infestation data suggests that repeated insecticide treatments at labelled rates can reduce seed weevils that target germplasm. Additionally, insecticide treatments did not affect ash seed germination rates between treatments. These results suggest that systemic insecticides may be effective at conserving the seed resource in addition to known benefits such as canopy preservation.

Temporal and spatial patterns of systemic insecticides in avian and insect pollinators and flowers in western Canada (2018, 2019)

Increasing awareness of the global impact of systemic insecticides on ecosystems prompted us to examine the spatial and temporal contamination of avian and insect pollinators and their floral resources within blueberry growing seasons in the Fraser River valley in BC, Canada where a mixture of urban, suburban and agricultural areas exist. We measured six systemic current-use insecticides in flowers, hummingbirds, honey bee (Apis mellifera) nectar, and honey sampled in April through July, 2018 and 2019, at 13 sites located 0.16 to 22.8 km from conventionally sprayed blueberry fields (CSBF). Across this landscape, there was widespread contamination in all of these media with mixtures of insecticides detected throughout the study period. The number of compounds detected in wildlife significantly increased with proximity to CSBFs. The mean concentrations of insecticides were highest in media collected near to CSBFs however there were no significant spatial or temporal patterns except that there were significantly higher concentrations of flupyradifurone (FPF) in flowers in 2018. The results indicate substantial pesticide exposure continues throughout the growing season and the Fraser valley in flowers, hummingbirds, and bees. The imidacloprid concentrations detected exceeded sublethal effect levels in honey bees. The combined concentrations and chronic presence of neonicotinoids are of concern for hummingbird health. However, the butenolide, flupyradifurone, was detected at the highest concentrations in all media but the effect level in wildlife is unknown. Concentration of 10.7 ng/ml FPF in hummingbirds was an order of magnitude above the maximum imidacloprid detected (0.43 ng/ml).

Effect of the Systemic Neonicotinoid Insecticide Dinotefuran on Leaf-level Photosynthesis in Loblolly Pine (Pinus taeda)

ABSTRACT Bark beetles (Coleoptera: Curculionidae: Scolytinae) are a common pest in loblolly pine (Pinus taeda L.) plantations, and climate intensification threatens to increase the range of bark beetle infestation and vulnerability of loblolly pine. New insecticides and management options are needed to maintain loblolly pine plantation productivity, mitigating increased bark beetle risk. The systemic neonicotinoid insecticide dinotefuran (Safari 20SG systemic insecticide, Valent USA, LLC), is utilized by nursery managers to protect loblolly pine from bark beetles, but there is little published literature on the insecticide’s potential phytotoxicity. The objective of this study was to evaluate the effect of dinotefuran on the leaf-level photosynthesis of three loblolly pine genotypes. Dinotefuran was applied to lower tree boles, and photosynthetic measurements occurred two months later. Dinotefuran did not significantly impact leaf-level gross photosynthesis (Pgmax), light-saturated net photosynthesis (Pnet) or dark respiration (Rd); nor was there any significant genotypic variation in responses. Dinotefuran appears to be a promising insecticide for bark beetle prevention without risk of foliar toxicity.