Biorational substitution of piperonyl butoxide in organic production: effectiveness of vegetable oils as synergists for pyrethrums

Field agrochemical exposure impacts locomotor activity in wild bumblebees

Agricultural intensification has been identified as one of the key causes of global insect biodiversity losses. These losses have been further linked to the widespread use of agrochemicals associated with modern agricultural practices. Many of these chemicals are known to have negative sublethal effects on commercial pollinators, such as managed honeybees and bumblebees, but less is known about the impacts on wild bees. Laboratory-based studies with commercial pollinators have consistently shown that pesticide exposure can impact bee behavior, with cascading effects on foraging performance, reproductive success, and pollination services. However, these studies typically assess only one chemical, neglecting the complexity of real-world exposure to multiple agrochemicals and other stressors. In the summer of 2020, we collected wild-foraging workers of the common eastern bumblebee, Bombus impatiens, from five squash (Cucurbita) agricultural sites (organic and conventional farms), selected to represent a range of agrochemical, including neonicotinoid insecticide, use. For each bee, we measured two behaviors relevant to foraging success and previously shown to be impacted by pesticide exposure: sucrose responsiveness and locomotor activity. Following behavioral testing, we used liquid chromatography-tandem mass spectrometry (LC-MS/MS) chemical analysis to detect and quantify the presence of 92 agrochemicals in each bumblebee. Bees collected from our sites did not vary in pesticide exposure as expected. While we found a limited occurrence of neonicotinoids, two fungicides (azoxystrobin and difenoconazole) were detected at all sites, and the pesticide synergist piperonyl butoxide (PBO) was present in all 123 bees. We found that bumblebees that contained higher levels of PBO were less active, and this effect was stronger for larger bumblebee workers. While PBO is unlikely to be the direct cause of the reduction in bee activity, it could be an indicator of exposure to pyrethroids and/or other insecticides that we were unable to directly quantify, but which PBO is frequently tank-mixed with during pesticide applications on crops. We did not find a relationship between agrochemical exposure and bumblebee sucrose responsiveness. To our knowledge, this is the first evidence of a sublethal behavioral impact of agrochemical exposure on wild-foraging bees.

P450 gene CYP6a13 is responsible for cross-resistance of insecticides in field populations of Spodoptera frugiperda

Continuous and long-term use of traditional and new pesticides can result in cross-resistance among pest populations in different fields. Study on the mechanism of cross-resistance and related genes will help resistance management and field pest control. In this study, the pesticide-resistance mechanism in Spodoptera frugiperda (FAW) was studied with field populations in 3 locations of South China. Field FAW populations were highly resistant to traditional insecticides, chlorpyrifos (organophosphate) and deltamethrin (pyrethroid), and had higher levels of cytochrome P450 activity than a non-resistant laboratory strain. Inhibition of P450 activity by piperonyl butoxide significantly increased the sensitivity of resistant FAW in 3 locations to chlorpyrifos, deltamethrin and chlorantraniliprole (amide), a new type of insecticide, suggesting that P450 detoxification is a critical factor for insecticide resistance in field FAW populations. Transcriptomic analysis indicated that 18 P450 genes were upregulated in the field FAW populations collected in 3 regions and in 2 consecutive years, with CYP6a13, the most significantly upregulated one. Knockdown of CYP6a13 messenger RNA by RNA interference resulted in an increased sensitivity to the 3 tested insecticides in the field FAW. Enzyme activity and molecular docking analyses indicated that CYP6a13 enzyme was able to metabolize the 3 tested insecticides and interact with 8 other types of insecticides, confirming that CYP6a13 is a key cross-resistance gene with a wide range of substrates in the field FAW populations across the different regions and can be used as a biomarker and target for management of FAW insecticide resistance in fields.

Occurrence, distribution, and translocation of legacy and current-use pesticides in pomelo orchards in South China

Pomelo (Citrus grandis) is a highly popular and juicy member of the citrus family. However, little is known regarding the occurrence and distribution of pesticides in pomelo. In this study, we determined the levels of legacy (n = 25) and current-use pesticides (n = 2) in all parts of pomelo (i.e., epicarp, mesocarp, endocarp, pulp, and seed) and paired soil and leaf samples collected from two pomelo orchards in South China. At least one target pesticide was detected in the pomelo fruit, soil, and leaf samples, indicating that these pesticides were ubiquitous. The spatial distribution of the total concentration of pesticides in the pomelo parts was in the order of epicarp (216 ng/g) > mesocarp (9.50 ng/g) > endocarp (4.40 ng/g) > seed (3.80 ng/g) > pulp (1.10 ng/g), revealing different spatial distributions in pomelo. Principal component analysis was performed based on the concentrations of the target pesticides in the pulp and paired samples of epicarp, leaf, topsoil, and deep soil to examine the translocation pathway of the pesticides in pomelo. Close correlations were found among the target pesticides, and the pesticides in the pulp were mainly transferred from the epicarp, topsoil, or deep soil. We also explored the factors that affected such transport and found that the main translocation pathway of the non-systemic pesticide (i.e., buprofezin) into the pulp was the epicarp, whereas the systemic pesticide (i.e., pyriproxyfen) was mainly derived from the soil. The cumulative chronic dietary risks of all the pesticides resulting from pomelo consumption were much lower than the acceptable daily intake values for the general population. However, the prolonged risk of exposure to these pesticides should not be underestimated. The potential health risks posed by legacy and current-use pesticides, which are widely and frequently utilized, should be given increased attention.

Long-Chain Molecules with Agro-Bioactivities and Their Applications

Long-chain molecules play a vital role in agricultural production and find extensive use as fungicides, insecticides, acaricides, herbicides, and plant growth regulators. This review article specifically addresses the agricultural biological activities and applications of long-chain molecules. The utilization of long-chain molecules in the development of pesticides is an appealing avenue for designing novel pesticide compounds. By offering valuable insights, this article serves as a useful reference for the design of new long-chain molecules for pesticide applications.

Transcriptomics and Metabolomics for Co-Exposure to a Cocktail of Neonicotinoids and the Synergist Piperonyl Butoxide

Here, the transcriptomics and metabolomics on a model of exposure to a cocktail of neonicotinoids (Neo) containing seven commercial compounds and a synergist piperonyl butoxide (PBO) were established. The results showed that Neo and PBO disrupted mRNA and metabolite levels in a dose-dependent manner. Neo caused tryptophan pathway-related neurotoxicity, reduced lipolysis, and promoted fat mass accumulation in the liver, while PBO induced an increase in inflammatory factors and damage to intercellular membranes. Co-exposure enhanced Neo-induced liver steatosis, focal necrosis, and oxidative stress by inhibiting oxidative phosphorylation (OXPHOS). Furthermore, diglycerides and metabolic biomarkers demonstrated that the activation of insulin signaling is associated with restricted OXPHOS, which commonly leads to a high risk of non-alcoholic fatty liver disease (NAFLD) and Alzheimer's disease (AD) as the result of over-synthesis of lipids, low energy supply, and high thermogenesis. The study demonstrates that chronic disease can be induced by Neo and the synergist PBO at the molecular level.

Piperonyl butoxide, a synergist of pesticides can elicit male-mediated reproductive toxicity

A semi-synthetic methylenedioxyphenyl compound piperonyl butoxide (PBO) has been used as a ubiquitous synergist to increase the insecticidal effect of pesticides for agricultural and household use. Despite previously demonstrated effects of PBO, the detailed mechanism of PBO in spermatozoa and reproductive toxic effects on male germ cells have not been fully elucidated. Therefore, this study evaluated the effects of PBO on various sperm functions during capacitation and clarified the mechanisms of reproductive toxic effects on male fertility at different concentrations of PBO (0.1, 1, 10, and 100 μM). Sperm motility and kinematics were assessed using computer-assisted sperm analysis and the status of capacitation was evaluated using combined H33258/chlortetracycline (CTC) staining. Intracellular adenosine triphosphate (ATP) and cell viability levels were also measured. In addition, protein kinase A (PKA) activity and protein tyrosine phosphorylation were evaluated. In addition, in vitro fertilization was performed to determine the effects of PBO on cleavage and blastocyst formation rates. We found that PBO significantly decreased sperm motility, kinematics, and acrosome-reacted and capacitated spermatozoa. In addition, PBO suppressed the intracellular ATP levels and directly affected cell viability. Moreover, PBO detrimentally decreased the activation of PKA and altered the levels of tyrosine-phosphorylated proteins. Consequently, cleavage and blastocyst formation rates were significantly reduced in a dose-dependent manner. In line with our observations, the synergist of pesticides PBO may directly and/or indirectly cause disorder in male fertility. Hence, we suggest that careful attention is made to consider reproductive toxicity when using PBO as a synergist.

Mycotoxins, Pesticide Residues, and Heavy Metals Analysis of Croatian Cereals

Cereals are still one of the most important food and feed sources, thus determining cereal’s safety, i.e., compliance with legislation, is extremely important. As systematic investigations of nowadays unavoidable secondary fungal metabolites and other common legally regulated contaminants occurrence in Croatian cereals are still lacking, this research aims to monitor the contamination levels of nation-wide crops by mycotoxins, pesticide residues, and heavy metals by employing UHPLC-MS/MS, GC-MS/MS, and atomic absorption spectrometer (AAS) validated analytical methods. The most common secondary fungal metabolites were found to be Fusarium mycotoxins, with DON being the most occurring present in 73.7% of the samples. At least one pesticide residue was found in 331.8% of the samples, and Hg and Cd were the most occurring heavy metals. A total of 8.5% of the samples was non-compliant to the European Union (EU) legislation for food regarding the found mycotoxins concentrations, 4.5% regarding pesticide residues and none regarding heavy metals. The unusual presence of certain pesticide residue and heavy metal indicates the importance of systematic control of the contaminant presence, in order to gather enough occurrence data for proper risk assessment that these contaminants represent for the consumer’s health.