Tebuconazole and myclobutanil are two widely used triazole fungicides, both comprising two enantiomers with different fungicidal activity. However, their non-target toxicity and environmental ...behavior with respect to enantioselectivity have received limited attention. In the present study, tebuconazole and myclobutanil enantiomers were isolated and used to evaluate the occurrence of enantioselectivity in their acute toxicity to three non-target organisms (Scenedesmus obliquus, Daphnia magna, and Danio rerio). Significant differences were found: R-(-)-tebuconazole was about 1.4-5.9 times more toxic than S-(+)-tebuconazole; rac-myclobutanil was about 1.3-6.1 and 1.4-7.3 more toxic than (-)-myclobutanil and (+)-myclobutanil, respectively. Enantioselectivity was further investigated in terms of fungicide degradation in seven soil samples, which were selected to cover a broad range of soil properties. In aerobic or anaerobic soils, the S-(+)-tebuconazole degraded faster than R-(-)-tebuconazole, and the enantioselectivity showed a correlation with soil organic carbon content. (+)-Myclobutanil was preferentially degraded than (-)-myclobutanil in aerobic soils, whereas both enantiomers degraded at similar rates in anaerobic soils. Apparent correlations of enantioselectivity with soil pH and soil texture were observed for myclobutanil under aerobic conditions. In addition, both fungicides were configurationally stable in soils, i.e., no enantiomerization was found. Enantioselectivity may be a common phenomenon in both aquatic toxicity and biodegradation of chiral triazole fungicides, and this should be considered when assessing ecotoxicological risks of these compounds in the environment.
Natural products are a source of many novel compounds with biological activity for the discovery of new pesticides and pharmaceuticals. Quinoxaline is a fused
-heterocycle in many natural products ...and synthetic compounds, and seven novel quinoxaline derivatives were designed and synthesized
three steps. Pesticidal activities of title quinoxaline derivatives were bioassayed. Most of these compounds had herbicidal, fungicidal, and insecticidal activities. The compounds 2-(6-methoxy-2-oxo-3-phenylquinoxalin-1(2
)-yl)acetonitrile (
) and 1-allyl-6-methoxy-3-phenylquinoxalin-2(1
)-one (
) were the most active herbicides and fungicides. Mode-of-action studies indicated that
is a protoprophyrinogen oxidase-inhibiting herbicide. Compound
also possessed broad-spectrum fungicidal activity against the plant pathogen
species. Some of these compounds also had insecticidal activity. Molecular docking and DFT analysis can potentially be used to design more active compounds.
Many compounds derived from living organisms have found a use in crop protection. These compounds have formed the basis of chemical synthesis programmes to derive new chemical products; they have ...been used to identify new biochemical modes of action that can be exploited by industry-led discovery programmes; some have been used as starting materials for semi-synthetic derivatives; and many have been used or continue to be used directly as crop protection agents. This review examines only those compounds derived from living organisms that are currently used as pesticides. Plant growth regulators and semiochemicals have been excluded from the review, as have living organisms that exert their effects by the production of biologically active secondary metabolites.
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Quinone outside inhibitors (QoIs) are one of the major agricultural fungicide groups used worldwide. However, the development of resistance by different pathogenic species associated ...with specific mutation at the target gene site is becoming a critical issue for the sustainable use of QoIs. The authors aimed to design a novel QoI molecule to overcome the aforementioned issue. A rational approach to avoid steric hindrance between the QoI molecule and the mutated target site was successfully employed. The resulting compound, metyltetraprole, is characterized by 3-substituted central ring with a tetrazolinone moiety, the key structure to retain potent activity against QoI-resistant mutants. Metyltetraprole is a promising new fungicide under commercial development, and its development in this study has paved the way to overcoming resistance to QoI fungicides.
Greenhouse studies were conducted to evaluate the dissipation rate kinetics and estimate the behavior of selected pesticides after washing, peeling, simmering, and canning of tomato expressed as ...processing factor (PF). Two varieties (
Marissa
and
Harzfeuer
) were treated by six fungicides: azoxystrobin, boscalid, chlorothalonil, cyprodinil, fludioxonil, and pyraclostrobin at single and double dose and risk assessment defined as hazard quotient was performed. The QuEChERS method was used for sample preparation followed by liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS). The dissipation of fungicides approximately fitted to a first-order kinetic model, with half-life values ranging from 2.49 and 2.67 days (cyprodinil) to 5.00 and 5.32 days (chlorothalonil) for Marissa and Harzfeuer variety, respectively. Results from processing studies showed that treatments have significant effects on the removal of the studied fungicides for both varieties. The PFs were generally less than 1 (between 0.01 and 0.90) and did not depend on variety. The dietary exposure assessed based on initial deposits of application at single and double dose on tomatoes and concentration after each process with PF correction showed no concern to consumer health. Our results would be a useful tool for monitoring of fungicides in tomatoes and provide more understanding of residue behavior and risk posed by these fungicides.
The increased use of pesticides has caused concern over the possible direct association of exposure to combinations of these compounds with bee health problems. There is growing proof that bees are ...regularly exposed to mixtures of agrochemicals, but most research has been focused on managed bees living in farmland, whereas little is known about exposure of wild bees, both in farmland and urban habitats. To determine exposure of wild bumblebees to pesticides in agricultural and urban environments through the season, specimens of five different species were collected from farms and ornamental urban gardens in three sampling periods. Five neonicotinoid insecticides, thirteen fungicides and a pesticide synergist were analysed in each of the specimens collected. In total, 61% of the 150 individuals tested had detectable levels of at least one of the compounds, with boscalid being the most frequently detected (35%), followed by tebuconazole (27%), spiroxamine (19%), carbendazim (11%), epoxiconazole (8%), imidacloprid (7%), metconazole (7%) and thiamethoxam (6%). Quantifiable concentrations ranged from 0.17 to 54.4 ng/g (bee body weight) for individual pesticides. From all the bees where pesticides were detected, the majority (71%) had more than one compound, with a maximum of seven pesticides detected in one specimen. Concentrations and detection frequencies were higher in bees collected from farmland compared to urban sites, and pesticide concentrations decreased through the season. Overall, our results show that wild bumblebees are exposed to multiple pesticides when foraging in agricultural and urban landscapes. Such mixtures are detected in bee tissues not just during the crop flowering period, but also later in the season. Therefore, contact with these combinations of active compounds might be more prolonged in time and widespread in the environment than previously assumed. These findings may help to direct future research and pesticide regulation strategies to promote the conservation of wild bee populations.
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•Bumblebees are exposed to agrochemical mixtures in agricultural and urban landscapes.•Exposure to agrochemicals was higher in agricultural compared to urban landscapes.•Levels detected were higher in spring and early summer and decreased through the season.
There is a widespread presence of multiple pesticide residues in free-flying wild bumblebees, with different levels and frequencies of detection according to the species, sampling period and landscape context.
is considered an important plant pathogen and is responsible for significant crop yield losses. With the frequent application of commercial fungicides,
.
has developed resistance to many frequently ...used fungicides. Therefore, it is necessary to develop new kinds of fungicides with high activity and new modes of action to solve the increasingly serious problem of resistance. During our screening of fungicide candidates, one novel sulfonamide compound,
-(2-trifluoromethyl-4-chlorphenyl)-2-oxocyclohexyl sulfonamide (
), has been found to exhibit good fungicidal activity against
. In this work, the mode of action of
against
and the field control effect on tomato gray mold was studied.
had good control against
resistant to carbendazim, diethofencarb, and iprodione commercial fungicides in the pot culture experiments. SEM and TEM observations revealed that
could cause obvious morphological and cytological changes to
, including excessive branching, irregular ramification or abnormal configuration, and the decomposition of cell wall and vacuole.
induced more significant electrolyte leakage from hyphae than procymidone as a positive control.
had only a minor effect on the oxygen consumption of intact mycelia, with 2.15% inhibition at 50 μg/mL. In two locations over 2 years, the field control effect of
against tomato gray mold reached 83% at a rate of 450 g ai ha
, better than the commercial fungicide of iprodione. Moreover, toxicological tests demonstrated the low toxicological effect of
. This research seeks to provide technical support and theoretical guidance for
to become a real commercial fungicide.
Anthracnose is a destructive postharvest disease of mango fruit, especially after ripening. The application of antagonistic Bacillus spp. strains is one of many promising control strategies. B. ...amyloliquefaciens (PMB04) exhibits strong antagonistic activity against anthracnose in strawberry fruit, yet has not been explored for anthracnose control in mango fruit. Among seven tested rhizobacterial strains, PMB04 exhibited the strongest inhibition against Colletotrichum gloeosporioides (Cg) growth. PMB04 demonstrated better inhibitory activity against Cg mycelial growth than the fungicides pyraclostrobin and difenoconazole. A PMB04 fermentation broth (PMB04FB) was prepared and tested, and showed superior efficacy in the reduction of anthracnose disease severity in mangoes compared to a PMB04 suspension, difenoconazole, or pyraclostrobin. We further found PMB04FB increased the mortality ratio of Cg conidia. Our study demonstrates that treatment with PMB04FB is an effective control method for anthracnose in mango and represents a promising strategy for postharvest mango processing.
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