We developed a simulation model for predicting pesticide concentrations in succeeding leafy vegetables (PostPLANT-Soil), which includes the process of pesticide uptake from plant roots. To validate the model, we compared pesticide concentrations simulated by the model with values measured from field experiments in an upland Andosol. The model validation showed that pesticide concentrations in the plant shoot were correlated with the concentrations in the soil solution rather than those of the water-extracted pesticides. The model successfully simulated the concentration changes in plant shoots when the simulated concentrations of the pesticides in the soil solution were fitted to the measured values by considering the key parameter - the corrective coefficient for the soil adsorption coefficient. However, the simulated shoot concentrations at the appropriate harvest period exceeded the measured values. This indicates that the leafy vegetable used in this study may have some metabolic capacity for the pesticides.

Four nitromethylene analogues of imidacloprid (CH-IMIs) having a 4,5-dimethylated (diMe) imidazolidine ring were stereospecifically synthesized to evaluate their affinity for the nicotinic acetylcholine receptors of the housefly Musca domestica. Among the analogues, the 4S,5R-diMe analogue showed the highest receptor affinity (K_i=0.39 nM). The insecticidal activity against M. domestica of the synthesized compounds was also measured under synergistic and nonsynergistic conditions. Under nonsynergistic conditions, the insecticidal activity of the 4S,5R-diMe analogue was the highest. The order of the insecticidal potency of the four diMe-CH-IMIs (4S,5R->4R,5S-=4R,5R->4S,5S-diMe analogues) was the same as that of the receptor affinity. Piperonyl butoxide (PBO) did not synergize with the test compounds, but both PBO and NIA16388 applications strengthened the activity of analogues other than the 4S,5S-diMe analogue. This suggests that the configuration of the substituents on the imidazolidine ring should influence the metabolism process of CH-IMI in houseflies.

A method of quantifying glyphosate (Gly) in human urine by means of MonoSpin TiO extraction and 9-fluorenylmethoxycarbonyl chloride (FMOC-Cl) derivatization with isotope dilution mass spectrometry (IDMS) was investigated and optimized. The method’s quantification limit under optimized conditions was 0.3 µg/kg for FMOC-Gly, which was comparable to or lower than those described in previous studies. When a spike test using human urine samples was carried out with optimized analytical conditions, the trueness for FMOC-Gly was as follows: 101.6–104.9% for a spike level of 0.5 µg/kg and 99.2–101.0% for a spike level of 30 µg/kg. The intra-day repeatability and inter-day reproducibility were <6.5%. The spike test results for validation between the “with” and “without” derivatization methods were comparable at 1 µg/kg. Our results indicate that using MonoSpin TiO extraction and FMOC-Cl derivatization with IDMS is an accurate method for analyzing Gly in human urine.

Orobanchaceae root parasitic weeds cause significant damage to agriculture and become threats to global food security. Integrated pest management is a key concept in modern agriculture and requires chemicals with various modes of action. Planteose accumulates as a storage carbohydrate in the dry seeds of root parasitic weeds. In Orobanche minor seeds, planteose is hydrolyzed by an α-galactosidase, OmAGAL2, during germination. It was found that the OmAGAL2 inhibitor, PI-28, suppressed the radicle elongation of germinating O. minor seeds. This inhibitory activity against O. minor radicle elongation was evaluated for a series of aryloxyacetylthioureas synthesized based on the structure of PI-28. Compounds with a 3-Cl or 4-Cl substituent on the benzene ring in the phenoxy moiety in PI-28 exhibited more potent activity than the parent PI-28. This is the first report on the effect of aryloxyacetylthioureas on a root parasitic weed and will contribute to the development of control reagents for root parasitic weeds.

The excessive use of chemical pesticides in agricultural fields for controlling plant pathogenic microorganisms harms human health, the environment, and other beneficial microorganisms in the soil and plants. To address this challenge, it is essential to isolate and discover bioactive compounds from biological resources that could inhibit plant pathogenic microorganisms. In this study, the culture filtrate of the edible mushroom Pleurotus ostreatus was subjected to bioassay-guided isolation, and two phthalide derivatives—4,6-dimethoxyphthalide (1) and 5,7-dimethoxyphthalide (2)—were identified, along with an oxindole compound—3-hydroxy-3-methyloxindole (3). The inhibitory activities of the three compounds were evaluated against four fungal and five bacterial pathogens. Remarkably, 1 and 2 exhibited the lowest IC₅₀ values against the conidial germination and germ tube elongation of the rice blast fungus Pyricularia oryzae. However, their effectiveness against bacterial pathogens was relatively low. The (S) and (R)-enantiomers of 3-hydroxy-3-methyloxindole showed different activities against plant fungal pathogens and bacterial plant pathogens.

Flometoquin, 2-ethyl-3,7-dimethyl-6-[4-(trifluoromethoxy)phenoxy]quinolin-4-yl methyl carbonate, is a novel insecticide with a structurally unique phenoxy-quinoline. It was discovered in 2004 by the collaborative research of Nippon Kayaku and Meiji Seika Kaisha, Ltd. (currently, Mitsui Chemicals Crop & Life Solutions, Inc.). The compound demonstrates strong and quick insecticidal action against a variety of thrips species at the nymphal and adult stages through contact and feeding activity, which could minimize crop damage and economic loss by insect pest species. In addition, flometoquin is safe for tested non-target arthropods, which makes it suitable for controlling the insect pests mentioned above under Integrated Pest Management (IPM) programs. Here, we describe a structure–activity relationship study from lead generation to the discovery of flometoquin and its insecticidal properties, including knockdown activity and effects against non-targeted arthropods.

We validated a simulation model (PostPLANT-Soil) for predicting pesticide concentrations in succeeding leafy vegetables reported in our first paper in this series, which includes the pesticide sorption process into plant roots. As a result of the model validation with the measured data from a plant uptake study in a growth chamber, the model successfully simulated the concentration changes of pesticides in a plant shoot. However, the simulated shoot concentrations for several pesticides were overestimated compared to the measured values. The leafy vegetable (Brassica rapa) used in this study probably has a high metabolic ability for the fungicide flutolanil from the result of the uptake study under a hydroponic condition.

Fugacity models are used widely to predict the time-dependent behaviors of chemicals in environments containing several media (e.g., air, sediment, soil, and water). However, these fugacity models work on the assumption that the concentration of a chemical in each medium is uniform, so they cannot describe the spatial distribution of the chemical. We developed a new fugacity model, termed InPestCFD, incorporating computational fluid dynamics to describe both the time-dependent distribution and the spatial distribution of a chemical in a medium. InPestCFD was used to calculate the behavior of an insecticide released from an aerosol canister in a room. Indoor airflow and aerosol particle behavior were calculated via computational fluid dynamics and using a Lagrangian dispersion model. Transport of the insecticide among media (aerosol particles, air, ceiling, floor, and walls) was calculated using the fugacity model. The time-dependent distributions and spatial distributions of the insecticide in the media agreed well with real measurements.

Acynonapyr, discovered by Nippon Soda Co., Ltd., is a novel acaricide with N-pyridyloxy azabicycle as a unique core structure. Acynonapyr exhibits high activity against the spider mite species in the genera Tetranychus and Panonychus, with good efficacy at all life stages. Early in this research, cyclic amines substituted with (hetero)aryl(oxy) moieties were designed as target molecules and diversely synthesized, and 4-[4-(trifluoromethyl)phenoxy]-1-[5-(trifluoromethyl)-2-pyridyl]piperidine was found to show weak acaricidal activity. The structural optimization of this acaricidal active piperidine as the first lead compound led to the discovery of acynonapyr. In this report, our research process that led to the discovery of acynonapyr is described.

Flupentiofenox, which has a unique chemical structure, is a novel acaricide that has been developed by the Kumiai Chemical Industry Co., Ltd. Flupentiofenox exerted significant acaricidal activities against spider mites Tetranychus urticae and Panonychus citri at all developmental stages even at extremely low concentrations, as compared with its practical concentration (80 ppm) for use in mites and was effective against spider mite populations that are resistant to widely used commercial acaricides. These results suggested that flupentiofenox could be used effectively for the control and prevention of spider mite infestation. Additionally, flupentiofenox had a more rapid effect than acetyl CoA carboxylase inhibitors, but it had a relatively slower effect than mitochondrial electron transport inhibitors and glutamate-gated chloride channel modulators. Overall, flupentiofenox is assumed to have a new mode of action.

Spiral roots are induced in germinated rice seeds through treatment with nanomolar brassinosteroids (BRs) but not with other plant hormones. Here, we determined the minimum effective concentration (MEC) of various BRs to induce spiral roots in germinated rice seeds. The reciprocal logarithm of MEC, pMEC, was used as the BL-like activity index, which was linearly correlated with the reciprocal logarithm of a 50% effective dose (pED₅₀) as evaluated in the rice lamina inclination assay. Furthermore, a ligand-receptor docking simulation was performed against the BL receptor complex, Arabidopsis thaliana BRI1/SERK1, and the binding free energy (ΔG_bind) was calculated for the tested BRs. The ΔG_bind calculation was performed using the molecular mechanics/generalized Born surface area method on an ensemble of uncorrelated snapshots collected via molecular dynamics to predict biological activity.

Use of agro-chemicals in forage crops is restricted due to the fear of direct toxicity to livestock and risk of pesticide residue accumulation in the food chain. Wheat and barley can be used as green fodder and silage, and herbicide residue estimation in green fodder and silage is important for ensuring the safety of dairy cattle. A field experiment was conducted for two years to study pendimethalin residues in the green fodder and silage of wheat and barley. In both cereal crops, pendimethalin (1.125 kg a.i./ha) was applied as pre-emergence along with an unsprayed control. Pendimethalin residues in fodder, silage, and soil were estimated using gas chromatography-tandem mass spectrometry (GC-MS/MS). At harvest, pendimethalin residues in fodder and silage of wheat and barley were below the limit of quantification (<0.01 mg/kg) during both crop seasons. Pendimethalin can be safely used for weed control in winter cereals grown for fodder and silage.