Acute toxicity of pesticides to wild bee species is inferred by using the LD₅₀ values of the western honey bee, Apis mellifera, as a standard baseline. However, substantial discrepancies are often reported between the LD₅₀ values for wild bees and those for A. mellifera. Here, we conducted tests to compare acute toxicity between Japanese mason bees (Osmia spp.) and the western honey bee. For nearly all tested insecticides, the mortality rates of mason bees were equivalent to, or slightly lower than, those of the western honey bee. However, the LD₅₀ of acetamiprid in male mason bees was approximately five-fold lower than that in workers of the western honey bee. These results suggest that, although the current pesticide risk assessment is generally conservative for Japanese mason bees, continued attention is warranted to ensure that their sensitivity—particularly to acetamiprid—remains within the presumed safety factor.

The degradation behavior of inpyrfluxam (1) was investigated in aerobic aquatic water–sediment systems exposed to continuous artificial sunlight (λ>290 nm). Under irradiation in the presence of sediment, 1 preferentially underwent oxidation at the 1′- and 3′-positions of the indane ring, followed by cleavage of the amide linkage with the half-life of 16–18 days, and finally mineralized to carbon dioxide or exhibited extremely strong adsorption to sediment. Especially, as compared to systems kept in darkness, carboxylation at the 1′-position of the indane ring was remarkably accelerated in illuminated water–sediment systems and the aqueous photodegradation study due to the presence of photosynthetic microorganisms in the sediment soil. No significant degradation products were observed in the water–sediment in darkness and in the sterilized water–sediment under irradiation throughout the study. The fate of 1 and its degradation products in illuminated water–sediment systems was considered to better reflect realistic conditions, as it accounts for various effects attributed to sunlight, such as the presence of photosynthetic microorganisms.

This study investigated the accumulation of cultivar-specific phytoalexins in rice—abietoryzins and oryzalactone—as well as known phytoalexins—momilactone A, phytocassane A, and oryzalexins A and S—in response to sap sucking by the brown planthopper (BPH) and the green rice leafhopper (GRL). The analysis revealed that BPH feeding induced abietoryzin accumulation in a cultivar known to accumulate these phytoalexins following fungal infection. Additionally, oryzalactone and oryzalexin S accumulated after insect attack in specific cultivars, unlike oryzalexin A. Plant hormone profiling revealed distinct associations: momilactone A accumulation was strongly correlated with salicylic acid (SA); phytocassane A with jasmonic acid, jasmonic acid-isoleucine, isopentenyladenine, and abscisic acid (ABA); and oryzalactone/oryzalexin S with both SA and ABA. These findings suggest that distinct signaling pathways regulate the induction of specific phytoalexins. The analysis of phenolic metabolites showed only minor changes in response to insect feeding. The findings highlight the broad inducibility of phytoalexins in rice and reveal the complex hormonal regulation underlying their biosynthesis during herbivore attack.

Tests of sensitivity to isofetamid conducted with Botrytis cinerea isolated from Hokkaido (2011–2016) and other districts in Japan (2017–2018) revealed the absence of isolates with reduced sensitivity. Isolates of B. cinerea with mutation H272Y/R in sdhB, collected in Germany and Japan, resulted in high and moderate resistance to boscalid and many other succinate dehydrogenase inhibitors (SDHIs), respectively. However, these isolates were as sensitive as wild-type isolate to isofetamid. In contrast, isolate BC-50 [P225F] and BC-49 [H272L] caused moderate to high resistance to isofetamid. Considerable differences in mycelial growth, conidiation, conidial germination, and pathogenicity were not observed between these resistant isolates and sensitive isolates. A competitive assay between resistant isolate BC-50 [P225F] and BC-49 [H272L] and B05.10 [wild type], however, revealed the disappearance of resistant isolates after several generations of mixed incubation in in vitro and in vivo conditions.

New asteltoxins U (1) and V (2) were obtained from the solid-state fermentation of Pochonia suchlasporia TAMA 87. The spectroscopic characterization of 1 and 2 revealed that their chemical structures are similar to that of asteltoxin H, except for the modification of the α-pyrone moiety. Specifically, the methyl group on the γ-position of the α-pyrone moiety in asteltoxin H is replaced with a hydroxymethyl group in 1 and 2. In addition, 1 and 2 are a pair of isomers that differ in the geometry of the double bond between C-11 and C-12 in the conjugated triene moiety and that contain an all-trans (9E, 11E, 13E) moiety and a 9E, 11Z, 13E conjugated triene moiety, respectively. Compound 1 showed inhibitory activity toward the first cleavage of sea urchin embryos with a minimum inhibition concentration value of 3.1 µg/mL, whereas compound 2 did not show inhibitory activity up to a concentration of 25 µg/mL.

This study evaluated the matrix effect (ME) in a multiresidue analysis with the modified official Japanese method for agricultural products using liquid chromatography-tandem mass spectrometry (LC-MS/MS). In ME comparisons between the vegetable and fruit samples, it was found that more numerous analytes exhibited ion suppression in the vegetable samples than in the fruit samples, and substantial ion enhancement was not observed in most of the analyte–sample combinations. The ME could significantly vary, even within the same commodity, and it was suggested that sampling has greater influence than measurement when there is a wide ME variability. Dilution, the internal standard calibration method and the matrix-matched calibration method are practical countermeasures against MEs, but certain limitations in their applications should be considered. Moreover, a novel cleanup procedure suitable for hydrophilic neonicotinoid pesticides that minimized the usage of expensive internal standard solutions was suggested.