Journal of Pesticide Science最新文献

Tomato leaf mold caused by Passalora fulva is a significant disease in tomato production. We isolated several types of boscalid-resistant isolates in the Gifu and Mie Prefectures of Japan. Sequencing analysis of succinate dehydrogenase (Sdh) subunits B, C, and D genes strongly indicated that four amino acid substitutions-T78I, N85K, N85S, and H151R in SdhC-conferred boscalid resistance. We conducted SNP assays to detect each mutation using qPCR techniques and revealed that all 35 resistant isolates had one of these mutations in the SdhC. Among the four resistance types, N85K isolates exhibited the highest, N85S isolates showed the lowest, and T78I and H151R isolates displayed moderate resistance to boscalid. These mutations also conferred cross-resistance to other succinate dehydrogenase inhibitor (SDHI) fungicides, including penthiopyrad, pyraziflumid, fluopyram, and isofetamid. A predicted SdhC protein structure, created by I-TASSER, suggests that the amino acid at position 151 is located close to those of positions 78 and 85, likely forming the SDHI-binding pocket of the protein.

N-(3-Phenylisoxazol-5-yl)benzamides (5-benzoylamino-3-phenylisoxazoles: IOXs) with various substituents at two benzene rings were synthesized, and the chitin synthesis inhibition was measured in the cultured integumentary system of Chilo suppressalis. Larvicidal effects against C. suppressalis and Spodoptera litura were also examined, and the larvicidal activity in terms of the 50% lethal dose (LD₅₀) was determined for some compounds. Among IOXs with various substituents at the benzoyl moiety, 2,6-difluoro-substituted (2,6-F₂) benzoyl analogs showed the highest chitin synthesis activity. The larvicidal activities against C. suppressalis and S. litura were 1/138 and 1/35 that of diflubenzuron, a representative benzoylphenylurea-type insecticide, respectively. In a further study, 2,6-F₂ benzoyl analogs with various substituents at the phenyl moiety, such as Br, CF₃, CN, OEt, Ph, and alkyls (CH₃, Et, i-Pr, n-Bu, and t-Bu), were synthesized, and their chitin synthesis inhibition in the Chilo integument and their larvicidal activity against S. litura were quantitatively measured. The introduction of bulky CF₃ and t-Bu at the phenyl moiety of 2,6-F₂ benzoyl analog favorably enhanced the larvicidal activity against S. litura.

Oxazosulfyl, a novel insecticide originally discovered and developed by Sumitomo Chemical Co., Ltd., belongs to a new chemical class, the sulfyl group, structurally characterized by its ethylsulfonyl moiety. It exhibits excellent control against a broad range of major rice insect pests, including Coleoptera, Hemiptera, Lepidoptera, and Orthoptera, through nursery-box application. With a novel structural backbone and mode of action, this insecticide is classified by the Insecticide Resistance Action Committee as the sole member of novel code 37, vesicular acetylcholine transporter inhibitor. A substantial number of field studies in rice paddy fields have demonstrated that oxazosulfyl, registered in Japan in April 2021 as ALLES® granules, is highly effective against populations that have developed reduced sensitivity or resistance to existing insecticides. Given these favorable properties, oxazosulfyl is expected to contribute to the management of insecticide resistance, the reduction of agricultural chemical use, labor savings, and sustainable agriculture as a next-generation insecticide.

Capsaicin inhibits the current flow in the voltage-gated sodium channels (VGSCs) of mammals and insects. The aim of the present study was to elucidate capsaicin toxicity in pyrethroid-susceptible and knockdown resistant (kdr; with reduced pyrethroid sensitivity) strains of the German cockroach (Blattella germanica) and its effects on VGSCs carrying the kdr mutation. Injection tests revealed that adult cockroaches from susceptible and kdr strains exhibited sluggish movement and paralysis upon abdominal capsaicin administration, consistent with its inhibitory effect on VGSC currents. The LD₅₀ values of capsaicin were 16 and 36 µg per insect for the susceptible and kdr strains, respectively, yielding a resistance ratio of 2.3. Two-electrode voltage clamp assays showed that the EC₅₀ values for the capsaicin-mediated inhibition of VGSC currents were 4.27 and 9.19 µM for susceptible and kdr mutant channels, respectively, yielding a resistance ratio of 2.2. The findings indicate that capsaicin retains inhibitory activity against insect VGSCs even in the presence of kdr mutations.

Emulsifiable concentrates and oil suspensions are typical pesticide formulations. Many pesticides on the market use aromatic hydrocarbons as solvents. However, studies have revealed their potential risks to humans and the environment. Ethylene glycol diacetate (EGDA) is a low-toxicity and eco-friendly solvent with low utilization in pesticides. This study explores EGDA's potential to replace xylene. Results indicate that EGDA formulations enhance droplet adhesion to leaves, boosting pesticide efficiency. They exhibit lower surface tension and contact angles, with a 24%-40% increase in leaf retention. Bioassays show that 15% cyhalofop-butyl EC and 10% nicosulfuron OF with EGDA offer weed control that is superior to xylene-based formulations by 9.1%-30.5% in greenhouses and 4.8%-6.7% in fields. Xylene preparations are 2-3 times more cytotoxic to human bronchial cells than EGDA-based ones. Thus, EGDA is a promising pesticide solvent, outperforming traditional aromatic solvents in environmental friendliness and reducing adverse effects.

Polyoxin D is purified from the culture broth of actinomycetes and used as an agricultural fungicide. This compound shows antifungal activity against various plant pathogenic fungi, especially Rhizoctonia solani, by inhibiting germination, hyphal growth, and sporulation of the fungi. Its mode of action is thought to be via the competitive inhibition of chitin synthase, which causes incomplete cell wall formation and swelling in germ tubes, hyphae and septa. This action is unique and results in the suppression of diseases in various crops through fungistatic rather than fungicidal activity. Although the polyoxin complex shows not only fungicidal but also insecticidal activity, polyoxin D has less activity against insects, no negative impacts on the environment and is suitable for organic agriculture. Polyoxin D has the potential to control soil-borne and post-harvest diseases and to inhibit mycotoxin production via a new mode of action.

Root parasitic weeds from the Orobanche genus significantly damage crop production in African and European countries. Previous studies identified the metabolism of planteose, a storage trisaccharide in root parasitic weeds, as a potential control target. In Orobanche minor, α-galactosidase OmAGAL2 hydrolyzes planteose into sucrose upon perceiving germination stimulant strigolactones. Subsequently, invertases break down sucrose into glucose and fructose, essential for germination. This study screened chemical libraries to identify inhibitors against OmAGAL2-mCherry, secreted from transgenic tobacco BY-2 cells. Two inhibitors, 82-G8 and 85-B10, which significantly reduced the OmAGAL2 activity to less than 70% of the control, were evaluated for their impact on O. minor germination and sugar profiles. Results showed that OmAGAL2 inhibitors suppressed O. minor radicle elongation by inhibiting planteose metabolism, with effects more pronounced when applied at the start of conditioning rather than during germination stimulation. Further structural optimization could yield a novel class of chemicals for controlling Orobanche spp.

We investigated the synthesis and herbicidal activity of C5-substituted cinmethylin analogs. For the benzyl ether at the C2 position, we found that electron-withdrawing groups, such as halogen groups on the benzene ring have high herbicidal activity. Analogues with ketone, fluorine, and methoxy groups at the C5 position also showed excellent herbicidal activity.

The development of preventive methods against the invasive wood-boring beetle Aromia bungii, which infests Rosaceae trees, is required in Japan. We investigated the effect on eggs of several commercial insecticides whose active ingredients are registered to kill A. bungii adults or larvae by tree injection or spray. The ovicidal activity was evaluated using the corrected egg hatch rates based on the control (distilled water) after dipping pieces of cardboard, on which eggs were deposited, in liquid insecticide solutions for 10 sec. The egg-dipping tests revealed highly effective ovicidal activity in the following insecticides: more than 8000 ppm for fenitrothion, 1000 ppm for acetamiprid, 400 ppm for clothianidin, and 500 ppm for dinotefuran (corrected egg-hatch rates of approximately less than 5%). In terms of current registration in Japan, only fenitrothion (SUMIPAIN emulsion) and acetamiprid (MATSUGREEN liquid solution 2) by trunk spraying during the A. bungii reproductive period are adulticidal insecticide candidates with preventive potential through incidental ovicidal activity.