Journal of Pesticide Science Vol. 41(2016) No. 3

Indoxacarb is commonly used to effectively control pests, cockroaches, termites, fleas, and houseflies. Although the toxicological profile of indoxacarb had already been well characterized, we examined the possible toxicological interaction with indoxacarb and endotoxin. Male Swiss albino mice aged 8–10 weeks were orally administered indoxacarb dissolved in groundnut oil at 4 mg/kg/day and 2 mg/kg/day for 90 days. On day 91, five animals from each group were challenged with lipopolysaccharides (LPS) at 80 µg/mouse, administered intranasally. Indoxacarb at 4 mg/kg significantly decreased Total leukocyte count, lymphocytopenia, and neutrophilia. Both doses of indoxacarb combined with LPS resulted in significant lymphocytopenia. Indoxacarb did not produce DNA damage in comet assay, but when combined with LPS, it resulted in a significant increase in tail length, tail moment, and olive moment. The data indicate that indoxacarb at 4 mg/kg administered orally for 90 days induced immune-response change. Further, both doses of indoxacarb, when combined with LPS, accelerate immunotoxicity and endotoxin-induced DNA damage.

Knowledge about strigolactone biosynthesis and signaling is increasing and the crystal structure of strigolactone receptor protein D14 has been resolved. Although a variety of strigolactone biosynthesis inhibitors and strigolactone agonists are known, no inhibitors of strigolactone signaling have been reported. Here, we conducted virtual screening in silico to identify chemical regulators that inhibit SL reception. We used LigandScout to analyze a pharmacophore model based on structural information about D14 protein and complex D14–D-OH (a hydrolysis product of strigolactone formed by D14). We identified a candidate compound, XM-47, and confirmed that it inhibits D14–SLR1 and D14–D53 interactions. A possible product of XM-47 hydrolysis, 2-methoxy-1-naphthaldehyde (2-MN), inhibits D14–SLR1 and D14–D53 interactions and restores the growth of rice tillering buds suppressed by strigolactone.

Polyamines are involved not only in fundamental cellular processes such as growth, differentiation, and morphogenesis, but also in various environmental stresses. We demonstrated that spermidine, a polyamine, confers resistance to rice blast accompanied by the up-regulation of marker genes for the salicylic acid-mediated signaling pathway PR1b and PBZ1 and of phytoalexin biosynthesis genes CPS4 and NOMT. This is the first report about the involvement of spermidine in rice disease resistance.

Trypsin-modulating oostatic factor (TMOF) is an effective mosquito larvicide, but information on its potential toxicity to non-target organisms is limited. To investigate this, triplicate groups of 10 Macrobrachium rosenbergii were exposed to 0, 10, 50 or 100 mg/L nominal TMOF concentrations for 12 days. Tail moisture, crude protein, and hepatopancreatic glycogen/histopathology were unaffected, but increasing TMOF linearly decreased survival and growth. TMOF at the lowest concentration employed significantly decreased trypsin and chymotrypsin activities.

Many of the commercially available insecticides target the nervous system of insects, which are important targets of insecticides. We investigated the mechanism of action of the compound acts on voltage-sensitive sodium channel (Vssc) and nicotinic acetylcholine receptor (nAChR), and the associated mechanism of resistance, mainly using an electrophysiological method. The mechanism of resistance to pyrethroids in A. aegypti, that to neonicotinoids in A. gossypii, and the mechanism of action of the natural product asperparaline A were clarified. We also demonstrated that similar compounds that interacted on the same target with slightly different substituents exhibited different effects on the target molecule with different amino acid residues at the activity site, and that natural products exhibited specific activity and selectivity to insect ion channels.

Actinomycetes produce a number of useful secondary metabolites with antibiotic, insecticidal and herbicidal activities. Actinomycetes are prokaryotes, but the morphology of their mycelia is similar to that of fungi. Our research into the regulators of aerial mycelium-differentiation and spore germination and the surrounding research is discussed.

Metazosulfuron is a novel sulfonylurea herbicide discovered and developed by Nissan Chemical Industries, Ltd., which exhibits excellent herbicidal activity against Echinochloa spp., annual and perennial weeds including sulfonylurea resistant biotypes in paddy fields at 60–120 g a.i./ha with good crop safety to rice. In addition, it has favorable toxicological, ecotoxicological and environmental profile. Metazosulfuron (trade name; Altair^®) was registered and launched in Japan in 2013, and has been also introduced in Korea and China as of 2016. This paper describes a history of discovery, syntheses, herbicidal characteristics and crop safety of metazosulfuron.

Pyroxasulfone, which was discovered and developed by K-I Chemical Research Institute Co., Ltd.; Kumiai Chemical Industry Co., Ltd.; and Ihara Chemical Industry Co., Ltd., is a novel pre-emergence herbicide for wheat, corn, and soybean. Pyroxasulfone inhibits the biosynthesis of very-long-chain fatty acids in plants and has shown excellent herbicidal activity against grass and broadleaf weeds at lower application rates compared with other commercial herbicides. This pesticide has been registered in Japan, Australia, the USA, Canada, Saudi Arabia, and South Africa, and we sell pyroxasulfone products through domestic partner companies in each of these countries. With its high efficacy and relatively low application rates, we believe that pyroxasulfone will contribute to efficient global food production in the future.

Hokko Chemical Industry Co., Ltd. found a novel triazolinone class herbicide regarded as 1-aryl-4-carbamoyl-1,2,4-triazolinone derivatives that shows high level of safety to paddy rice, and high activity and long residual activity against Echinochloa spp. and other weeds. We selected a new paddy rice herbicide ipfencarbazone as the optimum compound. Ipfencarbazone is a pre-emergence and early post-emergence rice herbicide that controls annual grass weeds, annual sedge weeds and some annual broadleaf weeds at a rate of 250 g a.i./ha. It inhibits the biosynthesis of fatty acids in plants (VLCFA). Two formulations containing ipfencarbazone, Winner^® and Fighter^®, have been registered in Japan since 2013 and various combinations have been launched.