Ipfencarbazone exhibits excellent herbicidal activity against Echinochloa spp. and is safe for transplanted rice at a dose of 250 g a.i./ha. However, the effect of various environmental factors on its activity has not been verified. The present study evaluated the factors affecting the herbicidal activity of ipfencarbazone against Echinochloa spp. and its phytotoxicity to transplanted rice. The herbicidal activity and phytotoxicity of ipfencarbazone were barely affected by temperature, soil texture, water leakage, or flooding water depth. When an overflow was conducted artificially 6 hr after application, the herbicidal activity was stable. Furthermore, ipfencarbazone completely inhibited the emergence of Echinochloa spp. for 56 days regardless of the soil texture, water leakage and overflow conditions. When the period between application and reflooding was within 24 hr of herbicide application, the phytotoxicity of ipfencarbazone on transplanted rice was slight. These results suggest that ipfencarbazone shows stable efficacy in practical use.
We cultivated Brassica rapa var. perviridis in soil mixed with four pesticides (fenobucarb, procymidone, flutolanil, and tolclofos-methyl) at different temperatures, day lengths, and soil water contents. We compared plants’ uptake and translocation abilities of the pesticides as affected by growth conditions. The root concentration factor (RCF) of pesticides tended to increase with rising temperature; however, but the influence of temperature on the transpiration stream concentration factor (TSCF) differed for each pesticide. The RCFs and TSCFs of pesticides were high for short days. The soil water content had little or no effect on the uptake and translocation of pesticides. These results showed that it is necessary to consider growth conditions, especially the temperature and day length in plant uptake models for these pesticides.
To investigate root uptake and translocation of heptachlor and its degradates (cis-heptachlor epoxide and 1-hydroxychlordene) in soil, zucchini and tomato seedlings were transplanted to soil approximately four months after treatment with 14C-heptachlor. The results indicated that a relation between the root concentration factor and the log Pow did not follow Briggs’ theory, probably due to the contribution of plant metabolism. It also appeared that a compound with a lower log Pow tends to show higher mobility from root to shoot.
The defense allomones of two haplodesmid millipedes, Eutrichodesmus elegans (Miyosi) and E. armatus (Miyoshi) (Polydesmida: Haplodesmidae), are known as a mixture of the following three nitro compounds: (2-nitroethyl)benzene and (Z)- and (E)-(2-nitroethenyl)benzenes. Administrations of a mixture of 2H-labeled (Z)- and (E)-phenylacetaldoximes and of 2H-labeled phenylacetonitrile as precursors resulted in the same production of three 2H-labeled nitro compounds, [2′-nitroethyl][2,3,4,5,6-2H5]benzene and [(Z)- and (E)-2′-nitroethenyl][2,3,4,5,6-2H5]benzenes, in both species. Oxime administration at an appropriate dose resulted in the production of three nitro compounds with similar natural ratios more effectively than nitrile administration. Conversion from oximes to nitrile and vice versa was evidenced during administration. Occurrences of three precursors (Z- and E-oximes and nitrile) were detected sporadically in millipede extracts by selected ion chromatography.
Three peptaibols, trichorzins HA II (1), HA V (2), and HA VI (3), were isolated from okara fermented with Trichoderma harzianum HK-61 as anti-plant viral agents. Their structures were confirmed by spectroscopic and chemical methods. At micro molar concentrations, the trichorzins inhibited infections by Cucumber mosaic virus in the cowpea plant Vigna sesquipedalis.
The flower thrips Frankliniella intonsa strain showing resistance to spinosad was established in the laboratory. The resistant strain showed an LC50 value of 1398.7 mg/L in a leaf dipping/contact assay. The LC50 value was ca. 280 times higher than that of the most susceptible strain. An insecticidal assay using synergists suggested no involvement of degradation enzymes, such as cytochrome P450, glutathione S-transferase, and carboxyl esterase, in the resistance. Glycine at amino acid position 275 of the nicotinic acetylcholine receptor (nAChR) α6 subunit was mutated to valine in the resistant strain. These results suggest that spinosad resistance in F. intonsa is conferred by the reduced sensitivity of nAChR.
We compared the soil sorption coefficient (Kd) measured by batch and centrifugation methods using a Japanese andosol and ten pesticides. Although the Kd values measured by both methods increased with time, those obtained via the batch method tended to be higher during the test period. The difference in Kd values between the two methods affected pesticide concentrations estimated in the soil solution, and the results estimated using Kd values obtained via the batch method underestimated the observed trends.
The action mechanism of cyclopyrimorate, a novel herbicide for weed control in rice fields, was investigated. Cyclopyrimorate caused bleaching symptoms in Arabidopsis thaliana similar to those caused by existing carotenoid biosynthesis inhibitors, mesotrione and norflurazon. However, cyclopyrimorate treatment resulted in significant accumulation of homogentisate and a reduction in the level of plastoquinone. A metabolite of cyclopyrimorate, des-morpholinocarbonyl cyclopyrimorate (DMC), was detected in plants. These data suggested that cyclopyrimorate and/or DMC inhibit homogentisate solanesyltransferase (HST), a downstream enzyme of 4-hydroxyphenylpyruvate dioxygenase in the plastoquinone biosynthesis pathway. In vitro assays showed that A. thaliana HST was strongly inhibited by DMC and weakly by cyclopyrimorate, whereas other commercial bleaching herbicides did not inhibit HST. DMC derivatives showed a positive correlation between HST inhibition and in vivo bleaching activities. These results indicate that the target site of cyclopyrimorate and DMC is HST, a novel target site of commercial herbicides.
The Indian livestock population is huge. Most (99%) of the livestock owners still follow traditional animal husbandry practices and graze their livestock, especially small ruminants, on natural pastures where no pesticides are used. In order to feed the ever-increasing livestock population, efforts are being made to increase quality fodder productivity from limited land resources. In such situations, pesticides play an important role by minimizing the loss of green fodder due to disease and pest attack. In countries such as Canada, Israel, the UK, and other European countries, pesticides have been registered for forage crops; in India, however, although pesticides have been registered for cultivable grain, horticultural and cash crops, etc., there are no registration guidelines or authenticated information regarding pesticide use with regard to forage crops. Hence, there is a need to take necessary steps in this direction, keeping in view the importance of fodder and livestock in the country. In this review, detailed aspects of the status and use of pesticides in forage crops in India are discussed.