Comparative effects of the herbicides dicamba, 2,4-D and paraquat on non-green potato tuber calli

The effects of the herbicides 1,1"-dimethyl-4,4"-bipyridylium dichloride (paraquat), 3,6-dichloro-2-metoxybenzoic acid (dicamba) and 2,4-dichlorophenoxyacetic acid (2,4-D) on cell growth of non-green potato tuber calli are described. We attempted to relate the effects with toxicity, in particular the enzymes committed to the cellular antioxidant system. Cell cultures were exposed to the herbicides for a period of 4 weeks. Cellular integrity on the basis of fluorescein release was strongly affected by 2,4-D, followed by dicamba, and was not affected by paraquat. However, the three herbicides decreased the energy charge, with paraquat and 2,4-D being very efficient. Paraquat induced catalase (CAT) activity at low concentrations (1muM), whereas at higher concentrations, inhibition was observed. Dicamba and 2,4-D stimulated CAT as a function of concentration. Superoxide dismutase (SOD) activity was strongly stimulated by paraquat, whereas dicamba and 2,4-D were efficient only at higher concentrations. Glutathione reductase (GR) activity was induced by all the herbicides, suggesting that glutathione and glutathione-dependent enzymes are putatively involved in the detoxification of these herbicides. Paraquat slightly inhibited glutathione S-transferase (GST), whereas 2,4-D and dicamba promoted significant activation. These results indicate that the detoxifying mechanisms for 2,4-D and dicamba may be different from the mechanisms of paraquat detoxification. However, the main cause of cell death induced by paraquat and 2,4-D is putatively related with the cell energy charge decrease.

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Determination of imidacloprid pencycuron 29% FS by HPLC

A HPLC method was developed for the determination of imidacloprid pencycuron 29% FS using C18 column, uv-detector and mobile phase of acetonitrile-water.The results showed that the variation coefficients and average recoveries of imidacloprid and pencycuron were 0.69%, 99.7% and 0.78%, 99.6% respectively.

Initial transformation step of dicamba by a sulfate-reducing consortium enriched from sediment of the Pearl River of China

Dicamba is a readily detectable chemical in run-off and groundwater of agricultural areas. Biotransformation of dicamba was investigated in laboratory anaerobic microcosms incubated at two temperatures (15 and 25 degree C) under sulfate-reducing condition using sediment from the Pearl River of Southern China as a source of microorganisms. Initial results of sulfate- reducing microcosms showed that dicamba was transformed by 86% in 120 days of incubation at 25 degree C compared with the sterile controls. In comparison, only <60% of the initial dicamba concentrations disappeared at 15 degree C. Subsequent enrichment cultures were established from the initial microcosms and accelerated transformation of dicamba was observed in the enrichment transfer cultures by 30 days of incubation for 95% and 78% removal at 25 and 15 degree C, respectively. Through enrichment transfer technique, the lag phase and the time required for dicamba biotransformation were all shortened from the initial microcosms, indicating the enrichment of microorganisms capable of transforming dicamba. Addition of 0.1% yeast extract enhanced the dicamba biotransformation by the dicamba-transforming consortium. Transformation of dicamba was further investigated by incubating super(14)C-ring labeled dicamba with the dicamba-transforming consortium. Results confirmed that dicamba was transformed by the consortium but no substantial amount of super(14)CO sub(2) was recovered, suggesting that the initial degradation was an demethoxylation reaction removing the o-methyl group forming 2-hydroxy-3,5- dichlorobenzoic acid. Our results suggest that dicamba is quickly transformed through demethoxylation, but further degradation of the transformation intermediate is much slower in the environment.

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Use of dicamba-degrading microorganisms to protect dicamba susceptible plant species

Three strains of dicamba-degrading microorganisms wrer ale to reduce the herbicidal activity of dicamba in the rhizosphere quickly enough to allow dicamba susceptible crop species to grow. Pea seedlings planted immediately after inoculation had higher wetghts over the uninoculated controls at the 0.5 and 4.0 lb/acre rates in growth chamber studies. Peas seedlings planted 2 or 5 days after inoculation had higher mass over the uninoculated controls at all treatment rates. The concentration of dicamba in the soil was reduced dramatically at all treatment rates as compared to uninoculated controls.Dicamba-degrading bacteria also showed activity in field test plots, where soybeans were protected from dicamba damage even at the 8 lb/acre application rate.

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Effect of carbendazim and pencycuron on soil bacterial community

Soil bacterial composition is used as one of the important indicators of negative effects of the use of pesticides in agriculture. Very little is known on the effects of fungicides, particularly carbendazim and pencycuron on soil bacterial community. In this study, laboratory experiments were conducted to examine the effects of various concentrations of carbendazim and pencycuron on diversity of bacterial community in soils collected from strawberry field and incubated at different temperature conditions. The degradation rate of fungicides both in sterile and non-sterile soils were also investigated. Residues of fungicides were measured using high performance liquid chromatography (HPLC) and the change in bacterial community was examined by comparing the 16S rDNA bands on patterns by denaturing gradient gel electrophoresis (DGGE). The dissipation of carbendazim was affected by concentration applied, whereas that of pencycuron was affected by both concentration applied and incubation temperature. The microbial community could recover to its previous composition after 126 days of cultivation with the application of 10 mg/kg of carbendazim but not with the application of a high concentration, 100 mg/kg, of pencycuron. From cluster analysis, the bacterial community structure showed approximately 50% similarity throughout the experimental period, which indicated that the soil microbiota composition was not stable throughout the 120 cultivation days.

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The Use of Dicamba in Agricultural and Industrial Sites

Previously, Health Canada"s Pest Management Regulatory Agency (PMRA) completed an assessment of the lawn and turf uses of the herbicide dicamba. Details are available in Proposed Acceptability for Continuing Registration document PACR2007-02, Re-evaluation of Dicamba for Lawn and Turf Uses.
The PMRA has now reviewed the available information on use of dicamba in industrial sites for vegetation control and in agriculture. Under the authority of the Pest Control Products Act, the PMRA is proposing the continued registration of all currently registered uses of dicamba and its end-use products with the implementation of additional mitigation measures to further protect human health and the environment.
This Proposed Re-evaluation Decision (previously called a Proposed Acceptability for Continuing Registration [PACR] document) is a consultation document1 that summarizes the science evaluation for the remaining uses of dicamba. It also describes risk-reduction measures that will be required to further protect human health and the environment.
The proposed mitigation measures for non-turf uses of dicamba include the following:
1.a phase-out of the diethanolamine (DEA) form of dicamba unless further data are provided;
2.a new maximum application rate of 0.01 kg a.e./L a maximum spray liquid concentration of 0.01 kg a.e./L when high-volume handwands are used for non-cropland applications;
3.buffer zones to protect terrestrial habitat; and specified or upgraded personal protective equipment, grazing restrictions and preharvest intervals.

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Determination of Butachlor and Pencycuron Residues in Vegetables and Rice:Application of the Macroporous Diatomaceous Earth Column

Butachlor and pencycuron are commonly used pesticides in Taiwan. but still lack official methods for determining butachlor and pencycuron residues in agricultural products. An analytical method using a macroporous diatomaceous earth (MDE) column and florisil cartridge for cleanup procedure was developed for determination of butachlor and pencycuron in vegetables and rice. Butachlor and pencycuron were extracted from crops with acetone and the concentrated extract was transferred into the MDE column. eluted with n-hexane.
The eluate was concentrated and applied on a florisil cartridge. The cartridge was washed with 5% diethyl ether in n-hexane (E/H), and
then eluted with 15% E/H (fraction l) and 15% ethyl acetate in n-hexane (EA/H) (fraction iD. Butachlor residue in fraction I was determined by GC-ECD. Pencycuron residue in fraction Il was determined by HPLC-UV at 248 nm. Chinese mustard and rice samples were
fortified with butachlor and pencycuron at levels of 0.25-0.75 ppm and analyzed. The recoveries of butachlor and pencycuron were
between 84.9_94.g% and 88.3-94.8%, respectively. The detection limits of both pesticides in Chinese mustard and rice were 0.05 ppm.
　　 MDE liquid/liquid extraction cartridges provide a means of simplifying and speeding up multiple liquid/liquid extractions.
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