Herbicides

Herbicides are commonly used by farmers to get rid of deleterious weeds. There is a common believe by beekeepers that herbicides have no harmful impacts on bee colonies. In this study, the effects of tow
glyphosate herbicides (herbazed and glypho-up) on some parameters of honey bee workers were investigated. Three concentrations of each herbicide were tested. Concerning survival, the highest concentrations of
herbazed and glypho-up showed significant impacts on caged bees than the control group (bees supplied with sugar syrup only) while the low concentrations showed the vice versa. The highest concentration of glypho-up caused the highest reduction in survival of caged bees. The tested herbicides showed no significant impacts on the navigation ability of bee workers than the control group. The proboscis extension reflex test was used to evaluate the learning ability of bee workers. The results showed insignificant impacts of the tested herbicides on the learning ability of bee workers than the control group. The survival was low when Nosema infected bees were exposed to the high concentration of glypho-up unlike Nosema infected bees and healthy ones. This study has a significant contribution towards understanding the potential impacts of herbicides on honey bees.

Fluorochloridone (FLC) is a herbicide used worldwide that is thought to be safe. However, due to its potential genotoxicity, cytotoxicity, and even systematic toxicity, there are increasing concerns about human exposure to this compound. Thus, the metabolism and bioactivation of FLC was investigated. After oral administration to mice, 27 metabolites were identified by ultrahigh performance liquid chromatography-electrospray ionization-quadrupole time-of-flight-mass spectrometry and with further structural identification by nuclear magnetic resonance spectroscopy. Hydroxylation and oxidative dechlorination were the major phase I pathways, while glutathione (GSH) and N-acetylcysteine conjugations were two major phase II pathways, indicating the formation of a reactive intermediate. In vitro microsomal and cytosolic studies revealed that a GSH conjugate (M13) was the predominant metabolite of FLC formed through a nucleophilic SN2 substitution of 3-Cl by GSH; this pathway is NADPH indep...

The production of coca and poppy as well as the processing and production of cocaine and heroin involve significant environmental impacts. Both coca and poppy are grown intensively in a process that involves the clearing of land in remote areas, the planting of the crop, and protection against pests such as weeds, insects, and pathogens. The aerial spray program to control coca and poppy production in Colombia with the herbicide glyphosate is conducted with modern state-of-the-art aircraft and spray equipment. As a result of the use of best available spray and navigation technology, the likelihood of accidental off-target spraying is small and is estimated to be less than 1% of the total area sprayed. Estimated exposures in humans resulting from direct overspray, contact with treated foliage after reentry to fields, inhalation, diet, and drinking water were small and infrequent. Analyses of surface waters in five watersheds showed that, on most occasions, glyphosate was not present ...

An optical biosensor based on vegetal cells entrapped in an inorganic translucent matrix and fluorescence detection has been developed. The biosensor uses Chlorella vulgaris immobilized in a translucent support produced from sol–gel technology. The translucence of the structure enables the algal active layer to be placed directly in contact with the optical fibers for fluorescence detection. This configuration has many advantages over the use of an opaque support because no space between the optical fibers and the active layer is required to collect fluorescence. This reagentless biosensor allows determination of diuron as an anti-PSII herbicide and its long term activity is assessed.

Few studies have been done to evaluate the transfer of catabolic plasmids from an introduced donor strain to indigenous microbial populations as a means to remediate contaminated soils. In this work we determined the effect of the conjugative transfer of two 2,4-D degradative plasmids to indigenous soil bacterial populations on the rate of 2,4-D degradation in soil. We also assessed the influence of the presence of 2,4-D on the number of transconjugants formed. The two plasmids used, pEMT1k and pEMT3k, encode 2,4-D degradative genes (tfd) that differ in DNA sequence as well as gene organisation, and confer different growth rates to Ralstonia eutropha JMP228 when grown with 2,4-D as a sole carbon source. In an agricultural soil (Ardoyen) treated with 2,4-D (100 ppm) there were ca. 10(7) CFU of transconjugants per gram bearing pEMT1k as well as a high number of pEMT3k bearing transconjugants (ca 10(6) CFU/g). In this soil the formation of a high number of 2,4-D degrading transconjugan...

On/off patch spraying based on weed maps is used in site-specific weed management. Two prerequisites for realising patch spraying are accurate weed detection and targeting of the herbicides on weed patches. There is plenty in the literature about weed detection, but little attention has been paid to the spatial accuracy of herbicide application. This study was conducted in order to assess the extent to which patch-sprayed herbicides are targeted precisely according to pre-loaded prescription maps and to evaluate a new spatial assessment method. The new method consisted of spraying with red Ponceau 4R dye, unmanned aerial vehicle (UAV) imagery and spatial image analysis based on a geographic information system (GIS). The sprayed dye was clearly visible in aereal images and the locations of the sprayed areas were compared with the locations given by the prescription maps. Four different commercial sprayers with boom section width in the range of 0.5 to 3 m and driving speed in the range of 2.5 to 8 km h −1 were used in ten experiments. All the experiments were carried out in autumn in stubble fields. The results showed that the new method was fast and reliable. The incorrectly sprayed area outside targeted areas on prescription maps averaged 81% for three different sprayers with 3 m boom sections, and 5% for a sprayer with 0.5 m boom sections (individual spray nozzle control). The target areas not sprayed within the planned weed patch areas averaged 6% of the pre-defined patch area for spray-ers with 3 m boom sections, and 14% for the sprayer with 0.5 m boom sections. This study revealed that the sprayer with 0.5 m boom sections had a controller that was not quick enough at opening and closing spray nozzles at normal driving speeds. Log files from the sprayer console overestimated the sprayed area by 24% and were less accurate than the spatial analysis of the sprayed areas.

The LC/ESI/MSMS method allows the trace quantification (ng/l) of the new triketone herbicides, i.e. sulcotrione and mesotrione, and important herbicides and metabolites, in natural waters. Solid phase extraction (SPE) for sample enrichment is performed with OASIS® (recoveries 94–112% for parent herbicides). Neutral and acidic compounds were analyzed separately with ESI in positive and negative mode, respectively. Quantification limits varied between

Plants with specific resistance to a single class of herbicides have been genetically engineered by introduction of genes encoding rationally designed mutant acetohydroxyacid synthase (AHAS) enzymes. Suitable substitution mutations were identified from a three-dimensional model of an AHAS-inhibitor complex. The structural model was generated based on homology to pyruvate oxidase and an imidazolinone inhibitor was positioned in the proposed binding site using structure-activity data for this class of herbicide. Biochemical analysis of the mutant proteins expressed in Escherichia coli enabled iterative optimization of the mutant genes. Expression of recombinant proteins in tobacco plants conferred resistance in vivo. The novel approach coupling molecular modeling and molecular biology has many advantages over traditional random mutagenesis and selection methods and will be crucial to the future development for environmentally safe and sustainable agricultural systems.