The Fate of Thiophanate-methyl Fungicide and Its Metabolites on Plant Leaves and Glass Plates

The persistence of thiophanate-methyl, dimethyl 4, 4′-o-phenylenebis (3-thioallophanate), and its metabolites on plant leaves and glass plates was examined using a radiolabeled compound. Apple and grape leaves and glass plates treated with thiophanate-methyl-phenyl-¹⁴C were kept outdoors, except on rainy days and nights when they were kept in green house.

Half lives of thiophanate-methyl on apple and grape leaves were around 15 and 12 days, respectively. On glass plates half life was around 3 days. The per cent of abundance of the parent compound and a major degraded product, methyl 2-benzirnidazolecarbamate, versus applied thiophanate-methyl at 14 days after treatment was as follows; 52.6 and 10.1% on apple leaves, 49.5 and 8.9% on grape leaves, and 5.5 and 24.1% on glass plates, respectively.     

The mechanics of pulling a glass micropipette.

The pulling of micropipette electrodes from glass tubing has been treated as a problem of viscous flow coupled with the Newtonian dynamics of the pulling apparatus. Analytical solutions are given from which the taper profile, tip diameter, and pulling time can be obtained. The physical principles of operation of micropipette pullers are discussed.     

FIELD METHOD FOR THE DETERMINATION OF THE PARTICLE SIZE OF OIL MISTS

For the control of plant pests, e.g. insects, spraying machines have of late been developed, especially in the U.S.A., with which low dosages of fairly concentrated solutions of toxicants in mineral oils are sprayed. The efficiency of such products is no doubt influenced by the fineness of the spray. An accurate method of determining this fineness was desirable both for the control of the spraying operation and for evaluation of the merits of spraying apparatus.
Knowledge of the average drop size is inadequate in this respect; it is necessary to know the distribution of the oil in droplets of different sizes. A reliable impression of this percentage can be obtained only if a large number of particles are measured. These measurements can be used to plot frequency curves based on number or volume distribution.
A simple microphotographic method is described whereby these measurements can be made both in the laboratory and in the field. The procedure makes it possible to obtain, shortly after spraying, a good idea of the size of the oil drops in the deposit.
An apparatus was designed and constructed to determine the diameter frequency curve and the volume distribution curve of oil droplets deposited in field spraying on coated glass plates.
The method gave characteristic results for field sprayings with the Strawsonizer and a helicopter fitted with a spraying boom and also in the laboratory when using a spraying apparatus with different arrangements of the nozzle.     

High‐throughput screening method for evaluating spatial repellency and vapour toxicity to mosquitoes

Spatial repellents are an essential tool for personal protection against mosquitoes that bite and transmit disease pathogens to humans. Current repellent screening methods, such as olfactometers and alternative choice tests, are complex systems that require a relatively large quantity of compound (mg). The present study validates a high‐throughput spatial repellent screening method using a glass tube that has the ends covered with netting, in addition to treated filters and plastic end caps. The apparatus occupies relatively little space, is easy to decontaminate, and requires small amounts of compound (μg). In a horizontal tube orientation, DEET (N,N‐diethyl‐meta‐toluamide), citronella oil and IR3535 had 1 h half repellent concentration (EC₅₀) values of 32, 32 and 298 μg/cm², respectively, against the Orlando strain of Aedes aegypti (L.) (Diptera: Culicidae). Vertical tube orientation increased EC₅₀ values by approximately two‐fold, except IR3535, which remained essentially unchanged. Transfluthrin showed concentration‐dependent spatial repellency (1 h EC₅₀ = 0.5 μg/cm²) without any knockdown, although only in vertical tubes. Transfluthrin showed 50% knockdown in 1 h at 0.5 μg/cm² and 50% mortality at 0.15 μg/cm² in horizontal tubes. In conclusion, this high‐throughput screening method is useful for assessing vapour toxicity and the spatial repellency of candidate molecules prior to semi‐field and field studies.     

Laboratory Efficacy of Chemical Repellents for Reducing Blackbird Damage in Rice and Sunflower Crops

Abstract: Nonlethal alternatives are needed to manage blackbird (Icterids) damage to rice and sunflower production in the United States. We evaluated 4 registered fungicides on rice seeds (i.e., Allegiance® FL, Thiram 42-S, Trilex®, and Vitavax® 200 preplant seed treatments) and 2 foliar pesticides on sunflower seeds (Cobalt™ insecticide and Flock Buster bird repellent) as candidate blackbird repellents. Red-winged blackbirds (Agelaius phoeniceus) preferred untreated rice relative to rice treated with Thiram (P < 0.001) and Vitavax (P < 0.001), and untreated sunflower relative to sunflower treated with Cobalt (P < 0.001). Blackbirds preferred untreated sunflower relative to sunflower treated with Flock Buster repellent on day 1 of a 4-day preference test (P < 0.001). We observed no difference in consumption of treated versus untreated rice during the Allegiance preference test (P = 0.928), and blackbirds preferred rice treated with Trilex relative to untreated rice (P = 0.003). Although repellency was positively related to tested concentrations of Thiram (P = 0.010), Trilex (P = 0.026), and Vitavax (P < 0.001), maximum repellency was < 50% during our concentration-response tests of these seed treatments. Repellency was also positively related to tested concentrations of Cobalt (P < 0.001), and we observed >80% repellency of sunflower treated with Cobalt at ≥50% of the label rate. We observed no concentration-response relationship for the Allegiance seed treatment (P = 0.341) and Flock Buster repellent (P = 0.952). We recommend implementation of supplemental field studies to compare laboratory efficacy, repellency, and chemical residues of effective avian repellents throughout periods of needed crop protection.     

Evaluation of a Pour-on Formulation of Fipronil Against Boophilus Annulatus (Acari: Ixodidae) Under Natural South Texas Field Conditions

A long-term field study (60 consecutive weeks) was conducted to determine whether a Boophilus annulatus (Say) population could be eradicated through repeated applications of a 1% pour-on formulation of fipronil on cattle held in an infested pasture. Animals treated repeatedly over time (seven applications) were infested with significantly fewer (p < 0.05) female ticks (5 mm in size) than untreated animals in all except one of the 57 weekly tick counts conducted after the first treatment was applied. As the number of treatments increased over time, there was a progressive decrease in the number of instances in which engorging females were observed on the treated cattle. Tick numbers obtained from sentinel cattle placed in pasture with untreated and treated cattle at various intervals throughout the study indicated that a single fipronil treatment had no observable adverse effect on the field tick population. However, after two treatments had been applied, there were always dramatically fewer ticks obtained from sentinel animals placed with treated cattle than were observed on sentinel animals placed with untreated cattle. Furthermore, tick numbers obtained from sentinel cattle placed with treated cattle over time indicated that the tick population in the pasture declined by stages. While a single treatment had no effect on the tick population, the application of two to four fipronil treatments at various intervals dramatically reduced the tick population, even though substantial numbers of females were still present on the sentinel animals. Ultimately, the application of five to seven fipronil treatments resulted in an extremely low tick population in the pasture, although total eradication of the population was not achieved during the study. The mean weight gain of treated animals was significantly higher (p < 0.05) than untreated animals during the study, indicating that the fipronil treatments had a highly beneficial impact on weight gain production.     

Separation of the two high molecular weight spectrin bands by a newly designed preparative slab electrophoresis technique.

Constructions and operation of an inexpensive preparative slab gel electrophoresis apparatus is described. A slab is made from two wide glass plates with symmetrical windows cut out from both sides. Coating the plates with a silane reagent allows good adhesion of a low concentration acrylamide sodium dodecyl sulfate gel. The migration of extracted chromatographed and fluorescent spectrin mixture is monitored with a uv light. At the end of the run, the slab is turned upside down and the material cluted upward in the small space formed by a dialyzing membrane placed in between the slab and the upper buffer reservoir. Using this apparatus and technique, the two heavy molecular weight spectrin bands can be purified. Advantages of this new system are discussed.     

A separation chamber to sort cells and cell organelles by weak physical forces: III. Preparative electrophoresis of cells in stationary density gradients at low electric field strength

An apparatus was designed for preparative density gradient electrophoresis of mammalian cells. In a low conductivity isotonic Ficoll density gradient of 1.5 cm length, human erythrocytes treated with neuraminidase were separated from untreated erythrocytes at an electric field strength of approximately 2.7 v/cm. Within 5 min two bands of erythrocytes were visible. Electrophoretic separation was completed within 25 min. The fractionation is performed in a design consisting of three Perspex circular plates, bottom and top plates of which can be displaced simultaneously relative to the stationary middle plate by a worm-gear mechanism. The middle plate contains a cylindrical separation chamber of 50 cm² and 1.5 cm high. Top and bottom plates contain cones and flow deflectors for the undisturbed thin layering of cell suspensions and for introduction of the density gradient. Also present in top and bottom plates are electrode compartments containing a large platinum electrode and a cellophane membrane that isolates the separation chamber hydrodynamically but not electrically from the electrode compartment. The electrode compartments were flushed with electrophoresis buffer to remove products of electrophoresis as well as the (low) generated Joule heat.     

Sub-lethal effects of deltamethrin residues on the within-crop behaviour and distribution ofCoccinella septempunctata

The behaviour and distribution of adultCoccinella septempunctata L. (Coleoptera: Coccinellidae) were recorded in two plots of winter wheat infested with the cereal aphidsSitobion avenae (F.) andMetopolophium dirhodum (Walk.) (Homoptera: Aphididae). One plot was sprayed with the pyrethroid insecticide deltamethrin at a rate of 6.25 g a.i./ha and the other was left unsprayed. Single ladybird beetles were released sequentially on the ground at the centre of the sprayed and unsprayed plots and their behaviour and position in the crop canopy were recorded at 30 second intervals for a total of 15 min per beetle. Assessments, with fresh beetles, continued for four days after spray application with a total of eighty ladybird beetles observed. The 15 min period was selected to avoid lethal effects and no ladybird beetles were killed or knocked down as a result of exposure to deltamethrin residues during this period. Significant differences were found between the overall behaviour patterns ofC. septempunctata in the untreated and deltamethrin treated plots up to three days after the spray application. Ladybird beetles exposed to deltamethrin residues were observed to walk and groom significantly more frequently and to rest significantly less frequently than those in the unsprayed plot. Significant differences were also found between the observed distribution of ladybird beetles in the sprayed and unsprayed crop canopies, with higher numbers of observations towards the bottom of the crop canopy and on the ground in the deltamethrin treated plot than in the untreated plot during the first two days after deltamethrin application. Upon the foliage itself, ladybird beetles were observed significantly more frequently on the abaxial leaf surface in the deltamethrin treated crop compared with the untreated crop. The results are discussed in terms of possible evidence for the repellency of deltamethrin toC. septempunctata and also the implications for integrated pest management of changes in predator behaviour and crop distribution resulting from sub-lethal uptake of insecticides.     

A silica gel plate-based qualitative assay for acetylcholinesterase activity: a mass method to screen for potential inhibitors.

A procedure for the qualitative assessment of inhibitory activity towards acetylcholinesterase for a given compound is described. Solutions of the compounds of interest are spotted on silica gel TLC plates in a matrix pattern. The silica gel plate is sprayed with a solution of acetylthiocholine iodide and 5,5-dithiobis(2-nitrobenzoic acid) followed by a solution of acetylcholinesterase. The enzyme reaction produces a yellow background color with inhibitor compounds exposed as white zones where color has failed to develop. The results for a test set of compounds were compared to those obtained using the standard Ellman assay procedure and found to agree for virtually all of these compounds. The conditions of silica gel plate thickness, reagent concentration, and enzyme source under which this procedure is suitable were investigated. This represents an extremely rapid method to screen large numbers of compounds to uncover new inhibitors of acetylcholinesterase and potentially other enzymes as well.     

Evaluation of a semiautomatic filtration technique for receptor binding studies.

A filtration apparatus, originally designed for cell culture harvesting, has been adapted for the use in receptor binding studies. The incubations are performed in titration plates, with eight rows of twelve wells. The wells in each row are filtered simultaneously on separate filters, and the washing of the filters is performed automatically. The total time consumed per row is less than one minute. The results obtained by using this equipment are in good agreement with those obtained with earlier types of filtration equipments, and the intraassay and interassay variation is very small.     

A vertical submarine electrophoresis apparatus for polyacrylamide minigels

A vertical submarine electrophoresis apparatus for use with minislab polyacrylamide gels is described. The design allows polyacrylamide gels to be run with the same ease and convenience that agarose gels are run with horizontal submarine apparatuses. The vertical submarine features a single buffer chamber with a restriction between the upper and the lower portions of the chamber. Acrylamide gels, cast between 9 X 10-cm glass slides, are inserted into the restriction and are completely immersed in buffer. Thus, current flows primarily through the gel itself, but some current flows through the buffer in the restriction surrounding the gel. Because water-tight separation of buffer chambers is not necessary, time-consuming and/or expensive procedures such as sealing with agarose or using fragile notched glass plates are eliminated. The apparatus can be set up to run a gel in less than 30 s. It is versatile in that gels of varying thickness (0.5, 0.8, 1.5, and 3 mm) can be run on a single apparatus. The apparatus has been used for sodium dodecyl sulfate gels, low ionic strength native gels for nucleoprotein complexes, and composite acrylamide-agarose gels.     

Enzymatic Digestion of Roots for Recovery of Root-knot Nematode Developmental Stages

Developmental stages of Meloidogyne javanica were successfully released from roots by treatment with commercially available cellulase and pectinase. The average percentage recovery of nematode developmental stages from Dolichos lablab, Elymus glaucus, and Lycopersicon esculentum were as follows: eggs = 526%, J2 = 272%, J3 = 783%, J4 = 549%, adult females = 285%, and total = 425%, expressed as percentages of the counts obtained from stained roots spread on glass plates. Root digestion was more accurate and sensitive in detecting low numbers of nematodes in roots than was the glass plate method. No simple linear, quadratic, or cubic relationship was found between the two methods that would allow a conversion factor to be developed.     

Effect of arena size on behaviour and mortality of the oriental cockroach Blatta orientalis in arenas with a cypermethrin deposit adjacent to harbourage access points

Activity and survival of adult female Blatta orientalis was investigated using tagged cockroaches in periodically illuminated arenas (LD 12:12 h) with a harbourage at one end. The arenas were rectangular with a width of 50 cm and lengths up to 480 cm. A cypermethrin-treated plywood plate (50 × 11 cm) substrate across the harbourage access points caused cockroaches to be exposed to the insecticide deposit by tarsal contact as they entered or left the harbourage. The effects of varying arena length and cypermethrin concentration were tested at 28°C. The LC50 following 3 days exposure ranged from 5.7 to 11.8 mg/m² on the plywood plate for arena lengths of 60 to 480 cm, respectively; cypermethrin at 30 mg/m² produced 100% knockdown of B. orientalis within one 12 h dark period.
During darkness, active cockroaches spent most time close to the harbourage or around food and water stations, at the far end of the arena, and made frequent returns into the harbourage. For arena length 120 cm, the mean duration of contact with treated plates during the first hour of the dark period was significantly less than contact time on untreated plates, but during 12 h the cumulative contact times were not significantly different between treated and untreated plates. During the first 4 h of the dark period, mean cockroach numbers on the treated plate declined as arena length increased, but not as rapidly as the mean number/unit area over the rest of the arena. The arena design is considered suitable for comparative testing of fast-acting neuroactive insecticide deposits against cockroaches.     

An ultrastructural study of cell plate modifications induced by 2,6-dichlorobenzonitrile in onion root meristems

Summary The effect of 2,6-dichlorobenzonitrile on cytokinesis of meristematic cells of onion root during both treatment and recovery has been studied by electron microscopic techniques. 2,6-dichlorobenzonitrile interferes with cell plate formation in such a way that Golgi apparatus vesicles of treated cells appear to be different than controls and seem to coalesce as anomalous partial cell plates. During recovery, an apparently normal progression of cytokinesis is observed and abnormal portions of the cell plate are retained. Nuclear constrictions are observed frequently during recovery as a result of temporal alterations in cytokinesis. Our results show that 2,6-dichlorobenzo-nitrile induces anomalous and/or incomplete cell plates, which might be caused by an altered function of Golgi apparatus.     

AN IMPROVED METHOD FOR OBTAINING AXENIC CLONES OF PLANKTONIC BLUE-GREEN ALGAE1,2

Axenic clones from 5 isolates of Anabaena flosaquae, 1 isolate of Microcystis acruginosa, and 1 isolate of Aphanizomenon flos-aquae were obtained by a combination of steps that provided a 1000-fold reduction in the bacteria-algae ratio and permitted bacteria-free filaments or cells to be isolated and grown from agar pour plates. The first step consisted of the addition of phenol to a dark-treated culture to selectively reduce the numbers of actively growing bacteria while leaving the resting algal cells viable. The next steps involved washing the treated algal suspension on a Millipore filter pad or membrane followed by plating in washed agar containing buffered mineral medium plus vitamins and soil extract. The final steps consisted of incubating the agar pour plates, coring bacteria-free filaments or cells, culturing the agar cores in a buffered mineral medium, and rigorously testing the resulting cultures for bacteriological contamination. Between 50 and 90% of the cores grew, and of these about 50% were judged axenic. The method, with appropriate adaptations, should be suitable for obtaining axenic clones of other freshwater and marine algae.     

Trends in arthropod defensive secretions,an aquatic predator assay

Summary Twenty-five arthropod defensive chemicals were tested on a potential fish predator to assay basic repellency, interniche effectiveness and mimetic interactions among repellents, and predator tolerance to repellents.The defensive secretions of aquatic arthropods are more effective repellents than those of terrestrial or cryptozoic arthropods. Phenolic compounds are more effective than carbonylic or acidic compounds. Repellency is most effective in compounds of reduced water solubility. Repeated exposure to gradually increasing molar concentrations of benzoic acid resulted in a greater acceptability of this compound to fish predators. It is suggested that Mullerian mimicry systems based on large numbers of species may be susceptible to dilution effects in terms of effectiveness.     

Targeting Biocontrol with the Slug-Parasitic Nematode Phasmarhabditis hermaphrodita in Slug Feeding Areas: a Model Study

The nematode Phasmarhabditis hermaphrodita was applied to soil in an outdoor miniplot experiment to protect Chinese cabbage seedlings from damage by the field slug Deroceras reticulatum. The aim was to investigate the possibility of reducing the numbers of nematodes applied by only partially spraying soil in the area where slug control was needed. Nematodes sprayed as overall applications were compared with band applications along plant rows and spot applications around individual plants, in plots with nine or 18 plants. Band and spot applications were applied at two rates, designated the full rate (same number of nematodes per plot as in the overall application) and the area rate (same number of nematodes per unit area comprising 43% (band) and 18% (spot) of the overall application). In plots with 18 plants, where spot-treated plant alternated with untreated plants, no significant difference in damage was found between spot-treated plants and untreated plants. This indicates that slugs were not repelled from nematode-treated areas and that any effects in reducing slug damage were not due to repellency. All nematode treatments resulted in a significant reduction in the mean level of slug damage to seedlings from six or more days after treatment. However, there were significant interactions between nematode treatment, the number of plants per plot, the position of plants within plots (edge or middle) and time after treatment. The effect of time after treatment was modelled. The log time to 50% reduction in slug damage (t 50 ) was related to the area treated and the dose applied. In plots with band or spot treatments at the full dose, there was a relatively small increase in t 50 with declining area treated. In plots treated with band or spot treatments at the area dose, t 50 increased consistently with declining relative area treated. The final level of damage, expressed as a percentage of damage on untreated plots (P), was influenced by both the dose and area treated. Final damage was greatest on spoti treated plots where half the plants were untreated. We conclude that partial treatment of soil around all plants to be protected from slug damage is a potentially valuable method of reducing the overall nematode dose required for control of slug damage, provided that some damage can be tolerated.     

Rapid DNA sequencing by horizontal ultrathin gel electrophoresis.

A horizontal polyacrylamide gel electrophoresis apparatus has been developed that decreases the time required to separate the DNA fragments produced in enzymatic sequencing reactions. The configuration of this apparatus and the use of circulating coolant directly under the glass plates result in heat exchange that is approximately nine times more efficient than passive thermal transfer methods commonly used. Bubble-free gels as thin as 25 microns can be routinely cast on this device. The application to these ultrathin gels of electric fields up to 250 volts/cm permits the rapid separation of multiple DNA sequencing reactions in parallel. When used in conjunction with 32P-based autoradiography, the DNA bands appear substantially sharper than those obtained in conventional electrophoresis. This increased sharpness permits shorter autoradiographic exposure times and longer sequence reads.     

Water repellency of post-boggy soils with a various content of organic matter

The objective of this study was to estimate the water repellency of post-boggy soils in north-eastern Poland. Potential water repellency was determined based on the water drop penetration time (WDPT) test and the molarity of an ethanol droplet (MED) test. A total of 276 soil samples with a varied organic carbon (OC) content, ranging from trace amounts in sandy subsoils to 44.4% in organic soils, were analyzed. The investigated material represents peat-muck soils (Eutri-Sapric Histsols) and muck-like soils (Arenic Gleysols, Areni-Humic Gleysols, Gleyic Arenosols). The mineral matter of the analyzed soils comprised loose sand. The obtained results indicate that peat soil formations are marked by higher potential water repellency than muck soil formations. The highest WDPT values (16 390 s) were reported in respect of an alder peat sample with 41.9% OC content, collected at a depth of 55–60 cm. In the group of muck soils, a sample with 36.7% OC content, collected at a depth of 15–20 cm, was marked by the highest water repellency (WDPT 10 492 s). The water repellency of the studied soils is dependent on organic matter content, and it is manifested only when organic matter content is higher than 20%. Soils with OC content of up to 12% show low water repellency or are hydrophilic. Organic soil formations (>12% OC) are characterized by a varied degree of water repellency, but WDPT values in excess of 2000 s are reported only in respect of soils containing more than 35% OC. A significant positive correlation between the content of organic matter, organic carbon, total nitrogen and water repellency was observed in the entire studied population (n = 276). A significant positive correlation was also found between WDPT values and the C:N ratio, while a significant negative correlation was reported in respect of .