Search

An acryloyl β-cyclodextrin-silica hybrid monolithic column for pipette tip solid-phase extraction and high-performance liquid chromatography determination of methyl parathion and fenthion has been prepared through a sol-gel polymerization method. The synthesis conditions, including the volume of cross-linker and the ratio of inorganic solution to organic solution, were optimized. The prepared monolithic column was characterized by thermogravimetric analysis, scanning electron microscopy, and Fourier transform infrared spectroscopy. The eluent type, volume and flow rate, sample volume, flow rate, acidity, and ionic strength were optimized in detail. Under the optimized conditions, a simple and sensitive pipette tip solid-phase extraction with high-performance liquid chromatography method was developed for the determination of methyl parathion and fenthion in lettuce. The method yielded a linear calibration curve in the concentration ranges of 15-400 μg/kg for methyl parathion and 20-400 μg/kg for fenthion with correlation coefficients of above 0.9957. The limits of detection were 4.5 μg/kg for methyl parathion and 6.0 μg/kg for fenthion, respectively. The recoveries of methyl parathion and fenthion spiked in lettuce ranged from 96.0 to 104.2% with relative standard deviations less than 8.4%.

Development of an acute oral toxicity test with a terrestrial-phase amphibian was considered necessary to remove the uncertainty within the field of agrochemical risk assessments. The bullfrog (Lithobates catesbeianus) was selected for use as it is a representative of the family Ranidae and historically this species has been used as an amphibian test model species. Prior to definitive study, oral gavage methods were developed with fenthion and tetraethyl pyrophosphate. Dimethoate and malathion were subsequently tested with both male and female juvenile bullfrogs in comprehensive acute oral median lethal dose (LD50) studies. Juvenile bullfrogs were administered a single dose of the test article via oral gavage of a single gelatin capsule of dimethoate technical (dimethoate) or neat liquid Fyfanon® Technical (synonym malathion), returned to their respective aquaria, and monitored for survival for 14 d. The primary endpoint was mortality, whereas behavioral responses, food consumption, body weight, and snout-vent length (SVL) were used to evaluate indications of sublethal toxicity (secondary endpoints). Acute oral LD50 values (95% fiducial interval) for dimethoate were 1459 (1176-1810, males) and 1528 (1275-1831, females), and for malathion they were 1829 (1480-2259, males) and 1672 (1280-2183, females) mg active substance/kg body weight, respectively. Based on the results of these studies, the methodology for the acute oral gavage administration of test items to terrestrial-phase amphibians was demonstrated as being a practical method of providing data for risk assessments. Environ Toxicol Chem 2018;37:436-450. © 2017 SETAC.

The susceptibility values for field-collected (BG-BG) and laboratory (KS-BG) strains of German cockroaches (BS-BG), Blattella germanica (L.) to five synthetic pyrethroid and three organophosphate insecticides were assessed by topical application. Both KS-BG and BS-BG strains demonstrated the highest levels of susceptibility to deltamethrin with LD50 values of 0.0035 μg/female and 1.5744 μg/female, respectively. The KS-BG strain demonstrated the lowest susceptibility level to fenthion with an LD50 value of 0.0698 μg/female, while the BS-BG field population showed the lowest susceptibility to bifenthrin with 4.6811 μg/female. The BS-BG field population showed resistance levels of 50 to 640 fold higher against the eight pesticides evaluated compared to the KS-BG strain. The resistance ratios (RR) of the eight pesticides were compared using populations of B. germanica that were collected from the same locality during 2007 and 2014. The field population of B. germanica collected during 2014 demonstrated significantly high resistance to an organophosphates and all pyrethroids when compared with those collected during 2007, but RR values were

The present study was designed to understand the effects of piperonyl butoxide (PBO), modulator of cytochrome P450 (CYP 450), on the neurotoxicity of organophosphate pesticide fenthion in the brain of Oreochromis niloticus used as a model organism. Fish were exposed to one-fourth of the LC50 value of fenthion (0.567 mg/L) and 0.5 mg/L PBO concentration for 24 h, 96 h, and 15 days. Glutathione (GSH)-related antioxidant system, lipid peroxidation, stress proteins, and acetylcholinesterase (AchE) activity were investigated. Our results showed that PBO induced the neurotoxic effect of fenthion with increasing oxidative stress in long-term exposure. GSH-related antioxidant system might take a role in protecting the brain from these oxidative effects. PBO possibly inhibited the biotransformation of fenthion by inhibiting CYP 450; thereby preventing the brain from AChE inhibition in short-term exposure. Changes in parameters indicated that PBO caused biphasic response by affecting CYP 450 in the brain of O. niloticus.

The relative toxicity of different concentrations of temephos and fenthion with petroleum ether root extract of Solanum xanthocarpum (Schrader) at 1 : 1, 1 : 2 and 1 : 4 ratios was evaluated against Anopheles stephensi (Liston) larvae. All combinations exhibited antagonism at concentrations lower than LC50 values and synergism at concentrations higher than their LC90 values. A 1 : 1 product ratio was the most effective.

BACKGROUND: Red-billed quelea (Quelea quelea) are controlled at breeding colonies and roosts by organophosphate sprays or explosions. Contamination with organophosphates after sprays and with petroleum products and phthalates after explosions was assessed. RESULTS: Concentrations in soil of the organophosphate fenthion the day after sprays were uneven (0–29.5 μg g−1), which was attributable to excess depositions at vehicle turning points, incorrect positioning of nozzles and poor equipmentmaintenance. A laboratory study using field-collected samples provided an estimate of 47 days for the half-life of fenthion. After sprays,fenthion persisted in soil for up to 188 days. High concentrations were detected 5 months after negative results at the same sites, providing indirect evidence of leaching. Concentrations of total petroleum hydrocarbons (TPHs) and phthalates ranged from 0.05 to 130.81 (mean 18.69) μg g−1 and from 0 to 1.62 (mean 0.55) μg g−1 respectively in the craters formed by the explosions, but declined to means of 0.753 and 0.027 μg g−1 at 10m away. One year after an explosion, mean TPHs of 0.865 and mean phthalates of 0.609 were detected. CONCLUSION: Localisation of high concentrations of fenthion likely to have effects on soil biota could be mitigated by improved spray management. Given a half-life in the soil of 47 days for fenthion and the possibility of its leaching months after applications raises concerns about its acceptability. The pollutants left behind after explosions have been quantified for the first time, and, given their long-term persistence, their continued use poses a threat to environmental health.

The susceptibility of Culex tritaeniorhynchus collected from Gwangju, Jeollabuk Province, Republic of Korea (ROK) to insecticides was evaluated under laboratory conditions using ten insecticides (7 pyrethroids and 3 organophosphates) that are currently applied by local public health centers in the ROK. Based on the values of median lethal concentration (LC50), Cx. tritaeniorhynchus larvae were most susceptible to chlorpyrifos (0.006 ppm), fenitrothion (0.022 ppm), fenthion (0.035 ppm) and bifenthrin (0.038 ppm), and were least susceptible to esbiol (1.722 ppm). In comparative resistance tests, the resistance ratios (RRs) of seven insecticides were compared among each other using two strains of Cx. tritaeniorhynchus that were collected from the same locality during 1992 and 2010. Culex tritaeniorhynchus demonstrated significantly increased RRs to pyrethroids over time, while demonstrating decreased RRs among the organophosphates. Among the pyrethroids, permethrin had the highest RR values of 182.1- and 833.3-fold differences, followed by etofenprox with RRs of 138.4- and 224.1-fold differences in values of LC50 and concentration that produced 90% mortality (LC90), respectively. Culex tritaeniorhynchus strains demonstrated the least amount of change in susceptibility to the organophosphates, chlorpyrifos, fenitrothion and fenthion with 0.020-, 0.019- and 0.001-fold differences in resistance ratios (RRLC50), respectively.

To assess the risk of mixtures of six paddy insecticides and their transformation products (TPs) to aquatic organisms in the Sakura River, Japan, their concentrations in the river water were monitored during the rice cultivation season in 2008 and 2009, and acute toxicity tests for Cheumatopsyche brevilineata (caddisflies) and Daphnia magna (daphnids), surrogate test species for caddisflies and cladocerans, respectively, were conducted. The mixture of fipronil, applied in the rice nursery box, and its desulfinyl, sulfide, and sulfone TPs were detected in the river for several months after transplanting, and they were more toxic to C. brevilineata than the other tested compounds. The toxicities of the parent compound and its TPs, such as fipronil and its TPs, may be related to their hydrophobicities. Risk quotients for mixtures (RQmix) of only parent compounds did not exceed 1, but, in mid-June 2009, the RQmix of parent compounds and TPs for caddisflies exceeded 1. Diazinon, fenitrothion, and fenthion sprayed on the rice crop and their TPs posed a sporadic risk for cladocerans, depending on the application timing, whereas fipronil TPs contributed to the RQmix for caddisflies for several months after transplanting. The risk of mixtures of insecticides and their TPs differed seasonally between caddisflies and cladocerans, depending on insecticide application timing and the persistence and toxicity of TPs. Environ. Toxicol. Chem. 2011; 30:1834–1842. © 2011 SETAC

This study investigates the effects of fenthion and terbufos, two organophosphorous pesticides, on DNA damage, tumor-related gene expression, and apoptosis in HepG2 cells. We found that exposure to concentrations ranging from 50 to 200 μM of fenthion and terbufos for 2 hr caused significant death in HepG2 cells. Both compounds induced DNA damage in a concentration-dependent manner as measured using the alkaline comet assay. Tumor-related genes (jun, myc, and fos) and apoptosis-related genes (socs3, tnfaip3, ppp1r15a, and nr4a1) were up-regulated by both compounds. Finally, both compounds induced apoptosis. The results demonstrate that both terbufos and fenthion induce DNA damage and should be considered potentially hazardous to humans.

Summary The effects of acute and chronic toxicity due to Lebaycid (0.0-dimethyl-3-methyl 4-methylthiophenyl phosphorothionate) and Metasystox-R (0.0-dimethyl-S-2 [ethylsulphinyl] ethylthiophosphate) on lipid metabolism in various tissues of White Leghorn birds (Gallus domesticus) were studied by using 2-14C-acetate, U-14C-glucose and 32P-phosphate. The incorporation of 14C glucose into total lipids of brain, spinal cord, sciatic nerves, liver and kidneys was increased and that of 2-14C-acetate was decreased by Metasystox-R. Lebaycid had similar effects on the incorporation of U-14C-glucose but did not decrease the incorporation of 2-14C-acetate. The results suggest that Metasystox-R inhibits the fatty acid synthetase complex and the enzymes of the TCA cycle, whereas Lebaycid does not inhibit the former. In nervous tissues and kidneys the two pesticides increase the degradation of phospholipids, whereas in liver they inhibit their biosynthesis as well. The possible mechanism of action of these pesticides involving the inactivation of coenzymes is discussed. Zusammenfassung Wirkungen von Metasystox-R und Lebaycid auf den Lipidstoffwechsel verschiedener Organe des Haushuhnes Mittels 2-14C-Acetat, U-14C-Glukose und 32P-Phosphat wurden bei Huhnern (weise Leghorn) Effekte der akuten und chronischen Toxizitat von Lebaycid(0,0-Dimethyl-3-Methyl 4-Methylthiophenyl Phosphorothionat) und Metasystox-R (0,0-Dimethyl-S-2 [Aethylsulphinyl] Aethylthiophosphat) auf den Lipidstoffwechsel verschiedener Gewebe untersucht. Metasystox-R erhohte die Aufnahme von 14C-Glucose in die Totallipide des Gehirns sowie des Ruckenmarks des N. ischiadicus, der Leber und Nieren, reduzierte hingegen diejenige von 2-14C-Acetat. Lebaycid hatte ahnliche Effekte auf die Inkorporation von U-14C-Glukose, reduzierte jedoch diejenige von 2-14C-Acetat nicht. Die Ergebnisse sprechen dafur, das Metasystox-R den Komplex der Fettsaure-Synthetase sowie die Enzyme des Citronensaure-Zyklus hemmt, wahrend Lebaycid diese Enzyme nicht blockiert. Die zwei Pestizide erhohen den Abbau von Phospholipiden im Nerven- und Nierengewebe wahrend sie in der Leber auch deren Biosynthese hemmen. Der Wirkungsmechanismus der Pestizide hinsichtlich der Enzyminaktivierung wird besprochen. Resume Actions de Metasystox-R et de Lebaycid sur le metabolisme des lipides de differents organes chez la poule domestique On a recherche au moyen de 2-14C-acetate, U-14C-glucose et 32P-phosphate chez des poules (Leghorn blanche) les effets de la toxicite aigue et chronique de Lebaycid (0,0-dimethyle-3-methyle-4-methylthiophenyle phosphorothionate) et de Metasystox-R (0,0-dimethyle-S-2 [ethylsulphinyle]ethylthiophosphate) surle metabolimsme des lipides de differents tissus. Le Metasystox-R a augmente l'inclusion de 14C-glucose dans les lipides totaux du cerveau, de la moelle epiniere, de N. ischiadicus, du foie et des reins, alors que l'inclusion de 2-14C-acetate fut diminuee. Le Lebaycid a eu les memes effets sur l'incorporation du U-14C-glucose, mais n'a pas reduit celle du 2-14C-acetate. Les resultats indiquent que la Metasystox-R inhibe le complexe de la synthetase des acides gras ainsi que l'enzyme du cycle de l'acide citrique, alors que le Lebaycid ne bloque pas ces enzymes. Les deux pesticides augmentent la destruction des phospholipides dans les tissus nerveux et renaux, et inhibent leur biosynthese dans le foie. Le mecanisme d'action des pesticides est discute en fonction de leur activation enzymatique. Resumen Efectos de Metasystox-R y Lebaycid sobre el metabolismo de los lipidos de diversos organos de la gallina domestica Se examinaron mediante 2-14C-acetato, U-14C-glucosa y 32P-fosfato los efectos de la toxicidad aguda y cronica de Lebaycid (0,0-dimetil-3-metil 4-metiltiofenil fosforotionato) y Metasystox-R (0,0-dimetil-S-2 [etilsulfinil] etiltiofosfato) sobre el metabolismo de los lipidos de varios tejidos de la gallina. Metasystox-R aumentaba la incorporacion de 14C-glucosa en los lipidos totales del cerebro y de la medula espinal, del nervio ciatico, hidago y rinones, reduciendo a su vez la de 2-14C-acetato. Lebaycid ejercia efectos similares sobre la incorporacion de U-14C-glucosa, mas no reducia la correspondiente de 2-14C-acetato. Los resultados insinuan que Metasystox-R inhibe el complejo de la sintetasis del acido graso y las enzimas del ciclo del acido citrico, mientras que Lebaycid no bloquea estos fermentos. Ambos pesticidas aumentan la degradacion de los fosfolipidos en el tejido nervioso y renal, mientras que en el higado inhiben tambien su biosintesis. Se discute el mecanismo de accion de los pesticidas incluyendo la inactivacion de las coenzimas.

An acetylcholinesterase (AChE)-lecithin biomimetic structure was constructed at the oil/water interface for the direct determination of fenthion in cyclohexane. Indophenol acetate in oil phase was hydrolyzed by AChE at the two-phase interface to produce indophenol. Square wave voltammetry was used to monitor the current decrease of substrate to assess AChE activity. The AChE incorporated in the lecithin-based biomimetic layer possessed higher enzymatic activity and was more sensitive to fenthion inhibition than freestanding AChE. A linear relationship between the inhibition percentage and logarithm of fenthion concentration was obtained in a concentration range from 1 ng/mL to 1 mg/mL.

The efficacy of the entomopathogenic fungus, Cephalosporium lecanii against coffee green scale, Coccus viridis in combination with subnormal concentrations of two insecticides, viz. fenthion and phosphamidon was evaluated in field. The fungus in combination with fenthion inflicted the highest percentage mortality (93.7) of the scales at the lowest dosages of both. The efficacy of fungus - phosphamidon combination was improved with increase in the concentration of either the fungus or phosphamidon. However, in vitro studies showed that fenthion significantly affected the radial growth, mycelial dry weight and germination of spores of the fungus while phosphamidon had lesser effect only at higher concentration. This variation in the results in the laboratory and field studies might be due to the influence of weather under field conditions and difference in the interaction between the fungus and insecticide in culture medium and insect system. Zusammenfassung Zur Wirkung unternormaler Konzentrationen von Insektiziden in Kombination mit dem Pilz Cephalosporium lecanii Zimm. bei der Bekampfung der Grunen Kaffee-Schildlaus, Coccus viridis Green (homopt., Coccidae) Es wurde die Wirksamkeit des entomopathogenen Pilzes Cephalosporium lecanii auf die an Kaffee schadliche Schildlaus Coccus viridis in Kombination mit unternormalen Konzentrationen zweier Insektizide (Fenthion und Phosphamidon) im Freiland untersucht. Die Kombination Pilz + Fenthion verursachte die hochste Mortalitat (93,7 %) der Schildlause bei gleichzeitig niedrigster Dosis der beiden Komponenten. Die Wirksamkeit der Kombination Pilz + Phosphamidon stieg mit der Konzentration von einer der beiden Komponenten. In vitro-Studien zeigten, das Fenthion signifikant das Wachstum und Myceltrockengewicht sowie die Keimung der Pilzsporen negativ beeinfluste, wahrend Phosphamidon geringere Wirkung zeigte, und dies auch nur bei hoherer Konzentration. Die Unterschiede zwischen den Labor- und Freilandergebnissen konnten auf dem Einflus der Witterungsbedingungen sowie der Interaktion zwischen dem Pilz und dem Insektizid in der Kultur und im Insektenkorper beruhen.

This study was designed to elucidate the effect of the organophosphate fenthion exposure on cholinesterase-specific activities in brain, liver, and kidney tissues of juvenile Oreochromis niloticus, and to define the best indicator tissue to fenthion exposure. The 96-h LC50 value was determined as 2.27 mg/L and fish were exposed to 20% of this concentration for 24-, 48-, and 96-h. Recovery periods in similar durations were provided to evaluate the ChE activities. AChE and BChE activities were determined spectrophotometrically. The activities of these enzymes were significantly inhibited in all the tissues tested, liver was the most and kidney was the least affected tissues. The inhibition percentages of AChE and BChE were at similar levels in the liver while BChE was more affected in kidney. BChE was not detected in the brain. A significant positive correlation in ChE inhibitions was found among tissues, and the effect of fenthion on ChE activities was tissue specific. In general enzymes activities were not significantly recovered in 96-h recovery period; however, an elevation in AChE inhibition was observed in brain. Based on the data of this study, the liver may be suggested as the best indicator tissue especially for phosphorothioate exposure. © 2009 Wiley Periodicals, Inc. Environ Toxicol 25: 391–399, 2010.

The susceptibility of members of the Anopheles sinensis Group in Korea to insecticides was evaluated under laboratory conditions using 15 insecticides currently used by local public health centers in Korea. The insecticides included eight pyrethroids, six organophosphates and a pyrazol analogue. Based on their LC50 values, the order of susceptibility of An. sinensis larvae to the insecticides was bifenthrin, chlorfenapyr, α-cypermethrin and λ-cyhalothrin, with values of 0.009, 0.04, 0.06 and 0.08 p.p.m., respectively. The least susceptibility was obtained with fenitrothion, with an LC50 of 7.7 p.p.m. In the comparative resistance test, the resistance ratios (RR) of 14 insecticides were compared to each other using two strains of members of the An. sinensis Group collected in the locality in 2001 and 2008. Anopheles spp. demonstrated higher RR to organophosphates such as fenthion, and low RR for the pyrethroids. Among the organophosphates, fenthion had the highest RR of 33.3 and 270.0 fold differences for LC50 and LC90 values, respectively. Among the pyrethroids, permethrin was observed to have the highest RR of 3.8 and 1.8 fold differences for LC50 and LC90 values, respectively. However, there were no significant differences in susceptibility to chlorfenapyr, chlorpyrifos, deltamethrin and fenitrothion. An. sinensis s. l. was more susceptible to the six insecticides bifenthrin, λ-cyhalothrin, α-cypermethrin, cypermethrin, cyfluthrin and pyridafenthion, showing 0.03, 0.06, 0.3, 0.3, 0.4 and 0.4 fold differences in resistance rates (RR LC50), respectively.

To develop new population control methods for the Mediterranean fruit fly, Ceratitis capitata, a study comparing bait application techniques (BAT) with a female-biased mass trapping strategy was carried out in seven citrus orchards in Mallorca (Balearic Islands, Spain). In the BAT treatment, fenthion, lambda-cyhalothrin and spinosad were applied separately in three of the orchards. In the other three, the mass trapping strategy (Probodelt traps baited with Biolure©) was adopted at a density of 50 traps/ha, reinforced when necessary with the same insecticide bait application (MTR). The seventh orchard was organically farmed and only mass trapping was used for control, but with a higher trap density (80 traps/ha). For pest monitoring, 2 traps/ha baited with Biolure© (for females and males) and 2 traps/ha baited with trimedlure (for males only) per orchard were inspected weekly. The most effective treatment was the MTR (with fenthion) programme, reducing the C. capitata female population by up to 68% [an average of 3.9 females/trap/day (f/t/d) were obtained vs. 12.6 f/t/d from BAT]. However, the lowest average C. capitata population (between the MTR programmes) was obtained by mass trapping supplemented with lambda-cyhalothrin (only 3.3 f/t/d). When only BAT was applied, applications with lambda-cyhalothrin proved to be the most effective (7.1 f/t/d). However, MTR carried out in the organic orchard resulted in the lowest female captures (2.0 f/t/d). Very little fruit damage was recorded in the treatment orchards. In all BAT treatments, the relative number of males and females was similar; however, in the MTR treatments fewer females than males were recorded in the same orchard.

BACKGROUND: This study was aimed at assessing the toxicity of ethyl cinnamate and ethyl p-methoxycinnamate (EMC) identified in Kaempferia galangal L. (Zingiberaceae) rhizome and another 12 known compounds to third-instar larvae from laboratory-reared Culex pipiens pallens Forskal, Aedes aegypti L. and Ochlerotatus togoi Theobald and field-collected C. pipiens pallens (Jinhae colony). Results were compared with those for fenthion and temephos. RESULTS: Ethyl p-methoxycinnamate was the most toxic of the test compounds to larvae of the three mosquito species (LC50 12.3–20.7 mg L−1) but less toxic than either fenthion (0.0096–0.021 mg L−1) or temephos (0.0039–0.0079 mg L−1). Ethyl cinnamate and 3-carene were highly active against C. pipiens pallens larvae (24.1 and 21.6 mg L−1) but less toxic to A. aegypti and O. togoi larvae (ca 40 and 60 mg L−1 respectively). The toxicity of these compounds to larvae from the Jinhae colony of C. pipiens pallens was almost the same as their toxicity to the laboratory-reared larvae, although the larvae from the colony exhibited low levels of resistance to fenthion (resistance ratio 9.1) and temephos (5.8). CONCLUSION:Kaempferia galanga rhizome-derived materials, particularly ethyl p-methoxycinnamate, merit further study as potential mosquito control agents for protection of humans and domestic animals from vector-borne diseases and nuisance caused by mosquitoes. Copyright © 2008 Society of Chemical Industry

Organophosphate poisoning is a common cause of severe morbidity and mortality among patients admitted to emergency departments. Tissue damages as a consequence of organophosphate poisoning are frequently reported, but preventing this potentially severe complication has not been the subject of much research. We tested whether interleukin-10, a cytoprotective agent, could prevent or diminish pathological signs of tissue damages caused by organophosphate poisoning. Thirty rats were divided into three equal groups (n = 10). Group I (sham) did not receive any agent during the experiment. Group 2 (control) received 0.8 g/kg of fenthion intraperitoneally, followed by 6 ml/kg of intraperitoneal normal saline 30 min. and 3 hr later. Group 3 (treatment) received 0.8 g/kg of fenthion intraperitoneally, followed by 2 mu g/kg of interleukin- 10 intraperitoneally 30 min. and 3 hr later. All rats were killed under anaesthesia after 6 hr and tissue samples were obtained from liver, kidneys and lungs. Even organophosphate poisonings do not cause significant clinical problems; several degrees of damages could be observed in liver, kidneys and lungs. These damages could be reduced by interleukin-10 treatment.

The side-effects of six pesticides used on peaches in Brazil were tested on the hymenopteran egg parasitoid Trichogramma cacoeciae using four laboratory tests: (a) adult parasitoid exposure to fresh pesticide residue on glass plates (worse case); (b) direct spray of host eggs enclosing the parasitoid egg, larvae or pupae (less-exposed life stages); (c) exposure of adults to pesticide residues on plant leaves at different intervals after application (persistence); (d) Dose–response pesticide exposures of adults on glass plates. Two dose rates were used: (1) The highest recommended field dosage (FD) and (2) the predicted initial environmental concentrations (PIEC). The results showed that the preparations greatly differed in their initial toxicity and persistence. The insecticide Valient® (methoxyphenozide) and the fungicide Venturol® (dodine) were considered harmless to T. cacoeciae adults as they fell into the class 1 category according to the guidelines of the International Organization for Biological Control (IOBC) when parasitoids were directly exposed to chemical residues. The insecticide/acaricide Assist® (mineral oil) was slightly harmful at the rate of PIEC 0.4 (40% of FD) and moderately harmful at FD. Pesticides in the categories harmless and moderately harmful can be considered for use in integrated pest management (IPM). The fungicide/acaricide Kumulus DF® (sulphur) and the insecticides Dipterex® 500 (triclorfon) and Lebaycid® 500 (fenthion) were harmful at both concentrations. In the persistence test, Assist® was short lived and therefore may in special cases (i.e. reduced direct contact) be considered for use in IPM, but Kumulus® DF, Dipterex® 500 and Lebaycid® 500 constantly reduced parasitism between 77 and 100% and were rated as persistent (more than 30 days). The direct spray of parasitized host eggs at intervals after parasitism showed that Assist® and Kumulus® DF were harmless to the parasitoid egg, larvae and pupae within the host eggs. Dipterex® 500 was slightly harmful when sprayed one day after parasitism (parasitoid egg) and moderately harmful to the other two stages (larvae and pupae). Lebaycid® 500 was harmful to the parasitoid egg and larvae and moderately harmful to the pupae. The dose–response test showed that Kumulus® DF and Dipterex® 500 were toxic to T. cacoeciae. Kumulus® DF was harmful from 1 PIEC 0.4 to 0.125 PIEC 0.4 dosages and was slightly harmful with 0.0625 PIEC 0.4 dosage. Dipterex® 500 was harmful to T. cacoeciae in all the dosages tested.

ABSTRCT A study was conducted to determine the susceptibility of Anopheles sinensis larvae, malaria vector, from Paju-shi (Gyonggi-do) to 24 pesticides including 11 pyrethroids, 11 organophosphates, 1 pyrazole analogue and another pesticide. The mosquito larvae showed the most highly susceptible to chlorfenapyr with LC50 of 0.0063 ppm followed by spinosad, temephos, fenthion and beta-cyfluthrin with 0.03, 0.0366, 0.0367 and 0.0998 ppm, respectively, and fluvalinate (>128 ppm) was the least susceptible. Also, 11 pesticides of them were compared with Goyang strain (Gyonggi-do) of data 1992. The development of resistance was noticed to cypermethrin and permethrin as much of 73.59 and 6.23 folds at LC50, respectively, and also fluvalinate was showed high resistance development. In generally, the pyrethroid insecticides were showed higher development of resistance than organophosphorus insecticides.

1 To contribute to the development of IPM strategies in olive groves, the selectivity of several insecticides to Pullus mediterraneus Fabr. (Coleoptera: coccinellidae) was investigated in the laboratory. The study assessed the toxicity of seven chemical pesticides and one bacteriological insecticide to adult P. mediterraneus. 2 The LC50 was estimated by applying the pesticides on the dorsal side of adults. Lambda-cyhalothrin, methomyl and cypermethrin resulted in the highest toxicity followed, in decreasing order of toxicity, by malathion, fenthion and dimethoate. Parathion had the least effect on the coccinellid. 3 Consumption of Bacillus thuringiensis bacteria (applied as a commercial formulation), over a period of 10 consecutive days, resulted in low mortality of adult P. mediterraneus. 4 The results of these laboratory experiments indicate that the most widely used chemical pesticides were toxic to P. mediterraneus. Their use in olive groves must take account of the activity period of this predator. In contrast, B. thuringiensis seemed to be a suitable candidate to be included in pest management systems.

Pesticides with N,N-dimethyl and thiomethyl moieties (aminocarb, methiocarb and fenthion) were irradiated under artificial light (λ > 290 nm) in an amorphous wax phase from Persica laevis DC. The effect of the presence of the wax on the photolysis rate differed in the three pesticides, increasing it in aminocarb, having little effect in methiocarb and slowing it down in fenthion. The presence of the wax affected the qualitative photodegradation behaviour of all the pesticides. The data obtained were compared with those for pirimicarb, which had been studied earlier. © 2001 Society of Chemical Industry

Insecticide susceptibility of a 1995 Townsville Aedes aegypti (L.) population was investigated in the laboratory according to World Health Organization guidelines. Using baseline data from two Townsville populations (1955 and 1989), larval bioassays detected significant increases in susceptibility to synthetic pyrethroids and malathion, and significant reductions in susceptibility to most organophosphates and propoxur. Adult bioassays detected significant resistance to bendiocarb and DDT. Comparison of larval data with the international reference ROCK strain showed substantial resistance to have developed to malathion and fenthion. Further analysis revealed the presence of distinct substrains in the baseline 1989 population, which displayed varying levels of temephos susceptibility. We concluded that susceptibility investigations should assess mosquito populations collected from many sites within an area rather than taking a single population from one site, and that the 1989 Ae. aegypti colony would be unsuitable for use as a susceptible reference population.

A child with severe organophosphate (fenthion) poisoning was successfully treated by repeated administration of activated charcoal with infusion of atropine sulfate and PAM (pyridine 2-aldoxime methiodine). A 19-month-old girl ingested fenthion and was admitted 1.5 hours later. Her serum cholinesterase level was 59IU/l on admission and diminished to 2.7% of the lower limit of normal range over the subsequent 4 days. It then rose gradually over the next 10 days and the clinical symptoms also improved. The serum fenthion value reached its maximal level of 0.66μg/ml at the time of a seizure that occurred 20 hours after exposure, and the half-life of fenthion was 11 hours. The patient recovered from the poisoning smoothly and there were no signs or symptoms indicating a relapse. Assuming that repeated administration of activated charcoal inhibits reabsorption of organophosphate in the entero-hepatic circulation, we can easily understand the fenthion value course or this clinical course. Infusion of atropine sulfate every 2-3 hours was effective in controlling muscarinic reactions, but PAM was not in nicotinic and other toxic reactions. The patient's conciousness was transiently dulled by chloral hydrate during recovery. The use of chloral hydrate should be avoided in the acute phase, because it induces transient disturbances of consiousness.

Laboratory studies were conducted to determine the effect of the naturally derived compound spinosad on Ceratitis capitata Wied. (Diptera, Tephritidae). The organophosphate fenthion was used as a standard. Direct dose-dependent mortality and reduced fecundity were observed in oral treatment of adults with spinosad. The LC 90 values 14 h and seven days after treatment were 19.50 and 0.49 mg litre -1 respectively. Fenthion was less active (the LC 50 eight days after treatment was 1.17 mg litre -1 ) and did not affect the fecundity of the fly. Adults were also very susceptible to spinosad and fenthion via residual contact. For spinosad, 100% mortality was recorded 48 h after treatment for a dose of 10 mg litre -1 . Spinosad was more effective than fenthion in suppressing larval development when neonate larvae were reared on treated diet supplemented with a range of concentrations from 0.02 to 0.83 mg kg -1 diet. Last-instar larvae were much less susceptible to spinosad or fenthion when exposed via dipping or when they pupated in treated medium and both products had similar performance. A lack of ovicidal activity was observed in direct egg-treatments with spinosad but significant reductions from 1 mg litre -1 onwards were recorded for fenthion.

The ecological risks of pesticides to wildlife are assessed by the United States Environmental Protection Agency with a simple quotient model. A risk factor is calculated by dividing the estimated dietary concentration by the chemical’s dietary toxicity. The risk factor, which can be used to predict population mortality, serves as a regulatory criterion to identify compounds that could pose unacceptable risk. Under the “New Paradigm,” the Environmental Protection Agency recently cut by 50% the critical risk factor, yielding more-rigorous decision-making criteria by decreasing acceptable wildlife mortality from 50 to 8.8% following one pesticide application and by increasing the number of pesticides that pose unacceptable risk to wildlife. The quotient model depends on at least one implicit and approximately 11 explicit assumptions; deviations from these assumptions may bias outputs and consequent regulatory decisions. To correct error-prone assumptions we present three modifications that improve ecological risk estimates. We used the agency’s quotient model to survey risks to a regional avifauna (Florida birds) in relation to mosquito pesticide exposure (fenthion, malathion, and naled). Certain groups (small-bodied, insectivorous passerines) were predicted to face the highest ecological risk due to taxonomy, diet, and body mass. Finally, we performed a risk assessment for Black-whiskered Vireos (Vireo altiloquus barbatulus) exposed to fenthion. The results revealed that this species could potentially suffer 42% mortality in a population exposed to one application of fenthion. Ecological risk assessments increasingly will be based on mathematical models. To improve predictions of the effects of xenobiotic compounds on wildlife, biologists-especially conservationists-should work with ecotoxicologists to improve current models, develop new models, and provide data to parameterize models. Equally important, conservationists should participate in defining regulatory levels of ecological risk for wildlife. Los riesgos ecologicos de los pesticidas para la fauna silvestre son evaluados por la Agencia de Proteccion Ambiental de los Estados Unidos con un simple modelo de cociente. Se calcula un factor de riesgo dividiendo la concentracion dietetica estimada por la toxicidad dietetica quimica. El factor de riesgo que puede ser usado para predecir la mortalidad poblacional, sirve como un criterio regulador para identificar compuestos que podrian representar riesgos inaceptables. La Agencia de Proteccion Ambiental recientemente ha reducido en un 50% el factor de riesgo critico, creando un criterio mas riguroso para la toma de decisiones al disminuir la mortalidad aceptable de la fauna silvestre, despues de una aplicacion del, pesticida del 50% at 8.8% y al aumentar el numero de pesticidas que representan riesgos inaceptables para la vida silvestre. El modelo del cociente depende de, por lo menos, un supuesto implicito y aproximadamente 11 supuestos explicitos; desviaciones en estos supuestos podrian sesgar los resultados y las consiguientes decisiones reguladoras. A los efectos de corregir supuestos propensos a errores, presentamos tres modificaciones que mejoran las estimaciones del riesgo ecologico. Usamos el modelo del cociente de la Agencia para evaluar el riesgo para una avifauna local (las aves de la Florida) en relacion con la exposicion a los pesticidas contra mosquitos (fenthion, malathion y naled). Se predijo que ciertos grupos (pequenos paserinidos insectivoros) enfrentan un riesgo ecologico mas alto debido a taxonomia, la dieta y masa corporal. Finalmente llevamos a cabo su una evaluacion del riesgo para Vireo altiloquus barbatulus expuesto al fenthion. Los resultados revelaron que esta especie podria sufrir potencialmente un 42% de mortalidad en una poblacion expuesta al fenthion. Para mejorar las predicciones de los efectos de compuestos xenobioticos sobre la fauna silvestre, los biologos (especialmente los conservacionistas) deben trabajar con ecotoxicologos para mejorar los modelos corrientes, desarrollar nuevos modelos y proveer datos para parametrizar los modelos. De igual importancia es que los conservacionistas participen en la definicion de los niveles de regulacion del riesgo ecologico para la fauna silvestre.

The vertical pattern in olive fruit fly infestations was studied in the Tlemcen region (western part of Algeria) in 1990. The infestation rate of olives, measured by punctures, eggs, larvae, exit holes and pupae, was always higher in the lowest stratum (up to 2 m) than in the upper (3 m), the middle stratum being infested at an intermediate level. Differences were largest in October. In 1992 this result was used by spraying insecticide in an orchard half as intensely in the two higher strata as in the lower stratum. This led to relatively good protection in comparison with unsprayed orchard.

Thermal analysis of controlled-release formulations of fenthion, prepared by its entrapment in cross-linked carboxymethylcellulose and carboxymethylcellulose–gelatin matrices was carried out by thermogravimetric analysis and under accelerated storage conditions. Thermograms of samples of sodium carboxymethylcellulose, cross-linked polymer samples, and the formulations were studied. The thermogravimetric analysis showed improved heat resistance and retention of fenthion or its decomposition products in the formulated samples. The decomposition maximum of technical-grade fenthion was 260°C and the corresponding weight loss was about 90%, whereas fenthion or its decomposition products appear to be retained up to temperatures ranging from 400 to 500°C in the formulations. The half-life of fenthion in the mechanical mixture with the carrier polymer was found to range from 19.92 to 29.98 days, whereas in the formulated samples, it was found to range between 41.54 and 113.35 days. © 1994 John Wiley & Sons, Inc.

Effects of toxic chemicals on estuarine and marine crustaceans are often evaluated using the mysid Mysidopsis bahia. In a literature survey of results of acute toxicity tests with estuarine crustaceans, Mysidae and Penaeidae were generally the two most sensitive families. However, neither family was consistently more sensitive (higher LC50 divided by lower LC50 > 2). Mysids were 54 times more sensitive to pyrethroids than were penaeids (N = 3 studies). Yet penaeids were 36 times more sensitive (N = 4 studies) to organochlorines and 5 times more sensitive (N = 17 studies) to organophosphates than were mysids. Acute exposures of ≤24-h-old mysids and second postlarval pink shrimp Penaeus duorarum were conducted to compare responses of these crustaceans to each other, and to values from the literature for other estuarine crustaceans. The test compounds were chloride salts of cadmium, copper, and zinc; the organophosphates diazinon, fenthion, and malathion; and several pyrethroids – cypermethrin, fenvalerate, and permethrin. Results showed that pyrethroid toxicities to mysids and postlarval pink shrimp were similar, organophosphate toxicities were within a factor of 2.6 for both species, and mysids were 3 to 26 times more sensitive to the metals than were larval pink shrimp.

The promotion of hydrolysis of some organophosphorus pesticides by mercury(II) ion was studied. The presence of mercuric chloride at 20 mg litre−1 increased the initial hydrolysis rates of malathion, fenitrothion, fenthion and parathion-methyl in pH 5.5 buffer by two to three orders of magnitude. The hydrolysis was found to be first order with respect to both mercury(II) ion and the pesticide. The main hydrolysis product was 3-methyl-4-nitrophenol for fenitrothion, and 4-nitrophenol for parathion-methyl. It is postulated that the reaction involves the formation of a 1:1 complex and a very slow regeneration of the mercury(II) ion from the reacted complex. Mercury(II) ion had little effect on the organophosphorus pesticide dichlorvos.

The influence of post-treatment temperatures of 5, 10, 17 5, and 25°C on the efficacy of three pesticides, Karate (10 g a i/ha lambda cyhalothnn), Sumicidin 10 (30 g a i/ha fenvalerate), and Afugan (294 g a i/ha pyrazophos), applied to Poecilus cupreus (Coleoptera Carabidae) was investigated in the laboratory The results indicate a negative correlation between the temperature and the effects of all three products With the two pyrethroids Karate and Sumicidin, the recovery period of knocked down beetles and their food consumption showed this negative temperature correlation The reason seems to be a temporarily arrested detoxification of the pyrethroids inside the beetles at reduced temperatures Final mortality seven weeks after application of pyrethroids was unaffected by temperature With the organophosphorus compound pyrazophos final mortality was negatively correlated with temperature Male beetles seemed to be more sensitive than females with all products and temperatures

Queletox® (Fenthion) is widely used in Africa to kill birds that eat cereal crops. Applications of Queletox have been reported to kill nontarget animals and contaminate areas used by livestock and humans. In 1988, we evaluated Queletox treatments to wetland roosts at the Njoro dam (2.88 kg/ha) and Gicheha farm (12.0 kg/ha) near Nakuru, Kenya. Fenthion deposits measured in the roosts ranged up to 1,100 g/ha, but were >1 0 g/ha at distances of 100 m or more from roosts. Following applications, 61 birds of 14 species at the Njoro dam and 22 birds of eight species at the Gicheha farm were found dead or severely debilitated. However, the general abundance of waterfowl, wading birds, plovers, doves, and passerines seemed unaffected. Residues in crop contents of 11 dead birds ranged up to 11.0 ppm, substantiating death from fenthion. Fenthion residues (2.2-750 μg) recovered from skin and feathers of 36 dead birds were sufficient to have been hazardous to predators and scavengers. Neither amphibians nor fishes were affected by treatments. At the Njoro dam, scarabids, dytiscids, and notonec-tids were killed, and their numbers decreased; many insects also were killed at the Gicheha farm. The abundance of these groups, however, had increased within 6 d post-treatment. Fenthion residues of 1.8 to 17 ppb were found in positive water samples for up to 5 d post-treatment. All sampled vegetation had temporarily hazardous residues; levels ranged up to 83 ppm on grasses but had decreased to

The level of fenthion residues was followed for up to one year in olive oil samples. The concentration of the parent compound decreased slowly following a double-phase first-order decay model, both in the freezer and laboratory, while the total concentration (parent compound and its sulfoxide) remained unchanged. Storage, therefore, cannot be used as a decontamination technique for oil containing higher than the toxicologically acceptable residues of this compound.

American kestrels (Falco sparverius), eastern screech-owls (Otus asio), and northern bobwhites (Colinus virginianus) were given single acute oral doses of four widely diverse anticholinesterase pesticides: EPN, fenthion, carbofuran, and monocrotophos. LD50s, based on birds that died within 5 d of dosage, were computed for each chemical in each species. Sex differences in the sensitivity of northern bobwhites in reproductive condition were examined. American kestrels were highly sensitive to all chemicals tested (LD50s 0.6–4.0 mg/kg). Eastern screech-owls were highly tolerant to EPN (LD50 274 mg/kg) but sensitive to the remaining chemicals (LD50s 1.5–3.9 mg/kg). Northern bobwhites were highly sensitive to monocrotophos (LD50 0.8 mg/kg) and less sensitive to the remaining chemicals (LD50s 4.6–31 mg/kg). Female bobwhites (LD50 3.1 mg/kg) were more sensitive to fenthion than males (LD50 7.0 mg/kg). Mean percent depression of brain cholinesterase (ChE) of birds that died on the day of dosing exceeded 65% for all chemicals in all species. The response of one species to a given pesticide should not be used to predict the sensitivity of other species to the same pesticide. The need for research on several topics is discussed.

Organophosphorus insecticide residues have been monitored for two years in virgin olive oil after dimethoate and fenthion treatments to control the olive fruit fly. No dimethoate residues were detected in any of the samples. For the first and second years, 50% and 21%, respectively, of the samples contained no detectable fenthion residues, while 4% and 6%, respectively had residue concentrations exceeding the Codex Alimentarious Maximum Residue Limit (1 mg kg−1). The mean concentration was 0·236 mg kg−1 oil and the estimated daily intake of fenthion 0·0002 mg kg−1 body weight (Acceptable Daily Intake 0·001 mg kg−1 body weight). The parent compound was the most important residue in fresh samples, while aged samples contained a higher amount of the metabolite fenthion sulfoxide. The contribution of the oxygen analogues (P= 0 metabolites) of fenthion to the total residue concentration was

Resistance to a number of organophosphorus insecticides and the carbamate propoxur has been detected in a field population of Culex quinquefasciatus Say from Jeddah, Saudi Arabia. Cross resistance studies indicate that the same mechanism(s) may produce resistance to the full range of these compounds.

Four groups of six cats were kept in carpeted pens similarly infected with Ctenocephalides felis . One group was left untreated, but the other groups were treated every 28th day with either an insecticide (fenthion at 30 mg); or an inhibitor of insect development (lufenuron at 133 or 266 mg) or with both. A sudden upsurge in the numbers of fleas occurred on the control cats after 50 days. At this time, the three control strategies had reduced the counts by 91.3, 72.5 and 98.6 per cent, respectively. Thereafter, welfare considerations demanded the limitation of the flea burden on the control cats, but conditions were shown to be favourable for flea development throughout the study. The mean numbers of fleas on the treated groups after six months were 1.2, 11.0 and 0.4, respectively. After this, in addition to the fleas acquired in the pen, the cats were each infected weekly with five fleas to mimic roaming animals introducing extraneous fleas into the home. This produced no obvious effect on the counts and the mean values three months later were 0.5, 11.0 and 0.2, respectively. None of the strategies eradicated the flea population but they all reduced the numbers considerably and worked equally well whether or not small numbers of new fleas were introduced into the system. Significantly lower flea counts were maintained in the early and later stages of the study by the strategies including the insecticide.

In a series of three replicated and controlled trials, nine dogs artificially infected with Ctenocephalides felis were treated with a systemically active ‘spot-on’ formulation of fenthion, six with a topical spray containing dichlorvos and fenitrothion and six with a surface active ‘spot-on’ preparation containing permethrin, all at recommended dose rates. Good knockdown efficacy was apparent at eight hours with the dichlorvos/fenitrothion combination and at 24 hours with the other formulations. Efficacy values in excess of 95 per cent persisted for at least 22 days in the case of the systemic fenthion preparation and the permethrin product and eight days for the dichlorvos and fenitrothion combination. Twenty-nine days after treatment there was still substantial protection in the fenthion- and permethrin-treated animals, indicated by an 88 and a 77 per cent reduction in flea counts in the two groups, respectively.

Commercial formulations of chlorpyrifos, trichlorfon, malathion, diazinon, temephos, fenthion, chlorfenvinphos and chlorpyrifos-methyl were bioassayed at 25 ± 1 °C against fourth-instar larvae of the rice bloodworm, Chironomus tepperi. Chlorpyrifos was the most toxic, with an LC50 of 1.3 ppb. The relative order of LC50s in ppb was (LC50 values in brackets); chlorpyrifos (1.3) < chlorpyrifos-methyl (2.5) < temephos (2.8) < chlorfenvinphos (6.0) < malathion (8.4) < diazinon (35.5) < trichlorfon (67.4) < fenthion (159.4). All compounds are sufficiently toxic to be effective against C. tepperi in the field, but the results suggest that some insecticides, particularly chlorpyrifos, are being applied at excessive rates.

Keywords: allergic contact dermatitis; organophosphorus pesticides; chlorpyriphos-methyl; fenthion; methidathion; parathion-methyl; malathion; cross-sensitivity; occupational; agriculture

A controlled study was carried out in two replicated trials, each using three groups of domestic cats artificially infested with Ctenocephalides felis. In each trial three cats were treated with fenthion, three were treated with a dichlorvos/fenitrothion formulation, both at the recommended dose rate and the remainder acted as untreated controls. Good knockdown efficacy was evident 24 hours after both treatments. Efficacy values of 85 per cent or more were maintained for at least 15 days with fenthion and for less than eight days with dichlorvos/fenitrothion.

The efficiency of 2-cyclopropylamino-4, 6-diamino-s-triazine CGA-72662 (proposed common name: cyromazine) for the control of blowfly strike was tested in fly cage and field trials on sheep. The safety to sheep and physico-chemical properties of the compound as they relate to blowfly control were also assessed. When the sheep were thoroughly jetted with a solution of CGA-72662 containing 1g of active ingredient per litre, the mean incidence of fly strike in 7 field trials was reduced from 16.5% to 1.5% over a period of 9 weeks. The incidence of strike in the treated sheep in 2 insectary tests, which imposed levels of fly activity far in excess of that usually encountered in the field, was reduced from 93% and 73% in untreated sheep to 2% and nil respectively over a period of 8 weeks. Jetting with CGA-72662 solutions 100 times greater than the recommended concentration did not produce any side effects in sheep. Three treatments at twice the recommended concentration during the first trimester did not affect pregnant ewes nor their progeny. The compound was safe to use in combination with common anthelmintics and with sheep dips used for control of lice. CGA-72662 was stable in solution. No stripping occurred in dips and it persisted on wool for a considerable period. A satisfactory alternative to the organophosphorus insecticides has been found in CGA-72662, since it provided a substantial increase in residual protection against blowfly strike with a high degree of safety.

Acute, lethal effects of fenthion (an organophosphate insecticide) on mysids (Mysidopsis bahia), grass shrimp (Palaemonetes pugio), pink shrimp (Penaeus duorarum) and sheepshead minnows (Cyprinodon variegatus) were determined in laboratory tests and after field applications. Exposures at four field sites ranged from short-term exposures (12 h or less) of rapidly decreasing fenthion concentrations to extended intervals (more than 72 h) with slowly increasing or decreasing fenthion concentrations. Laboratory-derived LC50s provided a reliable benchmark for predicting acute, lethal effects of fenthion on caged animals in the field when exposures persisted for 24 h or more but overestimated the toxicity for exposures of less than 24 h. Laboratory pulse-exposure tests with rapidly changing concentrations for 12 h were predictive of the nonlethal and lethal effects observed for short-term field exposures.

Adult male northern bobwhite (Colinus virginianus) were fed diets containing organo-phosphorus pesticides, and the birds' discrimination acquisition and reversal performance was evaluated. The birds received the pesticide-laced diets continually, beginning 2 d before behavioral testing and ending after the birds completed the test series consisting of an acquisition and 10 reversals. Bobwhites fed a diet containing 0.18 ppm monocrotophos made 118% more errors (p ± 0.05) than did controls during reversals but not during acquisition. The behavior of bobwhites fed diets containing 0.02 and 0.06 ppm monocrotophos was not different from that of controls. Acquisition performance of bobwhites fed a diet containing 7 ppm fenthion was not different (p > 0.05) from that of controls; however, bobwhites fed the fenthion diet made 48% fewer errors (p ± 0.05) in the reversals. When retested after 18 (monocrotophos) and 73 (fenthion) d on clean diets, no residual behavioral effects were detected. Brain cholinesterase activity was inhibited in all treatment groups.

Fenthion (Baytex), an organophosphate insecticide, is frequently applied to salt-marsh environments to control mosquitoes. Shake-flask tests were used to study rates of abiotic and biotic degradation of fenthion and the environmental parameters that affect these rates. Water or water-sediment (500 mg dry weight/L) slurries from salt marshes located along the Northwest Florida Gulf Coast were used. Flasks contained 200 μg fenthion/L, and degradation rates were determined by following decrease of fenthion over time. Hydrolysis and biodegradation in water were relatively insignificant fate processes; fenthion disappeared from flasks containing water, formalin-sterilized water, or formalin-sterilized sediment very slowly (half-life ≥ 2 weeks). The presence of nonsterile sediment resulted in a rapid exponential disappearance of fenthion (half-life ≥ 3.8 d). Biodegradation was assumed since sterile sediment systems showed a much slower decrease of fenthion, and the production of polar compounds (hexane-unextractable) from radiolabeled fenthion was greater in the presence of sediment than sterilized sediment. The effect of environmental pH levels (5.0–7.0) on degradation was insignificant. No biotic degradation occurred at low oxygen concentration. An 8°C decrease in incubation temperature decreased the rate of sediment biodegradation 2.5-fold. Light caused a slight, but significant, increase in the biotic and abiotic degradation rates of fenthion in water. A two-fold variation in sediment-mediated degradation was noted among sediment samples from three stations within one field site. Inclusion of whole marsh plants or plant parts increased the disappearance rate of fenthion in test systems.

The fate of fenthion was examined in laboratory microcosms to describe interaction between sediment and biodegradation in the field. A mathematical model also was calibrated to calculate distribution of fenthion in microcosms. Intact sediment cores, with and without a salt-marsh plant, Juncus roemerianus (black needlerush), were placed in microcosm vessels to simulate an undisturbed sediment bed of a salt marsh and areas containing Juncus. In a formalin-sterilized microcosm without plants, fenthion disappeared exponentially from the water column with a half-life of 105.0 h. Fenthion had a half-life of 35.5 h in a nonsterile microcosm without plants. In the nonsterile microcosm with plants, the half-life was slightly shorter, 33.2 h. The sediment was fractionated into 0.5 cm layers. Fenthion was found at greater sediment depths in nonsterile systems than predicted by diffusion and sorption in the sterile microcosm, possibly because of bioturbation. Distribution of fenthion in sediment was not appreciably different between microcosms with and without plants. Fenthion appeared to be biodegraded in the upper (1 to 7 mm) sediment layers.

Twenty-seven insecticides, including organochlorine, organophosphorus compounds and carbamates were tried for potentiation of the toxic effect of malathion. Carbaryl, diazinon, fenthion, gamma-BHC, parathion and tetrachlorvinphos potentiated the action of malathion. Fourteen insecticides gave additive effects while seven proved antagonistic. Insecticides which showed potentiation, were further tested by mixing with malathion in the ratios of 1:9, 3:7, 5:5, 7:3 and 9:1. All the five combinations in the six mixtures gave potentiating effects. Maximum potentiation of 17.6 times was observed in 1:9 combination of malathion and gamma-BHC. The proportions in which the insecticides were mixed had a pronounced effect on the toxic effect of malathion.

Experiments were carried out in East Africa to determine the effects of single-drop applications of the avicide Queletox (active ingredient fenthion) on the Red-billed Quelea Q. quelea, an important agricultural pest. Birds treated with relatively large amounts of Queletox died within a few hours, as expected. Most of those receiving the smallest lethal doses died 12 to 48 h after treatment. From their terminal fat and muscle condition it was concluded that they died of starvation, despite their apparently healthy appearance following treatment and the easy availability of suitable food. LD50's of 80 and 220 mg/kg were obtained for Queletox applied to the feathers of the back in drops of varying sizes or concentrations, the amount of solvent having an important effect on the toxicity. The possibility is raised of reducing the amounts of Queletox used in control operations against the birds, making them safer and cheaper.

SUMMARY Laboratory methods are described for testing soil insecticides against wireworms, and the results obtained with some organophosphorus and carbamate compounds tried as possible alternatives to chlorinated hydrocarbons are reported. The most promising compounds in the laboratory tests were thionazin, O-ethyl S-p-tolylethylphosphonodithioate (Bayer 38156) and fenthion. These were tested in a small-plot field trial with cereals, on land severely infested with wireworms: the compounds were applied to the soil as sprays at 2·7 lb./acre active ingredient before the crop was drilled. Fenthion was ineffective, but thionazin and Bayer 38156 each increased yields significantly and the increases were associated with diminished wireworm populations.