Disposition kinetics of cypermethrin and fenvalerate in black bengal lactating goats

Disposition kinetics of cypermethrin and fenvalerate were investigated in lactating black Bengal goats following single dose intravenous administration at 57 and 45 mg kg^?1 respectively. The maximum and minimum blood concentrations of cypermethrin were 18.49 (±3.17) and 0.06 (±0.002) μg ml^?1, while the corresponding values for fenvalerate were 14.58 (±2.37) and 0.04 (±0.005) μg ml^?1 respectively. Both cypermethrin and fenvalerate remained present in blood for 36 h. The mean t1/2β) and Vd_area values were 5.56 (±0.28) h and 10.38 (±2.20) litre kg^?1 for cypermethrin and 5.66 (±0.35) h and 11.31 (±2.20) litre kg^?1 respectively for fenvalerate. Both cypermethrin and fenvalerate persisted in goat milk for 36 h. The t1/2β) and AUC values of fenvalerate were 7.37 (±1.84) h and 122.38 (±11.65) μg h ml^?1 whilst the corresponding values for cypermethrin were 6.66 (±1.54) h and 99.48 (±7.81) μg h ml^?1 in milk respectively.     

Toxico‐kinetics,recovery efficiency and microsomal changes following administration of deltamethrin to black Bengal goats

A study of the toxico‐kinetics, recovery percentage from different substrates, cytotoxicity and role of cytochrome P₄₅₀ and b₅ of liver microsome in the metabolism of deltamethrin were carried out in female black Bengal goat. The ALD₅₀ value of deltamethrin in goat by intravenous route lies between 0.2 and 0.6 mg kg^?1. Intravenous disposition kinetics using a dose of 0.2 mg kg^?1 showed that the maximum blood concentration of deltamethrin was recorded at 0.5 min, followed by rapid decline, and a minimum concentration was detected at 6 min after administration. The following values were obtained : Vd_area 0.148 (± 0.02) litre kg^?1; t_1/2 (α) 0.22 (± 0.02) min; t_1/2 (β) 2.17 (± 0.37) min; K_el 1.05 (± 0.24) min^?1; AUC 4.30(± 0.45) µg min ml^?1; Cl_B 0.05 (± 0.006) litre kg^?1 min^?1; T～B 1.93 (± 0.58); fc 0.40(± 0.05). After 10 min, liver retained the maximum residue, and heart, adrenal gland, kidney, spleen, fat and brain also held the insecticide; liver, fat, heart and spleen retained residue after 30 min, and bone, liver and fat retained residue after 60 min of intravenous administration. Oral absorption of deltamethrin was poor and inconsistent, and approximately 65% of administered dose was recovered from faeces and gastrointestinal contents. The excretion of deltamethrin through urine was meagre, and only 0.01 and 0.013% of the administered dose was recovered after 3 and 5 days of oral administration respectively. All the tissues retained the residue after 3 days; while fat, rumen, reticulum, omasum, abomasum, large and small intestine and bone retained the residue after 5 days of oral administration; and the percentage recoveries were 1.73 and 0.027 respectively. Deltamethrin reduced the level of cytochrome P₄₅₀ content of liver microsomal pellet of goat after 5 days of oral administration. Histopathological examination of liver, kidney, heart, spleen brain and lung sections of treated goats did not reveal any pathological changes. © 2001 Society of Chemical Industry     

Pharmacokinetics of fenvalerate after intravenous administration to sheep

The pharmacokinetics of total radioactivity and of intact fenvalerate were determined in sheep treated intravenously with radiolabelled or non-radiolabelled fenvalerate. Mean residence times (MRT) of total radioactivity and intact fenvalerate in plasma were 910 (±75) and 39 (±3) min, while harmonic mean elimination-phase half-lives (TM_β) were 990 and 82 min, each respectively. Systemic clearance values (Cl_S) of total radioactivity and intact fenvalerate were 2·8 (±0·3) ml min⁻¹ kg⁻¹ and 51·3 (±5·9) ml min⁻¹ kg⁻¹, respectively. Volumes of distribution at steady state (V_SS) were each near 2500 ml kg⁻¹. Elimination of radioactivity occurred, in part (33·3 (±3·3)% of dose), by renal excretion, at a rate (0·9 (±0·1) ml min⁻¹ kg⁻¹), similar to that of glomerular filtration. These data are consistent with a disposition model according to which intact fenvalerate was rapidly distributed into a peripheral compartment, where metabolism occurred. In addition, since the elimination half-life of fenvalerate from plasma was less than 90 min after intravenous injection, ‘flip-flop’ kinetics should be considered when longer elimination half-lives are observed after oral or dermal exposures.     

Interception and persistence of parathion and fenvalerate on cotton plants as a function of application method

Parathion (O,O-diethyl O-4-nitrophenyl phosphorothioate) and fenvalerate [(RS)-α-cyano-3-phenoxybenzyl (RS)-2-(4-chlorophenyl)-3-methylbutyrate] were applied by controlled droplet applicators (CDAs) and conventional hydraulic nozzles in refined soybean oil, soybean oil + water, or water, to mature cotton plants (Gossypium hirsutum L.) as ULV (ultra-low volume, < 5 litre ha^?1), VLV(very low volume, 5-50 litre ha^?1), or LV(low volume, 50–200 litre ha^?1) carrier rates. The use of CDA or soybean oil applied as ULV and VLV sprays did not produce greater deposition or persistence for either insecticide during the 49-h test period following application. In general, insecticide persistence was greatest when applied with water or soybean oil + water as LV sprays using the conventional TX8 hydraulic nozzle.     

Efficacies of low- to high-volume (960-10 700 litre ha− 1) citrus sprayers for applying petroleum spray oil to control chinese wax scale

Petroleum spray oil (2, 4 and 6% in water) was applied to Valencia orange, Citrus sinensis (L.) Osbeck, for the control of Chinese wax scale, Ceroplastes sinensis del Guercio, using a low-volume ( <2000 litre ha^?1)air-blast (LV AB) sprayer, a low- to high-volume (L-HV) (up to 7000 litre ha^?1) sprayer with four fan-assisted rotary atomiser (FARA) spray heads mounted on a vertical tower, and a high-volume (>7000 litre ha^?1) oscillating boom (HV OB) sprayer. The most effective sprayer was the L-HV FARA sprayer. The most cost-effective treatment was a 20 ml litre^?1 (60 litre oil ha^?1) spray applied at 3000 litre ha^?1 by the L-HV FARA sprayer. It gave mortality equivalent to a standard 20 ml litre^?1, 10 700 litre ha^?1 spray (214 litre oil ha^?1) applied by the HV OB sprayer but with 72% less spray and significantly less oil deposited per cm² of leaf area. Equivalent or significantly (P = 0·05) higher mortality than that given by the 10 700 litre ha^?1 HV OB spray was given by the 40 ml litre^?1, 3000 (120 litre oil ha^?1) and 60 ml litre^?1, 2180 and 3000 litre ha^?1 (130·8 and 180 litre oil ha^?1) L-HV FARA sprays, but the 60 ml litre^?1 sprays deposited more oil per cm² than the 20 ml litre^?1 HV OB spray and were considered to be potentially phytotoxic. The least effective sprayer was the LV AB sprayer, which applied a 60 ml litre^?1 spray (57·6 litre oil ha^?1) at 960 litre ha^?1. Linear relationships were established for Chinese wax scale mortality, transformed using an angular transformation (arcsin proportion), versus log₁₀ spray volume for the 20, 40 and 60 ml litre^?1 sprays applied by L-HV FARA at 1260,2180 and 3000 litre ha^?1, mortality versus log₁₀ μg oil cm^?2 and log₁₀ μg oil versus log₁₀ volume of oil sprayed.     

Pharmacokinetics of Intravenous Fenvalerate in Cattle Treated Topically with a Low Dose of Piperonyl Butoxide

Experiments were conducted to identify pharmacokinetic interactions between topically applied piperonyl butoxide and intravenous fenvalerate in cattle (Angus steers). Intact fenvalerate in plasma was derivatized by condensation with acetone and measured by negative chemical ionization gas chromatography/mass spectrometry. Noncompartmental pharmacokinetic analyses indicated that the elimination-phase rate constant (β, 0·00069 (±0·00006) min^-1), mean residence time (172 (±14) min), systemic clearance (10·4 (±0·7) ml min^-1 kg^-1) or volume at steady state (1800 (±230) ml kg^-1) were not changed (P>0·05) after topical application of a low dose of piperonyl butoxide. These data indicate that topical application of a low dose of the metabolic synergist piperonyl butoxide would not be expected to modify the in-vivo disposition of fenvalerate in cattle. © of SCI.     

Pharmacokinetics of sulfluramid and its metabolite desethylsulfluramid after intravenous and intraruminal administration of sulfluramid to sheep

Pharmacokinetic properties and tissue residues of the insecticide sulfluramid (I) and its major metabolite desethylsulfluramid (II) were determined in healthy sheep after bolus intravenous (IV) administration (5 and 15 mg kg⁻¹; n = 10) and bolus intraruminal (IR) administration (100 and 400 mg kg⁻¹; n = 12) of I . Depression, lethargy, and dyspnea were noted for 4 h after the higher IV dose, but not after the other IV or IR doses. The time courses of the mean blood concentrations of I and II were best described by a two-compartment open model with rapid distribution and slow elimination phases. The blood-to-plasma concentration ratios for I and II were 1.43 (± 0.50) and 26.7 (± 9.41), respectively, suggesting binding of II to red blood cells. The T_1/2β values for I and II for the higher IV dose of I were 15.3 (± 4.68) h and 63.4 (± 4.75) h and for the higher IR dose of I , 31.5 (± 5.41) h and 74.9 (± 7.49) h, respectively. Bioavailability was 28.6 (± 2.96)% for the lower IR dose and 19.5 (± 0.99)% for the higher IR dose. C_max values for II were higher in female than male sheep after IR administration of I . Only II was found in tissue samples, with the highest concentration being in liver (9.4 (± 5.2) µg g⁻¹). © 1999 Society of Chemical Industry     

Organophosphorothioates and synergised synthetic pyrethroids as grain protectants on bulk wheat

Organophosphorothioates and synergised synthetic pyrethroids were used in duplicate field trials carried out on bulk wheat in commercial silos in Queensland and New South Wales. Laboratory bioassays using malathion-resistant strains of insects were carried out on samples of treated grain at intervals over 9 months. These established that all treatments were generally effective. Deltamethrin (2 mg kg^?1)+ piperonyl butoxide (8 mg kg^?1), fenitrothion (12 mg kg^?1)+ fenvalerate (1 mg kg^?1)+ piperonyl butoxide (8 mg kg^?1), fenitrothion (12 mg kg^?1)+ phenothrin (2 mg kg^?1)+ piperonyl butoxide (8 mg kg^?1) and pirimiphos-methyl (4 mg kg^?1)+ permethrin (1 mg kg^?1)+ piperonyl butoxide (8 mg kg^?1) controlled common field strains of Sitophilus oryzae (L.) and Rhyzopertha dominica (F.). Against a highly resistant strain of S. oryzae, deltamethrin (2 mg kg^?1)+ piperonyl butoxide (8 mg kg^?1) was superior to the remaining treatments. All treatment combinations completely prevented progeny production in Tribolium castaneum (Herbst), T. confusum Jacquelin du Val and in Ephestia cautella (Walker). Residues of deltamethrin, fenvalerate, permethrin and phenothrin were determined and shown to be highly persistent on stored wheat. During milling, residues accumulated in the bran fractions and were reduced in white flour. They were not significantly reduced during baking.     

Residues of synthetic pyrethroid insecticides on horticultural crops

Foliar applications of synthetic pyrethroids were made to several crops to determine residue levels at various intervals after application. On onions, residues of cypermethrin, permethrin and fenvalerate were negligible > 0.1 mg kg^?1, 7 days after application. On lettuce, residues of fenvalerate and permethrin were 0.8 mg kg^?1. On celery, residues of fenvalerate did not decline and ranged from 0.12 to 0.25 mg kg^?1 during the 14-day period. On green bush-beans, residues of permethrin and cypermethrin did not decline during the 14-day period and ranged from 0.1 to 0.6 mg kg^?1. By day 7, residues of cyfluthrin, cypermethrin, deltamethrin, fenvalerate and permethrin on strawberries were less than the acceptable maximum tolerance of 0.1 mg kg^?1 with the exception of cypermethrin, applied at the rate of 0.14 kg a.i. ha^?1 which gave a residue of 0.14 mg kg^?1.     

Carbofuran occupational dermal toxicity, exposure and risk assessment

BACKGROUND: Carbofuran is a carbamate insecticide that inhibits AChE. Although toxic by ingestion in mammals, it has low dermal toxicity, with relatively few confirmed worker illnesses. This risk assessment describes its time of onset, time to peak effect and time to recovery in rats using brain AChE inhibition in acute and 21 day dermal studies; in vitro rat/human relative dermal absorption for granular (5G) and liquid (4F) formulations; occupational exposure estimates using the Pesticide Handlers' Exposure Database and Agricultural Handlers' Exposure Database (PHED/AHED). RESULTS: The point of departure for acute risk calculation (BMDL₁₀) was 6.7 mg kg^?1 day^?1 for brain AChE inhibition after 6 h exposure. In a 21 day study, the BMDL₁₀ was 6.8 mg kg^?1 day^?1, indicating reversibility. At 75 mg kg^?1 day^?1, time of onset was ?30 min and time to peak effect was 6–12 h. Rat skin had ca tenfold greater dermal absorption of carbofuran (Furadan^® 5G or 4F) than human skin. Exposure estimates for 5G in rice and 4F in ten crops had adequate margins of exposure (>100). CONCLUSION: Rat dermal carbofuran toxicity was assessed in terms of dose and time‐related inhibition of AChE. Comparative dermal absorption in rats was greater than in humans. Worker exposure estimates indicated acceptable risk for granular and liquid formulations of carbofuran. Copyright © 2011 Society of Chemical Industry     

Residues of Mecoprop in Post-emergence-Treated Wheat and Oat

The dissipation of mecoprop in wheat (Triticum aestivum L.) and oat (Avena sativa L.) was monitored over a growing season following post-emergence application of the dimethylamine salt of mecoprop to each crop at 1·1 kg ha^?1. Residues of mecoprop, as its methyl ester, were determined gas chromatographically using electrolytic conductivity detection. Initial residues in wheat (119 (±20) mg kg^?1) and oat (95·3 (± 10·0) mg kg^?1) on the day of application (four-leaf stage of wheat and four- to five-leaf stage of oat) decreased to 0·1 to 0·2 mg kg^?1, respectively, within six weeks. Residues were non-detectable in the mature seed of both crops. Recoveries of mecoprop were in the order of 90% from the green tissue and seed of both crops fortified at 0·05 mg kg^?1.     

棉铃虫对菊酯类药剂的抗性狭义遗传力

通过单对交配设计不同的交配家系,采用半同胞法分析了棉铃虫对三氟氯氰菊酯和氰戊菊酯的抗性狭义遗传力,并对2种菊酯类药剂的抗性发展速度进行评价。结果表明,棉铃虫对三氟氯氰菊酯和氰戊菊酯的抗性狭义遗传力分别为0.2476±0.0248和0.4625±0.1578,说明棉铃虫对氰戊菊酯的抗性发展速度要快于三氟氯氰菊酯。另外,通过方差分析发现,在棉铃虫对拟除虫菊酯类药剂的抗性遗传中,母体效应对其没有影响。     

The metabolism of fenvalerate in plants: The conjugation of the acid moiety

The metabolism of the pyrethroid insecticide fenvalerate [(RS)-α-cyano-3-phenoxybenzyl (RS)-2-(4-chlorophenyl)-3-methylbutyrate] ( I ), and of its most insecticidal (αS,2S) isomer ( II ), has been examined in cabbage plants grown and treated under laboratory conditions with [¹⁴C]chlorophenyl- and [ring-¹⁴C]benzyllabelled preparations of the two compounds. Both insecticides disappeared from the treated leaves with similar half-lives of approximately 12–14 days; they underwent ester cleavage to a significant extent, together with some hydroxylation at the 2- or 4-position of the phenoxy ring, and hydrolysis of the nitrile group to amide and carboxyl groups. Most of the carboxylic acids and phenols thus produced occurred as glycoside conjugates. In separate experiments, the uptake and metabolism of 2-(4-chlorophenyl)-3-methylbutyric acid ( X ), the acidic half of the molecule, were examined in the laboratory, using abscised leaves of kidney bean, cabbage, cotton, cucumber and tomato plants. The acid X was found to be readily converted, mainly into glucose and 6-O-malonylglucose esters in kidney bean, cabbage and cucumber plants, into glucosylxylose, sophorose and gentiobiose esters in cotton, and into two types of triglucose esters with differing isomerism in tomato. One of the acetyl derivatives of the trisaccharide conjugates was identical with the synthetic deca-acetyl derivative of the [1 → 6]-triglucose ester.     

In vivo pharmacokinetics of pyribenzoxim in rats

Pyribenzoxim, benzophenone O‐[2,6‐bis(4,6‐dimethoxypyrimidin‐2‐yloxy)benzoyl]oxime, is a new post‐emergence herbicide providing broad‐spectrum weed control in rice fields. [¹⁴C]Pyribenzoxim was used to study the pharmacokinetics of the compound after oral administration of a dose of 1000 mg kg^?1 to male Sprague–Dawley rats. The material balance ranged from 97.3 to 99.7% of the administered dose and urinary and fecal recovery accounted for 97.1%, with the majority of radioactivity recovered in feces (88.6%) by 168 h after treatment. Elimination as volatile products or as carbon dioxide was negligible. The following values were obtained for the compound in the blood: AUC_0–168h, 28400 µg equiv h g^?1; T_max, 12 h; C_max, 372 µg equiv g^?1; half‐life, 53 h. Radioactivity in tissue decreased from 96.1% of applied radiocarbon at 6 h to 0.4% at 168 h and the highest concentration of radioactivity among the tissues was observed in liver while the lowest residues were found in brain. The elimination half‐lives of radioactivity from tissues was in the range of 7 to 77 h and T_max values of 12, 24 and 12 h were observed for blood, liver and kidney, respectively. Except for that in the digestive tract, the tissue‐to‐blood ratio (TBR) was highest in the liver. © 2001 Society of Chemical Industry     

Disappearance of carbosulfan residues in peaches

The disappearance kinetics of the carbamate insecticide, carbosulfan, applied at 2 kg AI ha^?1 (‘Marshal’ 250 g litre^?1 EC) in peaches was studied. Degradation took place in two consecutive stages (0–28 and 28–57 days), with half-lives of 7.4 and 17.5 days, respectively. The residues obtained 57 days after treatment did not exceed 0.2 mg kg^?1. When treatments were carried out 30, 21 and 14 days before the probable date of harvest (date of fruit maturation) with two doses (1.0 and 2.0 g formulated product litre^?1) and two volumes applied (750 and 1500 litre ha^?1), the residual levels detected were between 0.122 mg kg^?1 (30 days before harvest) and 0.4 mg kg^?1 (14 days before harvest). The major metabolite, carbofuran, was never detected above its determination limit of 0.004 mg kg^?1 throughout the whole study.     

Cholinesterase inhibition by methamidophos and its subsequent reactivation

Methamidophos (O,S-dimethylphosphoramidothioate, Monitor) is an organophosphorus, cholinesterase-inhibiting insecticide. The rate constant (k_i) for inhibiting rat plasma cholinesterase (ChE) was 1.57 ± 0.03 × 10³M^?1 min^?1, for rat erythrocyte ChE was 8.86 ± 1.10 × 10³M^?1 min^?1, and for rat brain ChE was 6.58 ± 0.42 M^?1 min^?1. Brain and plasma cholinesterases spontaneously recovered from over 90% inhibition at 30 min to 50% inhibition in 4 and 14 hr, respectively. Pralidoxime increased the rate of reactivation in vitro. In vivo, rats poisoned with methamidophos exhibited signs of cholinergic stimulation. The LD₅₀ of ip methamidophos in male rats was 15 ± 0.7 mg/kg. Pralidoxime (60 mg/kg) and atropine (10 mg/kg) given with the methamidophos increased the LD₅₀ to 52 ± 4.9 mg/kg and 60 ± 0.4 mg/kg, respectively. In rats given 12.5 mg methamidophos (an LD₂₀), ChE activity was depressed 95 ± 12.5% in plasma, 92 ± 0.6% in stomach, and 88 ± 1% in brain at 1 hr after injection. At 48 hr after injection ChE activity had returned to 60% or more of control values in each of the tissues. Administration of a single dose of 60 mg/kg of pralidoxime along with methamidophos did not increase ChE activities at the times and places it was measured.     

Potential of piperonyl butoxide‐synergised pyrethrins against psocids (Psocoptera: Liposcelididae) for stored‐grain protection

BACKGROUND: Piperonyl butoxide (PB)‐synergised natural pyrethrins (pyrethrin:PB ratio 1:4) were evaluated both as a grain protectant and a disinfestant against four Liposcelidid psocids: Liposcelis bostrychophila Badonnel, L. entomophila (Enderlein), L. decolor (Pearman) and L. paeta Pearman. These are key storage pests in Australia that are difficult to control with the registered grain protectants and are increasingly being reported as pests of stored products in other countries. Firstly, mortality and reproduction of adults were determined in wheat freshly treated at 0.0, 0.75, 1.5, 3 and 6 mg kg^?1 of pyrethrins + PB (1:4) at 30 ± 1 °C and 70 ± 2% RH. Next, wheat treated at 0.0, 1.5, 3 and 6 mg kg^?1 of pyrethrins + PB (1:4) was stored at 30 ± 1 °C and 70 ± 2% RH and mortality and reproduction of psocids were assessed after 0, 1.5, 3 and 4.5 months of storage. Finally, the potential of synergised pyrethrins as a disinfestant was assessed by establishing time to endpoint mortality for adult psocids exposed to wheat treated at 3 and 6 mg kg^?1 of synergised pyrethrins after 0, 3, 6, 9 and 12 h of exposure. RESULTS: Synergised pyrethrins at 6 mg kg^?1 provided 3 months of protection against all four Liposcelis spp., and at this rate complete adult mortality of these psocids can be achieved within 6 h of exposure. CONCLUSION: Piperonyl butoxide‐synergised pyrethrins have excellent potential both as a grain protectant and as a disinfestant against Liposcelidid psocids. Copyright © State of Queensland, Department of Employment, Economic Development and Innovation, 2010. Published by John Wiley and Sons, Ltd.     

Dissipation of cyproconazole and quinalphos on/in grapes

The persistence of cyproconazole and quinalphos on/in grapes was investigated when both compounds were applied to vines at the locally recommended application frequencies and rates and at double these rates, using commercially available formulations. Residues of cyproconazole applied at recommended and double the recommended rates of application in/on grapes immediately after the last application were 0-049 (±0.034) and 0.077 (±0.008) mg kg^?1, respectively, reduced to 0.011 (±0.003) and 0.018 (±0.010) mg kg^?1 respectively seven days after the last application. The corresponding residue levels of quinalphos immediately following the last application were 1.42 (±0.10) and 3.36 (±0.07) mg kg^?1, reduced to 0.043 (±0.002) and 0.072 (±0.028) mg kg^?1 respectively 21 days after the last application. Cyproconazole, being systemic, is rapidly absorbed by the grape tissues and its residues dissipate with a half-life of three to four days, while quinalphos, being non-systemic, dissipates faster with a half-life of two or three days. The residues of both pesticides were analysed by a GLC-NPD system.     

Spirosultam LY219048: A new chemical class of insecticide acting upon the GABA receptor/chloride ionophore complex

This study assessed the toxicity and mode of action of a new experimental insecticide, LY219048 in insects and mammals. LY219048 produced rapid convulsions in mice and had LD₅₀ values of 0.7 mg kg^?1 and 4 mg kg^?1 after intracerebral and intraperitoneal injection, respectively. In initial screens against insects, LY219048 showed low activity against the German cockroach (Blatella germanica L.). Lethality from dietary exposure required one to two weeks, even at concentrations as high as 10000 mg kg^?1 (LC₅₀ = 485 mg kg^?1). In contrast, it had an LC₅₀ value of 8.3 mg kg^?1 against insecticide-susceptible Drosophila melanogaster (Meig.) when synergized with piperonyl butoxide. Significant resistance to LY219048 (> 12-fold) was detected in a cyclodiene-resistant strain of D. melanogaster possessing an altered target site resistance mechanism. This finding suggested that LY219048 blocked the 4-aminobutyric acid (GABA)-gated chloride channel in a manner similar to that of the cyclodienes. In physiological studies in larval D. melanogaster central neurons, LY219048 antagonized the reduction of firing caused by 1 mM GABA. Dose-response experiments showed that the ED₅₀ for blocking inhibition under these conditions was c. 1 μ. Studies of ³⁶CI uptake into bovine brain synaptosomes found that LY219048 was a potent antagonist. At 10 μ it completely blocked chloride flux stimulated by 50 μM GABA. LY219048 competitively displaced [³H]TBOB binding from bovine brain membranes, with an IC₅₀ of 42 nM, which was comparable to values determined for TBPS (35 nM) and picrotoxinin (267 nM). There was little or no displacement (<25%) of [³H]flunitrazepam or [³H]muscimol binding by 10 μM LY219048. Taken together, these results provide strong evidence that this new chemical class of insecticide manifests its acute toxicity by blocking the GABA-gated chloride channel.     

Effects of different potato cultivars on life history and demographic parameters of Phthorimaea operculella Zeller (Lepidoptera: Gelechiidae)

Potato tuber worm, Phothorimae operculella Zeller (Lepidoptera: Gelechiidae) is a common pest of potato which causes a heavy loss in yield either in fields or storage. The effect of six potato cultivars (Agria, Florida, Impala, Picasso, Satina, and Sprint) were evaluated on the life history, life table and demographic parameters of P.operculella under laboratory conditions, which could be appropriate indices in resistance and susceptibility evaluation of potato cultivars. The longest development time was on Picasso (28.76 ± 0.36d) cultivar. The male longevity ranged from 4.83 ± 0.44d on Sprint to 7.45 ± 0.60d on Picasso. Impala and Satina with 53.22 ± 7.78 and 28.74 ± 3.54 eggs/individual had the highest and the lowest net reproductive rates (R₀). The highest values for the intrinsic rate of increase (r_m) and finite rate of increase (λ) were on Impala (r_m: 0.119 day^?1, λ: 1.75 day^?1), and the lowest value was on Sprint (r_m: 0.090 day^?1, λ: 1.01 day^?1). The results indicated that Sprint was the most resistant cultivar for the feeding of P.operculella, which could be useful in the development of integrated pest management programs for this pest.