Risk posed to honeybees (Apis mellifera L,Hymenoptera) by an imidacloprid seed dressing of sunflowers

In a greenhouse metabolism study, sunflowers were seed‐treated with radiolabelled imidacloprid in a 700 g kg^?1 WS formulation (Gaucho® WS 70) at 0.7 mg AI per seed, and the nature of the resulting residues in nectar and pollen was determined. Only the parent compound and no metabolites were detected in nectar and pollen of these seed‐treated sunflower plants (limit of detection <0.001 mg kg^?1). In standard LD₅₀ laboratory tests, imidacloprid showed high oral toxicity to honeybees (Apis mellifera), with LD₅₀ values between 3.7 and 40.9 ng per bee, corresponding to a lethal food concentration between 0.14 and 1.57 mg kg^?1. The residue level of imidacloprid in nectar and pollen of seed‐treated sunflower plants in the field was negligible. Under field‐growing conditions no residues were detected (limit of detection: 0.0015 mg kg^?1) in either nectar or pollen. There were also no detectable residues in nectar and pollen of sunflowers planted as a succeeding crop in soils which previously had been cropped with imidacloprid seed‐treated plants. Chronic feeding experiments with sunflower honey fortified with 0.002, 0.005, 0.010 and 0.020 mg kg^?1 imidacloprid were conducted to assess potential long‐term adverse effects on honeybee colonies. Testing end‐points in this 39‐day feeding study were mortality, feeding activity, wax/comb production, breeding performance and colony vitality. Even at the highest test concentration, imidacloprid showed no adverse effects on the development of the exposed bee colonies. This no‐adverse‐effect concentration of 0.020 mg kg^?1 compares with a field residue level of less than 0.0015 mg kg^?1 ( = limit of detection in the field residue studies) which clearly shows that a sunflower seed dressing with imidacloprid poses no risk to honeybees. This conclusion is confirmed by observations made in more than 10 field studies and several tunnel tests. © 2001 Society of Chemical Industry     

Acaricides and their residues in Spanish commercial beeswax

BACKGROUND: The purpose of this work was to determine residues of acaricides in recycled Spanish beeswax. RESULTS: Chlorfenvinphos, fluvalinate, amitraz, bromopropylate, acrinathrin, flumethrin, coumaphos, chlorpyrifos, chlordimeform, endosulfan and malathion residues were determined by GC‐µECD/NPD/MS detection. Owing to the extreme instability of amitraz, this analyte was transformed into the stable end‐metabolite 2,4‐dimethylaniline, later derivatised with heptafluorobutyric anhydride and determined by GC‐µECD/MS. Recoveries from spiked samples ranged from 86 to 108%, while quantification limits varied from 0.10 to 0.30 mg kg^?1 using GC‐µECD/NPD, and from 12 to 85 µg kg^?1 by GC‐MSD. Of a total of 197 samples analysed, only eight samples (4%) were free of residues of chlorfenvinphos (0.019–10.6 mg kg^?1), fluvalinate was present in 93.6% of samples analysed (0.027 –88.7 mg kg^?1), while coumaphos was confirmed in only five of the 134 samples analysed at concentrations of less than 195 µg kg^?1. The remaining acaricides were identified with different levels of incidence at concentrations from 12 to 231 µg kg^?1. CONCLUSIONS: Residues of acaricides were found in an extensive number of beeswax samples. The contamination with chlorfenvinphos and tau‐fluvalinate was very relevant, particularly as chlorfenvinphos is not legally authorised for use in beekeeping. The possible impacts of the main acaricides detected on larval and adult honey bees are discussed. Copyright © 2010 Society of Chemical Industry     

Toxicity of formic acid to red imported fire ants, Solenopsis invicta Buren

BACKGROUND: Ants often compete with other ants for resources. Although formic acid is a common defensive chemical of formicine ants, it does not occur in any other subfamilies in Formicidae. No information on toxicity of formic acid to red imported fire ants, Solenopsis invicta, is available. This study examined its contact and fumigation toxicity to S. invicta in the laboratory. RESULTS: In a contact toxicity bioassay, 24 h LD₅₀ values of formic acid for workers ranged from 124.54 to 197.71 µg ant⁻¹. Female alates and queens were much less sensitive to formic acid than workers. At a concentration of 271.72 µg ant⁻¹, which killed 81.09 ± 16.04% of workers, the 24 h mortality was up to 39.64% for female alates and 38.89% for queens. In fumigation bioassays, 24 h LC₅₀ values ranged from 0.26 to 0.50 µg mL⁻¹ for workers, 0.32 µg mL⁻¹ for male alates and 0.70 µg mL⁻¹ for female alates. Complete mortality (100%) in queens occurred 24 h after they had been exposed to 1.57 µg mL⁻¹ of formic acid. At a concentration of 2.09 µg mL⁻¹, KT₅₀ values ranged from 23.03 to 43.85 min for workers, from 37.84 to 58.37 min for male alates, from 86.06 to 121.05 min for female alates and from 68.00 to 85.92 min for queens. CONCLUSION: When applied topically, formic acid was significantly less toxic than bifenthrin to red imported fire ants. Although its fumigation toxicity was lower than that of dichlorvos, formic acid had about an order of magnitude higher toxicity to S. invicta than to other insects studied so far. It may be worth investigating the use of formic acid for managing imported fire ants. Published 2012 by John Wiley & Sons, Ltd.     

A laboratory evaluation to determine the compatibility of microbiological control agents with the pollinator Bombus terrestris

BACKGROUND: This study was undertaken to identify any potential adverse side effects of the use of seven microbiological control agents (MCAs) on the bumblebee, Bombus terrestris L., in the context of combined use in integrated pest management (IPM). AQ10^® (Ampelomyces quisqualis), Binab‐T‐vector^® (Hypocrea parapilulifera + T. atroviride; 1/1), Prestop‐Mix^® (Gliocladium catenulatum J1446), Serenade^® (Bacillus subtilis QST713), Trianum‐P^® (Trichoderma harzianum T22), Botanigard^® (Beauveria bassiana GHA) and Granupom^® (Cydia pomonella granulovirus), comprising five biofungicides and two bioinsecticides, were investigated. Bumblebee workers were exposed under laboratory conditions to each MCA at its maximum field recommended concentration (MFRC) via three different routes of exposure: dermal contact and orally via either treated sugar water or pollen. RESULTS: The tested MCAs were found to be safe for workers of B. terrestris, with the exception of Botanigard^® and Serenade^®. Exposure to Botanigard^® via contact at its MFRC caused 92% mortality after 11 weeks, while the 1/10 MFRC killed 46% of exposed workers. For Serenade^®, topical contact and oral delivery via sugar water resulted in 88 and 100% worker mortality respectively. With lower concentrations (1/2, 1/5 and 1/10 MFRC) the toxicity decreased, but the effect depended on the route of exposure. In addition to lethal effects, nests were also evaluated for sublethal effects after treatment with the seven MCAs at their respective MFRCs over 11 weeks. In these bioassays, only Botanigard^® and Serenade^® gave rise to a significant (P < 0.05) decrease in drone production. Sublethal effects on foraging behaviour were also evaluated, and only Botanigard at its MFRC delivered via treated sugar water induced negative effects. CONCLUSION: The results demonstrated that most of the MCAs tested can be considered safe for use in combination with B. terrestris, based on the International Organisation for Biological Control of Noxious Animals and Plants (IOBC) classification. However, some can be harmful, such as the biofungicide Serenade^® and the bioinsecticide Botanigard^®. Therefore, it is recommended that all should be tested before use in combination with pollinators. In this context, it is also advisable that these MCAs should be evaluated in more realistic field situations for the assessment of potentially deleterious effects on foraging behaviour. Copyright © 2009 Society of Chemical Industry     

Environmental behaviour and translocation of imidacloprid in eggplant,cabbage and mustard

The recently registered insecticide, imidacloprid, was applied to three vegetable crops at 20 and 40 g AI ha⁻¹. The persistence of the parent insecticide and its translocation, along with the quantification of the metabolites formed on these crops are presented. The parent insecticide dissipated with a half‐life of 3–5 days and persisted longest on mustard leaves. The detectable limit of the HPLC method was 0.01 µg g⁻¹. The metabolites 1‐(6‐chloropyridin‐3‐yl‐methyl)imidazolidin‐2‐one and 6‐chloronicotinic acid were found to be translocated by day 10 in eggplant, cabbage leaves and mustard leaves but not in cabbage curd. The MRL of imidacloprid is not documented by the FAO/WHO on these crops and comparison of the MPI with the TMRC, calculated on the residue data generated in this study, establishes the safety of the schedule. © 2000 Society of Chemical Industry     

Methyl isothiocyanate volatilization from fields treated with metam‐sodium

Emission of methyl isothiocyanate (MITC) from fields treated with metam‐sodium (sodium N‐methyldithiocarbamate) is a potential environmental and human safety hazard. Concentrations of MITC at three heights above four arable fields were measured following the application of metam‐sodium at a rate of 480 litre ha⁻¹ (166 kg AI ha⁻¹). Two of these fields were treated by injection into a center‐pivot irrigation system (chemigation), while in the other two fields the fumigant was applied through injection directly into the soil. Generally, higher MITC air concentrations were observed above chemigated than above injected fields. Maximum MITC air concentrations were 11.2 and 7.4 µg m⁻³ recorded 10 cm above ground 6–8 h following application and the minimum concentrations were 0.7 and 0.2 µg m⁻³ observed at 200 cm 30–35 h after application above chemigated and injected fields, respectively. The estimated MITC respiratory exposure a worker might encounter during the re‐entry period ranged between 1.37 and 0.03 mg day⁻¹ in chemigated fields and between 0.35 and 0.02 mg day⁻¹ in the injected fields. These results suggest that application of the fumigant through injection reduced MITC volatilization losses in comparison with the chemigation method, thus posing a relatively lower risk of exposure to MITC emissions. © 2000 Society of Chemical Industry     

Ovicidal,larvicidal and juvenilizing activity of a picolinephenoxyanilide against Cydia pomonella

N‐(4‐phenoxyphenyl)‐2‐pyridinecarboxamide (1) was synthesized from commercially available materials and its ovicidal and larvicidal activity against Cydia pomonella (L) was tested. The compound showed a LC₅₀ of 0.98 mg ml⁻¹ when eggs less than 24 h were sprayed using a Potter Tower, but it had no effect when eggs older than this were sprayed. The compound did not have larvicidal activity when larvae were treated with 1200 µg g⁻¹. However, the larval head capsules were smaller than those in the controls when treated at this concentration. To assess its possible juvenile‐hormone‐like activity, the compound was topically applied to young pupae of Tribolium confusum duVal, where it produced clear juvenilization effects, which were dependent on the applied dose. © 2000 Society of Chemical Industry     

Residues in apples and sweet cherries after methyl bromide fumigation

Methyl bromide fumigations are used to treat apples, Malus domestica Borkh, and sweet cherries, Prunus avium (L), before export to Japan. In order to expand existing markets, additional cultivars are being prepared for export to Japan. As part of the approval process, residue analyses must be conducted and residues must be at acceptable levels. Five apple cultivars (‘Braeburn,’ ‘Fuji,’ ‘Gala,’ ‘Jonagold,’ and ‘Granny Smith’) were fumigated at 40 g m⁻³ for 2 h at 10 °C, and six sweet cherry cultivars (‘Brooks,’ ‘Garnet,’ ‘Lapin,’ ‘Rainier,’ ‘Sweetheart,’ and ‘Tulare’) were fumigated for 2 h with 64 g m⁻³ at 6 °C, 48 g m⁻³ at 12 °C, 40 g m⁻³ at 17 °C, and 32 g m⁻³ at 22 °C. Three replicates of fruit from each fumigation were analyzed for methyl bromide and bromide ion residues periodically with time. Methyl bromide residues for both apples and cherries were the highest immediately after fumigation, but rapidly declined so that only ‘Braeburn’ had residues >8 µg kg⁻¹ after 13 days and, except for ‘Lapin,’ all cherries were <1 µg kg⁻¹ after seven days. Average bromide ion residues were between 3.3 and 4.9 mg kg⁻¹ among apple cultivars, and between 3.7 and 8.0 µg kg⁻¹ among cherry cultivars. Published in 2000 for SCI by John Wiley & Sons, Ltd     

The mode of action of RH‐1965: a new phenylpyrimidinone bleaching herbicide

RH‐1965 is a new bleaching herbicide which causes newly developing leaf tissue to emerge devoid of photosynthetic pigments. Mode‐of‐action studies revealed that RH‐1965 inhibited the accumulation of both total chlorophyll and β‐carotene. Concomitantly, it induced the accumulation of the β‐carotene precursors, phytoene, phytofluene and, in particular, ξ‐carotene. Inhibition of chlorophyll accumulation by RH‐1965 is attributed to the photo‐oxidative destruction of chlorophyll in the absence of β‐carotene because RH‐1965 blocked chlorophyll accumulation to a greater extent under high light (50–330 µE m⁻² s⁻¹) than under low light (0.8 µE m⁻² s⁻¹) conditions. Radish (Raphanus sativus L) and barnyardgrass (Echinochloa crus‐galli (L) Beauv) were very senstive to RH‐1965. Under high light (330 µE m⁻² s⁻¹), the I₅₀ values for inhibition of chlorophyll accumulation were 0.10 and 0.15 µM , respectively. Wheat (Triticum aestivus L), on the other hand, was much less sensitive to RH‐1965 (I₅₀ = 1.4 µM ). It is concluded that the mode of action of RH‐1965 involves the inhibition of ξ‐carotene desaturation. © 2000 Society of Chemical Industry     

Toxicity and horizontal transfer of chlorantraniliprole against the Asian subterranean termite Coptotermes gestroi (Wasmann): effects of donor:recipient ratio, exposure duration and soil type

BACKGROUND: The effectiveness of chlorantraniliprole and other insecticides (bifenthrin, fipronil, indoxacarb, imidacloprid and chlorfenapyr) were tested against Coptotermes gestroi (Wasmann). Four experiments were conducted: a topical bioassay, a horizontal transfer study, an insecticide bioavailability test and a feeding bioassay. RESULTS: The topical bioassay showed that chlorantraniliprole was significantly less active to C. gestroi at 24 h post‐treatment compared with the other insecticides tested. Nevertheless, it is likely that a lesser amount of chlorantraniliprole was required to cause 50% mortality of C. gestroi at 7 and 14 days post‐treatment. The exposure duration and donor:recipient ratio affect the mortality of recipient termites. Mortality after exposure to chlorantraniliprole in sandy clay was significantly lower than in sand; however, by 14 days, > 90% of donor and recipient termites died in both substrates, irrespective of concentration. Fipronil and imidacloprid showed faster action, and high to moderate toxicity to C. gestroi. Termite workers also ceased to feed after exposure for 1 h to 50 mg kg^?1 chlorantraniliprole‐treated sandy clay. CONCLUSION: Chlorantraniliprole demonstrated delayed toxicity at the lowest label rate (50 mg kg^?1) in sandy clay. Its slow action will enable greater transfer of toxicant between nestmates, while feeding cessation will promote greater social interaction between healthy and exposed termites. Copyright © 2011 Society of Chemical Industry     

Use of bentonite and humic acid as modifying agents in alginate-based controlled-release formulations of imidacloprid

In order to prepare a formulation to be used for controlled release, imidacloprid was incorporated into alginate granules by using calcium chloride as gellant. The formulation prepared (alginate–imidacloprid–water) was modified by the addition of different sorbents. The effects on release rate of the addition of natural bentonite desiccated at 105 °C, untreated, acid-treated with sulfuric acid solutions over a concentration range between 0.5 mol dm⁻³ and 2.5 mol dm⁻³, and a commercial humic acid, were studied by immersion of the granules in water under static conditions. The time taken for 50% of the active ingredient to be released into water, (T₅₀), was calculated from the data obtained. On the other hand, the sorption–desorption processes of imidacloprid from a 0.01 M aqueous calcium chloride solution at 25 °C, by natural, acid-treated bentonite samples, and humic acid, have been studied by using batch experiments in order to evaluate the potential of these materials for their application in controlled-release formulations of pesticides. The experimental data have been fitted to the Freundlich equation in order to calculate the adsorption capacities (K_f). K_f values ranged from 1.76 mg kg⁻¹ for the untreated bentonite up to 126.9 mg kg⁻¹ for the humic acid. A correlation study was performed with T₅₀, the surface area (S) and the Freundlich parameter (K_f) of the bentonite samples in order to know the factors that affect release rate of imidacloprid from bentonite granules. A linear correlation of the T₅₀ values and both S and K_f parameters was observed. © 1999 Society of Chemical Industry     

Species-specific insecticide resistance to imidacloprid and fipronil in the rice planthoppers Nilaparvata lugens and Sogatella furcifera in East and South-east Asia

BACKGROUND: In 2003 the development of insecticide resistance against neonicotinoids in the brown planthopper (BPH), Nilaparvata lugens (Stål) (Homoptera: Delphacidae), was first observed in Thailand and has since been found in other Asian countries such as Vietnam, China and Japan. However, the LD₅₀ values of BPH and the whitebacked planthopper (WBPH), Sogatella furcifera (Horváth), against both neonicotinoid and phenylpyrazole insecticides have been poorly reported in many Asian countries. RESULTS: The topical LD₅₀ values for imidacloprid in the BPH populations collected from East Asia (Japan, China, Taiwan) and Vietnam in 2006 were 4.3–24.2 µg g^?1 and were significantly higher than those collected from the Philippines (0.18–0.35 µg g^?1). The BPH populations indicated a positive cross‐resistance between imidacloprid and thiamethoxam. Almost all the WBPH populations from Japan, Taiwan, China, Vietnam and the Philippines had extremely large LD₅₀ values (19.7–239 µg g^?1 or more) for fipronil, except for several populations from the Philippines and China. CONCLUSION: Species‐specific changes in insecticide susceptibility were found in Asian rice planthoppers (i.e. BPH for imidacloprid and WBPH for fipronil). Insecticide resistance in BPH against imidacloprid occurred in East Asia and Indochina, but not in the Philippines. In contrast, insecticide resistance in WBPH against fipronil occurred widely in East and South‐east Asia. Copyright © 2008 Society of Chemical Industry     

Lethal and sub-lethal effects of a novel sulfoximine insecticide,sulfoxaflor, against Asian citrus psyllid and its primary parasitoid under laboratory and field conditions

The Asian citrus psyllid, Diaphorina citri Kuwayama, is the most important international pest of citrus because it transmits the bacteria that cause huanglongbing (HLB). HLB limits citrus production globally. We evaluated the toxicity of sulfoxalor against D. citri and its parasitoid, Tamarixia radiata Waterston. Sulfoxaflor was as toxic as imidacloprid to adult D. citri. The LC₅₀ values for sulfoxaflor and imidacloprid were 8.17 and 5.7 µg AI mL^?1, respectively. The LC₅₀ of sulfoxaflor for T. radiata adults was 3.3 times greater than for D. citri adults. Treatment with sulfoxaflor resulted in reduced oviposition, development of nymphs, and emergence of adult D. citri on plants, as compared with controls. The lowest concentration that reduced adult emergence was 0.6 µg AI mL^?1. There was reduced feeding by D. citri adults on leaves treated with sulfoxaflor. The residual toxicity of sulfoxaflor was equivalent to imidacloprid. Under field conditions, formulated sulfoxaflor reduced populations of D. citri compared with untreated controls. Sulfoxaflor is a novel mode of action and is an effective tool for D. citri management.     

Acaricidal activities of the active component of Lycopus lucidus oil and its derivatives against house dust and stored food mites (Arachnida: Acari)

BACKGROUND: Recent studies have focused on materials derived from plant extracts as mite control products against house dust and stored food mites because repeated use of synthetic acaricides had led to resistance and unwanted activities on non‐target organisms. The aim of this study was to evaluate the acaricidal activity of materials derived from Lycopus lucidus against Dermatophagoides farinae, D. pteronyssinus and Tyrophagus putrescentiae. RESULTS: The LD₅₀ values of L. lucidus oil were 2.19, 2.25 and 8.45 µg cm^?2 against D. farinae, D. pteronyssinus and T. putrescentiae. The acaricidal constituent of L. lucidus was isolated by chromatographic techniques and identified as 1‐octen‐3‐ol. In a fumigant method against D. farinae, the acaricidal activity of 1‐octen‐3‐ol (0.25 µg cm^?2) was more toxic than N,N‐diethyl‐m‐toluamide (DEET) (36.84 µg cm^?2), followed by 3,7‐dimethyl‐1‐octen‐3‐ol (0.29 µg cm^?2), 1‐octen‐3‐yl butyrate (2.32 µg cm^?2), 1‐octen‐3‐yl acetate (2.42 µg cm^?2), 3,7‐dimethyl‐1‐octene (9.34 µg cm^?2) and benzyl benzoate (10.02 µg cm^?2). In a filter paper bioassay against D. farinae, 1‐octen‐3‐ol (0.63 µg cm^?2) was more effective than DEET (20.64 µg cm^?2), followed by 3,7‐dimethyl‐1‐octen‐3‐ol (1.09 µg cm^?2). CONCLUSION: 1‐Octen‐3‐ol and 3,7‐dimethyl‐1‐octen‐3‐ol could be useful as natural agents for the management of three mite species. Copyright © 2011 Society of Chemical Industry     

The effect of initial concentration of carbofuran on the development and stability of its enhanced biodegradation in top‐soil and sub‐soil

Carbofuran was incubated in top‐soil and sub‐soil samples from a pesticide‐free site at a range of initial concentrations from 0.1 to 10 mg kg⁻¹. Amounts of the incubated soils were removed at intervals over the subsequent 12 months, and the rate of degradation of a second carbofuran dose at 10 mg kg⁻¹ was assessed. An applied concentration as low as 0.1 mg kg⁻¹ to top‐soil resulted in more rapid degradation of the fresh addition of carbofuran for at least 12 months. The degree of enhancement was generally more pronounced with the higher initial concentrations. When the same study was conducted in sub‐soil samples from the same site, an initial dose of carbofuran at 0.1 mg kg⁻¹ resulted in only small increases in rates of degradation of a second carbofuran dose. However, degradation rates in the sub‐soil samples were, in many instances, considerably greater than in the corresponding top‐soil samples, irrespective of pre‐treatment concentration or pre‐incubation period. Initial doses of 0.5 mg kg⁻¹ and higher applied to sub‐soil successfully activated the sub‐soil microflora. Application of the VARLEACH model to simulate carbofuran movement through the soil profile indicated that approximately 0.01 mg kg⁻¹ of carbofuran may reach a depth of 70 cm 400 days after a standard field application. The results therefore imply that adaptation of the sub‐soil microflora (c 1 m depth) by normal field rate applications of carbofuran is unlikely to occur. In experiments to investigate this in soils exposed to carbofuran in the field, there was no apparent relationship between top‐soil exposure and degradation rates in the corresponding sub‐soils. The results further confirmed that some sub‐soil samples have an inherent capacity for rapid biodegradation of carbofuran. The high levels of variability observed between replicates in some of the sub‐soil samples were attributed to the uneven distribution of a low population of carbofuran‐degrading micro‐organisms in sub‐surface soil. There was no apparent relationship between soil microbial biomass and degradation rates within or between top‐soil and sub‐soil samples. © 2001 Society of Chemical Industry     

Fumigant toxicity is the major route of insecticidal activity of citruspeel essential oils

Dosages (>10 ml mg⁻¹ against Callosobruchus maculatus F. or Sitophilus zeamais Motsch; >20 ml kg⁻¹ against Dermestes maculatus Deg.) of citruspeel oils reduced oviposition or larval emergence through parental adult mortality, but had no residual activity on the eggs or larvae produced by survivors. Oil-treated grains (7 ml kg⁻¹ against C. maculatus) or dried fish (28 ml kg⁻¹ against D. maculatus) which caused 100% mortality 1 h after application lost all activity within 24 h, thus confirming the non-residual nature of the effects. The activity of limepeel oil against test insects was found to be dependent on the time interval between the application of oil and start of bioassays. The non-volatile residues of limepeel oil were not toxic to insects on glass and dried-fish surfaces. Topical toxicity trials against D. maculatus adults also illustrated the relative unimportance of contact toxicity of citrus oils, as appreciable mortality (at application rates of up to 2 μl per insect) was obtained only when treated insects were confined in air-tight glass chambers. The volatility of toxic constituents in the oils was further illustrated by mortality of untreated C. maculatus adults confined in air-tight chambers with topically treated D. maculatus. A more efficient way to use citruspeel essential oils to control insects would be as a fumigant in relatively enclosed or air-tight systems.     

Effects of temperature and concentration of the accelerators ethoxylated alcohols,diethyl suberate and tributyl phosphate on the mobility of [14C]2,4‐dichlorophenoxy butyric acid in plant cuticles

Intrinsic activities of monodisperse ethoxylated dodecanols (MEDs), diethyl suberate (DESU) and tributyl phosphate (TBP) were investigated using Stephanotis floribunda leaf cuticular membranes (CMs) and [¹⁴C]2,4‐dichlorophenoxy butyric acid (2,4‐DB) as a model solute. When sorbed in cuticular membranes, MEDs, DESU and TBP increase solute mobility and are called accelerators for this reason. With MEDs, dose‐effect curves (log mobility vs accelerator concentration) were linear but, with DESU and TBP, curves convex to the x axes were obtained that approached a maximum at 90 and 150 g kg⁻¹, respectively. Accelerators increased the mobility of 2,4‐DB in the CMs by 9‐ to 48‐fold, and effects were larger at lower temperatures (range 15–30 °C). Activation energy for diffusion of 2,4‐DB was 105 kJ mol⁻¹, decreasing with increasing accelerator concentrations to 26 kJ mol⁻¹ with DESU at 90 g kg⁻¹ and 64 kJ mol⁻¹ with TBP at 150 g kg⁻¹. Thus, the intrinsic activity of DESU was much higher than that of TBP, which implies that, for a given effect, less DESU than TBP would be needed. MEDs were also very effective accelerators, lowering activation energies to 36 kJ mol⁻¹. Data are discussed in relation to increasing rates of foliar penetration of active ingredients at low temperatures. © 2001 Society of Chemical Industry     

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     

A new aqueous suspension concentrate formulation of cis‐permethrin and its insecticidal activity

Isomers of pyrethroids usually have different insecticidal activities. Permethrin, a non‐cyano pyrethroid, is not an exception and cis‐permethrin is much more active than the trans‐isomer against Triatoma infestans, vector of Chagas' Disease in Argentina. The large‐scale separation of cis‐ and trans‐permethrin was performed by successive recrystallizations from ethanol‐water mixtures. An aqueous suspension concentrate (flowable) formulation of pure crystalline cis‐permethrin was prepared and assayed for its insecticidal activity on wood and ceramic surfaces against nymph V of T infestans. This formulation was at least three times more effective than deltamethrin, with LC₅₀ values on ceramic of 0.11 µg cm⁻² and 0.33 µg cm⁻² respectively. On wood surfaces, the LC₅₀ value was 0.57 µg cm⁻² compared with 3.20 µg cm⁻² for deltamethrin. Against other insect species such as Periplaneta americana, Aedes aegypti and Culex quinquefasciatus, the suspension concentrate formulation of cis‐permethrin was, however, less effective than similar formulations of deltamethrin or β‐cypermethrin. © 2000 Society of Chemical Industry     

Development of strategies for monitoring indoxacarb and gel bait susceptibility in the German cockroach (Blattodea: Blattellidae)

BACKGROUND: Advion^® cockroach gel bait (6 g kg^?1 indoxacarb) is in widespread use for Blattella germanica (L.) control in the United States. However, baseline susceptibility levels to indoxacarb in German cockroach field populations are not known. Hence, this research sought to develop monitoring strategies to estimate the susceptibility of German cockroach populations to indoxacarb. RESULTS: Four bioassays were evaluated: topical lethal dose (LD), formulated gel bait lethal time (LT), vial lethal concentration (LC) and gel bait matrix LD. Of these methods, the vial LC and gel bait matrix LD bioassays were the most economical and relevant assessment strategies. For indoxacarb susceptibility monitoring, a two‐tiered approach was developed that utilizes diagnostic concentrations and doses in vial LC (30 and 60 µg vial^?1) and gel bait matrix LD (1.0, 1.5 and 2.5 µg insect^?1) formats. CONCLUSIONS: A two‐tiered susceptibility monitoring strategy was developed that includes testing field populations at diagnostic concentrations and doses in first‐tier vial LC bioassays and second‐tier gel bait matrix LD bioassays. The vial method facilitates rapid identification of field strains with reduced susceptibility. The feeding bioassay effectively simulates field exposure to Advion^® and therefore has utility for secondary confirmation of susceptibility shifts and identification of behavioral resistance (i.e. bait aversion). Copyright © 2010 Society of Chemical Industry