Organophosphorus and synergised synthetic pyrethroid insecticides as grain protectants for stored sorghum

A field experiment was carried out on bulk sorghum stored for 26 weeks in concrete silos in South Queensland. No natural infestation occurred. Laboratory bioassays of treated grain, in which malathion-resistant strains of insects were added to grain samples, indicated that all the treatments were generally effective. Deltamethrin (2mg kg⁻¹)+piperonyl butoxide (8mg kg⁻¹), fenitrothion (12mg kg⁻¹)+fenvalerate (1 mg kg⁻¹)+piperonyl butoxide (8mg kg⁻¹), and fenitrothion (12mg kg⁻¹)+phenothrin (2mg kg⁻¹)+piperonyl butoxide (8mg kg⁻¹) controlled typical malathion-resistant strains of Sitophilus oryzae (L.), Rhyzopertha dominica (F.), Tribolium castaneum (Herbst) and Ephestia cautella (Walker). Pirimiphos-methyl (6mg kg⁻¹)+permethrin (1mg kg⁻¹)+piperonyl butoxide (8mg kg⁻¹) allowed some survival of adults and progeny production by S. oryzae after 12 weeks, and by one strain of R. dominica throughout. Chemical assays established that the residues and rates of breakdown of these grain protectants on sorghum conformed to the general pattern on other cereal grains. Residues at the conclusion of the experiment were below the individual Maximum Residue Limits recommended by the Codex Alimentarius Commission.     

Grain protectants for the control of malathion-resistant insects in stored sorghum

Duplicate experiments were carried out on bulk sorghum stored in South Queensland and in Central Queensland. Bioassays of treated grain, conducted during 6 months' storage, established that fenitrothion (12 mg kg^?1)+ bioresmethrin (1 mg kg^?1), and pirimiphos-methyl (4 mg kg^?1)+ carbaryl (8 mg kg^?1), controlled typical malathionresistant strains of Sitophilus oryzae (L.), Rhyzopertha dominica (F.), Tribolium castaneum (Herbst), and Ephestia cautella (Walker). Chlorpyrifos-methyl (10 mg kg^?1)+ pyrethrins (1.5 mg kg^?1)+ piperonyl butoxide (12 mg kg^?1), and fenitrothion (12 mg kg^?1)+ (1R)-phenothrin (1 mg kg^?1), also controlled the strains of S. oryzae, T. castaneum and E. cautella, but were only partly effective against R. dominica. Methacrifos (15 mg kg^?1) controlled all the tested species except E. cautella. Chemical assays established that the residues and rates of breakdown of these grain protectants on sorghum conformed to the general pattern for other cereal grains; residues from the above treatments were below the individual Maximum Residue Limits recommended by the Codex Alimentarius Commission.     

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.     

Chlorpyrifos-methyl plus bioresmethrin; Methacrifos; Pirimiphos-methyl plus bioresmethrin; and synergised bioresmethrin as grain protectants for wheat

Field trials with various pesticide combinations were carried out on bulk wheat in commercial silos in Queensland, South Australia and Western Australia. Laboratory bioassays on samples of treated grain at intervals over 8 months using malathion-susceptible and malathion-resistant strains established the following orders of efficacy: against Sitophilus oryzae (L.), chlorpyrifos-methyl 10 mg kg^?1 + bioresmethrin 1 mg kg^?1 = methacrifos 15 mg kg^?1 in aerated storage > pirimiphos-methyl 4 or 6 mg kg^?1 + bioresmethrin 1 mg kg^?1 = bioresmethrin 4 mg kg^?1 + piperonyl butoxide 16 mg kg^?1; against Rhyzopertha dominica (F.), bioresmethrin 4 mg kg^?1 + piperonyl butoxide 16 mg kg^?1 > methacrifos 15 mg kg^?1 > chlorpyrifos-methyl 10 mg kg^?1 + bioresmethrin 1 mg kg^?1 = pirimiphos-methyl 4 or 6 mg kg^?1 + bioresmethrin 1 mg kg^?1. All treatments completely prevented production of progeny in Sitophilus granarius (L.), Tribolium castaneum (Herbst), T. confusum Jackquelin du Val and Oryzaephilus surinamensis (L.). The biological efficacy of methacrifos was greater and the rate of degradation lower in aerated than in non-aerated storage. Residue levels of all compounds were determined chemically and were below proposed international residue levels to be considered by the Codex Alimentarius Commission.     

Fenitrothion plus (1R)-phenothrin,and pirimiphos-methyl plus carbaryl,as grain protectant combinations for wheat

Duplicate field trials were carried out on bulk wheat in commercial silos in Queensland and New South Wales. Laboratory bioassays on samples of treated grain at intervals over 9 months, using malathion-resistant strains of insects, established that treatments were generally effective. Fenitrothion (12 mg kg^?1)+ (1R)-phenothrin (2 mg kg^?1) was more effective than pirimiphos-methyl (6 mg kg^?1) + carbaryl (10 mg kg^?1) against Sitophilus oryzae (L.) and Ephestia cautella (Walker); the order of effectiveness was reversed for S. granarius (L.). Against Rhyzopertha dominica (F.), Tribolium castaneum (Herbst), T. confusum Jackquelin du Val and Oryzaephilus surinamensis (L.), both treatments effectively prevented the production of progeny. The order of persistence was pirimiphos-methyl> (1R)-phenothrin>carbaryl or fenitrothion. During processing from wheat to white bread, residues were reduced by 98% for carbaryl, >44% for (1R)-phenothrin, 98% for fenitrothion and 85% for pirimiphosmethyl.     

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.     

The persistence and activity of insecticide spary deposits on woven polypropylene fabric

Wettable powder formulations of the organophosphorus insecticides, fenitrothion and pirimiphos-methyl, and the pyrethroids, permethrin and deltamethrin, have been compared for persistence and activity on woven polypropylene fabric; the residues produced in maize kept under the test sheets have also been measured. The test insects were Sitophilus oryzue (L.) and Tribolium custuneum (Herbst). Permethrin at 41 and 83 mg m^?2 was completely effective for the full 12 weeks of the experiment. Deltamethrin at 6.2 and 12.5 mg m^?2 was almost equally effective but after 4 weeks the deposit was slower acting against S. oryzae. The organophosphorus compounds were effective only up to 2 weeks at 250 mg m^?2 and up to 4 weeks at 500 mg m^?2. No residues could be detected under the pyrethroids but the organophosphorus insecticides gave residues of 2–4 mg kg^?1 on a thin layer of grain. This residue was biologically effective against the test insects.     

Synthetic pyrethroids: Toxicity and synergism on dietary exposure of Tribolium castaneum (Herbst) larvae

The potency of six dietary pyrethroids, as toxicants and inhibitors of weight gain in first- and fourth-instar Tribolium castaneum (Herbst) larvae, decreased in the order of cis-cypermethrin and deltamethrin > trans-cypermethrin and cis-permethrin > fenvalerate and trans-permethrin. Dosages that reduced larval weight also delayed pupation and emergence, probably due to their antifeeding activity. Three oxidase inhibitors (piperonyl butoxide, O, O-diethyl O-phenyl phosphorothioate, and O-isobutyl O-prop-2-ynyl phenylphosphonate), at a dietary concentration of 100 mg kg^?1, had little or no effect on the toxicity of trans-permethrin, but strongly synergised the toxicity of cis-cypermethrin by about 3-, 3- and 10-fold, respectively. Piperonyl butoxide also synergised the toxicity of cis-permethrin, trans-cypermethrin and deltamethrin, but not that of fenvalerate. On the other hand, an esterase inhibitor, profenofos, did not enhance the potency of any of the α-cyano-3-phenoxybenzyl pyrethroids. Oxidases appear to be more important than esterases in pyrethroid detoxification by T. castaneum larvae.     

Synergised cyfluthrin and cypermethrin as grain protectants on bulk wheat

Duplicate field trials were carried out on bulk wheat in commercial silos in Queensland and New South Wales. Laboratory bioassays on samples of treated grain at intervals over 8 or 9 months storage using malathion-resistant strains of insects established that treatments were generally effective. Cyfluthrin (2 mg kg^?1) plus piperonyl butoxide (10 mg kg^?1) and cypermethrin (4 mg kg^?1) plus piperonyl butoxide (10 mg kg^?1) completely controlled two strains of Sitophilus oryzae L. Control of a third strain by the cypermethrin combination was incomplete after 11/2 months and neither controlled a multi-resistant laboratory strain. Both combinations were effective against Rhyzopertha dominica F., Tribolium castaneum Herbst and Ephestia cautella Walker. No natural infestation developed in the treated grain in any silo. Mean residues of cyfluthrin and cypermethrin after 9 months storage were 58% and 52% of the calculated application rates, respectively. Compared with overall concentrations in the wheat, residue levels were higher in bran and pollard and lower in white flour. During baking, residues decreased by up to 29%. Operators experienced respiratory irritation associated with exposure to both combinations and alternative formulations would be required for use of these materials in grain storage.     

Surface contact toxicity and synergism of several insecticides against different stages of the tropical bed bug, Cimex hemipterus (Hemiptera: Cimicidae)

BACKGROUND: Five formulated insecticides (lambda‐cyhalothrin at 10 mg m^?2, bifenthrin at 50 mg m^?2, fipronil at 10 mg m^?2, fenitrothion at 50 mg m^?2, imidacloprid at 5 mg m^?2) and one active ingredient (DDT at 500 mg m^?2) were evaluated using a surface contact method against early and late instars and adults of two strains of the tropical bed bug, Cimex hemipterus (F.). Synergism of lambda‐cyhalothrin and fipronil using piperonyl butoxide (PBO) was also assessed. RESULTS: The order of susceptibility of different stages of bed bugs was as follows: early stage ? lambda‐cyhalothrin > bifenthrin = imidacloprid > fipronil > fenitrothion > DDT; late stage—lambda‐cyhalothrin > bifenthrin > fenitrothion > imidacloprid > fipronil > DDT; adult—lambda‐cyhalothrin > imidacloprid > bifenthrin > fenitrothion > fipronil > DDT. The late instars exhibited significantly higher LT₅₀ among the life stages. The addition of PBO to fipronil increased the susceptibility of the insects. CONCLUSIONS: Lambda‐cyhalothrin, bifenthrin, fenitrothion and fipronil at the recommended application rates were effective against C. hemipterus. Although imidacloprid demonstrated good initial response against C. hemipterus, the insects showed substantial recovery 72 h post‐treatment. The late instars (fourth and fifth instars) should be used as the model for toxicological evaluation. Copyright © 2011 Society of Chemical Industry     

Stability of pyrethroids on wheat in storage

The four pyrethroids, permethrin, phenothrin, fenvalerate and deltamethrin were applied to wheat which was stored for 52 weeks at 25 or 35°C, and either 12 or 15% moisture content. Rates of loss were calculated from residue analyses of the wheat at five intervals during storage. Calculated half-lives (weeks) for the pyrethroids at 25°C (12% moisture) and 35°C (15% moisture) were: permethrin 252 and 44, phenothrin 72 and 29, fenvalerate 210 and 74, and deltamethrin 114 and 35, respectively.     

Permethrin and deltamethrin residues on lettuce

Permethrin and deltamethrin, two synthetic pyrethroid insecticides, are registered in several countries for use on lettuce. Both chemicals were applied on autumn and spring grown lettuce in the glasshouse. When applied at the normal prescribed dose rates of 25 and 12.5 g a.i. ha^?1, < 1 mg kg^?1 of either compound was found in the lettuce at harvest, even when applied only a few days before harvest. The total amount of active ingredient applied was too low to reach the 1 mg kg^?1 level when evenly applied on marketable lettuce heads weighing about 200 g each. Applying a higher dose than 25 g permethrin a.i. ha^?1 or 12.5 g deltamethrin a.i. ha^?1, or applying two applications in the 2 weeks prior to harvest, may well result in residue levels higher than the maximum residue limit of 1 mg kg^?1 for permethrin and certainly higher than the maximum residue limit of 0.2 mg kg^?1 for deltamethrin, which is more persistent.     

Protective action of fenvalerate,deltamethrin, and four stereoisomers of permethrin against black flies (Simulium spp.) attacking cattle

Fenvalerate, deltamethrin, (1R)-cis-permethrin, (1R)-trans-permethrin and (1S)-trans-permethrin, applied topically to the entire body surface of steers at a rate of 1 mg a.i. kg⁻¹, provided 70% or better protection from black flies on cattle for 16, 9, 8, 6 and 6 days, respectively. The (1S)-cis stereoisomer of permethrin was ineffective as a protectant against black flies at a rate of 1 mg a.i. kg⁻¹ when applied as a total body spray. One poly(vinyl chloride) ear tag containing 10% permethrin, in each ear of steers, provided protection from black fly attack for up to 13 days under field conditions. Poly(vinyl chloride) ear tags containing 8% fenvalerate, installed in each ear of steers, did not provide satisfactory protection from black flies under field conditions.     

Extensive pilot use of the grain protectant combinations,fenitrothion plus bioresmethrin and pirimiphos-methyl plus bioresmethrin

Each of the combinations, bioresmethrin (1 mg kg^?1) plus pirimiphos-methyl(6 mg kg^?1) or fenitrothion (12 mg kg^?1), was applied in 1976 to grain in 21 commercial storages. Grain condition and protectant residues were regularly monitored. Three storages became infested with Rhizopertha dominica (F.), but all storages remained free of other insect species. In two of the three infested storages, application of protectant was uneven, and the third became infested only after 8 months of storage. Despite some variations in recovered residues between sites, the mean residue levels were accurately described by predictive models. Falls in temperature during storage varied considerably, and were related to factors other than climate and bin size. There was a marked effect by aeration with ambient cold air on both the grain temperature and the rate of loss of residues. Results of collaborative studies on the determination of residues indicate a need for regular check programmes of analysis, and confirm previous conclusions that residues of fenitrothion and pirimiphos-methyl can be accurately and conventionally determined.     

Laboratory studies on the mechanisms of resistance to permethrin in a field-selected strain of house flies

Enhanced oxidative metabolism appeared to be a major factor involved in resistance to permethrin in a field strain of house flies, selected with permethrin over 4 years. This was shown in the 7.8-fold synergism by piperonyl butoxide which reduced the resistance ratio from 97 to 15. The rate of permethrin detoxication was significantly higher (P=0.05) in the resistant flies compared with a susceptible strain or resistant flies pretreated with piperonyl butoxide. The esterase inhibitor S,S,S-tributyl phosphorotrithioate did not reduce the level of resistance to permethrin in the resistant strain, although some hydrolytic metabolism was apparent. Rates of penetration were similar in susceptible and resistant flies and in resistant flies pre-treated with piperonyl butoxide. A minor unidentified resistance factor, possibly reduced sensitivity of the nervous system, may also have been present in the resistant strain.     

Repellent action of permethrin,cypermethrin and resmethrin against black flies (Simulium spp.) attacking cattle

Permethrin, cypermethrin, and resmethrin were tested under field conditions as repellents to protect cattle from black flies (Simulium spp.). The chemicals were applied topically to the entire body surface of steers. Ethanolic solutions of technical permethrin, at doses of 1, 2, 4 and 6 mg a. i. kg^?1 of body weight, effectively repelled black flies by preventing at least 70% of the flies present from taking a blood meal for up to 8 days, and for at least 11 days at a dose of 12 mg a. i. kg^?1. Aqueous mixtures of a 20% permethrin emulsifiable concentrate (e. c.), at doses of 1, 2 and 6 mg a. i. kg^?1, effectivelyrepelled black flies for 2, 10 and 11 days, respectively. Aready-to-use 5% permethrin dust, at doses of 1, 2, and 4 mg a. i. kg^?1, effectively repelled black flies for 4, 5 and 8 days, respectively. Ethanolic solutions of technical cypermethrin, at doses of 1 and 2 mg a. i. kg^?1, repelled black flies for 3 and 4 days, respectively. Aqueous mixtures of a 40% cypermethrin e. c., at doses of 2 and 4 mg a. i. kg^?1, repelled black flies for at least 5 days. Ethanolic solutions of technical resmethrin, at doses of 2 and 6 mg a. i. kg^?1, repelled black flies for 1 and 2 days, respectively.     

Disposition kinetics,cytotoxicity and residues of fenvalerate in tissues following oral administration to goats

Disposition kinetics in goats of fenvalerate [(RS)-α-cyano-3-phenoxybenzyl (RS)-2-(4-chlorophenyl)-3-methylbutyrate] were studied after oral administration at 5 mg kg^?1. The insecticide persisted in blood for up to 48 h. The V_d(area), t_1/2(β), and t_1/2(Ka), of fenvalerate were 12.14 (±0.39) litre kg^?1, 12.25 (±0.25) h and 0.63 (±0.11)h, while the AUC and Cl_B values were respectively 7.35 (±0.39) μg h ml^?1 and 0.68 (±0.04) litre kg^?1 h^?1. The residues in tissues reached a peak four days after insecticide administration and then started to decline. Maximum residue was found in the adrenal gland, followed by liver, kidney and intestine. Both GOT and GPT activities in kidney tissue, but only GPT activities in liver tissue had decreased significantly 4, 8 and 22 days post-administration. The fenvalerate did not produce any significant effects on serum acetylcholinesterase, cholesterol or protein levels in goats. Histopathological examination showed fatty changes in the periphery of lobule, congestion in sinusoid, haemolysis in central vein, necrosis and periportal fibrosis around the central vein of liver, and necrosis in kidney of fenvalerate-treated goats.     

A comparison of permethrin and methomyl insecticides for the control of a multiresistant strain of houseflies (Musca domestica)

A methomyl sugar bait formulation and permethrin residual spray were compared for the control of a multi-insecticide resistant strain of housefly in a UK pig farm. The methomyl was applied as a granular scatter bait at the manufacturer's recommended rate of 25 mg m^?2 active ingredient (a.i.) to the treated floor area. Permethrin was applied at 32, 64 and 128 mg m^?2 a.i. to structural surfaces. The highest deposit rate of permethrin used was four times that recommended by the manufacturer for the control of flying insects. The methomyl bait gave effective control but the permethrin spray failed at all deposit rates tested. The use of permethrin increased resistance to this compound at the KD50 level from x 13 to x 560 within 10 weeks and significantly increased the proportion of flies resistant to natural pyrethrins synergised with piperonyl butoxide (P<0.01).     

Efficacy of selected pesticides against synanthropic mites under laboratory assay

BACKGROUND: The efficacies of organophosphate pesticides, single‐compound versus multicompound pyrethroid formulations and relatively novel unclassified insecticides/acaricides were compared to find the lowest dosage and highest efficacy for the control of Dermatophagoides farina (Hughes), D. pteronyssinus (Trouessart) and Tyrophagus putrescentiae (Schrank). Formulated active ingredients (AIs) were diluted in water and applied onto filter paper in experimental chambers with ten unsexed adult mites in six replicates. Mite mortality was checked after 24 h. The security index (SI) was calculated for all of the AIs by dividing the recommended rate by the LD₉₀ determined for each species. RESULTS: The tested organophosphates had high LD₉₀ and low SI values. The single‐compound pyrethroids were ineffective (deltamethrin and beta‐cyfluthrin) or had high LD₉₀ and low SI values (cyphenothrin, permethrin, pyrethrum and bifenthrin). The multicompound miticides had low LD₉₀ and high SI values which increased from deltamethrin/S‐bioallethrin to permethrin/S‐bioallethrin/piperonyl butoxide to permethrin/pyriproxyfen/benzyl benzoate. Abamectin, pyridaben, propargite and flufenoxuron were highly active against Dermatophagoides spp. Neem (Acarosan duo) was highly active against all mite species tested. CONCLUSION: The available formulations of multicompound pyrethroids (permethrin/S‐bioallethrin/piperonyl butoxide, permethrin/pyriproxyfen/benzyl benzoate), benzyl benzoate, neem and some field acaricides are effective in suppression of synanthropic mites in laboratory assays. Their LD₉₀ are lower than those of traditionally used organophosphates or single‐compound pyrethroid formulations. Copyright © 2011 Society of Chemical Industry     

Residues of cypermethrin,fenvalerate and deltamethrin on cauliflower

Following the application of Cypermethrin, fenvalerate and deltamethrin to a cauliflower crop at rates of 50, 50 and 12 g a.i. ha^-1, the maximum initial deposits of these insecticides on heads and leaves were 1.10 and 0.75, 1.14 and 0.60, and 0.32 and 0.12 mg kg^-1, respectively. These residue values for fenvalerate were less than the maximum residue limit (MRL) of 2 mg kg^-1 for this crop. While the maximum initial deposits of Cypermethrin and deltamethrin on cauliflower leaves were less than their respective MRL values of 1 and 0.2 mg kg^-1 for brassica leafy vegetables, it took one day for their residues on cauliflower heads to decline below this level.