Use Of Synthetic Pyrethroids Research Articles

Effects of deltamethrin exposure on the cytochrome P450 monooxygenases of Aedes albopictus (Skuse) larvae from a dengue-endemic region of northern part of West Bengal, India.

Aedes albopictus is highly prevalent in the northern part of West Bengal and is considered to be responsible for the recent dengue outbreaks in this region. Control of this vector is largely relied on the use of synthetic pyrethroids, which can lead to the development of resistance. In the present study, larvae of three wild Ae. albopictus populations from the dengue-endemic regions were screened for deltamethrin resistance, and the role of cytochrome P450 monooxygenases (CYPs) was investigated in deltamethrin exposed and unexposed larvae. Two populations were incipient resistant, and one population was completely resistant against deltamethrin. Monooxygenase titration assay revealed the involvement of CYPs in deltamethrin resistance along with an induction effect of deltamethrin exposure. Gene expression studies revealed differential expression of five CYP6 family genes, CYP6A8, CYP6P12, CYP6A14, CYP6N3 and CYP6N6, with high constitutive expression of CYP6A8 and CYP6P12 in all the populations before and after deltamethrin exposure. From these findings, it was evident that CYPs play an important role in the development of deltamethrin resistance in the Ae. albopictus populations in this region.

Understanding the resistance mechanisms of Rhipicephalus microplus ticks to synthetic pyrethroids and organophosphates in south-west regions of Haryana, North India

Chemical control of tick infestation on dairy farms in India strongly relies upon the use of synthetic pyrethroids (deltamethrin) and organophosphate (coumaphos) drugs. Therefore, the present manuscript aims to investigate the resistance status of Rhipicephalus microplus ticks against these acaricides. Fully engorged adult R. microplus ticks were randomly collected from 8 dairy farms in North India and evaluated for acaricide resistance by using the Larval Packet Test (LPT). Of these, ticks collected from one and three farms showed the emergence of Level I acaricide resistance against deltamethrin and coumaphos, respectively. Significant positive correlations were found in the enzymatic activity (α-esterase, β-esterase, glutathione-S-transferase, and mono‐oxygenase) of R. microplus tick resistant against coumaphos. Native electrophoretogram analysis showed six different types of esterase activity in R. microplus (EST-1b to EST-6b), and EST-5b activity was more predominantly expressed in resistant ticks. Further, inhibitor studies using various esterase inhibitors suggested that EST-5b is a putative acetylcholine-esterase (AchE), and increased expression of one of the AchE might be responsible for the emergence of acaricide resistance. Further, no mutations were detected in the carboxylesterase (G1120A) and domain II S4‐5 linker region (C190A) of the sodium channel genes of resistant R. microplus ticks, indicating that increased expression of detoxification enzymes was the probable mechanism for the development of acaricide resistance in the resistant ticks.

Evaluation of Trap Devices for Mass Trapping of Ceratitis capitata (Diptera: Tephritidae) Populations.

Simple SummaryThe Mediterranean fruit fly, Ceratitis capitata, is considered one of the world’s most damaging pests, able to infest the fruits of over 300 plant species and adapt to a wide range of climatic zones. It can attack commercially important fruits and losses caused by this pest can be enormous without appropriate control measures. To contribute to the management of Mediterranean fruit fly infestations, in the present paper, we report the effectiveness of commercially available trapping devices (Decis Trap, Tephri Trap Ecological and Conetrap) baited with two types of female attractants (Econex Trypack and Biodelear). The performance of trapping devices was evaluated in semi-field cages in different thermal conditions. Our results showed that the Tephri Trap baited with Trypack or Biodelear and the Decis Trap reported the same performance in capturing females and could all be used for medfly mass trapping. The mass trapping technique can be considered an eco-friendly method to use in combination with other control systems.The Mediterranean fruit fly (medfly), Ceratitis capitata, is a key pest of fruit crops in a wide range of climatic zone. Its economic importance is increasing due to its invasion and establishment in new geographical areas caused by global warming. Generally, the management of medfly infestation has been carried out with the use of synthetic pyrethroids and phosphorganic insecticides. Other containment approaches include attract-and-kill, biological control, and the sterile insect technique. The mass trapping technique can be considered an eco-friendly method to use in combination with other control systems. The present study reported the trapping effectiveness of commercially available devices (Decis Trap, Tephri Trap Ecological, and Conetrap) baited with different types of female attractants (Econex Trypack and Biodelear) under different thermal conditions. The performance of trapping systems was evaluated in semi-field cages. Our results showed that the combination of Conetrap with Biodelear was not proven effective, while the Tephri Trap baited with Trypack or Biodelear and the Decis Trap reported the same performance in capturing females and could be used for medfly mass trapping.

Fitness Cost of Sequential Selection with Deltamethrin in Aedes aegypti (Diptera: Culicidae).

In Mexico, Aedes aegypti (L.) is the primary dengue vector, chikungunya, and Zika viruses. The continued use of synthetic pyrethroids has led to the development of resistance in target populations, which has diminished the effectiveness of vector control programs. Resistance has been associated with disadvantages that affect the biological parameters of resistant mosquitoes compared to susceptible ones. In the present study, the disadvantages were evaluated by parameters related to survival and reproduction ('fitness cost') after selection with deltamethrin for five generations. The parameters analyzed were the length of the development cycle, sex ratio, survival, longevity, fecundity, egg viability, preoviposition, oviposition and postoviposition periods, and growth parameters. In the deltamethrin-selected strain, there was a decrease in the development cycle duration, the percentage of pupae, the oviposition period, and eggs viability. Although mean daily fecundity was not affected after the selection process, this, together with the decrease in the survival and fecundity levels by specific age, significantly affected the gross reproductive rate (GRR), net reproductive rate (Ro), and intrinsic growth rate (rm) of the group selected for five generations with deltamethrin compared to the group without selection. Identifying the 'cost' of resistance in biological fitness represents an advantage if it is desired to limit the spread of resistant populations since the fitness cost is the less likely that resistant individuals will spread in the population. This represents an important factor to consider in designing integrated vector management programs.

Genetic analysis and screening of pyrethroid resistance mutations in Varroa destructor populations from Turkey.

Varroa destructor is the most common ectoparasite of the Western honey bee (Apis mellifera L.) worldwide and poses a serious threat to bee health. Synthetic acaricides, particularly pyrethroids, are frequently used to control Varroa mites. However, long-term and repeated use of synthetic pyrethroids has led to the development of resistance. In this study, we report on the presence of resistance mutations in the voltage-gated sodium channel in V. destructor populations from Turkish beekeeping areas. Two resistance mutations, L925V and L925I, that were previously associated with pyrethroid resistance, were found in more than 75% of the populations. A general correlation between the presence of mutations and the history of acaricide usage was observed for the sampled hives. In addition, we show there is only a low genetic distance among the sampled V. destructor populations, based on the analysis of three mitochondrial genes: cytochrome b (cytb), ATP synthase subunit 6 (atp6), and cytochrome c oxidase subunit III (cox3). Revealing the presence and geographical distribution of pyrethroid resistance mutations in V. destructor populations from Turkish apiaries will contribute to create more effective mite management programmes.

Activity of Cytochrome P450 Monooxygenase (CYPs) Metabolic Enzymes as Markers of Insecticide Resistance in Anopheles vagus Muara Enim Mosquitoes, Indonesia

A B S T R A C TThe use of synthetic pyrethroids in insecticide-treated bed nets (LLINs) and sprayform (IRS) has been carried out since 2012 in Muara Emil Village and since 2016 inall villages in Tanjung Agung District, Muara Enim Regency. Biochemical resistancecan occur to the enzymes that play a role in detoxifying the insecticide. This studyaims to identify whether there is an increase in the levels of the enzyme CytochromeP450 monooxygenase (CYPs) through the enzyme biochemical test on the malariavector mosquito Anopheles vagus originating from Pagar Dewa Village and MuaraEmil Village, Muara Enim Regency. The sample of female Anopheles mosquitoes wasnot full. Blood was taken at night using the resting collection method. Mosquitoesthat have been identified as Anopheles vagus species are used to check CYPs enzymelevels using the ELISA method. The results of the biochemical test showed thatenzyme levels increased from the Muara emil and Pagar Dewa village mosquitoeswith a percentage of 71% and 61.53% (with cut off point OD> 0.165). The value ofCYPs enzyme levels for mosquitoes from Muara Emil village was higher than that ofthe mosquitoes from Pagar Dewa Village (mean 0.005027 ± 0.007). The increasedactivity of the CYPs enzyme plays a role in the detoxification of synthetic pyrethroidinsecticides that can cause resistance. The high levels of enzymes from the villagesof Muara Emil and Desa Farah Dewa are in line with intensive insecticide exposurein eradicating malaria vectors in the highest malaria transmission areas in MuaraEnim Regency.

Chronic cypermethrin exposure alters mouse embryonic stem cell growth kinetics, induces Phase II detoxification response and affects pluripotency and differentiation gene expression

Worldwide uncontrolled use of synthetic pyrethroids contaminates water and soil leading to health hazards. Cypermethrin (CYP), the most used pyrethroid, induces detrimental effects on adults and embryos at different stages of development of several vertebrate species. In Mammals, CYP-induced alterations have been previously described in adult somatic cells and in post-implantation embryos. It remains unknown whether CYP has effects during pre-implantation development. Studies to access pre-implantation embryo toxicity are complicated by the restricted number of blastocysts that may be obtained, either in vivo or in vitro. Embryonic stem cells (ESCs) are an in vitro model study that overcomes these limitations, as millions of pluripotent cells are available to the analysis. Also, ESCs maintain the same pluripotency characteristics and differentiation capacity of the inner cell mass (ICM) present in the blastocyst, from which they derive. In this work, using mouse R1 ESCs, we studied CYP-induced cell death, ROS production, the activation of oxidative stress-related and detoxification responses and the population growth kinetics following 72 h exposure at the 0.3 mM LD50 dose. Also, the expression levels of pluripotency genes in exposed ESCs and of markers of the three germ layers after their differentiation into embryoid bodies (EBs) were determined. Two apoptotic waves were observed at 12-24 h and at 72 h. The increase of ROS production, at 24 h until the end of the culture period, was accompanied by the induction, at 48 h, of redox-related Cat, Sod1, Sod2, Gpx1 and Gpx4 genes. Up-regulation of Cyp1b1, but not of Cyp1a1, phase I gene was detected at 72 h and induction of Nqo1, Gsta1 and Ugt1a6 phase II genes began at 24 h exposure. The results show that exposed R1 ESCs activate oxidative stress-related and detoxification responses, although not sufficient, during the culture period tested, to warrant recovery of the growth rate observed in untreated cells. Also, CYP exposure altered the expression of Oct-4 and Nanog pluripotency genes in ESCs and, when differentiated into EBs, the expression of Fgf5, Brachyury and Foxa2, early markers of the ectoderm, mesoderm and endoderm germ layers, respectively. NIH/3T3 cells, a differentiated cell line of embryonic origin, were used for comparison.

Susceptibility Profiles of Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae) to Deltamethrin Reveal a Contrast between the Northern and the Southern Benin.

Helicoverpa armigera is an indigenous species in Africa and has been reported in the destruction of several crops in Benin. Management of H. armigera pest is mainly focused on the use of synthetic pyrethroids, which may contribute to resistance selection. This study aimed to screen the susceptibility pattern of field populations of H. armigera to deltamethrin in Benin. Relevant information on the type of pesticides used by farmers were gathered through surveys. Collected samples of Helicoverpa (F0) were reared to F1. F0 were subjected to morphological speciation followed by a confirmation using restriction fragment length polymorphism coupled with a polymerase chain reaction (RFLP-PCR). F1 (larvae) were used for insecticide susceptibility with deltamethrin alone and in the presence of the P450 inhibitor Piperonyl Butoxide (PBO). Deltamethrin and lambda-cyhalothrin were the most used pyrethroids in tomato and cotton farms respectively. All field-sampled Helicoverpa were found to be H. armigera. Susceptibility assays of H. armigera to deltamethrin revealed a high resistance pattern in cowpea (resistance factor (RF) = 2340), cotton (RF varying from 12 to 516) and tomato (RF=85) farms which is a concern for the control of this major polyphagous agricultural pest. There was a significant increase of mortality when deltamethrin insecticide was combined with piperonyl butoxide (PBO), suggesting the possible involvement of detoxification enzymes such as oxidase. This study highlights the presence of P450 induced metabolic resistance in H. armigera populations from diverse cropping systems in Benin. The recorded high levels of deltamethrin resistance in H. armigera is a concern for the control of this major agricultural pest in Benin as the country is currently embarking into economical expansion of cotton, vegetables and grain-legumes cropping systems.

Genetic variability and pyrethroid susceptibility of the parasitic honey bee mite Varroa destructor (Acari: Varroidae) in Iran.

The ectoparasitic honey bee mite Varroa destructor Anderson & Trueman (Acari: Varroidae) is one of the major concerns for worldwide beekeeping. The use of synthetic pyrethroids for controlling the mite was among the most popular treatments until resistance evolved in the mid 1990's. In Iran, beekeepers are dealing with the parasite and they also used pyrethroids for controlling the mite for a long time. After the evolution of resistance to pyrethroids, they based mite control mostly on treatments with amitraz, organic acids and several management practices. Here we conducted a comprehensive characterization of V. destructor populations parasitizing Apis mellifera in Iran. We determined the genetic variability of mites collected from 28 localities distributed throughout the country. The haplotype of V. destructor was determined by PCR-RFLP, analyzing a fragment of the mitochondrial cox1 gene. It was found that only the Korean haplotype was present in samples from all localities. DNA fragments from cox1, atp6, cox3 and cytb mitochondrial genes were sequenced and the results showed that all samples were identical to the K1-1 or the K1-2 V. destructor haplotypes. Moreover, as it has been reported that resistance to pyrethroids in V. destructor is associated with mutations at position 925 of the voltage-gated sodium channel, a TaqMan®-based allelic discrimination assay was conducted to genotype the mites collected. The results showed that all the mites tested were homozygous for the wild-type allele and, therefore, susceptible to treatment with pyrethroids.

Bifenthrin-induced neurotoxicity in rats: involvement of oxidative stress

Extensive use of synthetic pyrethroids has resulted in serious human health issues. Induction of oxidative stress is an important mechanism of action of most pesticides including pyrethroids. In the present study, we have elucidated the possible role of oxidative stress in bifenthrin-induced neurotoxicity. Adult male Wistar rats were administered bifenthrin (3.5 and 7 mg per kg body weight p.o.) for 30 days. Behavioral studies were conducted on a set of randomly selected rats from each treatment group after completion of treatment. Neurochemical parameters were assessed 24 h after the last dose was administered. The selected behavioral and neurochemical endpoints were also assessed 15 days after cessation of exposure to reveal whether the neurobehavioral changes produced by bifenthrin were temporary or permanent. Deficits in motor activity, motor incoordination, and cognitive impairment were observed after exposure to bifenthrin. Levels of biogenic amines viz. dopamine (DA) and its metabolites, i.e. 3,4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA), epinephrine (EPN), norepinephrine (NE), and serotonin (5-HT) altered in the frontal cortex, corpus striatum, and hippocampus of bifenthrin-treated rats. A decrease in the activity of acetylcholinesterase (AChE) occurred in all regions of the brain. Both doses of bifenthrin significantly induced lipid peroxidation (LPO) and increased protein carbonyl levels in the frontal cortex, corpus striatum, and hippocampus of rats. The activities of antioxidant enzymes, i.e. catalase, superoxide dismutase, and glutathione peroxidase, were also suppressed in all selected regions of the brain. A trend of recovery was, however, observed in all the behavioral and neurochemical endpoints 15 days after withdrawal of exposure. Oxidative stress seems to play an important role in bifenthrin-induced neurotoxicity. Our study suggests that long-term exposure to these compounds can produce detrimental effects.

Acaricide resistance status in Indian isolates of Hyalomma anatolicum

The multi host tick, Hyalomma anatolicum, is the commonest Hyalomma species in India and cattle serves as the main host of this species. A study to evaluate the acaricide resistance of H. anatolicum to deltamethrin, cypermethrin and diazinon was conducted in 20 areas located in three agro climatic regions known to have abundance of the species. Results obtained by the "larval packet test" (LPT) showed a low grade resistance (level-I, RF <5) in the tick species to both deltamethrin and cypermethrin in 10 areas and higher grade resistance (level-II, RF <25) to deltamethrin in one area, where intensive use of synthetic pyrethroids are practiced for tick control. Low grade resistance to diazinon (level I) was recorded in six areas where organophosphates compounds are extensively used for agricultural practices allowing increased exposure of the moulting instars of the ticks to these chemicals. Biochemical analysis of the samples suggested involvement of esterase and alterations of acetylcholinesterase in the resistance mechanisms.

The role of oxidative stress in enantiomer‐specific, bifenthrin‐induced cytotoxicity in PC12 cells

With the widespread use of synthetic pyrethroids (SPs), the various toxic effects of these compounds have attracted much interest with respect to the investigation of involved mechanisms. However, research on molecular mechanisms of enantioselective toxicity of SPs has been limited. Our previous investigations suggested that enantiomers of cis-bifenthrin (cis-BF) behaved enantioselectively in endocrine disruption and mammalian cytotoxicity. While little is known about the molecular mechanism of the enantioselective toxicity of cis-BF, recent experiments implicated oxidative stress in the cytotoxicity of many SPs. Therefore, the aim of this study was to determine whether cis-BF enantioselectively induced oxidative stress lead to enantioselective cytotoxicity. In this article, we used the rat pheochromocytoma PC12 cell line as an in vitro model to evaluate the involvement of the oxidative stress pathway in enantioselective cytotoxicity of cis-BF. Following exposure of cells to cis-BF and its enantiomers, a significant reduction in cell survival and superoxide dimutase, as well as increased production of lactate dehydrogenase, intracellular reactive oxygen species and malondialdehyde, was observed in 1S-cis-BF, while 1R-cis-BF exhibited these effects to a lesser degree. These results clearly demonstrated that enantiomer-specific cis-BF-induced oxidative damage is possibly an initiating event and contributes, at least in part, to the mechanism of cis-BF-induced enantioselective cytotoxicity. Furthermore, our study also indicated that enantioselectivity should be considered when evaluating the ecotoxicological effects and the health risks of chiral contaminants.

Preliminary Evidence that Copper and Zinc Inhibits the Dissipation of Synthetic Pyrethroid in Red Soil

Extensive use of synthetic pyrethroids has resulted in concerns regarding their potential effects on human health and ecosystems. In the present study, we evaluated the influence of coexisting Cu2+, Zn2+, soil water contents (15%, 25%, 40% by weight and waterlogged) and temperature levels (15°C, 25°C, 35°C, and 45°C) on the dissipation of cypermethrin, fenvalerate and deltamethrin in red soil. To further clarify the influence of Cu2+ and Zn2+ on biological and chemical dissipation processes, serial concentrations of the synthetic pyrethroids containing Cu2+ (21.3, 50, 100, and 400 mg kg−1) and Zn2+ (35.8, 100, 250, and 500 mg kg−1) were used to spike the soil and then incubated at 25°C in the dark at 25% moisture. The results revealed a very severe inhibitory effect on the dissipation rates with increasing Cu2+ and Zn2+ levels. Conversely, there were no significant decreases in dissipation rates in response to exposure to 50 mg kg−1 Cu2+ or 100 mg kg−1 Zn2+, and the dissipation rates decreased significantly (p < 0.05) when the Cu2+ and Zn2+ concentration increased to 100 and 250 mg kg−1, respectively, which were the respective maximum field recommended rates. When compared with unsterilized batch treatments, the t 1/2 in sterilized (chemical dissipation) batch treatments increased by 1.0–4.8-fold. Additionally, there was a highly significant difference in the dissipation of pyrethroids in the 15% water content treatments and waterlogged treatments (p < 0.05). Finally, the difference in the dissipation rates at 15°C and 25°C was significant (p < 0.05).

Evaluation of the benefits of an insecticide resistance management programme in Punjab in India

In India, many IPM programmes have been implemented, but they have not achieved the desired level of success in reducing insecticide use and increasing adoption of IPM practices. This inter-disciplinary study evaluated an Insecticide Resistance Management-based Integrated Pest Management (IRM-IPM) programme in cotton and compared it with non-IRM production for a range of IPM and economic measures. The IRM-IPM programme has been implemented in 28 districts of 10 states of India since 2002 to help rationalize and reduce the use of insecticides and to overcome the development of resistance in cotton pests, especially Helicoverpa armigera. The IRM-IPM strategy includes applying insecticides only when pests exceed economic threshold levels, using selective insecticides that are compatible with biological control, and rotating between different insecticide classes. The IRM-IPM programme we evaluated resulted in a reduction in insecticide consumption (technical grade material) by 30%, and it reduced the number of sprays by 15%; however, it did not result in a significant change in productivity. The majority of IRM farmers avoided using highly toxic insecticides such as monocrotophos, avoided use of synthetic pyrethroids beyond 140 days after sowing to avoid resurgence of Bemisia tabaci, and rotated the insecticide compounds/groups to delay the development of resistance and ensured effective management of H. armigera. On average, the IRM-IPM programme resulted in a return of US $24.05 ha−1 (at 2005 rates: US $1 = 45 Indian rupees), by saving on insecticide costs. While the farmers gained significantly in knowledge of IPM practices, the level of adoption of IPM techniques was low. Further studies based on impact evaluation methodology, employing a with/without and before/after quasi-experimental design, would provide feedback to help in the formulation of future IPM strategies.

Chronic toxicity and cytotoxicity of synthetic pyrethroid insecticide cis-bifenthrin

With the increasing use of synthetic pyrethroids (SPs), the significance of ecological safety and health risk is an emerging concern. In this study, we evaluated the chronic aquatic toxicity of cis-bifenthrin (cis-BF) in Daphnia magna and its cytotoxicity in Chinese hamster ovary (CHO) cells as well as human cervical carcinoma (Hela) cells. Chronic aquatic toxicity tests showed that cis-BF could significantly affect the reproduction of D. magna. The lowest observed effective concentration and the non-observed effective concentration of cis-BF to D. magna were 0.02 and 0.01 microg/L, respectively, and the chronic value was 0.014 microg/L. The intrinsic rate of natural increase was significantly decreased (p < 0.05) to 0.02 microg/L. The cytotoxicity assay demonstrated that cis-BF decreased cell viability in CHO and Hela cells in a concentration- and time-dependent manner. The IC50 values for Hela and CHO cells were 4.0 x 10(-5) and 3.2 x 10(-5) mol/L, respectively. Together, these results indicated that cis-BF induced chronic toxicity in both aquatic invertebrate animals and mammalian cells. These findings assist in understanding the impact of SPs on health and environmental safety. Considering the wide spectrum of SPs, a more comprehensive understanding of the negative effects is indispensible for planning future application and regulation of these pesticides.

Biodegradation of beta-cyfluthrin by Pseudomonas stutzeri strain S1

beta-Cyfluthrin [alpha-cyano-4-fluoro-3-phenoxybenzyl-3(2,2-dichlorovinyl)-2,2-dimethylcyclopropane carboxylate] pesticide has been in agricultural use in the recent years for controlling Lepidopteran pests affecting solanaceous crops. The extensive use of synthetic pyrethroids like beta-cyfluthrin has resulted in wide spread environmental contamination. The purpose of this study was to isolate bacteria from soil and to determine their ability to degrade beta-cyfluthrin and identify the intermediates in culture broth using spectroscopy. An aerobic bacterium capable of degrading beta-cyfluthrin was isolated by enrichment culture. The 16S ribosomal DNA sequence of the isolate (strain S1) had 100% identity to the sequence from Pseudomonas stutzeri. Finally products formed during degradation of beta-cyfluthrin have been identified as alpha-cyano-4-fluoro-3-phenoxybenzyl-3(2,2-dichlorovinyl)-2,2-dimethylcyclopropane carboxylate (M.W. 341); 4-fluoro-3-phenoxy-alpha-cyanobenzyl alcohol (M.W. 243) and 3(2,2-dichlorovinyl)-2,2-dimethyl cyclopropanecarboxylic acid (M.W. 208).

Cotton pests and their natural enemies in Madagascar

An update on the cotton pest complex and its associated natural enemies in Madagascar is provided. Since the end of the 1970s, when the previous reports had been published, the population dynamics of the principal pests in Malagasy cotton have undergone considerable changes. The American bollworm Helicoverpa armigera Hübner (Lep., Noctuidae) is still a limiting factor for production and can be considered the key pest, whereas the Egyptian leaf worm Spodoptera littoralis Boisduval (Lep., Noctuidae) and the cotton aphid Aphis gossypii Glover (Hom., Aphididae) have become significant pests as a result of indiscriminate use of synthetic pyrethroids in the 1980s. New records of beneficials, in particular the discovery of the aphidopathogenic fungus Neozygites fresenii (Nowakowski) (Entomophthorales) in cotton aphid populations, are reported. Strategies to preserve predator populations in view of reducing disruptive insecticide treatments are discussed.

Topical treatment of calves with synthetic pyrethroids: effects on the non-target dung fly Neomyia cornicina (Diptera: Muscidae).

Dung from calves treated with synthetic pyrethroids negatively influenced, in varying degrees, survival, reproduction and size of the common dung fly Neomyia cornicina (Fabricius). This was documented in assays where the coprophagous larvae and adults of N. cornicina were exposed to dung collected from calves dosed with topical preparations of deltamethrin, flumethrin, cyfluthrin, and alpha-cypermethrin. Larval mortality was significantly increased in dung collected up to at least seven days after treatment with deltamethrin, alpha-cypermethrin and cyfluthrin. Alpha-cypermethrin caused significant mortality of adults allowed to feed on moist dung. Nulliparous flies fed for six days on dung collected three days after treatment of calves with alpha-cypermethrin or deltamethrin showed little or no ovarian development. A tendency for a comparable effect with flumethrin was also observed. A connection between ovarian development and inhibition of feeding was indicated by the observation of significantly lowered excretion rates in flies exposed to residues of deltamethrin, alpha-cypermethrin and flumethrin. Larvae that survived exposure to dung from calves dosed with deltamethrin, alpha-cypermethrin, or cyfluthrin gave rise to smaller flies. The effect on adult fly size decreased when larvae were exposed to dung collected at longer times after treatment of the calves. Adult fly size was significantly reduced in dung collected up to 14 days (alpha-cypermethrin) or up to 28 days after treatment (deltamethrin and cyfluthrin). Fluctuating asymmetry of a wing vein character did not reflect the anticipated levels of exposure. The study strongly indicated that the use of synthetic pyrethroids affected the insect dung fauna and that such use may reduce dung decomposition.

Comparative insecticide resistance of New Zealand and North American populations of diamondback moth, Plutella xylostella (Lepidoptera: Piuteiiidae)

The susceptibility of two New Zealand populations of diamondback moth, Plutella xylostella, to insecticides from three classes was compared with the susceptibility of a standard North American population (Geneva 88) in laboratory assays at the New York Experiment Station during 1993. Leaf dip assays showed that the New Zealand populations had developed moderate resistance to permethrin compared with the Geneva 88 population, but were still susceptible to methamidophos, Bacillus thuringiensis subsp. kurstaki, and B. thuringiensis subsp. aizawai. One of the New Zealand populations, Pukekohe 1, was 10 times more resistant to permethrin at the LC50 compared to the Geneva 88 population. This level of resistance was consistent with the greater use of synthetic pyrethroids, particularly permethrin, compared with other insecticides on vegetable brassicas at Pukekohe. Use of the Pukekohe 1 population as a standard for resistance assays in New Zealand indicated that diamondback moth from a reported control failure in Pukekohe were 4.9 times more resistant to lambdacyhalothrin, and may be as resistant to synthetic pyrethroids as the most resistant North American populations reported in Sheltonetal. (1993b).

A review of the use of synthetic pyrethroids in public health and vector pest control

AbstractThe last 40 years has seen significant evolution of the synthetic pyrethroids from their relatively restricted usage in domestic fly and mosquito control to their adoption in all major areas of public health pest control. The use of the synthetic pyrethroids in national and international control campaigns and in village level self‐help pest‐control schemes for major disease vectors such as mosquitoes, tsetse and blackfly is examined. Their successful introduction into the urban public health sector for control of cockroaches, fleas, bedbugs and lice, etc., is reviewed.