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PubMed1994

The peach-potato aphid Myzus persicae and the tobacco aphid Myzus nicotianae have the same esterase-based mechanisms of insecticide resistance.

Biochemical and molecular studies have established that in the peach-potato aphid, Myzus persicae, insecticide resistance is conferred by amplification of genes encoding the insecticide-detoxifying esterases E4 or FE4. Here we report that two insecticide-resistant clones of the closely related tobacco aphid Myzus nicotianae have elevated esterases indistinguishable from E4 and FE4 and amplified esterase DNA sequences, and flanking regions, with identical restriction maps to the M. persicae genes. Furthermore, the DNA sequences of c. 630 bp fragments of the E4 and FE4 genes of M. persicae are different from each other but identical to the fragment from corresponding M. nicotianae clones. The existence of apparently identical insecticide resistance genes in the two species can be best explained by the selection of the amplified genes in M. persicae, transfer to hybrids of M. persicae and M. nicotianae by sexual reproduction and subsequent spread through M. nicotianae populations.

Animals↗
PubMed1997

[Resistance to organophosphorous and carbamates insecticides in a population of Culex quinquefasciatus].

The population of Culex quinquefasciatus breeding in the Pinheiros River (S. Paulo, Brazil) has been controlled with organophosphates since 1980. However, the biting has constituted a continual nuisance to the human population who live in the vicinity of the river. The occurrence of insecticide resistance to at least two organophosphates and one carbamate (malathion, fenitrothion and propoxur, respectively) to this insect population is reported. The results show the need to develop an insecticide management program. The susceptibility to permethrin (pyretroid) suggests the possibility of using this class of insecticide should the need for replacement of the insecticide in use arise.

Animals↗
PubMed2003

[Larval susceptibility of Aedes aegypti and Culex quinquefasciatus populations to chemical insecticides].

OBJECTIVE: To evaluate the susceptibility to chemical insecticides of Culex quinquefasciatus and Aedes aegypt larvae from areas subjected to control treatments or not. METHODS: Bioassays for diagnostic concentration and multiple concentration were performed for organophosphate and pyrethroid insecticides according to World Health Organization parameters. The susceptibility was assessed for mosquito larvae collected from an area not subjected to chemical control (Campinas, State of S o Paulo, SP) and from other areas (Campo Grande, Mato Grosso do Sul, MS, and Cuiabá, Mato Grosso, MT), in Brazil, subjected to such treatments. RESULTS: Tests for Culex quinquefasciatus larvae from Campinas, SP, allowed suspicion of resistance to cypermethrin and gave evidence of resistance to cyfluthrin. Larvae of this species collected in Campo Grande, MS, and Campinas, SP, presented resistance to temephos. For the colony from the latter locality, the following resistance rates were established: RR50=6.36 and RR95=4.94, in relation to a standard susceptible strain. Moreover, tests for Aedes aegypti showed similar susceptibility to temephos for a field population from Cuiabá, MT, and a laboratory population. CONCLUSIONS: The results indicate resistance of Culex quinquefasciatus to organophosphate and pyrethroid insecticides and make evident the need for evaluation and monitoring of the efficiency of insecticides to be used in mosquito control programs.

Aedes↗
PubMed2000

Performance of a pyrethroid-resistant strain of the predator mite Typhlodromus pyri (Acari: Phytoseiidae) under different insecticide regimes.

An organophosphate pyrethroid-resistant strain of Typhlodromus pyri Scheuten imported from New Zealand was reared on potted apple trees in an outdoor insectary. From 1988 to 1995, the population was selected one to three times per year with a dilute solution (1.7 ppm) of the pyrethroid cypermethrin. Petri dish bioassays with cypermethrin in 1995 indicated that the insectary-reared T. pyri had an LC50 of 81 ppm versus 0.006 ppm for native T. pyri taken from a research orchard. The bioassays suggested that recommended orchard rates of cypermethrin would cause heavy mortality in native populations of T. pyri but only moderate losses in the imported New Zealand strain. Bioassays in 1996 with the organophosphate insecticide dimethoate indicated both New Zealand and native T. pyri were susceptible and that recommended orchard rates of dimethoate likely would cause high mortality of T. pyri in apple orchards. These findings from bioassays were supported by data from orchard trials. In June and July 1993, insectary-reared New Zealand T. pyri were placed on five apple trees in each of eight 38-tree plots in the research orchard. In late August 1994, New Zealand T. pyri from orchard trees that had been sprayed twice by airblast sprayer with the full recommended rate of 50 g (AI)/ha (83 ppm) cypermethrin were placed on the other 33 trees in each of six plots. In the summers of 1994-1996, plots were treated with one of the following insecticide regimes: (1) conventional integrated pest management (IPM) (registered neurotoxic insecticides considered harmless or slightly toxic to T. pyri); (2) advanced IPM (use of newer, more selective insecticides); (3) pyrethroid (at least one full-rate application of cypermethrin); (4) dimethoate; and (5) dimethoate plus pyrethroid. Densities of European red mite, Panonychus ulmi (Koch), were highest in all plots treated with dimethoate and in pyrethroid plots not yet inoculated with New Zealand T. pyri. Densities of apple rust mite, Aculus schlechtendali (Nalepa), and of the stigmaeid predator Zetzellia mali (Ewing) were highest in plots treated with dimethoate and were nearly absent in the IPM plots. Densities of T. pyri were high enough for effective biocontrol in the IPM plots and in the pyrethroid plots 1-2 yr after release of the New Zealand strain, provided pyrethroid was applied just before the resistant strain was released in the orchard. A recurring theme of this study was the generally negative association between densities of phytophagous mites and those of T. pyri, suggesting the ability of this predator to suppress their prey. In contrast, the positive association between phytophagous mites and Z. mali suggests the inability of this predator to regulate their prey at least under the conditions of this study.

Animals↗
PubMed2000

Synergism of tebufenozide in resistant and susceptible strains of obliquebanded leafroller (Lepidoptera: Tortricidae) and resistance to new insecticides.

Cross-resistance of the obliquebanded leafroller, Choristoneura rosaceana (Harris), to tebufenozide was reported from laboratory studies before it had been used in commercial orchards in New York State. Bioassays with obliquebanded leafroller larvae from tebufenozide and organophosphate susceptible and resistant colonies were conducted with chlorfenapyr, emamectin benzoate, fenoxycarb, fipronil, spinosad, and tebufenozide to determine if cross-resistance was present before these new insecticides were introduced into commercial orchards. Resistance ratios ranged from 1.1 to 3.2 for all insecticides except tebufenozide (12.8). Significant differences between susceptible and resistant colonies were found with emamectin benzoate, fenoxycarb, and fipronil. The effect of the metabolic synergists piperonyl butoxide (PBO) and diethyl maleate (DEM) on tebufenozide toxicity was examined to determine mechanisms for obliquebanded leafroller resistance to tebufenozide and potential mechanisms for other new insecticides. At a concentration of 20 ppm, PBO and DEM significantly synergized the toxicity of tebufenozide in resistant and susceptible colonies (three- to fourfold). Obliquebanded leafrollers may be resistant to new insecticides with distinct modes of action even if these compounds have not been previously used in commercial orchards.

Animals↗
PubMed2001

Genetic variation and correlations among responses to five insecticides within natural populations of Drosophila melanogaster (Diptera: Drosophilidae).

To investigate the genetic basis of cross-resistance to insecticides, natural populations of Drosophila melanogaster (Meigen) were first collected from four different locations in Japan. After 10-80 isofemale lines of each population had been established in a laboratory, the susceptibility of each line to each of the insecticides permethrin, malathion, fenitrothion, prothiophos, and DDT was examined. Broad ranges of continuous variation in susceptibility to all the chemicals were observed within each natural population as a whole. In addition, highly significant correlations among responses to organophosphates were observed. However, based on the coefficients of determination, about less than half of variation in responses to one insecticide could be explained by variation in responses to another insecticide, suggesting that not only a common resistance factor but also other factors could be involved in a natural population. Genetic analyses by using resistant and susceptible inbred lines from the same natural population demonstrated that resistance to organophosphates in some resistant lines could be due to a single or tightly linked factors, and that resistance in the other line may be due to more than one major factor. These observations could suggest that several resistance factors may be involved within each natural population, and that some of major factors could contribute to correlations among responses to organophosphates. These major factors could then contribute to the broad ranges of continuous variation observed at the level of the populations.

Animals↗
PubMed2001

Distribution and abundance of insecticide resistant greenbugs (Homoptera: Aphididae) and validation of a bioassay to assess resistance.

Laboratory bioassays were conducted to determine the toxicity of four insecticides (ethyl parathion, chlorpyrifos, malathion, and carbofuran) to insecticide-susceptible and resistant populations of greenbug, Schizaphis graminum (Rondani). These bioassays were used to develop and validate a discriminating concentration for assessing insecticide resistance in greenbug populations in the field. Samples from wheat and sorghum in two states, Oklahoma and Kansas, indicated that insecticide resistance persists in greenbug populations over a large area at a low level.

Animals↗
PubMed2005

Bollgard cotton and resistance of tobacco budworm (Lepidoptera: Noctuidae) to conventional insecticides in southern Tamaulipas, Mexico.

Insecticide susceptibility in tobacco budworm, Heliothis virescens (F.) (Lepidoptera: Noctuidae), was determined for 8 yr (1991-2001) with larvae sampled from cotton in southern Tamaulipas, Mexico. Before 1996, when Bollgard cotton expressing the Cry1A(c) delta-endotoxin was introduced into the region, two important patterns were documented. The first was economically significant increases in resistance to certain insecticide groups. The second was occurrence of virtually complete control failures in the field during 1994 and 1995. The largest resistance changes were recorded for the type II pyrethroids cypermethrin and deltamethrin. These products are the most widely used products in the region. Resistance ratios for these products increased up to > 100-fold from 1991 to 1995. After 1996, the resistance levels declined. These findings did not occur with other products of scant use (e.g., permethrin, profenofos, and endosulfan) or low tobacco budworm efficacy coupled to a high use pattern (e.g., methyl parathion). This clear trend toward reversal of resistance to type II pyrethroids can be understood, in part, with respect to two factors: 1) the high adoption rate of transgenic cotton in the region, from 31.2% in the beginning (1996) to approximately 90% in 1998; this has considerably curbed the use of synthetic insecticides, with the attending loss of selection pressure on this pest; and 2) the potential immigration to the region of susceptible tobacco budworms from cultivated and wild suitable hosts as well as from transgenic cotton might have influenced the pest population as a whole. The influence of transgenic cotton on southern Tamaulipas can be more clearly seen by the drastic reduction of insecticide use to control this important pest. Now tobacco budworms in this region are susceptible to type II pyrethroids. Two effective and fundamentally different pest management tools are now available to cotton growers in southern Tamaulipas: transgenic cotton, coupled with careful use of pyrethroids, offers the possibility of sustainable and profitable cotton production.

Animals↗
PubMed2004

Insecticide resistance in Alabama and Florida mosquito strains of Aedes albopictus.

The susceptibility of four strains of Aedes albopictus (Skuse) to permethrin, deltamethrin, resmethrin, chlorpyrifos, malathion, propoxur, fipronil, imidacloprid, spinosad, and Bacillus thuringiensis variety israelensis (Bti) was determined. The HAmAal and MAmAal strains were collected in 2002 and 2003, respectively, from Huntsville and Mobile, AL, and the VBFmAal and SFmAal strains were collected in 1998 from Vero Beach and southern Florida, respectively. The HAmAal strain showed a 22-fold elevated level of resistance to deltamethrin compared with the susceptible Ikaken laboratory strain, whereas the VBFmAal strain showed a six-fold lower sensitivity to deltamethrin compared with Ikaken. However, comparison of resistance ratios for deltamethrin at LC50 and LC90 (21-fold) and the gradual slopes of dose-response curves indicated that the field population of this mosquito strain was heterogenous in response to deltamethrin. All four mosquito strains showed elevated levels of resistance to chlorpyrifos, with resistance ratios from 10 to 33. Nevertheless, except for the relatively low resistance to deltamethrin and chlorpyrifos, all mosquito strains showed a similar susceptibility or lower tolerance to the remaining insecticides tested compared with the susceptible Ikaken strain, even though some, such as permethrin, resmethrin, malathion, and Bti, have been used in the field for a long time, especially in Alabama. These results indicate that the development of resistance to insecticides in Ae. albopictus is slow and conventional insecticides, such as permethrin, resmethrin, malathion, and Bti, and relatively new insecticides, such as fipronil, imidacloprid, and spinosad, may all be valuable for the management of this important mosquito.

Aedes↗
PubMed1998

[The selection of a strain of Culex quinquefasciatus resistant to lambdacyhalothrin and its spectrum of cross-resistance to other insecticides].

A field strain of Culex quinquefasciatus resistant to pyrethroid lambda-cyhalothrin insecticide was selected to be used as a reference strain in the laboratory for conducting studies of biochemistry and genetics of resistance, to evaluate the utility of this insecticide for the control of mosquitoes in Cuba, and to determine the cross resistance to organophosphate insecticides, pyrethroids and a carbamate. A high resistance to lambdacyhalothrin was obtained after 6 generations of selective pressure. Lowe or no cross resistance to other pyrethroids (deltamethrin and cypermethrin), to a carbamate (propoxur) and to the organophosphate insecticides (clorpirifos and methyl-pyrimifos) was observed. A high cross resistance to malathion (organophosphate) was detected.

Animals↗
PubMed2001

Susceptibility of sand flies to selected insecticides in North Africa and the Middle East.

The purpose of this study was to determine the baseline susceptibility of 4 species of phlebotomine sand flies from North Africa and the Middle East to various insecticides. Susceptibility was determined using the World Health Organization test kits for measuring resistance in mosquitoes exposed to insecticide-impregnated papers. Fifty, 90, and 99% lethal doses were calculated for bendiocarb, cyfluthrin, DDT, malathion, permethrin, and resmethrin on Phlebotomus bergeroti, P. langeroni, P. papatasi. and P. sergenti. The least toxic insecticide to all species was DDT, followed by malathion and permethrin in order of increasing toxicity. Cyfluthrin was the most toxic to P. langeroni and P. papatasi, followed by resmethrin and bendiocarb in order of decreasing toxicity. Resmethrin exhibited the highest toxicity to P. bergeroti followed by cyfluthrin and bendiocarb, whereas bendiocarb was most toxic to P. sergenti, followed by cyfluthrin and resmethrin in order of decreasing toxicity. An attempt was made to obtain data for deltamethrin, but close response data were insufficient to determine regression lines for this insecticide on these species. However, analysis of preliminary data indicated that deltamethrin is highly toxic to these sand flies.

Africa, Northern↗
PubMedDate not supplied

[High esterases as mechanism of resistance to organophosphate insecticides in Aedes aegypti strains].

Five strains of Aedes aegypti L. one from Cuba and 4 from Venezuela were evaluated to determine their resistance to organophosphate insecticides (temephos, chlorpiriphos and pirimiphos methyl). In the Venezuelan strains only APURE showed resistance to temephos. In TACHIRA and MIRANDA moderate resistance values were noted (FR50 5 to 10x) for chlorpiriphos and high levels of resistance (FR > 10x) to this insecticide were found in ARAGUA. All the Venezuelan strains showed high levels of resistance to pirimiphos methyl. The Cuban strain from Santiago de Cuba revealed moderate resistance to temephos and pirimiphos methyl, but high resistance to chlorpiriphos. The results of the biochemical tests proved the presence of esterase and glutathione-s-transferase at high frequency in almost every strain. By the polyacrilamide gel electrophoresis, a strongly stained band was observed in all the strains with a Rf value of 0.779; it was named esterase A4 and was not seen in the susceptible reference strain. The meaning of this esterase in the resistance to organophosphate insecticides is yet to be determined. Resistance to these insecticides in Aedes aegypti is a serious problem for the control of this species therefore integrated management strategies were proposed to prevent or delay the appearance of this species in Cuba and Venezuela.

Aedes↗
PubMed2002

Field studies on the susceptibility of housefly to certain insecticides in nine Egyptian governorates.

Standard WHO test methods were used to determine the susceptibility of field population of housefly to four organophosphorous and two pyrethroid insecticides. Field population flies collected from nine governorates, Giza, Faiyoum, Suez, Behaira, Menoufia, Sharkia, Kafr El-Sheikh, Assiut and Aswan. The results indicated that, all tested insecticides were very effective on flies collected, from Sharkia, Kafr El-Sheikh and Aswan, but there was an evidence of increased vigor tolerance among those collected from Kafr El-Sheikh for bioresmethrin and tolerance for diazinon in Aswan. In Assiut, flies exhibited high sensitivity to diazinon, deltamethrin and bromophos while malathion was the least effective adulticide. Resistance to malathion, diazinon, fenthion and bioresmethrin was noticed in varying degrees at all governorates. The highest average resistance ratio was recorded for malathion in Behaira (55.3 folds) and in Suez (26 folds). Resistance was also more pronounced in Menoulia for diazinon (23.3 folds). As for bioresmethrin an apparent increase in the resistance ratio was detected in Suez (25 folds). In Giza. houseflies were resistant to fenthion (14.5 folds). Regarding the difference between the six insecticides used, deltamethrin was the most potent insecticide in all governorates.

Animals↗
PubMed1953

Dose and cycle of insecticide applications in the control of malaria.

The authors first review the doses and cycles of application normally recommended in different parts of the world for DDT, BHC, and dieldrin in controlling malaria, and then discuss the experimental evidence concerning their actual efficacy in the field. The irritant effect of the various insecticides is compared, DDT being found the most irritant and dieldrin the least. BHC appears to be highly irritant when solid, but not when vaporized. The problem of the application of residual insecticides to absorbent surfaces, such as mud, is considered; the wettable powders are generally accepted as the most efficient formulation for such surfaces, but even with these a marked loss in toxicity may occur, requiring higher initial doses and more frequent application than on non-absorbent surfaces. With volatile insecticides, such as BHC, some degree of absorption slows down the loss by volatilization, but at the usual field dosages of 0.1 g and 0.2 g of gamma-BHC per m(2) the decline in toxicity is still rapid. Experiments have also shown that mixtures of DDT and BHC may, in some circumstances, combine the initial high kill of the latter with the persistent moderate kill of the former.Considering the insecticidal efficiency needed for the control of malaria, the authors find that most natural circumstances would be met by attaining a mortality-rate of about 65% of mosquitos entering treated shelters; 85% mortality would be suitable for the most severe conditions and 65% mortality for controlling moderate transmission by endophilic mosquitos.

Animals↗
PubMed1957

Toxicity of some newer insecticides to larvae and pupae of Culex fatigans Weidemann.

The toxicity of DDT, dieldrin, endrin, malathion, parathion, Systox and P4 to larvae and pupae of Culex fatigans has been studied. Two colonies of mosquitos were maintained for the purpose-one at 88 degrees +/-2 degrees F (31.1 degrees +/-1.1 degrees C) and 70%-80% relative humidity, and the other at 72 degrees +/-3 degrees F (22.2 degrees +/-1.7 degrees C) and 45%-55% relative humidity.For test purposes 25 larvae or pupae were exposed to acetone solutions of insecticides in 25 ml of water, and mortality counts were taken at the end of 24 and 48 hours. The percent mortality was plotted on a logarithmic dosage-probit paper and the LC(50) (the concentration required to kill 50%) was read from the slopes obtained. The confidence limits for LC(50) and the slope functions were worked out statistically.Of the insecticides tested, parathion was found to be the most toxic to larvae. The others in their order of toxicity were endrin, dieldrin, DDT, malathion, P4 and Systox. The LC(50) at 24 hours ranged from 0.003 parts per million (p.p.m.) for parathion to 0.18 for Systox. The third-instar larvae were more susceptible to insecticides than those in the fourth-instar stage.Pupae were more resistant to insecticides than larvae. Parathion and endrin gave LC(50)'s of 0.034 and 0.04 respectively. P4 and malathion gave very poor results. Dieldrin and Systox acted slowly on pupae, and the 48-hour mortality is given for these. DDT showed extremely low toxicity to pupae.DDT, dieldrin, endrin and parathion were more toxic to larvae reared and tested at the lower temperature than to those reared and tested at the higher. The temperature after exposure to DDT altered toxicity to a greater extent than the temperature at which the larvae had been reared.

Animals↗
PubMed1959

Cross-resistance in insecticide-resistant strains of the German cockroach. Blattella germanica (L.

The authors describe a series of experiments designed to determine the extent to which cross-resistance exists in insecticide-resistant strains of the German cockroach. The tests were conducted by exposing females from a DDT-resistant strain, a chlordane-resistant strain, and a non-resistant strain to varying concentrations of several insecticides. From these tests mortality data were obtained and are presented in the form of regression lines.The insecticides used were DDT, methoxychlor, chlordane, dieldrin, Prolan, malathion, allethrin, and Lethane; these were chosen so that a wide variety of chemical types would be represented.The results indicate that the DDT-resistant strain is highly resistant to DDT and to its analogue, methoxychlor, but not to any of the other insecticides tested. Similarly, the chlordane-resistant strain is highly resistant to chlordane and to its analogue, dieldrin, but is susceptible to the other toxicants listed.From these results, as well as those obtained by others, it appears that the picture of cross-resistance in the German cockroach is in essential agreement with that which is emerging for other insects throughout the world.

Animals↗
PubMed2003

Insecticide susceptibility level of Anopheles arabiensis in two agrodevelopment localities in eastern Ethiopia.

Anopheles arabiensis strains reared from larvae and pupae collected from two different localities, Metehara and Melka-Worer, eastern Ethiopia, were evaluated against three insecticides. Resistance states of adult females were determined using the WHO test kits under field condition. The insecticides used were WHO discriminating doses of 4% DDT, 0.75% permethrin and 0.1% propoxur. The study revealed that 42.5% of the An. arabiensis population was resistant to DDT in Melka-Worer while only 30% of the species was resistant in Metehara to the same insecticide. In Metehara, 25% of An. arabiensis was also resistant to permethrin while the population was highly susceptible to the insecticide in Melka-Worer. Propoxur, which was not evaluated in Melka-Worer, was highly toxic to An. arabiensis in Metehara. The knocked-down time (KD50) for permethrin was 14.5 and 12.5 minutes in Metehara and Melka-Worer, respectively. The implications of these findings are discussed.

Animals↗
PubMed2005

[Susceptibility of Culex quinquefasciatus to insecticides in Bobo Dioulasso, Burkina Faso].

This study conducted from 1999 to 2000 in the suburbs of Bobo Dioulasso a town in the South of Burkina, aimed at investigating the susceptibility of the local population of Culex quinquefasciatus to various insecticides and proposing alternative strategies allowing a better management of insecticide resistance in the field. Eggs of C. quinquefasciatus were first collected in stagnant waste water places. The larvae were reared to early 4rth instar and tested by larval bioassays to determine the LC50/95 and the resistance ratios (RR50 and RR95) as well as their confidence intervals. A susceptible reference Strain "Slab" was used as control. Resistance was found to DDT and pyrethroids, but reduced susceptibility was found for carbamates, organophosphorates, phenyl pyrazole and in a less extend to Bacillus sphaericus. Resistance to pyrethroides is quite alarming since these insecticides are mainly used for bed net impregnation for the Roll Back malaria programme implemented in Africa. The high levels of insecticide resistance in C. quinquefasciatus suggest that alternative strategies have to be implemented to minimize the pressure of selection on resistant genes. The use of bio-larvicides (Bacillus sphaericus) alone or in rotation with different compounds may be a promising strategy for controlling C. quinquefasciatus in Bobo Dioulasso.

Animals↗