Concentration-mortality Regression Research Articles

Ivermectin resistance in the multi-host tick Hyalomma anatolicum (Acari: Ixodidae) in India

The multi-host tick, Hyalomma anatolicum is a widely distributed vector of many pathogens of veterinary and public health importance. Ivermectin (IVM), as an alternative to control pyrethroid-resistant ticks, has been used extensively for the past 4-6 years in tropical and sub-tropical countries including India resulting in declining tick control efficacy. The present study used adult immersion test (AIT) to examine the resistance status of H. anatolicum collected from three districts in the Indian state of Gujarat against ivermectin. Probit analysis was used for calculation of concentration-mortality regressions; concentrations required for 50% mortality (LC50) and 95% mortality (LC95), along with confidence intervals; slope of mortality; % inhibition of oviposition; and discriminating concentration (DC). The calculated LC50 and LC95 estimates were utilized to determine resistance ratios (RR50, RR95) and the resistance levels (RL) of the field ticks compared to the susceptible population. The DC (2 x LC95) for IVM was calculated as 84.48 ppm, using susceptible H. anatolicum ticks (KHD). Lower estimates of the coefficient of non-determination (1-R2) for AIT ranged from 0.06 to 0.27, and the range of RR50 and RR95 values against IVM was estimated to be from 1.43 to 52.06 and 1.14 to 71.99, respectively, which indicated a varying degree of resistance among the field tick populations. Based on RR50 values, tick populations from Danta and Palanpur showed resistance level IV and II, respectively. Another four populations (Vadgam, Kankrej, Saraswati and Sidhpur) were classified as having level I resistance status against IVM. To our knowledge, this is the first report of ivermectin resistance in H. anatolicum from Gujarat, India.

Susceptibility of Alphitobius diaperinus (Panzer) (Coleoptera, Tenebrionidae) to cypermethrin, dichlorvos and triflumuron in southern Brazil

Susceptibility of Alphitobius diaperinus (Panzer) (Coleoptera, Tenebrionidae) to cypermethrin, dichlorvos and triflumuron in southern Brazil. The lesser mealworm, Alphitobius diaperinus (Panzer), is an important insect pest in poultry houses in Brazil. Susceptibility of the lesser mealworm collected from eight poultry houses in Parana state, southern Brazil, was evaluated for cypermethrin, dichlorvos and triflumuron. Adult A. diaperinus were tested in bioassays with cypermethrin and dichlorvos. Larvae were fed rabbit feed wetted with a triflumuron-water solution. Concentration-mortality regressions were estimated using Probit analysis and resistance ratios were calculated based on the susceptible population. Among the field populations evaluated, cypermethrin LC50 values for adults, ranged from 68.1 to 6,263 ng (AI)/cm2. LC50 values for adults challenged with dichlorvos ranged from 10.3 to 1,385 ng (AI)/cm2. One population from Pato Branco showed reduced susceptibility to triflumuron (LC50 = 272 µg (AI)/ml of solution) when compared to the most susceptible population (LC50 = 109.8 µg (AI)/ml). Application of cypermethrin and dichlorvos analogues should be managed with caution to minimize insecticide resistance problems.

Evaluation of Resistance Pattern to Fenpyroximate and Pyridaben in Tetranychus Urticae collected from Ggreenhouses and Apple Orchards using Lethal Concentration-slope Relationship

This study aimed to monitor the present and future developments of the resistance of Tetranychus urticae Koch to fenpyroximate and pyridaben, using the relationship of the LC(50) and slope of the concentration-mortality line in a probit model, for the provision of reliable resistance management tactics. Tetranychus urticae populations were collected from 16 commercial greenhouses, where various crops were cultivated, as well as from 10 apple orchards throughout Korea. The resistance to fenpyroximate and pyridaben of each population was estimated by calculating the median lethal concentration (LC(50)), resistance ratio (RR) and slope of the concentration-mortality regression. Most of the greenhouse populations exhibited moderate levels of resistance, whereas the apple orchard populations showed only low levels, indicating that T. urticae populations in greenhouses were more strongly selected than those in apple orchards. Four population groups were established based on either the habitats (greenhouse and apple orchard) or acaricides (fenpyroximate and pyridaben). To test the hypothesis, "the slope is greatest at low and high levels of resistance," the slopes were regressed as a function of the LC(50), and fitted to a polynomial regression. The polynomial regression model explained this relationship well for the four population groups (p < 0.05), indicating that the development of resistance toward fenpyroximate or pyridaben was consistent with the gradient. A laboratory selection study agreed with the results from both acaricide field populations. These results suggest that the gradient was a good indicator of the susceptibility of T. urticae to genetic variations, which was related to the LC(50). The application of these findings is also discussed in relation to the resistance management of T. urticae.

Efficacy of insecticide mixtures against larvae of Culex quinquefasciatus (Say) (Diptera: Culicidae) resistant to pyrethroids and carbamates.

The efficacy of insecticide mixtures of permethrin (pyrethroid) and propoxur (carbamate) was tested by larval bioassays on two strains of Culex quinquefasciatus (Say), one resistant to pyrethroids and the other resistant to carbamates. The method consisted in combining one insecticide at the highest concentration causing no mortality (LC0) with increasing concentrations of the second one. The concentration-mortality regression lines were determined for permethrin and propoxur alone and in combination, and synergism ratios (SR) were calculated in order to determine the magnitude of an increase or decrease in efficacy with use of the mixtures. With the pyrethroid-resistant strain (BK-PER), the results showed that propoxur at LC0 significantly enhanced the insecticidal activity of permethrin (SR50 = 1.54), especially on the upper range of the concentration-mortality regression. Conversely, when permethrin at LC0 was tested with propoxur against the carbamate resistant strain (R-LAB), an antagonistic effect was observed (SR50 = 0.67). With the BK-PER strain, an increased oxidative detoxification (MFO) appeared to be the main mechanism responsible for the synergistic interaction. Nevertheless, antagonism in the R-LAB strain is probably due to a physiological perturbation implying different target sites for pyrethroid (ie sodium channel) and carbamate insecticides [ie acetylcholinesterase (EC 3.3.3.7) and choline acetyltransferase (EC 2.3.1.6)].

Seletividade de inseticidas a três Vespidae predadores de Dione juno juno (Lepidoptera: Heliconidae)

Dentre os insetos que atacam o maracujazeiro, Dione juno juno (Lepidoptera: Heliconidae) é considerada a praga-chave. Estudou-se a seletividade dos inseticidas fentiom, cartape, malatiom e deltametrina a Dione juno juno, em relação às vespas predadoras Polybia fastidiosuscula, Polybia scutellaris e Protonectarina sylveirae (Hymenoptera: Vespidae). Estimaram-se as curvas concentração-mortalidade e mediante o uso da concentração letal do inseticida em 90% dos indivíduos (CL90) calcularam-se os índices de seletividade diferencial e índices de tolerância. A deltametrina foi seletiva à P. scutellaris e P. fastidiosuscula e medianamente seletiva à P. sylveirae e o cartape foi medianamente seletivo às três espécies de vespas predadoras. O malatiom foi seletivo a P. sylveirae e medianamente seletivo a P. fastidiosuscula. As vespas predadoras P. fastidiosuscula eP. scutellaris foram mais tolerantes a deltametrina e ao fentiom do que P. sylveirae, enquanto o P. fastidiosuscula e P. sylveirae toleraram mais o cartape do que P. scutellaris. O malatiom foi mais tolerado pela espécie P. sylveirae do que por P. fastidiosuscula e P. scutellaris.

Survey of insecticide resistance in Mexican populations of maize weevil, Sitophilus zeamais Motschulsky (coleoptera: curculionidae)

Topical application bioassays of DDT, lindane, malathion, pirimiphos-methyl, deltamethrin, and permethrin were undertaken with 11 field strains of maize weevil, Sitophilus zeamais Motschulsky, collected from nine states in Mexico. Concentration-mortality regression lines were estimated to compare the resistance ratios for each insecticide and strain. For each insecticide, resistance ratios were determined relative to the most susceptible strain. The field-collected strains showed low to moderate levels of resistance to DDT (1.3- to 14.1-fold), moderate to high levels of resistance to lindane (4.7- to 20.9-fold), low to high levels of resistance to malathion (1.6- to 31.4-fold), and low levels of resistance to pirimiphos-methyl (3.0- to 3.7-fold), deltamethrin (1.2- to 1.8-fold), and permethrin (2.3- to 3.5-fold). This is the first report of high levels of lindane and malathion resistance in strains of S. zeamais in Mexico. Given this information, I conclude that insecticide resistance in S. zeamais in Mexico is important, and may become a more serious problem in the future.

Effects of carbon dioxide and phosphine mixtures on resistant populations of stored-grain insects

Populations of Rhyzopertha dominica (F.) and Sitophilus oryzae (L.) with high frequencies and high levels of resistance to phosphine (PH 3), as detected by the Food and Agriculture Organization (FAO) discriminating dose test, were submitted to various concentrations of phosphine in air and to various concentrations of phosphine plus 10% and 20% carbon dioxide (CO 2) for 20 h. Three resistant populations and one susceptible population of each species were tested. Concentration-mortality regression lines to obtain the LC 50 and LC 99.9 values were determined for each population. The resistance levels for these mortality rates were also obtained. The mixtures of phosphine plus 10% and 20% CO 2 reduced the resistance levels of the S. oryzae populations. The more susceptible portion of the R. dominica population showed a decrease in the required phosphine concentration with an increase in CO 2, but phosphine alone seemed to be more effective than the mixtures with CO 2 for the control of the more resistant portion. The mixtures of phosphine plus CO 2 reduced the resistance levels to phosphine in populations of R. dominica and S. oryzae, although a clear pattern could not be determined. Resistant populations of R. dominica and S. oryzae to phosphine showed different mortality responses to treatments with mixtures of phosphine plus 10% and 20% CO 2.

Resistance to Chlorpyrifos-Methyl, Pirimiphos-Methyl, and Malathion in Brazilian and U.S. Populations of Rhyzopertha dominica (Coleopera: Bostrichidae)

Resistance to chlorpyriphos-methyl, pirimiphos-methyl, and malathion was detected in lesser grain borer, Rhyzopertha dominica (F.), collected from 8 sites in the sates of Minas Gerais and Sao Paulo in Brazil and from 7 sites in northeast Kansas. These populations were screened for resistance by a discriminating concentration technique, which used vials impregnated with dried insecticide residues. Concentration-mortality regression lines were estimated to compare the resistance ratios for each insecticide and population. Malathion resistance ratios ranged from 2.1- to 12.2-fold at LC 50 ; pirimiphos-methyl resistance ratios ranged from 2.4- to 9.2-fold ; and chlorpyrifos-methyl resistance ratios ranged from 5.6- to 167.9-fold. Such high resistance levels to chlorpyrifos-methyl in lesser grain borer have never been reported before either in the United States or in Brazil. Because chlorpyrifos-methyl is not used against stored grain pests in Brazil, we conclude that chlorpyrifos resistance has evolved as a result of selection to other organophosphorus insecticides in Brazil.

Selection and genetic analysis of permethrin resistance in Amblyseius fallacis (Garman) (Acari: Phytoseiidae) from Ontario apple orchards

Gravid female phytoseiid mites, Amblyseius fallacis (Garman), were selected for resistance to permethrin using a table-top Petri dish (PD) technique. After 55 selections, the LC50 of the R population increased 964-fold to 12 241 p.p.m. (PD) and 3.6-fold to 167 p.p.m. by a slide-dip (SD) method. A genetic analysis was conducted to examine the mode of inheritance by a series of single-pair reciprocal interstrain crosses and backcrosses of female F1 progeny. Concentration-mortality regressions (PD) for parental populations showed a 69.4-fold difference between R and S strains. Regressions for F1 females resulting from both interstrain crosses were intermediate between parental strains and not significantly different, showing no obvious maternal effect. Resistance in the R strain was not completely dominant or recessive and the estimated dominance, D, for the F1 females from combined data of both reciprocal crosses was-0.18, for the female R x male S cross it was 0.24 and for the female S x male R cross it was-0.01. We concluded that more than one gene was responsible for the resistance in the selected R strain. No incompatibility was observed in any reciprocal interstrain crosses or backcrosses between the S strain and R strain.

TOXICITY OF INSECTICIDES USED IN CITRUS TO APHYTIS MELINUS DEBACH (HYMENOPTERA: APHELINIDAE) AND RHIZOBIUS LOPHANTHAE (BLAISD.) (COLEOPTERA: COCCINELLIDAE)

AbstractThe 48-h toxicities of freshly deposited residues of 28 insecticides against Aphytis melinus DeBach and Rhizobius lophanthae (Blaisd.) were evaluated at various rates. Rates as high as 4-fold the recommended field rate of several materials (formulated plant alkaloids, amitraz, formulated Bacillus thuringiensis Berliner endotoxin or exotoxin, and cryolite) revealed little mortality to either species. Concentration–mortality regressions were quantified for the remaining materials, which included five carbamates, a macrocyclic lactone, eight organophosphates, and four pyrethroids. Of these, pyrethroids in general were most toxic, followed by carbamates, and then organophosphates, to both species. Most materials tested were more toxic to A. melinus than to R. lophanthae.

Comparison of Slide Dip and Petri Dish Assays for Measuring Resistance to Permethrin in Amblyseius fallacis (Acari: Phytoseiidae)

The relative toxicity of permethrin to gravid female phytoseiid mites, Amblyseius Fallacies (Garman), was compared by slide dip and petri dish techniques, using two populations (P8, GBI) collected from Ontario apple orchards with different histories of pyrethroid use. By the slide dip assay, concentration-mortality regressions for both populations were linear with similar slopes. The LCso value was 5.5 ppm for P8 and 46.6 ppm for GBI. The latter is higher than any recorded in the literature from a commercial orchard. With the petri dish assay, the concentration-mortality regression for population P8 was linear and the LC50 was 2.3 ppm. In contrast, the regression for GBI was nonlinear and typical of a mixed population; 66% were similar to the susceptible P8 population but 33% were a more resistant population. The LC50 of the GBI population was 12.7ppm using the petri dish assay. The GBI, P8, and six other populations of A. fallacis from apple orchards were compared using the petri dish assay at two discriminating concentrations of permethrin to designate susceptible and resistant populations for genetic improvement to permethrin. Mortality at 20 and 80 ppm varied between 53–97% and 73–100%, respectively, for the eight populations and was related to the history of pyrethroid use in the orchards.

Susceptibility and Immune Response of Western Corn Rootworm Larvae (Coleoptera: Chrysomelidae) to the Entomogenous Nematode, Steinernema feltiae (Rhahditida: Steinernematidae)

Susceptibility of third-instar western corn rootworms, Diabrotica virgifera virgifera LeConte, to the Agriotos, All, Breton, and Mexican strains of the entomogenous nematode Steinemema feltiae was compared based on concentration-mortality regressions. Larvae were most susceptible to the Mexican strain, less susceptible to the Agriotos and Breton strains, and least susceptible to the All strain. The Mexican strain was 22 times more virulent than the Allstrain. Rootworm larvae encapsulated invading nematodes of all strains, but the frequency of encapsulation was lower for the Mexican and Agriotos strains. Apparently, the defensive response of encapsulation had only a minor effect on larval susceptibility. Frequency of encapsulation and larval susceptibility were not consistently related.

Dynamics of Azinphosmethyl Resistance in Epiphyas postvittana (Lepidoptera: Tortricidae)

Three insecticide application methods (topical application, direct spray, and diet incorporation) were used to estimate concentration-mortality regressions for azinphosmethyl resistant (R) and susceptible (S), and F1Epiphyas postvittana (Walker) larvae. The three techniques yielded different estimates of dominance. Topical application of mid-instar F1 larvae gave a dominant response with a degree of dominance of +0.61. Direct spray of insecticide onto first instars gave intermediate responses for the F1 generation, with a degree of dominance of -0.09 and +0.14 in tests on the same strains two generations apart. Backcross and F2 larvae showed greater susceptibility than F1 larvae, although the resistance was too low to allow Mendelian analysis. Concentration-mortality lines were estimated for 8-d-old larvae exposed to azinphosmethyl in artificial diet for 3 wk: the degree of dominance was +0.31. Tethered virgin female moths from the susceptible laboratory strain were placed within apple orchards in which E. postvittana resistant to azinphosmethyl were present, and they were allowed to mate at will with local males. Larval offspring were exposed to diagnostic concentrations that cause 100% mortality of susceptible larvae to determine the phenotypic frequency of resistance. The resistance phenotype frequency was >85%, and gene flow between resistant and susceptible individuals was demonstrated to have occurred in the field. Males from five replicate strains yielding survivors were backcrossed to a susceptible strain, and the offspring were again selected on artificial diet containing azinphosmethyl. Selection and backcrossing for five or six generations did not result in a decrease in the resistance with either direct spray or diet incorporation techniques. Monogenic inheritance could not be proven from the data, although no conflict with this hypothesis was detected.

Toxicity of Major Citrus Pesticides to Aphytis melinus (Hymenoptera: Aphelinidae) and Cryptolaemus montrouzieri (Coleoptera: Coccinellidae)

The 48-h residual toxicity of major pesticides used for control of citrus thrips, Scirtothrips citri (Moulton), and California red scale, Aonidiella aurantii (Maskell) , in California was evaluated for adults of Aphytis melinus DeBach and Cryptolaeumus montrouzieri Mulsant. Rates as high as 4-fold the highest recommended field rate revealed little effect of sabadilla to A. melinus or of sabadilla, dimethoate, formetanate, or chlorpyrifos to C. montrouzieri . Concentration-mortality regressions were quantified for the remainder of the materials; these showed toxicity (at LC50) of chlorpyrifos > carbaryl > dimethoate > acephate > parathion > formetanate > methidathion to A. melinus and carbaryl > acephate > parathion > methidathion to C. montrouzieri .

Monitoring Susceptibility to Azinphosmethyl in Field Populations of the Codling Moth (Lepidoptera: Tortricidae) with Pheromone Traps

A procedure was developed to screen field populations of Cydia pomonella (L.) directly for resistance to azinphosmethyl or other toxicants. Male moths were collected in the field with pheromone traps and assayed with azinphosmethyl by topical application to the dorsal thorax directly on the adhesive-coated trap surface. The first flight had a steeper concentration-mortality regression than the second flight, indicating an increase in variability of the toxicological response over the season. The LC50 of moths trapped during the spring flight was somewhat higher (0.22 µg/moth) than during the summer (0.08–0.16 µg). Assays of laboratory-reared moths from the same location kept in plastic cages or on sticky trap surfaces to simulate the test procedure with field-collected moths yielded LC50’s in the same range (0.10–0.14 µg/moth). The longevity of moths and their toxicological response was not affected by the polybutene adhesive provided it was applied as a thin uniform film to the trap surface. Susceptibility to azinphosmethyl increased considerably with age in both sexes and was not correlated with loss in body weight. Female moths were slightly more susceptible when azinphosmethyl was applied to the thoracic venter instead of the dorsum. Males were equally susceptible to either application.

The Toxicity of Insecticides to Larvae of Dioryctria abietella in Laboratory Screening Tests

Laboratory screening tests were devised to evaluate the toxicity of 13 insecticides to last-instar larvae of a destructive pine cone moth, Dioryctria abietella (Denis & Schiffermuller). Emulsifiable concentrates of aldrin, BHC, chlordane, DDT, dieldrin, endrin, heptachlor, malathion, toxaphene, Diazinon® ( O,O -diethyl O-(2 -isopropyl-4-wethyl-6-pyrimidinyl) phosphorothioate), Guthion® ( O,O dimethyl S-(4-oxo-1,2,3-benzotrinzin-3-(4 H )-ylmethyl) phosphorodithioate), Perthane® (a mixture of diethyl diphenyl diehlorocthane (95%) and related reactionproducts (5%)), and Sevin®(1-naphthyl N -methylearbamate) were screened. Mature larvae were exposed to pine cones which had been dipped in a range of water dilutions or these concentrates. L.C .-90 values, estimated from concentration-mortality regression lines for the 96-hour exposure period, were used to assess the toxicity of each insecticide. At this mortality level the most effective insecticides, in decreasing order of toxicity, were endrin, BHC, Guthion, DDT, dieldrin, and Diazinon.

デイルドリンのセンチニクバエ幼虫に対する効力特にその後作用について : 薬剤によるハエ幼虫駆除に関する研究第 8 報

The effects of dieldrin emulsion to Sarcophaga peregrina were studied by treating them in larval stage, comparing with that of lindane emulsion. The mortalities of larvae after 24, 48 hours, and those in the total larval stage and in larval and pupal stages, were obtained by treating the 3 rd instar larvae through the rice-husks immersion method, thus obtaining the retarded lethal effect of the chemicals. The lethal efficacy of concentration-mortality regression equation was lower in dieldrin than in that of lindane. The ratio of LC-50 of dieldrin to that of lindance were 1.6 for the larval mortality after 24 hours, 1.9 for after 48 hours, 2.0 for the mortality in total larval stage, and 9.7 for that in larval and pupal stages, so that it was concluded that the retarded lethal effect of dieldrin was higher than that of lindane. It was also recognized that the application of dieldrin or lindane to the larvae would tend to promote their emerging time, though the degree of the promotion was not so remarkable. The number of the flies emerged in the night time was greater than in the daytime, both in the treated and in the untreated by the chemical.