Life-Stage Variation in Insecticide Resistance of the Western Flower Thrips (Thysanoptera: Thripidae)
ABSTRACT The life-stage variations in insecticide resistance of western flower thrips, Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae), to selective insecticides (acrinathrin, formetanate, and methiocarb) were studied using resistant laboratory strains. In each strain, the second-instar larva was less susceptible to the insecticides tested than the adults. The lower the resistance level of the adults, the higher the difference between larva and adult susceptibility: 32-fold to methiocarb, 15.4-fold to formetanate, and 180-fold to acrinathrin in the reference strain. In laboratory-selected resistant strains, these differences were much lower: 5.8-fold to methiocarb, 4.8-fold to formetanate, and 2.0-fold to acrinathrin. In selected strains, higher resistance levels for each insecticide were found, both for larvae and adults, compared with the reference strain. These results show that after insecticide resistance selection in adults, the resistance is carried over to the larvae, but at lower levels.
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ABSTRACT: The vegetable leafminer, Liriomyza sativae Blanchard, is a key pest of vegetable and ornamental crops worldwide and is mainly controlled by insecticides. The toxicity of fenpropathrin on adult flies of F1 generation of six Iranian populations of the pest was assessed using the residual glass vial method. The bioassay results showed significant differences in susceptibility to fenpropathrin among the populations tested. Resistance ratios ranged from 5.09 to 28.32. The resistant populations were reared in the greenhouse under fenpropathrin pressure for 14 mo and then susceptibility of both larvae and adults of these strains to fenpropathrin was evaluated. The resistance levels significantly increased in these populations. Further study demonstrated that diethyl maleate and triphenyl phosphate had no synergistic effects on fenpropathrin, however, this compound was significantly synergized by piperonyl butoxide in all tested populations. S,S,S-tributyl phosphorotrithioate also showed a slight synergism with fenpropathrin. Enzyme assays for general esterases, glutathione S-transferases and monooxygenases were performed on adults and larvae of L. sativae. The activity of glutathione s-transferase in different resistant and susceptible strains was not significantly different. The activity of esterases in resistant strains was higher than the susceptible strain. Monooxygenase levels also were higher in resistant strains compared with the susceptible strain. Synergism and biochemical assays revealed that esterases and monooxygenases have a major role in resistance of L. sativae to fenpropathrin.Journal of Economic Entomology 10/2014; 107(5). DOI:10.1603/EC14181 · 1.61 Impact Factor
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ABSTRACT: Control of Frankliniella occidentalis (Pergande) is a serious problem for agriculture all over the world because of the limited range of insecticides that are available. Insecticide resistance in F. occidentalis has been reported for all major insecticide groups. Our previous studies showed that cytochrome P450-mediated detoxification is a major mechanism responsible for insecticide resistance in this pest. Degenerate polymerase chain reaction was used to identify P450 genes that might be involved in acrinathrin resistance, in a laboratory population of F. occidentalis. Associated sequences were classified as belonging to the CYP4 and CYP6 families. Real-time quantitative polymerase chain reaction analyses revealed that two genes, CYP6EB1 and CYP6EC1, were over-expressed in adults and L2 larvae of the resistant population, when compared with the susceptible population, suggesting their possible involvement in resistance to acrinathrin.Journal of Economic Entomology 06/2012; 105(3-105). DOI:10.1603/EC11335 · 1.61 Impact Factor
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ABSTRACT: The monitoring of the susceptibility of fleas to insecticides has typically been conducted by exposing adults on treated surfaces. Other methods such as topical applications of insecticides to adults and larval bioassays on treated rearing media have been developed. Unfortunately, baseline responses of susceptible strains of cat flea, Ctenocephalides felis (Bouchè), except for imidacloprid, have not been determined for all on-animal therapies and new classes of chemistry now being used. However, the relationship between adult and larval bioassays of fleas has not been previously investigated. The adult and larval bioassays of fipronil and imidacloprid were compared for both field-collected isolates and laboratory strains. Adult topical bioassays of fipronil and imidacloprid to laboratory strains and field-collected isolates demonstrated that LD50s of fipronil and imidacloprid ranged from 0.11 to 0.40 nanograms per flea and 0.02 to 0.18 nanograms per flea, respectively. Resistance ratios for fipronil and imidacloprid ranged from 0.11 to 2.21. Based on the larval bioassay published for imidacloprid, a larval bioassay was established for fipronil and reported in this article. The ranges of the LC50s of fipronil and imidacloprid in the larval rearing media were 0.07‐0.16 and 0.11‐0.21 ppm, respectively. Resistance ratios for adult and larval bioassays ranged from 0.11 to 2.2 and 0.58 to 1.75, respectively. Both adult and larval bioassays provided similar patterns for fipronil and imidacloprid. Although the adult bioassays permitted a more precise dosage applied, the larval bioassays allowed for testing isolates without the need to maintain on synthetic or natural hosts.Journal of Medical Entomology 05/2014; 51(3). DOI:10.1603/ME13240 · 1.82 Impact Factor