Browsing by Subject "insecticide resistance"
Now showing 1 - 2 of 2
Results Per Page
Sort Options
Item Insecticide Resistance of Alphitobius diaperinus (Coleoptera: Tenebrionidae) to ?-Cyfluthrin And Associated Heat Tolerance(2014-05-01) Lyons, Brandon NicholasThe lesser mealworm Alphitobius diaperinus (Panzer) (Coleoptera: Tenebrionidae) is an important economic pest to poultry producers globally that cause structural damage and spread pathogens to poultry. Adult lesser mealworms were collected from three farms in Mt. Pleasant, TX, USA (A-C) and three farms in Franklin, TX, USA (D-F) in order to assess insecticide resistance across populations, as well its relationship to heat tolerance. Filter papers were treated with a range of doses of the active ingredient (AI) ?-Cyfluthrin. Farms B and E displayed much higher LD_(50) of 0.320 mg/mL and 0.627 mg/mL respectively compared to the remaining four farms, which ranged from 0.048-0.161mg/mL. In addition, a field bioassay was conducted to determine adult beetle susceptibility to label rates of formulated permethrin, Vector Ban Plus? and a pyrethroid, Tempo SC Ultra?. These insecticides were applied to commonly found surfaces in poultry operations (concrete, wood chip particle board, and pressure treated wood). Adult beetles were exposed to the treated surfaces for 2 h and then placed in untreated sterile petri dishes. ?Mortality? refers to mortality and morbidity recorded together at 2, 24, and 48 h post-exposure for both bioassays. Insecticide resistance varied greatly based on observation period and compound. The range of mean mortalities measured at 2 h regardless of surface type for Tempo SC Ultra? was 58-100% and for Vector Ban Plus? 17-100%. The mean mortality range at 24 h regardless of surface for Tempo SC Ultra? (91-100%) had less than 10% variation, while Vector Ban Plus? (0.00-49.73%) displayed almost 50% variation. The mean mortality range at 48 h regardless of surface for Tempo SC Ultra? (72-100%) showed high knockdown and increased in variation by 30%, and Vector Ban Plus? (0-29%) had a similar variation, but with low knockdown. Mortality was similar for Tempo SC Ultra? for each substrate. ?-Cyfluthrin (AI) had varying effectiveness depending on the population?s resistance levels, however all the farms tested had LD_(50) well above the equivalent formulation dosage of 0.02mg/mL. The ?-Cyfluthrin formulation had high mortality on all the surfaces tested highlighting the importance of the other ingredients in a formulation. Heat tolerance experiments were conducted on the F_(1) progeny of populations B, D, and E (n=14). The heat shock results were inconclusive. Modification to the experimental design may be needed to yield comparable results.Item Resistance to Pyrethroid Insecticides in Helicoverpa zea (Boddie) (Lepidoptera: Noctuidae): Bioassay Validation, Voltage-Gated Sodium Channel Mutations and CYP6B Overexpression Analysis(2011-08-08) Hopkins, Bradley WayneHelicoverpa zea is one of the most costly insect pests of food and fiber crops throughout the Americas. Pyrethroid insecticides are widely applied for control as they are effective and relatively inexpensive; however, resistance threatens sustainability because alternative insecticides are often more expensive or less effective. Pyrethroid resistance has been identified since 1990 and monitoring has utilized cypermethrin in the adult vial test, but resistance mechanisms have not yet been elucidated at the molecular level. Here we examined field-collected H. zea males resistant to cypermethrin for target site and metabolic resistance mechanisms. We report the cDNA sequence of the H. zea sodium channel a-subunit homologous to the Drosophila para gene and identified known resistance-conferring mutations L1029H and V421M, along with two novel mutations at the V421 residue, V421A and V421G. An additional mutation, I951V, may be the first example of a pyrethroid resistance mutation caused by RNA-editing. We identified other specimens with significantly higher transcriptional expression levels of cytochrome P450 genes CYP6B8 and CYP6B9 compared to the susceptible, ranging from a factor of 3.7 to 34.9 and 5.6 to 39.6, respectively. In addition, we investigated if differences in insect growth stage and pyrethroid structure affect our ability to predict resistance in the adult vial test. Vial bioassays with cypermethrin, esfenvalerate, and bifenthrin were conducted on third instars and male moths from a susceptible laboratory colony and the F1 generation of a resistant field population. For the resistant population, vial assays using either growth stage gave similar resistance ratios for each of the three pyrethroids, respectively, proving the adult vial test accurately reflects larval resistance. However, resistance ratios varied considerably depending on the pyrethroid used, so values obtained with one pyrethroid may not be predictive of another. This dissertation is the first to identify molecular mechanisms associated with H. zea pyrethroid resistance. Our results suggest carefully chosen pyrethroid structures diagnostic for specific resistance mechanisms could improve regional monitoring programs and development of high throughput assays to detect the resistance mechanisms used in tandem with traditional monitoring may greatly improve our ability to identify and predict resistance and make better control recommendations.