Effects of Fatty Acid and Geraniol Repellent-Oil Mixtures Applied to Cattle on Blood Feeding and Reproductive Parameters in Field Populations of Haematobia irritans (Diptera: Muscidae).

California pastured cattle were treated with 250 ml of a 15% mixture of fatty acids (C8-C9-C10) or 125 ml of 2% geraniol in a mineral oil carrier to assess impacts on horn flies, Haematobia irritans (L.) (Diptera: Muscidae) over two summers. Horn flies were netted from cattle every 3-4 d for 2 wk before treatment, 2 wk during treatment (four treatments, with flies collected before each treatment), and 2 wk after treatments ceased. Blood meal weights were estimated by hemoglobin assay of excised abdomens. Other females were dissected to determine the number of active ovarioles and the stage of primary follicle development. Depending on year and herd, pretreatment males contained an average of 0.6-1.0 mg of blood, while females contained 1.7-2.7 mg. Pretreatment egg development (least developed oocytes were stage 1 and fully developed eggs were stage 5) averaged 3.7-4.3, and number of active ovarioles averaged 18.1 to 19.6/female. During treatment periods, significant reductions in blood weight were noted for females, but usually not for males, and females also often exhibited reduced mean oocyte stage and number of active ovarioles. Peaks in proportions of young nulliparous females (oocyte stages 1 or 2) were seen during some repellent application periods. This suggested older females had been killed or driven off from the local population by the treatments, and flies on cattle included more young flies that likely were recent arrivals. The repellent-oil mixture thus impacted blood feeding, reproductive fitness, and probably age structure in the field.

Field and laboratory trials of a novel metaflumizone house fly (Diptera: Muscidae) bait in California.

House fly responses to metaflumizone bait were studied in southern California. Field-strain, laboratory-reared flies in outdoor cages had access for 5 d to water and two containers of untreated sugar/dry milk (control), one container of untreated food and one container of metaflumizone bait, or one container of untreated food and one container of spinosad bait (positive control). Most fly mortality occurred between 0 and 48 h for spinosad and between 48 and 96 h for metaflumizone. On a commercial dairy, fly visitation and bait consumption were higher for metaflumizone bait than for sugar or imidacloprid bait. Flies seldom visited or consumed the imidacloprid bait. Approximately 32% of field flies collected directly from metaflumizone bait (single exposure) died when held in the laboratory with untreated food for 72 h versus < 5% mortality for flies from sugar or imidacloprid bait. Individual laboratory-reared females from a field strain and a susceptible laboratory strain were videotaped in the laboratory after exposure to untreated dry milk/sugar, metaflumizone bait, spinosad bait, and imidacloprid bait. Imidacloprid-induced mortality in field strain flies was low; when on the bait they spent proportionally less time feeding (38%) than did the laboratory strain flies (63%). Feeding by the field strain was more variable, and they fed less on all bait/food sources except metaflumizone. Metaflumizone has promise as a relatively slow-acting fly bait.