No abstract

The northern fowl mite (NFM), Ornithonyssus sylviarum (Canestrini and Fanzago), is the most widespread and damaging poultry ectoparasite in the United States [1,2]. The mites live in the vent feathers of hens, are obligate blood feeders as protonymphs and adults, and complete a life cycle in 5 to 12 d [3]. Mite infestations, in addition to being a nuisance for human workers and egg handlers, cause reductions in egg production, feed conversion efficiency, and BW gains and may affect egg size as well [4]. A key mechanism of damage is that NFM force the immune systems of hens to engage the mite infestation, and this metabolic cost diverts resources that might otherwise be devoted to normal body functions, including egg production [4].Mite control is currently based on exclusion or biosecurity [5] and pesticide applications. Resistance is high to the few remaining traditional registered materials [6], so producers are actually in a rather precarious position regard- SUMMARYLiquid formulations of nontraditional materials for northern fowl mite control were applied to the vent feathers of infested hens, and the mite populations on hens were monitored before and after treatment. High concentrations (≥5.3%) of sulfur eliminated mites for periods of at least 8 to 10 wk. A lower sulfur concentration (0.9%) essentially eliminated mites for approximately 4 to 5 wk and greatly reduced mites for 5 to 8 wk. Azadirachtin (derived from the neem tree) at 0.06% reduced, but did not eliminate, mites for approximately 3.5 wk after treatment. Of the inert dusts, kaolin (12% by wt, in water) somewhat reduced mites for approximately 1 wk after 1 application, but 2 consecutive weekly applications controlled mites for 2 to 3 wk. Diatomaceous earth (12% by wt, in water) reduced mites significantly only if applied for 2 consecutive weeks, and its effects then lasted <2 wk. Beauveria bassiana at 1 × 10 8 conidia/mL effectively killed mites in a glass tube, but showed only moderate on-hen control for 1 wk in 1 of 2 trials. In declining order of effectiveness, the materials were ranked as follows: high sulfur > low sulfur > neem > kaolin clay > diatomaceous earth > Beauveria.

Horn flies, Haematobia irritans (L.), were photographed on cattle and then immediately estimated visually in the field on pastured beef cattle in southern California. Horn flies were counted in the pictures later on a computer screen. For 479 counts on individual cattle, the concordance correlation coefficient between the visual and photo-based assessments was 0.790, but was better for the higher half of the counts (0.732) than for the lower half of the counts (0.217). Major axis regression indicated that visual estimates were consistently higher than the number of flies counted in the pictures across the entire density range. Based on average raw means, the visual estimates averaged 21% higher than the photo counts. Visual estimates included flies on the belly and lower legs that could not be seen in a photo, and lower densities may have been more susceptible to such error. Where flies can be seen well, e.g. for very tame animals, the visual estimates were much faster and more cost-efficient and were sufficient to track relative horn fly abundance changes.

The northern fowl mite, Ornithonyssus sylviarum (Canestri & Fanzago), is an ectoparasite of more than 70 species of North American wild birds, but it has a particularly significant impact on chickens, where it is a permanent resident of vent feathers. Improved control practices depend on a better understanding of host-mite relationships. ISA Brown hens were inoculated experimentally with northern fowl mite adults, and northern fowl mite populations developed naturally. Using a fast-response microprobe, temperatures of individual vent feathers (n = 15) were recorded at 5-mm increments along the length of the feather shaft. Immediately after temperatures were recorded, the individual feathers were quickly clipped at the skin surface and then flash-frozen between 2 small blocks of dry ice, freezing all northern fowl mite stages in situ. The feathers then were cut into 5-mm sections for careful mite enumeration by life stage. There were no overall differences among life stages in the distributions on the feather. Mite positions on feathers (distance from skin) varied distinctly with feather zone temperatures, as well as with ambient and average temperatures over the prior 24 hr. Ambient temperature at time of sampling affected the positions of the 2 mobile categories, adults and larvae/nymphs, but showed no statistical relationship with egg distribution. In contrast, ambient 24-hr temperature influenced the positions of all life stages. On-host feather temperatures reflected ambient temperatures. Feathers collected on hot days (ambient temperatures of 23-33 C) provided a narrow and quite warm range of temperature conditions for mites (often >30-36 C). Temperatures on cool days (ambient temperatures of <23 C) provided much wider on-host temperature ranges for mites to occupy (13-35 C). Mites were farther from the skin on warmer days. When mites had a broad range of temperatures, the feather temperature zone occupied by all life stages averaged 28-29 C. Mites move to occupy favorable temperature conditions on-host. When further out on feathers in warm weather, and under thermal stress, northern fowl mites either move off host or are dislodged. They then become a human pest, are noticed by farmers, and are more likely to disperse.

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.