Northern fowl mites (Ornithonyssus sylviarum) are the most common and economically important ectoparasites in US laying hen flocks. Mites are permanent ectoparasites and cause damage to birds via blood feeding. Once in a flock, they can be very difficult to eradicate from a property. Mite control has traditionally relied on chemical sprays directed at high pressure underneath the birds and into the vent region where mites live; these applications are most effective when birds are held in battery cages. However in recent years animal welfare concerns and consumer demand has affected how laying hens are housed. The transition to furnished-cage or cage-free production systems will require novel control techniques to achieve ectoparasite control. I investigated possibilities for ectoparasite control that would be effective in alternative poultry housing.

Breeding for parasite resistance is an attractive control method. Chickens develop resistance to the northern fowl mite (NFM) and this is under at least some genetic control. I tested whether the haplotype conferring NFM resistance had any effect on chicken resting metabolism (energy expenditure), physiology, or economic performance. Bird haplotype did not affect hen metabolism or production parameters. NFM infestations negatively affected economic performance.

Dustboxes have been shown to effectively decrease mite populations in cage-free flock when insecticidal dusts are used in combination with sand. I tested whether dustboxes with sand and diatomaceous earth could keep mites below economic thresholds before mite levels became damaging. When dustboxes were present in a flock, mite levels were on average kept below economic threshold regardless of percent of the flock that dustbathed.

Sulfur dust is effective for NFM control in very low doses, though it is not universally approved for organic use. I tested whether sulfur deployed in a dust bag would be effective in caged (non-organic) flocks and if the placement of the bag affected efficacy. Hanging dust bags offered the best NFM control.

Backyard chicken flocks are a growing trend in this country, and nothing is currently know about ectoparasite diversity on these birds. I surveyed 100 birds on 20 properties in southern California. Greater diversity was found on backyard flocks than on commercial birds.

Culicoides biting midges are the primary vectors of some of the most economically damaging pathogens of livestock worldwide, including bluetongue virus (BTV). Bluetongue disease affects mainly domesticated ruminant livestock, especially cattle and sheep. Morbidity and mortality can be very high in susceptible animals. In the United States, production losses and trade restrictions make BTV an economically important pathogen for the cattle industry. Both BTV and the primary North American vector species, C. sonorensis Wirth and Jones are endemic to California. Although temperatures in southern California are theoretically high enough to allow year-round transmission, adult vector activity and cattle seroconversions cease or exist at very low levels during the winter. Culicoides overwintering has been of considerable interest since BTV expanded into northern Europe in 2006, successfully overwintering in a temperate climate and causing consecutive epizootics that resulted losses of millions of animals and billions of dollars.

Little is known about the immature stages of Culicoides. I examined the desiccation tolerance of C. sonorensis eggs, and the low temperature tolerance of eggs, larvae, and pupae. Although previous literature had suggested that Culicoides eggs would be susceptible to environmental stress, I found that C. sonorensis eggs can withstand nearly complete desiccation and exposure to temperatures as low as -20°C without suffering complete mortality. Conversely, larvae succumbed to temperatures less than -4°C. Culicoides eggs are likely to be more important in seasonal persistence of vector populations than previously thought.

Our understanding of adult vector activity stems from trap collection data. However, trapping strategies can bias insect collections. I collected C. sonorensis on dairies in California using traps baited with either CO2, UV light, or CO2+UV, and placed either near cattle, oviposition sites, or in open fields. I found that traps placed in fields were more efficient at collecting adult midges. I also found that traps baited with UV collected insects with significantly lower BTV infection rates than traps baited with only CO2, suggesting that BTV+ midges are repelled by UV light. The use of UV traps runs the risk of missing active, infected vectors during periods of low activity, like winter, potentially resulting in a misunderstanding of true seasonal disease dynamics.

The egg, all four larval instars, and pupa of Culicoides sonorensis Wirth and Jones (Diptera: Ceratopogonidae) are described and imaged using a compound microscope and scanning electron microscopy. The differences between the larval instars have also been noted. The swimming speeds of the larvae as well as the location of the pupae and their responses to both changes in the waterline and prolonged submersion underwater have also been examined.

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As the rural-urban interface expands, controlling flies has become increasingly important on California poultry farms. Manure management is a critical component of keeping fly populations in check. Recent research demonstrates that the dry pad left behind after manure cleanouts in cagedlayer poultry systems aids manure drying because of the elevation and improved airflow. Most mites and beetles that prey on fly eggs and larvae are removed in a cleanout, although predator populations require longer than flies to recover. Leaving undisturbed manure (with a larger number of predators) adjacent to recently removed manure did not improve fly control significantly in open-sided layer houses, but might be more important in fully enclosed houses.

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