Domestic houseflies (Musca domestica Linnaeaus) were examined for their ability to harbor and transmit turkey coronavirus (TCV). Laboratory-reared flies were experimentally exposed to TCV by allowing flies to imbibe an inoculum comprised of turkey embryo-propagated virus (NC95 strain). TCV was detected in dissected crops from exposed flies for up to 9 hr postexposure; no virus was detected in crops of sham-exposed flies. TCV was not detected in dissected intestinal tissues collected from exposed or sham-exposed flies at any time postexposure. The potential of the housefly to directly transmit TCV to live turkey poults was examined by placing 7-day-old turkey poults in contact with TCV-exposed houseflies 3 hr after flies consumed TCV inoculum. TCV infection was detected in turkeys placed in contact with TCV-exposed flies at densities as low as one fly/bird (TCV antigens detected at 3 days post fly contact in tissues of 3/12 turkeys); however, increased rates of infection were observed with higher fly densities (TCV antigens detected in 9/12 turkeys after contact with 10 flies/bird). This study demonstrates the potential of the housefly to serve as a mechanical vector of TCV.

The house fly, Musca domestica L. (Diptera: Muscidae), is a disease vector of mechanically transmitted pathogens including bacteria, viruses, and protozoans. Opportunities for pathogen transmission can increase as fly longevity increases. Dietary preferences play an important role in insect longevity; therefore, we investigated house fly preferences, sucrose availability, and caloric constraints on house fly longevity. Experimental goals were: 1) to test the effects of calorie restriction on survival of house flies by manipulating concentrations of erythritol (low caloric content) and sucrose (high caloric content), and comparing commercial sweeteners of differing calorie content, 2) to identify house fly preferences for either erythritol or sucrose, and 3) to evaluate the insecticidal activity or toxicity of erythritol on house flies. Our data show that house flies may prefer high calorie options when given a choice and that house fly longevity likely increases as calorie content increases. Additionally, no significant differences in longevity were observed between the water only control (zero calories) and erythritol treatments. This suggests that decreased survival rates and death could be the result of starvation rather than insecticidal activity. This research furthers our understanding of house fly survival and sugar-feeding behavior.

Although apple (Malus domestica Borkh.) system yield differences are generally related to whole-canopy light interception, this study tested the hypothesis that these orchard yields are related primarily to total light intercepted by the spur canopy. Seasonal leaf area development of different shoot types, exposed bourse shoot leaf net photosynthesis, fruit growth, whole canopy light interception (by image analysis of fisheye photographs) and relative light interception by different shoot types (by a laser assisted canopy scanning device) were estimated within four 14-year-old `Empire' apple production systems (slender spindle/M.9, central leader/M.7, central leader/M.9/MM.111 and Y-trellis/M.26). The final LAI values were CL/M.7 = 1.8, CL/9/111 = 2.3, SS/M.9 = 2.6 and Y/M.26 = 3.6. Exposed leaf net photosynthesis showed few differences and was not dependent upon the production system. Yields of the pyramidal shaped tree forms were 40 to 42 t·ha-1 while Y-trellis produced 59 t·ha-1, with similar fruit sizes. Again, yields were primarily related to the percentage of light intercepted by the whole canopy, 48% to 53% for conic forms versus 62% for the Y-trellis system. Laser analyses showed that the Y-trellis system intercepted about 20% to 30% more light with the spur canopy than the conic tree forms, supporting the hypothesis. Yields were better correlated with spur canopy LAI and spur canopy light interception than with extension shoot canopy LAI and light interception.

The hypothesis was tested that effects of late-season European Red Mite (ERM) [Panonychus ulmi (Koch)] injury on apple (Malus domestica Borkh.) fruit development are better explained by carbon physiology than by pest densities. Midseason ERM populations were allowed to develop in mature semi-dwarf `Starkrimson Delicious'/M26 trees with moderately heavy crops, then were controlled with miticides at different mite-day (activity of one mite per leaf for 1 day) levels as estimated by weekly leaf sampling. The range of final mite-days was from 250 to 2100 on individual trees. Seasonal fruit growth patterns were monitored. Diurnal whole-canopy net CO2 exchange rate (NCER) was measured in eight clear flexible balloon whole-canopy chambers on several dates before and after mite infestations. Mite injury reduced fruit growth rates. Leaf and whole-canopy NCER were reduced similarly. Late season fruit growth and final fruit size were correlated with accumulated mite-days, but were better correlated to whole-canopy NCER per fruit. Fruit firmness, color, soluble solids and starch ratings showed no correlation to mite-days. Number of flower clusters per tree and final fruit per tree the following year were not related to accumulated mite-days, but final fruit per tree the following year were better correlated to whole-canopy NCER per fruit. These results generally supported the hypothesis.

The vectoR potential of adult house flies. Musca domestica L., for Yersinia pseudotuberculosis (Pfeiffer), a pathogen of domestic animals and humans, was investigated. Adult flies were allowed to feed on trypticase soy broth (TSB) containing Y. pseudotuberculosis for 6 h and then transferred to sterile containers with sterile TSB as a source of water and nutrients. At 6-h intervals, all flies were transferred to sterile containers with sterile TSB and 10 randomly selected flies were examined for the pathogen. Yersinia pseudotuberculosis did not establish a permanent population in the house fly colony; however, viable cells were detected from the digestive tract of flies for up to 36 h after the initial exposure, and flies contaminated their environment (sterile TSB) for up to 30 h after the exposure. These results demonstrated that house flies can carry Y. psedotuberculosis for a considerable period and therefore must be considered as a potential mechanical vector of pseudotuberculosis infection.