Bibliography: leaves 227-248.

Spine title: Systemic insecticides in grape vines. Typescript (copy). Includes bibliographical references (leaf. 82-84).

Bibliography: leaves 96-104.

Bibliography: leaves 111-120. This study investigated various aspects of genetic resistance in fava beans to Ascochta blight (A. fabae) with the objective to facilitate an efficient breeding strategy for long-term control. Pathogenic variability of A. fabae was found to be high, as was genetic variation between resistant fava bean accessions. A number of alternative resistance genes to that of Ascot cultivar were identified.

Seed piece to plant transmission of the potato late blight pathogen, Phytophthora infestans, occurred with isolates of the clonal lineages US-8 in Oregon and US-11 in Washington in field trials. Average transmission rate across potato cultivars was 0.5 and 2.4% with US-8, and 0.8 and 1.0% with US-11 in 1999 and 2000, respectively. Transmission rate with US-8 was 2.3% for Russet Burbank (RB) in 1999 and 1.7, 0.7, 4.3, 7.6 and 0.5% for Bannock, Bzura, Ranger, Russet Norkotah (RN), and Umatilla, respectively, in 2000. Transmission rate with US-11 in 1999 was 0.5, 4.9 and 1.4% for RB, RN, and Shepody, respectively, and 1.7% for RB in 2000. Seedborne inoculum of both clonal lineages significantly affected stand establishment and plant vigor. With US-8, final emergence, emergence rate, and aerial biomass of cvs Kennebec, RB, RN, and Shepody were significantly lower than Bzura in 1999, whereas in 2000, these same responses in Chieftain, Bannock, Ranger, and Shepody were significantly lower than Bzura, Umatilla and RN. With US-11, these same response variables were significantly lower in Kennebec, RN and Shepody compared to Bzura and RB in 1999, and were significantly lower in Bannock, Chieftain, Ranger and Shepody compared to RB and Umatilla in 2000. Plant growth responses of cvs RB and RN grown from seed pieces infected with US-8 or US-11 were evaluated in greenhouse trials. RN was equally susceptible to both clonal lineages whereas RB was more resistant than RN to seedborne inoculum of US-11. Compared to RN its final emergence was higher, emergence rate was faster, aerial biomass was greater, and seed piece decay was lower. US-8 was more aggressive than US-11 on RB. US-8 caused a greater reduction in final emergence, emergence rate, and aerial biomass, and a greater increase in seed piece decay. The two clonal lineages were similar in their aggressiveness on RN. This is the first report of cultivar*clonal lineage*inoculum density interactions for plant growth responses of potato grown from seed pieces infected with P. infestans. / Graduation date: 2002

The objectives of this study were: (1) to determine the etiology of bull's eye rot on pears grown in Oregon and Washington; (2) to determine periods of greatest susceptibility of pear wood to canker formation by the fungal pathogens Neofabraea alba and N.perennans; (3) to monitor conidial production in cankers; (4) to determine the timing of fruit infection; and (5) to determine the effect of environmental factors, cultural practices and chemical treatments on the development of bull's eye rot of pears. N. alba, N. perennans and N. sp. nova were identified in isolates obtained from bull's eye rot on pear fruit, using species-specific primers in a PCR reaction. N. alba was also found to be associated with naturally occurring small cankers and pruning stubs on pear trees. Pear trees were inoculated at monthly intervals with mycelia of N. alba and N. perennans to determine susceptibility to canker formation. Susceptibility was highest during autumn and winter months, with larger cankers bearing conspicuous acervuli produced after inoculations from October to February. Small cankers resulted from conidial inoculations with N. perennans on superficially wounded pear branches. Cankers induced after mycelial inoculations sporulated throughout the year with highest amounts of conidia produced from September to December. Pear fruit became naturally infected throughout the growing season, with increasing infection levels close to harvest. Contradictory effects of temperature on bull's eye rot development by N. perennans were observed between 2001 and 2002, where the highest levels of disease were found at 10°C and at 30°C, respectively. Wetness duration did not affect bull's eye rot development, while the concentration of conidia correlated positively with disease development. Over-tree irrigation and late harvest resulted in higher disease levels than under-tree irrigation and early to mid season harvest. The fungicides trifloxystrobin and ziram protected inoculated fruit for about one month, while copper sulfate reduced the sporulation rate of cankers induced by N alba. Thiabendazole applied as a postharvest dip reduced bull's eye rot on inoculated pears. / Graduation date: 2004

Volatile loss rates of pesticides from turfgrass were measured using the Backward-Time Lagrangian Stochastic Dispersion model (Flesch et al., 1995). Solar radiation, ambient temperature, surface temperature, relative humidity, wind direction, and wind speed were monitored continuously. Growth regulator was applied to the turf plot several days before pesticide application to maintain a constant grass height and aerodynamic roughness length during the experiment. No irrigation occurred following application. Pesticides were applied as mixtures to allow direct comparison of evaporative loss. Mixtures studied were chlorpyrifos + triadimefon + ethofumesate and triclopyr (acetic acid) + propiconazole + cyfluthurin. Airborne flux estimates correlated with temperature, solar radiation, wind speed, time, and vapor pressure of the active ingredient. A log vapor pressure vs. 1/Temperature (K) relationship was observed between flux and surface temperature over a single day for most pesticides. An exponential attenuation of flux was observed over a period of several days and correlated with attenuation of dislodgeable surface residues for two of the pesticides. A fugacity-based model for predicting initial evaporative loss rates from turf grass is presented. Input parameters include pesticide vapor pressure, molecular diffusion coefficient, surface temperature, wind speed profile, atmospheric stability, surface roughness, and average upwind fetch. The GC retention method (Jensen, 1966) was used to estimate pesticide vapor pressures over an environmentally relevant temperature range. The model predicts fluxes that are an order of magnitude greater than measured values. This bias may be due, in part, to deviation from the assumption of pesticide saturated vapor density at the foliar surface. In addition, sensitivity analysis suggests improved estimates of leaf surface temperature and pesticide vapor pressures have the greatest potential to improve model performance. / Graduation date: 2003

In broiler operations, various health problems develop during the final two weeks of the growing period, resulting in increased mortality and condemnation losses. At this stage, sickly birds were found to be systemically infected by various bacteria regardless of varied clinical signs. The main objective of the present study was to determine the prevalence and nature of systemic bacterial infections in unthrifty commercial broiler chickens and to establish a reproducible infection model in the laboratory. Thirty-one unthrifty 6-week-old broilers were obtained from three farms, and bacterial isolations were conducted on blood, liver, and hock joint. Bacteria were isolated from 87, 90, and 71% of the blood, liver and hock joint samples, respectively. Mean bacterial counts (log������ CFU/ml or g) of the blood and liver were 2.15 and 2.93, respectively. Among 132 bacterial isolates, major species were; Staphylococcus (60%), Corynebacterium (18%), Escherichia coli (5%), and Stomatococcus (4%). Among 79 Staphylococcus isolates, 77 were coagulase-negative. Major species of staphylococci were; S. lentus (19%), S. simulans (18%), S. cohnii (13%), S. gallinarum (10%) and S. captis (7%). In addition, 6 species of gram-positive and 5 species of gram-negative organisms were isolated. Apparently systemic infections were not caused by predominant pathogenic bacterial species, and adequately described as mixed infections. However, there were some significant relationships between isolated bacterial species and sampling sites, suggesting that certain organisms were abundant in the environment of a particular poultry house. These results indicate that systemic infections in market age broilers are caused by mixed bacterial species and suggest that they are caused by suppressed host antibacterial systems rather than pathogenic factors of microorganisms. Antibiotic susceptibility results showed 100% susceptibility of staphylococcal isolates (n=69) against vancomycin and enrofloxacin. Of these coagulase negative staphylococci showed 19% and 73% resistance against methicillin and penicillin G, respectively. There was also heterogeneity in antibiogram profiles within species of coagulase-negative staphylococci. Pathogenicity of representative field isolates from the above described study was tested in 5-day-old embryonated eggs and in 3- week-old broiler chicks. Consistent lethality was demonstrated with S. aureus in embryos. Staphylococcus intermedius or S. lentus demonstrated some pathogenicity, while S. gallinarum or Corynebacterium were non-pathogenic in embryos. In 3-week-old broilers, however, only S. aureus caused septicemia and death; other bacterial species mentioned above caused neither clinical signs of acute or chronic staphylococcosis nor mortality. / Graduation date: 1998

Graduation date: 1998

The Feldmannia sp. virus is a large icosahedral virus that persistently infects marine brown alga Feldmannia sp.. So far, there is no information available about viral genome replication, gene structure and gene expression in this unique viral-host system. The purpose of this study was to characterize the general features of viral transcripts in the virus producing sporophyte plants. Northern analysis, using four cosmid clones that cover the entire viral genome, showed that there were six major transcripts and at least eighteen minor transcripts in the virus producing sporophyte plants. These transcripts are not evenly distributed in the viral genome. A 5.7 kb BamHI fragment-R was found to encode a 1.5 kb and a 0.9 kb major transcript, and those two major transcripts were chosen for detailed sequence analysis. The 1.5 kb transcript was identified as the putative major capsid protein (MCP) gene. The FsV MCP has significant similarity with the major capsid protein of Chlorella virus-PBCV-1 and with iridoviruses, fish lymphocystis disease virus, frog virus 3, and with African swine fever virus. / Graduation date: 1996