THIS RESEARCH FOCUSES ON UNDERSTANDING AN EMERGING FUNGAL DISEASE WHICH CAUSES FRUIT ROT IN DECIDUOUS HOLLY, COMMONLY REFERRED TO AS WINTERBERRY. WINTERBERRY ARE ORNAMENTAL SHRUBS WHICH PRODUCE BRIGHTLY COLORED RED AND GOLD FRUIT. BRANCHES OF THESE PLANTS ARE CUT AND SOLD DURING THE FALL AND WINTER HOLIDAY SEASONS TO CREATE FESTIVE DECORATIONS SUCH AS WREATHS. DESPITE THE MAJORITY OF SALES OCCURRING ONLY THREE MONTHS OUT OF THE YEAR, THIS CROP ALONE HAS AN ANNUAL SALES REVENUE OF JUST UNDER HALF A MILLION DOLLARS IN THE UNITED STATES. RECENTLY, AN EMERGING FRUIT ROT DISEASE HAS THREATENEDTHIS INDUSTRY, PRODUCING FRUITS WHICH ARE UNDERSIZED, FAIL TO MATURE, SHRIVEL AND ROT. IF THE SYMPTOMS ALONE WEREN'T BAD ENOUGH, THE DEVELOPMENT OF THESE SYMPTOMS IS UNPREDICTABLE AND PROGRESSES RAPIDLY MERE WEEKS BEFORE HARVEST, OFTEN RESULTING IN ENTIRE CROP LOSS. SINCE 2015, THE ORNAMENTAL PATHOLOGY RESEARCH TEAM AT THE OHIO STATE UNIVERSITY HAS BEEN WORKING WITH NURSERY GROWERS THROUGHOUT THE MIDWEST AND NORTHEASTERN UNITED STATES TO DETERMINE THE PATHOGENS RESPONSIBLE FOR THIS DISEASE. IN 2018, SEVEN FUNGAL PATHOGENS WERE IDENTIFIED AS CAUSAL AGENTS; UNFORTUNATELY, THE CONDITIONS WHICH LEAD TO SYMPTOMS DEVELOPMENT REMAIN UNKNOWN. TO SUCCESSFULLY PREVENT YIELD LOSS, THIS PROPOSED RESEARCH PLAN WAS DEVELOPED TO UNDERSTAND THE FACTORS LEADING TO SYMPTOMS DEVELOPMENT AS WELL AS WHAT CONTROL METHODS ARE AVAILABLE TO HELP GROWERS AVOID DISEASE IN THEIR FIELDS.THE PROPOSED RESEARCH IS BROKEN DOWN INTO FOUR MAIN OBJECTIVES. THE FIRST OBJECTIVE INVOLVES USING ADVANCED IMAGING TECHNIQUES TO VISUALIZE HOW THE FUNGI COLONIZE THE WINTERBERRY FRUIT OVER THE COURSE OF A NORMAL GROWING SEASON. DURING THIS PORTION OF THE RESEARCH, WE CAN IDENTIFY ANY UNIQUE METHODS OR PATHWAYS THE FUNGUS UTILIZES AND GET A BETTER UNDERSTANDING OF THE TIMELINE OF DISEASE DEVELOPMENT. NEXT, WE WILL LOOK INTO THE CHEMICALS PRODUCED BY THE WINTERBERRY FRUIT AND MONITOR HOW THESE COMPOUNDS CHANGE AS THE FRUIT RIPENS. FRUITS TEND TO HAVE HIGHER CONCENTRATIONS OF DEFENSE-RELATED COMPOUNDS WHEN THEY ARE IMMATURE TO PROTECT THE SEEDS AS THEY DEVELOP. FOLLOWING MATURITY, THESE COMPOUNDS TEND TO DECREASE IN CONCENTRATION TO MAKE THE FRUIT MORE PALATABLE TO SEED-DISPERSING ORGANISMS. WE PREDICT THAT THE DECREASE IN THESE DEFENSE COMPOUNDS MAY BE A LARGE CONTRIBUTING FACTOR TO WHY SYMPTOMS DEVELOPMENT OCCURS IN MATURE FRUIT AND NOT IMMATURE FRUIT DESPITE THE FUNGI BEING PRESENT IN THE FRUIT THROUGHOUT THE SEASON. THE THIRD OBJECTIVE AIMS TO TEST WHETHER DIFFERENT VARIETIES OF WINTERBERRY ARE MORE SUSCEPTIBLE TO DISEASE DEVELOPMENT THAN OTHERS. THIS INFORMATION WILL BE USEFUL FOR NURSERY GROWERS BECAUSE IT WILL HELP THEM SELECT MORE RESISTANT WINTERBERRY VARIETIES IF THEY HAVE EXPERIENCED HEAVY DISEASE LOADS IN PREVIOUS YEARS. OUR FINAL OBJECTIVE IS TO USE ALL THE INFORMATION GATHERED, THROUGH COMPLETION OF THE RESEARCH-BASED OBJECTIVES, TO DEVELOP A MANAGEMENT PLAN TO HELPGROWERS AVOID DISEASE BY: (1) UTILIZING TARGETED FUNGICIDES, (2) APPLYING FUNGICIDES AT OPTIMAL TIMES IN THE DISEASE DEVELOPMENT CYCLE, (3) UTILIZING CULTIVAR RESISTANCE AND (4) IMPLEMENTING CULTURAL CONTROL METHODS SUCH AS PRUNING AND REMOVING DISEASED PLANT TISSUE PRIOR TO FLOWERING. COMPLETION OF THESE OBJECTIVES WILL SIGNIFICANTLY REDUCE WINTERBERRY CROP LOSS DUE TO LATENT FRUIT ROT AND ENSURE FESTIVE HOLIDAY SEASONS IN THE YEARS TO COME.