Cut branches of deciduous holly (Ilex spp.) carrying brightly colored fruit are commonly used for winter holiday decorations, providing nurseries with a source of revenue in low-income periods of the year. In 2012, a fruit rot disease arose in the US, often leading to significant loss of marketable branches. One of the pathogens, the fungus Diaporthe ilicicola, was found to infect flowers during bloom and cause fruit rot symptoms later in the season. The delayed symptom onset suggests that the fungus undergoes a quiescence period until conditions change to favor tissue colonization. We inoculated with D. ilicicola during bloom and monitored physiological changes throughout the growing season in the resulting fruit. A strong positive correlation was found between disease incidence and soluble sugar concentrations, and a negative correlation was seen between disease incidence and phenolic compound concentrations. We hypothesize that the observed increase in susceptibility may be facilitated by greater concentrations of available sugars serving as a carbon source for the pathogen, and/or by a decrease in phenolic-based antifungal compounds within the fruit tissue. These results will direct future research aimed to determine the roles of available sugar concentrations within Ilex fruits in initiating D. ilicicola infection and to identify phenolic antifungal compounds which may inhibit D. ilicicola spore germination or infection.