Why is the bloom period a critical control point for so many plant pathogenic diseases? Recognition of floral chemical signals would appear to be critical to the success of many fruit rotting pathogens, as flowers always precede fruit. Objective; in an effort to determine if plant signals produced during bloom play a critical role in the infection process and sporulation events of some fungi, the blueberry anthracnose pathosystem was investigated. In many growing regions blueberry anthracnose can only be adequately controlled with bloom period fungicide applications. This disease is most often caused by Colletotrichum fioriniae, a latent hemibiotrophic pathogen that can severely limit the production of numerous crops worldwide. In the current study in vitro floral extraction methods and field rainwater monitoring devices were developed to capture potentially bioactive host floral signals, also referred to as floral extracts (FE). These FE were co-incubated with C. fioriniae via a glass coverslip bioassay. The bioassay enabled quantification of pathogen responses such as spore germination, appressorial formation, and the production of secondary conidia with or without FE. Floral signals increased the rate and magnitude of secondary conidiation and appressorial formation from 12-18 h in sterile water to 6 h in the presence of FE. Thus, during bloom there should be a greater number of overall infection periods and sporulation events. The rainwater collections alluded to a critical factor; floral signals can become mobilized and therefor potentially activate and synchronize multiple overwintering / inoculum reservoirs during rain events. Additionally, as the distance from inflorescences decreased, bioactivity increased. In detached fruit assays, conidia in the presence of FE enabled more infection than conidia alone, indicating that appressoria forming in response to FE were viable. These data have partially elucidated ‘why’ the critical disease control window for blueberry anthracnose is during the bloom period. Armed with this knowledge, exploiting this pathogen:host relationship is the next step in moving towards grower recommendations, fungicide use patterns, and ‘trap-based’ sprays.