Fungicide applications are a common integrated pest management (IPM) tool, yet their use often follows a set schedule or crop stage rather than actual need. Overuse can drive fungicide resistance, undermining long-term effectiveness. The occurrence of plant disease requires a susceptible host, a pathogen, and favorable environmental conditions. Thus, fungicides should be applied only when conditions are favorable for disease development. To promote this approach, two experiments were conducted: one on apple (2021-2022) and one on soybean (2023-2024). In apple, three relative humidity-based organic fungicide spray thresholds were tested in central Iowa on three apple cultivars, with the most conservative threshold reducing fungicide applications by four per season without affecting marketable yield. Disease pressure remained low with an average incidence of Sooty Blotch and Flyspeck (SBFS) of 3.9% in 2021 and 1.9% in 2022. For soybean, a weather-based model for frogeye leaf spot was developed and tested in eight states across 10 sites in 2023, leading to a reduced number of fungicide applications. In three sites, a fungicide application at the R3 stage, reduced disease (AUDPC) but no effect on yield was observed in any site. In 2024, a new model was developed and validated in 10 states and 20 sites and data analysis is ongoing. Deciding if or when to apply a fungicide is an essential part of an IPM program, and continued efforts to refine predictive tools can offer agronomic, economic, and environmental benefits across cropping systems.