Powdery mildew, caused by the fungus Podosphaera xanthii, commonly occurs across Australian mungbean (Vigna radiata) production areas, and is more common in mungbean fields which are planted near the end of season (January – February). Crop losses from the disease are effectively managed using fungicides. Currently two fungicides, Folicur® and Veritas®, are labeled for use in mungbean to control powdery mildew. Trials conducted over several years in Queensland have shown that up to 39% (or 0.65 t/Ha) of yield can be saved due to fungicide applications. For optimum control of the disease a single fungicide application should be made at first sign of powdery mildew, with a second application two weeks later. In order to assist advisers and growers identify the critical timeframe to make management decisions for this high-value crop, a new decision support system (DSS) app has been developed and tested in southern Queensland. The app is designed to be used in the paddock on tablets. To use the app, users provide basic information on the crop, disease progression, anticipated yields, input costs and forecasted weather conditions. A summary table, and graphs, are returned describing the cost-benefit of spraying, the expected impact of the disease on yield and a probable range for the net yield return for both management with fungicide and without. The app should not only inform users when fungicide should be used, but also when a spray will not result in yield saving. This approach will help manage the pathogen population to avoid the development fungicide resistance due to unnecessary fungicide applications. The new app will be publicly available as a mobile application for Android and iOS for users to install after testing is completed.