Traditional methods of powdery mildew (PM) detection involve visual inspection. However, the PM symptoms must already be visible when the damage is already done and disease is already spreading. Laboratory tests are more accurate than visual inspection, but are time consuming and cannot provide information for immediate decision making. Near infrared (NIR) and shortwave infrared (SWIR) sensors can see the reflected light in 700 nm to 2500 nm spectral range, thereby helping early detection of PM and other diseases. When subjected to PM stress, grapes undergo changes in spectral reflectance due to physiological and biochemical alterations in their leaves, such as decreased chlorophyll content, destroyed cell structure, or water stress. This paper presents an investigation on the potential of hyperspectral data acquired from vineyards using unmanned aerial vehicles (UAVs) in detecting powdery mildew in grapes. A UAV equipped with a hyperspectral sensor has been flown over a Cal Poly Pomona vineyard. The hyperspectral data is used to determine various vegetation indices including normalized difference texture index (NDTI), powdery mildew index (PMI), and normalized difference water index (NDWI) that can provide information on the presence of the disease and plant stresses due to the disease. These indices are compared with the ground-truth data that include visual inspection data and proximal sensor data such as chlorophyll meter and NDVI meter.