Three applications of unmanned aerial systems (UAS) based imaging were explored in row, field, and horticultural crops at Washington State University (WSU). The applications were: to evaluate the necrosis rate in potato field crop rotation trials, to quantify the emergence rates of three winter wheat advanced yield trials, and detecting canker disease-infection in pear. The UAS equipped with green-NDVI imaging was used to acquire field aerial images. In the first application, one and two year crop rotation fields were imaged to evaluate the necrosis rates of 64 plots. The GNDVI data showed stronger relationship with ground-truth necrosis measurements (r = 0.949).

 

Winter wheat seeds planted in the 6 to 12 inch annual rainfall zones of Washington are normally sown deeper than usual (10 to 15 cm) for better availability of water to the germinating seed. Precipitation up to seven days after planting may result in formation of hard top-soil layers reducing seed emergence rates. Therefore, the second application evaluated applicability of aerial imaging to quantify the germination rates of the new winter wheat cultivars being developed by WSU wheat breeders. The aerial imaging showed good correlation to the ground scouting data with correlation of 0.78, 0.79 and 0.86 for soft white common, hard, and soft club wheat trials, respectively.

 

The pear orchards in the Pacific Northwest are usually very old and characterized by large and vigorous tree canopies. Such trees when irrigated by under the canopy system results in very humid microclimate that triggers the development of fungi. Many of these fungi are responsible for the formation of cankers in the bark growing inside the phloem and are difficult to control. If the trunk is infected, the tree health declines slowly with eventual death. Therefore, understanding the canker spread pattern is important to trigger appropriate management decisions. In the third application, UAS based imaging was successfully used to identify the canker infection areas in Red Anjou pear variety. Overall, the results suggest that UAS based high resolution imagining is a versatile and complementary technique useful to both the researchers and growers in field trails quantification and crop scouting for diseases.