D3319: Remote sensing for monitoring of spider mites (Tetranychus spp.) in California almonds

Spider mites (Tetranychus spp.) are known to infest almond (Prunus dulcis) orchards throughout the summer months in California’s Central Valley. They feed on the intracellular contents of leaves using piercing-sucking mouthparts causing stippling, necrosis, defoliation, and yield reductions in the years following severe infestation. While almond acreage in the Central Valley has nearly doubled over the past decade, spider mite monitoring methods remain largely unchanged, emphasizing time consuming in situ counts under a hand lens. Cameras mounted to Unmanned Aerial Vehicles (UAVs) have generated special interest among pest management professionals, as their high spatial resolution allows for the rapid detection of arthropod damage over extensive landscapes. Here we demonstrate the utilization of RGB (Red Green Blue) and multispectral sensors equipped to aerial UAVs to detect spider mite damage in almond blocks under differential spider mite feeding pressure. Correlation analysis between drone imagery and subjective visual assessments, were conducted to link relevant visual assessments with drone spectral data. Analysis reveals that RGB and multispectral sensors are sufficient in the detection of spider mite damage in almonds. Yet, the early detection of spider mite damage was not successful with the use of these technologies as only after severe damage detection was possible. However, future approaches will likely require sophisticated cameras capable of detecting spectra beyond the studied spectral bands.