Application of infrared thermal imaging for the rapid diagnosis of crop disease

Visual diagnosis of plant disease following a visually evident epidemic results in untimely and excessive application of pesticide. Conventional nondestructive testing methods are difficult for early recognition before the onset of symptoms. In this study, tomato mosaic disease and wheat leaf rust were taken as examples. Infrared thermal imaging technology was used to continuously detect the temperature information of the two crops during the incubation period following the introduction of inoculum. Diseases of tomato and wheat were induced by rubbing inoculation and spray inoculation, respectively. Maximum temperature difference (MTD) was calculated to characterize the continuous temperature change during the incubation period. The results showed that the MTD of tomato mosaic disease ranged from 0.2°C ~ 1.7°C, and that of wheat leaf rust 0.4°C ~ 2°C. As the disease progresses, the MTD of both plants showed an increasing trend while the average temperature decreased. The time to observe the symptoms earlier than the naked eye for tomato mosaic and wheat leaf rust is 5d and 7d respectively. Studies showed that it is feasible to realize the early determination of disease through the combination of infrared thermal imaging and MTD calculation. It provides the theoretical basis and method basis for the early and accurate application of spraying.