Use of Infrared Sensors for Early Detection of Bacterial Wilt Caused by Ralstonia solanacearum in Tomato Plants

Abstract

Infrared thermography can be used to detect water-stress induced temperature changes inplants. Bacterial wilt, a destructive disease of tomato caused by Ralstonia solanacearum,induces water stress in the host, leading to wilt and plant death. Fifty plants wereinoculated with a bacterial suspension of 108 colony forming units (CFU) and fifty noninoculatedplants were maintained as healthy controls. Leaf temperature of inoculated andnon-inoculated plants was measured with two infrared sensors, a low-cost infraredthermometer, and a thermal camera. The test was performed twice. In the firstexperiment, the incidence of bacterial wilt was 62%. Leaf temperature of healthy anddiseased plants was similar for four days after inoculation. On the fifth and sixth days,leaf temperature of inoculated plants was 0,9 °C and 1,9 ºC higher, respectively, than thetemperature of healthy plants. Wilt symptoms were first observed seven days afterinoculation. In the second experiment, which coincided with cooler weather conditions(15 ºC during the day), disease incidence was 38%. Wilt symptoms were observed 10days after inoculation, but temperature differences were observed seven days afterinoculation. The use of this methodology allowed detection of differences in temperaturetwo to three days before symptoms were visible. Application of this technology mayfacilitate management decisions for bacterial wilt.