Evaluation of Optimal Light Wavelength for the Attraction of Spodoptera Exigua as a Model Insect for Mass Trapping and Control of Spodoptera Frugiperda

Visual cues have been explored in the past for the management of pests of agronomic importance, including Spodoptera frugiperda (J.E. Smith) and Spodoptera exigua (Hübner). They are used to monitor, attract and kill, or to suppress the nocturnal behaviour of the insects. The current commercial universal traps, using reflected sunlight, are not effective for nocturnal insects like Spodoptera and current light traps may use a suboptimal or unattractive wavelength since the optimal wavelength has not been tested. This research focuses on testing the attractiveness of Spodoptera exigua as a model insect of Spodoptera frugiperda towards specific light wavelengths. Freshly enclosed moths were tested in the wind tunnel using light emitting diodes (LED) water trap and seven light colours (365, 385, 400, 470, 530, 592 and 650 nm) at the same light intensity (brightness). The roof top light was dimmed to 4.5% of daylight conditions tested on Western flower thrips in a wind tunnel to mimic dusk and UV-A at 3.5% of total dusk light. The number of moths trapped was recorded 30 minutes after the experiment started and at the end of the experiment after 14 hours. The results revealed a significant difference among the light colours. At 30 minutes the UV-A wavelengths (365, 385 and 400 nm) were significantly different from (470, 530, 592 and 650 nm) at p=0.01 whereas at 14 hours they were significantly different at p=0.001. These results show that UV-A has the potential to be utilized in water traps for the control of Spodoptera exigua as a model insect ofSpodoptera frugiperda. However, there is need for validating the results in the field on trapping S. frugiperda using UV-A light wavelengths and pheromones.