Development of an Insect Pest Control System using Pulsed Light from a Yellow-LED in the Production of Autumn-flowering Chrysanthemums
—Investigation of an Appropriate Irradiance Range for the Production of Autumn-flowering Chrysanthemums—

Abstract

In order to develop an insect pest control device using pulsed light from a yellow LED, the dependency of the production of autumn-flowering chrysanthemums on the irradiance was investigated. The Electro-Retino Gram (ERG) signals of the compound eyes of Helicoverpa armigera and Spodoptera litura due to irradiation with pulsed yellow light with 20 ms pulse width and 100 ms period were determined over the irradiance range from 1 to1000 mW m^-2. The ERG signals showed that these 2 types of noctuid moth continuously and reproducibly recognized pulsed illumination within the irradiance range from 1 to 100 mW m^-2. Therefore, the effects of the irradiance of pulsed light from a yellow LED (0，20，35 and 50 mW m^-2) on flowering and the cut flower characteristics of the autumn-flowering chrysanthemum, ‘Zimba’, were determined. No significant differences were found in the number of days to flower budding or flowering, or the cut flower characteristics below35 mW m^-2. However, the number of days to flowering and the cut flower length of plants exposed to 50 mW m^-2 irradiance increased significantly compared to those exposed at other irradiances. Thus, no delay in flowering occurred below 35 mW m^-2 irradiance and the maximum irradiance for which no delay occurred is between 35 and 50 mW m^-2.