Irradiation with green light at night has great effects on the management of Conopomorpha sinensis and maintains favorable litchi fruit quality

The photophobia of Conopomorpha sinensis was explored using eight kinds of LED lights, including those with single wavelengths as follows: 400, 460, 520, 600, 660 and 740 nm, and mixed wavelengths: MixW and MixY. The results showed that 460 nm (blue light), 520 nm (green light) and MixW (white light) were the most effective wavelengths for controlling C. sinensis, effectively reducing pest activity by 98.2%, 99.2% and 99.3%, respectively. Egg production decreased by 99.3%, 93.0% and 98.6% under these treatments with a light intensity of 0.5 μmol m−2 s−1, respectively. The C. sinensis damage rate was 72% in the dark control group and 10%, 6%, and 16% under continuous light at night with 460, 520 nm and MixW light, respectively. To further investigate the effect of different wavelengths of light applied to the whole plant at night on Yu-Her-Pao litchi fruit quality, the fruits under 460, 520 nm and MixW light at night were 23.4, 29.8 and 26.6 g in weight and 17.5, 19.3 and 17.8°Brix in total soluble solids, respectively. There was no significant difference in fruit weight or total soluble solids under 520 nm or bagging with no light at night. Thus, 520 nm green light at night had the least effect on fruit quality. HPLC results showed that the sucrose, glucose, fructose, citric acid, L-malic acid, and shikimic acid contents in fruits under 520 nm green light illumination at night were significantly higher than those under other light treatments. Only the fumaric acid content was significantly less than that under the other light treatments. There is no known previous research on the effects of continuous application of light to whole fruit trees and different light wavelengths on fruit quality. The results of this study showed that 520 nm green light at night could prevent and control C. sinensis and maintain fruit quality. These experimental results represent important progress in reducing the use of pesticides in the litchi industry.