Yones M S, Maamoun Shireen A M, Khidr Abd El Aziz A, Sayed Mahmoud, Al-Ashry Hend A A, Attia Radwa G
National Authority for Remote Sensing and Space Sciences, Cairo, Egypt.
Entomology department, Faculty of Science, Ain Shams University, Cairo, Egypt. shireen_ma'
Sci Rep. 2024 Dec 23;14(1):30603. doi: 10.1038/s41598-024-81182-8.
Photosensitizing compounds are eco-friendly promising organic dyes for managing insect pests without facing the risk of resistance. The photodynamic efficacy of four Photosensitizing compounds (rose Bengal, rhodamine B, methylene blue and methyl violet) was monitored against the third larval instar of Spodoptera littoralis (Boisduval), after exposure to sunlight. The LC values of the four compounds; rose Bengal, rhodamine B, methylene blue and methyl violet recorded 0.029 × 10, 0.24 × 10, 14.69 × 10 and 15.59 × 10 M, respectively. Therefore, rose Bengal was the most effective compound followed by rhodamine B, Methylene blue and methyl violet. Compared to similar previously documented photosensitizer compounds, these four tested compounds recorded higher mortality percentage. The effect of those compounds on the larval biochemical components was assessed by measuring larval spectral and thermal reflectance. Larvae fed on photosensitizing compounds showed distinct spectral reflectance patterns. Treated larvae had same reflectance manner; which were higher than that of control samples. Along the whole spectrum, the highest reflectance was after 60 min of exposure to sunlight in case of rose Bengal, rhodamine B and methylene blue. Methyl violet reflected sunlight mostly at zero time then the reflectance decreased after 30 min then increased again after 60 min. There was a noticeable absorption of IR wavelengths at ~ 1900, 1400, 1200 and 950 nm in all treated samples. Thermal imaging indicated abnormal larval warmth after treatment. Differences in reflectance were monitored immediately after feeding, confirming the speed and mode of action of those compounds.
光敏化合物是有前景的环保型有机染料，可用于防治害虫且不存在抗性风险。在暴露于阳光下后，监测了四种光敏化合物（孟加拉玫瑰红、罗丹明B、亚甲蓝和甲基紫）对滨海灰翅夜蛾（Boisduval）三龄幼虫的光动力效果。这四种化合物；孟加拉玫瑰红、罗丹明B、亚甲蓝和甲基紫的LC值分别为0.029×10、0.24×10、14.69×10和15.59×10 M。因此，孟加拉玫瑰红是最有效的化合物，其次是罗丹明B、亚甲蓝和甲基紫。与之前记录的类似光敏剂化合物相比，这四种受试化合物的死亡率更高。通过测量幼虫的光谱和热反射率来评估这些化合物对幼虫生化成分的影响。以光敏化合物为食的幼虫表现出明显的光谱反射模式。处理后的幼虫具有相同的反射方式；均高于对照样品。在整个光谱范围内，对于孟加拉玫瑰红、罗丹明B和亚甲蓝，在暴露于阳光下60分钟后反射率最高。甲基紫在零时刻反射阳光最多，然后在30分钟后反射率下降，60分钟后再次上升。所有处理过的样品在~1900、1400、1200和950 nm处对红外波长有明显吸收。热成像显示处理后幼虫体温异常。喂食后立即监测反射率差异，证实了这些化合物的作用速度和方式。
