Using rub visible light image of a plant to make rub mask for the infra red image of the same plant

Hello all and I appreciate guiding me through my answer in advance. I have an infrared and an RGB image of a plant. I should do segmentation on the infrared image.But the plant is not that visible and I don't know how should I do segmentation for such an image. How could I make RGB mask on the infrared image?I attached both images.Thanks so much.