Description: Blackening of Plumeria stems during propagation can be caused by fungal infections or cold damage. Causes: 1. Fungal infections: Pathogens, such as Phytophthora spp., can attack the stems, causing blackening and rot. 2. Cold damage: Exposure to freezing temperatures can damage the stems, leading to blackening and tissue death. Solutions: Fungicide treatment: Apply appropriate fungicides to control fungal infections and prevent further damage. Cold protection: Protect the cuttings from freezing temperatures by moving them indoors or providing proper insulation. Prune affected areas: If blackening occurs, carefully remove the affected parts using sanitized tools. Monitor and care: Regularly inspect the stems for any signs of blackening or rot and take appropriate action.