Hello. Yellowing of the leaves, drying of their edges, and the appearance of dark spots on their surface may be caused by environmental and care factors (high humidity in the soil and in the atmosphere, inadequate temperatures, insufficient or excessive light, inadequate watering, and fertilization, etc.) or by a disease. In this case, it is recommended to remove the heavily affected leaves and to remove the decorative layer of pebbles at the base of the plant, as it maintains a constant and high humidity in the soil, favoring the installation and development of phytopathogens. Subsequently, you may consider one treatment with a fungicide such as , in a dose of 20 g/10 L water, applied by uniform spraying on the plant ().
At the same time with the foliar treatment with fungicide, it is recommended to use a natural fertilizer that improves the quality of the soil, supports root development, increasing the plant’s resistance to stress factors, such as . Can be administered by watering, in a dose of 5 ml/1 liter of water. It is recommended to carry out 2-3 treatments at intervals of 10-14 days. As the symptoms of yellowing are similar to those caused by lack of nutrients (Nutrient deficiency and excess in plants), it is recommended to regularly apply a fertilizer with an optimal content of micro-nutrients, and iron-chelate, with the effect of increasing the optimal growth and development of plants: or , by foliar spraying, according to the instructions in the product description. The first application is recommended to be done 10-14 days after foliar fungicide treatment.
Further, it is recommended to follow the general care conditions detailed in our article: Strelitzia, plant care and growing guide. Given the current appearance of the plant and the above-mentioned, it is not possible to say exactly how it will develop in the future.