From my vantage point, as a Begonia, those brown spots on my leaves are a cry for help. They are a visible symptom of distress, disrupting my beautiful foliage and, more importantly, my ability to photosynthesize. These spots are not a single condition but a sign that my environment or my internal health is out of balance. It is crucial to correctly diagnose the cause, as the remedies for a fungal attack are vastly different from the remedies for a sunburn injury.
When a fungal pathogen, such as *Botrytis* (gray mold) or *Pythium*, attacks me, it is a systemic issue. The brown spots often begin as smaller, water-soaked lesions, typically on the lower or inner leaves where humidity is highest and air circulation is poor. These spots may have a yellow halo surrounding them, a clear indication of an active infection. As the fungus progresses, the spots can enlarge, merge, and develop a fuzzy, grayish, or dark, concentric ring appearance. The damage is often asymmetrical and can appear anywhere on my leaf surface. This is a disease spreading through my tissues, and without intervention, it can lead to leaf drop, stem rot, and a severe decline in my overall health.
In contrast, sunburn is a purely physical injury caused by excessive light intensity. My leaves are adapted to bright, indirect light. When suddenly exposed to intense, direct sunlight—especially through a window pane that acts like a magnifying glass—the delicate chloroplasts within my cells are literally scorched. The resulting brown spots are typically dry, crispy, and papery to the touch. They appear on the areas most exposed to the light source, often the topmost leaves or the side facing the sun. The spots are usually uniform in color (a light tan to dark brown) and lack the yellow halos or fuzzy growth characteristic of fungus. The damage is immediate and does not spread over time like an infection would.
Your response to my brown spots must be tailored to the cause. For a suspected fungal issue, I need you to immediately improve air circulation around me and avoid wetting my leaves during watering. Please remove the severely affected leaves with sterile shears to prevent further spore release. You may need to apply an appropriate fungicide, but the primary cure is correcting the damp, stagnant conditions the fungus thrives in. For sunburn, the solution is simpler but no less urgent. You must relocate me immediately to a spot with bright but filtered light. The damaged leaves will not recover their green color, but you can prune them for aesthetics once the plant has stabilized. Please acclimate me gradually to any new, brighter locations in the future to prevent a repeat of this trauma.
