Crested euphorbias (Euphorbia lactea 'Cristata') develop brown spots from several causes. Since the spots elongate with growth, they're likely physical damage or insect-related rather than spreading disease.
| Cause | Appearance | Timing | Action |
|---|---|---|---|
| Mechanical injury | Linear scars, elongate with growth | Appears weeks after damage | None needed; cosmetic only |
| Scale insects | Brown bumps; sticky residue | Progressive spread | Horticultural oil + systemic |
| Sunburn | Bleached then brown patches | After light change | Gradual acclimation |
| Fungal leaf spot | Concentric rings; yellow halo | Humid conditions | Fungicide; improve airflow |
| Edema | Corky, raised brown spots | Overwatering/cool temps | Reduce water; increase heat |
Important: Euphorbia sap is toxic—wear gloves, eye protection. Wash skin immediately if exposed.
Without photos, mechanical injury from handling or neighbor plants is the leading guess for elongating spots on crested forms.
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