Black Spots
Black spots on leaves can indicate fungal disease, bacterial infection, or severe environmental stress. The cause matters for treatment.
考えられる原因
Fungal Black Spot Disease
Why: Fungal pathogens cause dark spots that expand and may cause leaf drop. Common on roses and other susceptible plants.
Signs to check: Round black spots with fringed or feathery edges, leaves yellow around spots and drop.
Bacterial Infection
Why: Bacteria can cause dark, water-soaked lesions that turn black as tissue dies.
Signs to check: Irregular black areas that may appear greasy or water-soaked, may have a foul smell.
Cold Damage
Why: Exposure to freezing or near-freezing temperatures causes cell death, appearing as black patches.
Signs to check: Black areas appeared after cold exposure, tissue is soft and water-soaked initially.
Severe Overwatering
Why: Chronic overwatering can cause dark spots as root damage leads to tissue death in leaves.
Signs to check: Black spots accompanied by yellowing, mushy stems, and constantly wet soil.
確認ポイント
- 1Note the shape and texture of the black spots
- 2Check if spots are dry and crispy or wet and mushy
- 3Review recent temperature exposure — any cold events?
- 4Assess soil moisture and watering habits
- 5Check for spreading to other leaves or plants
対処法
- Remove and discard all affected leaves — do not compost them
- Improve air circulation and avoid wetting foliage
- If fungal, apply a copper-based fungicide following label directions
- If cold damage, move to a warmer location and avoid further exposure
- Sterilize pruning tools between cuts to avoid spreading pathogens
専門家に相談するタイミング
- Black spots are spreading rapidly across the plant
- Stems or crown are turning black (may be fatal)
- Strong foul odor accompanies the black areas
ポイント
Black spots are more serious than brown spots and often indicate disease. Remove affected tissue promptly and identify the cause to prevent spread.
アプリで回復を追跡
進捗を記録し、リマインダーを設定し、AI による診断を受けましょう。
情報源: Missouri Botanical Garden, RHS, NC State Extension. 教育目的で公開されている園芸資料をまとめたコンテンツです。情報源の組織は透明性のためにのみ記載されており、推薦を意味するものではありません。