Yellowing, scorching, rot and spots are common disease symptoms in crops

Look closely at orchid leaves: apart from the normalorchidtip seal, there is nothing but yellowing, scorching, rot and spots.

Yellowing: the leaf color fades from pale to yellow from top to bottom, until the whole leaf turns an aged yellow; this is the most normal sign of the plant receding;

Scorching: the leaf tip dries and scorches, brown or pale brown, spreading from top to bottom at varying speeds; this is often caused by excessive dryness;

Rot: the leaf tip shows black rot from top to bottom, often rotting one section for every section cut, at varying speeds. This is mostly caused by excessive fertilizer and water;

Spots: spots can be regular or irregular. Regular ones are usually caused by invasion of pathological bacteria; irregular ones are often due to cold damage, sunburn, excessive pesticide application, or viral infection.