nurtomiRust-colored spots
Rust diseases can produce small powdery pustules.
What to look for
Check leaf undersides for raised orange, brown or yellow pustules and compare them with marks on the upper surface. Similar spots can have other causes; the host plant and pattern matter.
What to do
Remove affected fallen leaves and, when practical, badly affected foliage. Give plants room for airflow and avoid overhead watering. If new leaves develop the same pattern, consult plant-specific guidance.