Is there an effective organic method to eliminate scale on lemon tree?

ive used dish soap mixed with water on crape myrtles. Just a kitchen sponge usually removes it easily.

Use a organic insecticide for Citrus trees.

if this is a potted plant, scale can be very difficult to remove. You have to treat them when the become active. also there are different kinds of scale. Sometimes you can wash them off with a mild spray of soapy water and wash the leaves thoroughly then take it outside and spray with garden hose to remove them then re apply spray to kill leftovers that you may have missed. you can also put a few drops of cooking oil in the water it would help smother the scale

Neem oil.