Scale insects are the most common pest on a staghorn fern.  Our preferred treatment is denatured alcohol applied with a fine brush or cotton swab directly to the insects on the undersides of the fronds. The brown shells on the scale insects protect them from most sprays, but the alcohol should cause the insects to release their grip so that you can wipe them away with a damp cloth.

You need to find every insect and remove it and then reinspect the plant every ten days and remove any remaining insects. It is tedious and time-consuming but natural remedies work through determination rather than toxic impact. Ultimately it is the best way for you and your plant.

If the plant is too badly infested and the leaves are turning yellow, eradication may be impossible.

Courtesy of NYBG Plant Information