Orchids are relatively pest-free, but they are susceptible to some common ornamental plant pests. Prevention, early treatment and maintaining healthy plants will keep unsightly and potentially damaging infestations under control.
Several sap-sucking insects will attack orchids such as hard and soft scale, aphids and mealy bugs. These insects are very small, sometimes too small to see with the naked eye in their juvenile form. They use piercing mouths to slowly suck the sap from leaves, stems flowers and roots, potentially causing deformations or plant death.
Mealy bugs are soft-bodied and look like they are covered with white or pinkish woolly coat. They are about an eighth of an inch at the largest and sometimes much smaller. They hide between leaves and under dried flower and stem sheaths as well as in the roots. They excrete a sticky dew that will develop a sooty mould covering over time that is attractive to ants.
For spot treatment of sap-sucking insects on orchids, including mealybugs, simply wipe them off with a cotton swab dipped in rubbing alcohol. Larger infestations may need commercial ornamental plant insecticide treatments or insecticidal soaps rated for orchids. Prevention is the best method of pest control. Stable humidity, good airflow and a sanitary growing area will aid in prevention.