Mealy Bugs

• Appearing as cotton-covered ellipses nestled in the crooks of stems, the underside surface of leaves and on plant roots, mealy bugs can spell doom for a fern. The first noticeable sign of an infestation is often the honeydew -- a clear, sticky fluid emitted by the bugs after they feed. The honeydew, in turn, fosters black sooty mold. Once the mealy bugs are removed, which can be done manually in slight infestations, the honeydew and mold can be gently washed away with a spray of water. In heavy infestations, a soil drench of an approved insecticide may be necessary to eliminate eggs and larvae.
  
  

Flying Pests

• Fungus gnats and thrips are two detrimental pests that favor ferns. Fungus gnats are 1/8-inch-long black flies that flit around your plant, excreting waste and feeding on fungus that grows on the soil surface. The damage they cause is from the transparent maggot-like larvae that feed on the roots and lowest parts of the plant, weakening its immunity against disease and infections. Fungus gnat adults can be seen scurrying over the leaves and soil surface more often than they are seen flying.
  
  Thrips are less than 1/20 inch in length, with a slender body and a fringe around their wings. They come in different colors depending on the species and feed on plant leaves. They transmit diseases to the ferns, and their feeding habits cause the leaves to curl and distort, leaving calluses and scars and affecting the plant's overall appearance.
  
  

Mites

• The mite that most often attacks ferns is called the false spider mite. They look like tiny red specks on your fern's leaves. They deposit oval red eggs on the leaves. Since they are so tiny, they sometimes are not noticed at all until the plant is severely damaged and dropping leaves. New shoots may also begin to die. Early symptoms are spots that are small and brown on the leaves; they later become a rusty color.
  
  

Scales

• These bugs are often perfectly camouflaged on their host plant, appearing like unmoving flecks of plant matter on leaves and stems. They can be smaller than a pinpoint or as long as 2 mm; their colors vary greatly. They stunt the growth of a plant, eventually killing it in the case of large infestations. They can be treated in the same way as mealy bugs.