Orchid infestation

(Question)

My orchid seems to have white bugs/white fluff all over it — what is the solution for this infestation?

 

 

(Answer)

There are several pests that can infest orchids.  It is important to correctly identify the pest so that you can understand how to get rid of it.   Your infestation sounds like mealybugs, although it could be spider mites.  I’ve outlined how to treat each infestation – note that there is considerable overlap in how these are managed.   And in the end, it may be difficult to eradicate the infestation (especially if it’s mealybugs) – if the plant continues to decline even after all your efforts, consider destroying it.

Mealybugs are nearly impossible to control when they are in the egg sac and it is also hard to get rid of the adults.  It is best to “attack” mealybugs when they are in the juvenile stage, when most soaps or sprays are effective.  These critters may be present on any part of the plants, but especially the roots and undersides of the leaves.  They can hide in the potting medium so may be difficult to find.  Mealybugs may wander away from the orchid, seeking food, and are sometimes found on pots and trays (check under the rims).  They love to crawl between plants and are even light enough to be spread among plants by air currents (both indoors and out).  To control mealy bugs:

  • Immediately isolate the infested plants from other houseplants
  • Horticultural oil and insecticidal soap sprays are available from your gardening centre and are effective against mealybugs (oils smother the critters – so the plant must be completely covered by the oil). If you use these agents, follow directions carefully.
  • Replace the soil/potting medium the orchid is in and flush the roots with distilled water before repotting it in fresh orchid soil.
  • Treat every 10-14 days to make sure you are getting rid of future generations of the bugs.

Spider mites can spin silky webs that are especially visible on the undersides of leaves.  Mites thrive when it is warm and dry and are a particular nuisance during the winter.  They suck the sap from cells on the surfaces of leaves. To combat mites:

  • Raise the humidity: wash the plant thoroughly, ensuring you wipe every leaf – both on the tops and undersides (be gentle and use a soft sponge). Mist the orchid regularly or place it in a tray that contains water and pebbles (so the plant will not be sitting directly in water).  Instead, you could gently spray water onto the orchid leaves to dislodge the mites. Keep doing this at least twice a week for 5-6 weeks.
  • If this is not enough, spray the plant with insecticidal soap (again, make sure you cover both sides of the leaves).
  • Horticultural oil and insecticidal soaps are available from your gardening centre and are effective against mites (oils smother the critters – so the plant must be completely covered by the oil). If you use these agents, follow directions carefully.
  • Once the weather is sufficiently warm, put the orchid outside so that the mites’ natural enemies can attack them.
  • It is also important to replace the soil the orchid is in (since it may harbour eggs and live mites); flush the roots with distilled water before repotting it in fresh orchid soil.
  • Keep the infested plant isolated from other plants until the mites are gone.

For more detailed information, see the American Orchid Society’s page on Orchid Ailments.

You could also refer to this page from the Canadian Orchid Congress: Do you have bugs? Don’t panic! https://www.canadianorchidcongress.ca/pests1.html

For a review of pesticides permitted in Ontario, here is a link to the government website: https://www.ontario.ca/environment-and-energy/pesticides-home-lawns-and-gardens