Mealy bugs

This is a mealybug (Pseudococcidae family - this one would be a female Pseudococcus longispinus), aka "the arch nemesis of many orchid growers", aka "teeny tiny kind-of-cute-Eldritch-Terror".

While it may look scary, there are some ways of preventing it and treating it efficiently:

• First of all, get a Safer's End-All spray if you don't have one already: this is an easy and efficient way to get rid of these pests without having to do a homemade blend of various substances.

• If you prefer making your own mix, you can use horticultural oil, a bit of rubbing alcohol, a few drops of dish soap or black soap and water. There are some very interesting techniques and recipes in this video: https://youtu.be/mYV2sdlvt-Y
  More info about horticultural oils here: https://extension.unr.edu/publication.aspx?PubID=3029

•  You can also dip a cotton ball swab in rubbing alcohol and dab the mealybugs: this will dry them out and kill them. Please note, however, that there might still be eggs and larvae left in some places that aren't easy to spot, so you'll have to pay a lot of attention over the next few weeks to make sure to eliminate all potential mealybug that would show.

• If there's a very large outbreak that you can't control easily, I would strongly advise unpotting the plants, putting them all bare roots in your bathtub or shower and spraying them thoroughly, both on the upper side and under side of the leaves, stems and roots. Let dry a bit, repeat the process in case you would have missed a few spots, and repot in fresh media.
  Make sure you properly wash all the pots and the grow space thoroughly as well, with water + soap + rubbing alcohol. You can also use bleach and rinse the pots thoroughly.

• Do a second spray application about two to three weeks after the first one, to eliminate potential larvae that would have hatched (they may not be visible yet), and keep close watch of your plants for at least a month (two months are better when the temperatures are cold since the developmental cycle can be slower in winter) to make sure that there's no surviving larva or adult.
  
   Hydrogen peroxide won't get rid of mealybugs, whether they are adults or larvae. Hydrogen peroxide is water-based and cannot break through the wax layer that Pseudococcidae excrete through their dermal pores. This wax (the white powdery substance they're covered in) is water-repellent, you need to add soap and/or alcohol to break this barrier down.
  Oil will coat the whole insect and make it suffocate but it is better to combine multiple techniques for maximum efficiency.

• It is important to note that females can and will reproduce asexually (same as for aphids), which means there can be larvae even if you've not seen any male flying around.
  

• Mealybugs like new growths, which are juicier than old ones. Inspect flower spikes, buds, new leaves on a daily basis if you suspect a mealybug infestation: these are the spots where you'll most likely see them.
  
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  For the ones who'd be wondering where this annoying sap-sucking bugger comes from, I bought a Calathea orbifolia a few weeks ago, there were both mealybugs and spider mites on her, I thought I had sprayed everything properly and kept her far enough from the orchids for the quarantine, but it seems some eggs or larvae might have fallen while I was unpacking the plant, hatched and one managed to get onto this orchid's blooms despite my careful (or at least I thought so) cleaning. Always make sure you clean very thoroughly and quarantine any new plant, in case that kind of issue would appear in the next few weeks following your purchase.

Oct 2021 - Diane Özdamar