Scale Insects from Orchid
On January 16, 2014, Sandy noticed that one of her orchids had little brown things stuck all over its leaves (mainly near the leaf bases). It was hard to tell what they were, they looked like little dried spatters of something. But, on close examination, it turned out that they were scale insects[1].
They came in several sizes. That first one was about 4 mm in diameter, and this next one was only about half that size. It doesn’t have much in the way of discernable features, other than two dark spots on the lower left edge that look like they might be eyes.
When I popped one of the biggest ones off and flipped it over, it turned out to have a whole bunch of newly-hatched nymphs under its shell, with the nymphs being about half a millimeter long (and practically impossible to photograph). The nymphs look like they have functional legs, and appear to be much more insect-like than their mother.
There are several common scale pests of potted orchids, and these look a great deal like Soft Brown Scale, Coccus hesperidium. This is a very common pest not only of orchids, but also of many different common houseplants, particularly ferns.
It is reportedly possible (but difficult) to eradicate these with a combination of scrubbing with insecticidal soaps, application of things like neem oil, and maybe even fumigating the plant with pesticides. But, given that this was just one of several inexpensive orchids that Sandy had bought on sale at WalMart[2] (and she’s chronically short of good windowsill space for plants anyway), we decided that simplicity was best, so we just put it outside. At the time, the outdoor temperature was around zero Fahrenheit[3], so that was pretty much all she wrote for both the plant, and for the scale insects. We haven’t found these scale on any other potted plants since then, so this was evidently the most appropriate solution to the problem.
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[1] These are distinct from the Fringed Orchid Aphids that we found on one of Sandy’s orchids back in 2010. The treatment was the same, though: set the plant out in subzero cold to freeze out the little buggers.
[2] Wal-Mart sells these rather pretty orchids, with individual blooms that last for weeks, and that are not all that cheap while the blooms are fresh. But then, once the blossoms start falling off, they sell off the plants at a steep discount just to get rid of them. But Sandy has found that if she buys the cheap ones and babies them along for a few months, they will re-bloom for her pretty reliably. So she can have beautiful flowers for a fraction of the cost.
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I might have to clear Wal-Mart’s good name here. I think the infected orchid may have been a gift from Tony.