The plant in the pics is already dead. I've checked the others and none seem to have it. How can I best prevent it from spreading to them?
Hey yoquierotacobell,
Unfortunate about your loss, but no point crying over spilt milk.
Scales destroy plants by sucking the sap out of it. As a by product they product a sticky sweet dew which subsequently attracts other undesired pests.
Although hard to notice you can first catch it with a stunt in growth of said plant. But generally looking for them around your stem joints is always good measure.
In terms of removal, people were right in recommending hand removal with rubbing alcohol. For the ones that have a tighter grip on your plant a sterile blade or tweezers will work.
As for prevention I wish I could say more than look out for them when you check your plants. I am not one for comercial pesticides but if you wanted a deterrent, these pests and many more of their sort are turned of by strong scents/tastes, i.e. hot sauce, strong citruses like lemons, garlic or even some neem. Typically you would create a liquid with elements like these which you can then spray coat your foliage with.
Hope that helps.
