Years go by and the regulars are out there on the trees -  red scale, broad mite, citrus thrips, bud mite, leafminer and more and more Asian citrus psyllid.  And then suddenly one that has seemed to be just in the background pops up all over the place.  What is it about the weather, the interaction of other agents like spray programs or harvest interval or rise of others that push the balance allowing an otherwise less common pest to show up?  Purple scale has generally been in the background, out there, but not prominent in backyard citrus.  In the last two weeks I've gotten six calls about the "sudden appearance" of this scale.  It likes cool, but not cold; warm, but not hot.  Perfectly adapted to the winter this year which probably slowed down the biocontrol agents, like wasps and ladybird beetles.

You can read more about the insect and its control at the UC Integrated Pest Management website.