Garden Pests and Diseases: Pest seems to be killing my lemon verbena tree. I don\'t know what it is! Help please!, 3 by acyment

acyment wrote:
Hi all! This is my first message to the forum. My garden is in Buenos Aires, Argentina (9a USDA equivalent). I believe my tree is a lemon verbena (we call it \"cedrón\" down here). It\'s had this pest for some time, but it seems to have gotten worse recently. I have asked a couple of gardeners about it, but they all either dismissed it or just plainly said they didn\'t know what the pest was.
Here are the pics. I hope someone can help me identify the pest!

Thanks in advance,
Alan