They are in plague proportions in some areas of Vic. They do a hell of a lot of damage on Pines especially JBP. They unravel the sheath and im guessing they chew around the base of the needles, resulting in the needles falling out very easily. I would also imagine that this causes damage to future buds. I have been running around the garden each morning for the last 2 weeks picking them off and squashing them. This weekend has been the worst, heaps of them. They do park on other trees but im sure they are just waiting for me to leave so they can jump back on my JBP's. They also like Juniper and i think they do the same thing there. Who ever has pines out there and sees these in their garden do not be fooled that they are harmless, they are not !!!
