What kind of eucs, folks?
Right now in my area, River Red Gums (Eucalyptus camaldulensis) have been hit particularly hard hit with lerp-forming-psyllid. The psyllids are relatives of aphids -- tiny, green to transluscent with sucking mouth parts. Preferred host is E. camaldulensis, hence the alternate common name, Red Gum Psyllid. There is enough info out there now that a web search will yield a ton of info for you.
Generally, the secretion is not the typical honeydew/syrup we are familiar with from the aphid family of insects. These secrete a sweet substance from the tail section as it whips it around forming a cone of the substance which crystalizes quickly (the lerp) (1/8- to 3/8-inch diameter dot, as tall). They live under this protective coating while they suck on the leaves. Can be a major stress on the host -- substantial leaf loss -- some trees in local neighborhoods eventually fail to produce new leaves.
UC has released some beneficials (parasites) in some neighborhoods. Other controls must get to psyllid in an early nymph stage before it forms the protective lerp. Else, the chemical of choice seems to be Merit(tm) as a soil injection taken up by the roots and translocated to the leaves being sucked on.
Though preferred host is Red Gum, heavy pressure will allow advance to other species (Blue Gum, Red Ironbark, Silver Dollar, etc.).
Then again, I could be completely on the wrong track as you mentioned "fish bones"....
Good Luck.
