Eucalyptus trees roots spread far and wide and also deep by the time they are 30 feet tall. Bare limbs, particularly on the upper part of the tree I usually associate with drought conditions. The trees are disease free as far as I know. Could some of the roots have gotten into an area with a weed killer? They may spread 40-50 feet depending where they an find water.

I think you have Koala bears. I'd look into that if I were you.

As Eucalptus grow, they lose older, lower branches; they get "pinched off" as the tree trunk grows in girth. Stripped leaves are common after wind storms and most Eucalyptus go through a heavier-than-normal leaf-drop period in spring, especially after frosts. There is an insect, called a eucalyptus psyllid or "Lerp" that is now found in California. The Psyllid forms a bump on the leaf and as it feeds, a sticky residue forms that can also attract black mold, much like when aphids feed. As far as anything actually eating leaves, nothing in the US as of yet...

Can Eucalyptus tree roots crack the slab of a house? I have two Eucalyptus trees within 30ft. of the house and I have a lot of cracks through out this house which is built on a slab. The cracks seem to have gotten worse over the last 5 yrs. Thanks Frank

If your trees are 30 feet from your home I don't think you have anything to worry about. Tree roots don't generally find their way under the stem wall which is usually 24 inches deep per code. However, there have been cases where the homeowner had a slab leak under the house that went undetected for a while and roots found their way in/under. Roots don't seek out water - its nearly impossible for them to grow through dry soil. The same can be said for septic lines. The roots get in because the line is cracked or has a bad seal.

That's really interesting about the roots. A Eucalyptus tree near our home that is over 40 years old just fell over. I wonder why.