Q.Why is Eucalyptus tree shedding leaves?
I planted a lovely rainbow eucalyptus tree four months ago and it is about four feet tall now. This week, some of the leaves have turned red/orange and fallen off. I am very concerned. What might the problem be and what can I do about it?
Check soil conditions and watering. It may be the tree is stressed from being newly planted and the summer heat.
Inspect the tree, leaves and trunk for any other signs of insect or disease.
I am listing a link with common disease and issues with a Eucalyptus Tree.
https://www.gardeningknowhow.com/ornamental/trees/eucalyptus/eucalyptus-tree-problems.htm
If you feel the tree has a disease issue I would certainly contact the nursery it was purchased from.
A reputable garden center will likely guarantee the trees health.