Q: This problem on my tulip poplar started twenty days ago. I noticed lots of the leaves are black and there are bumps on the twigs. Please look at the pictures and help me save my tree.
A: Your tulip poplar has a bad case of tuliptree scale. The bumps are female scale insects which stick tightly to the bark and suck sap from the tree. As she sucks, sap she can’t digest (honeydew) covers nearby leaves and sooty mold grown on it.
There are two good methods to control scale. First, control the baby scale in fall. Get a hose-end sprayer designed for use on trees and spray a garden insecticide (bifenthrin, esfenvalerate, lambda-cyhalothrin, etc) onto all branches you can reach.
Second, use the same sprayer to apply horticultural oil (Sunspray, dormant oil, Volck oil, etc) to the branches in February or March. The oil settles onto individual scales and suffocates them.
If you do this a couple of years in a row, the scale will disappear.
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