Carpenter ants often infest cherry blossom and other trees. Although they might be crawling all over your cherry blossom, they are not actually eating its wood. Carpenter ants eat insects and the honeydew that certain tree insects excrete. They do, however, tunnel through the dead or dying wood of cherry blossom trees. After you kill the carpenter ants, call a tree doctor to come out and inspect your tree.
Monitor the carpenter ants' activity to discover where their nests or main area of activity are. Carpenter ants are the most active between sundown and midnight.
Dust the tree with an insecticide such as Sevin or rotenone that is listed as safe to use on trees. Concentrate the dust on areas where you noticed carpenter ant activity. Get the dust into any cavities, visible ant tunnels or holes. Follow the manufacturer's instructions for application rates and amounts.
Examine the tree for and prune any dead or dying limbs.
Re-dust the cherry blossom tree with insecticide as needed at the intervals prescribed by the manufacturer.