Erwinia amylovora enters host tissue through

Erwinia amylovora enters host tissue through Nectaries.
Erwinia amylovora is the causative agent of fire blight, a devastating necrotic disease affecting apple, pear, and other rosaceous plants. Entry of the bacterium into plants can occur via flower blossoms or actively growing young shoots or through wounds.
The infected flowers remain attached to the cluster base even as it dies, allowing for infection to spread to other flowers on the same cluster.