Final answer:
The stage in the viral reproduction cycle that is only found in the lysogenic cycle is the integration stage.
Step-by-step explanation:
The stage in the viral reproduction cycle that is only found in the lysogenic cycle is the integration stage. During this stage, the viral genome is incorporated into the host cell's genome and becomes a part of it. The integrated viral DNA, called a prophage, is then replicated along with the host cell's DNA during cell division.