You can stop Apple Podcasts from automatically downloading new episodes by following these steps:

1. Open the Podcasts app on your iPhone or iPad.
2. Tap on "Library" at the bottom of the screen.
3. Select the show that you want to manage.
4. Tap on the three dots in the upper right corner.
5. Tap on "Settings."
6. Tap on "Custom Settings."
7. Under "Episode Downloads," select "Off."

This will stop new episodes from automatically downloading. You can still manually download episodes by tapping on the cloud icon next to the episode's title.