Is this catipillar poisonous
Hi - The caterpillars in your photo are out of focus. We would need to see a clearer photo in order to identify what these are. That said, there are few caterpillars that do have stinging hairs. They are pictured on this page of our website for comparison. https://extension.umd.edu/hgic/topics/stinging-caterpillars
You can wear gloves and pick off the caterpillars from your apple tree. You can drop them into a container of soapy water and discard them, or just toss them aside for birds to eat.