How to 'Parent' Image to Panning Background?

I painted a forest background and growing corn in Photoshop and imported them into Toon Boom. The background will be panning, however, I want the corn to pan with it but not appear until halfway through the scene. The way it’s working right now is the background is panning but the corn isn’t moving in tandem with the camera move like I want it to. Is there is a way to parent the corn movement with the background movement?

Parent them both to a peg. Move the peg and they will both move but now keyframe one independent of the other. For Transparency if you have Premium, you can add transparency as an effect to the corn layer and not to the background. You can then keyframe this effect independent of the background. I’m not familiar with Advance but that does have effects by layer. If transparency is one of those effects, you add transparency effect to that layer and keyframe it independent of the background. Since they are both parented to the peg, the peg provides the overall translation motions.