The Dreamstone (1990)

Zordrack comands the Uprneys to wipe out the Wutts, Sgt. Blob deploys special bugs which devour all of the Wutts' flying leaves and they soon begin attacking the entire forest. Only the power of Wildit's magic whistle, capable of controlling all of the Wutts' leaves and the forest animals, can save the day, but he is away teaching Rufus and Amberly flying lessons and is unaware of the destruction...