Xenocide (Ender, Book 3) (Ender Quartet)

On Lusitania, Ender finds a world where humans and pequeninos and the Hive Queen could all live together. However, Lusitania also harbors the descolada, a virus that kills all humans it infects, but which the pequeninos require in order to become adults. The Starways Congress so fears the effects of the descolada, should it escape from Lusitania, that they have ordered the destruction of the entire planet, and all who live there. With the Fleet on its way, a second xenocide seems inevitable.