In the sixth aliyah G-d starts the plague of noxious animals with serpents and scorpions swarming into Pharaoh's palace and everyone else's house in Egypt, and the land is ruined except for the land of Goshen. Pharaoh calls Moshe and Aharon and tells them that the Jews can sacrifice to G-d. The plague ends and Pharaoh changes his mind and reneges on his promise.
Next is the plague of heavy pestilence on the Egyptians' cattle, horses, donkeys, camels, herds and flocks. All of these animals die, but none of the Jews' animals are affected.
Next is the plague of extremely painful leprous boils that cover all Egyptian men and beasts; but Pharaoh still doesn't release the Jews.