They were given the plagues of the Rev. 15 seven angels. While the trumpets sound in heaven, the four angels on the earth caused the havoc for them.
to whom it was given
The four angels had to be given plagues after John saw them in Rev. 7:1. Six of those plagues had been given to them before the "another" angel spoke that had ascended from the east.
He also having a plague, now adds the trees being harmed to the four angels other chaos they will bring.