They were told not to harm the grass of the earth or any plant or tree, but only those who did not have the seal of God on their foreheads.
Textus Receptus (TR) - Revelation 9:4 >Καὶ ἐρρέθη αὐταῖς ἵνα μὴ ἀδικήσωσι τὸν χόρτον τῆς γῆς, οὐδὲ πᾶν χλωρόν, οὐδὲ πᾶν δένδρον, εἰ μὴ τοὺς ἀνθρώπους μόνους οἵτινες οὐκ ἔχουσι τὴν σφραγῖδα τοῦ Θεοῦ ἐπὶ τῶν μετώπων αὐτῶν.