Albert Barnes Commentary Exodus 10:5

"and they shall cover the face of the earth, so that one shall not be able to see the earth: and they shall eat the residue of that which is escaped, which remaineth unto you from the hail, and shall eat every tree which groweth for you out of the field:" — Exodus 10:5 (ASV)

The face - Literally, cover “the eye of the earth,” alluding to the darkness which follows, when the whole atmosphere is filled on all sides and to a great height by an innumerable quantity of these insects.

Shall eat every tree - Not only the leaves, but the branches and even the wood were attacked and devoured. The Egyptians were passionately fond of trees.