Jamieson, Fausset and Brown on Joel 1:7

7. barked--Bochart, with the Septuagint and Syriac, translates, from an Arabic root, "hath broken," namely, the topmost shoots, which locusts most feed on. Calvin supports English Version.

my vine ... my fig tree--being in "My land," that is, Jehovah's (Joe 1:6). As to the vine-abounding nature of ancient Palestine, see Nu 13:23, 24.

cast it away--down to the ground.

branches ... white--both from the bark being stripped off (Ge 30:37), and from the branches drying up through the trunk, both bark and wood being eaten up below by the locusts.