The reference to the devourer
is most often a reference to the plague of locusts which destroyed the crops (Joel 2:25; Psalm 78:46). It could also refer to blight and mildew, which also destroyed the fruit of the land (Amos 4:9), or to the caterpillar (1 Kings 8:37).
11 I will rebuke the devourer for you, so that it will not destroy the fruits of your soil, and your vine in the field shall not fail to bear, says the LORD of hosts.