Charles Spurgeon Commentary Malachi 3:11

"And I will rebuke the devourer for your sakes, and he shall not destroy the fruits of your ground; neither shall your vine cast its fruit before the time in the field, saith Jehovah of hosts." — Malachi 3:11 (ASV)

The locust and the caterpillar came up and ate their harvests, all because God was angry with them; and He alone could change their miserable circumstances.