Prior to insecticides, locusts were a terrible problem. Every few years a cloud of grasshoppers would descend and eat every green thing. In a field, they would reduce the crop to bare, brown earth. They would eat the grass in the lawn and the thistles in the vacant lot next door. Locusts have been known to eat the green spots out of a tablecloth hung on a clothesline.
Locusts destroy every living green thing.
A plague of locusts emotionally and spiritually devastates a community. That's the experience this woman has. Every living thing has been sucked out of her life. When she goes to the market, all she can do is look down, and she sees only the tops of dusty sandals coming toward her. Her life has no joy.