The locusts attacked the field of perennial grasses and destroyed all the green mass.

The locusts attacked the field of perennial grasses and destroyed all the green mass. The next year the field bore a special harvest. Why?

If locusts have destroyed old vegetation that prevented new growth from germinating, then the field could have yielded more abundant crops. But if the locusts destroyed the perennials that adapt well to the environment, then poisonous plants could grow in the field that adapted to the attacks of the locusts. Thus, the plant has developed protection from insects and in the future the locusts will simply die by eating these plants.