Compositions and methods for controlling plant pests are disclosed. In particular, novel nucleic acid sequences encoding modified Cry3A toxins having increased toxicity to corn rootworm are provided. By inserting a protease recognition site, such as cathepsin G, that is recognized by a gut protease of a target insect in at least one position of a Cry3A toxin a modified Cry3A toxin having significantly greater toxicity, particularly to western and northern corn rootworm is designed. Further, a method of making the modified Cry3A toxins and methods of using the modified cry3A nucleic acid sequences, for example in microorganisms to control insects or in transgenic plants to confer protection from insect damage, and a method of using the modified Cry3A toxins, and compositions and formulations comprising the modified Cry3A toxins, for example applying the modified Cry3A toxins or compositions or formulations to insect-infested areas, or to prophylactically treat insect-susceptible areas or plants to confer protection against the insect pests are disclosed.