Complex sentence: Neonicotinoids are the first new class of insecticides introduced in the last 50 years, and the neonicotinoid imidacloprid is currently the most widely used insecticide in the world.
Split into simpler sentences: Neonicotinoids are the first new class of insecticides to be developed in the last 50 years. The neonicotinoid imidacloprid is currently the most widely used insecticide in the world.