Significance Thrips are a group of piercing-sucking pest insects that do massive damage in agriculture and horticulture. The western flower thrip is a particularly notorious pest that has spread all over the world and is extremely difficult to control. In this work, we have shown that upon feeding, thrips take up substantial quantities of chloroplast RNA. When we expressed from the chloroplast genome long double-stranded RNAs that are targeted against essential thrip genes, the RNAs induced a potent RNA interference response and efficiently killed the insects. Our study demonstrates that an important group of nonchewing pest insects can be targeted by plant-mediated RNA interference and provides an efficient weapon to control thrips and other sucking plant pests.