Their goal is to eliminate any insect that might eat valuable crops.(B) To be effective , a pesticide needs to be absorbed through the surface of the plant tissue.(C) When a pets,like an insect.slug.snail or mouse starts to nilbble on a plant , the pets ingests the chemical and is destroyed.(D) One common type of pesticide is called a herbicide.Herbicides can be used to clear roadside weeds,trees and brush.They can also kill weeds that may cause environmental damage.