Certified Arborist Practice Exam

Systemic pesticides are taken up by the plant through its roots and are then spread throughout the plant's tissues, making them effective against pests that feed on different parts of the plant. Contact pesticides, on the other hand, only affect the parts of the plant that they come into direct contact with. Organophosphate pesticides are a type of contact pesticide and are not taken up by the plant. Protectant pesticides are applied directly to the surface of the plant and do not enter the plant's tissues, making them less effective against pests that feed on the plant's internal tissues. Therefore, systemic pesticides are the most effective choice for controlling pests that are present throughout the plant.