Pesticides can be classified based upon their biological mechanism function or application method. Most pesticides work by poisoning pests. A systemic pesticide moves inside a plant following absorption by the plant. With insecticides and most fungicides, this movement is usually upward (through the xylem) and outward. Increased efficiency may be a result. Systemic insecticides, which poison pollen and nectar in the flowers[citation needed], may kill bees and other needed pollinators[citation needed].
What is the main way that peticides perform their function?
{'text': 'by poisoning pests', 'answer_start': 120}