A systemic pesticide is a pesticide that is absorbed by a plant and transported through its tissues, allowing it to protect the plant from within rather than remaining only on the surface. Depending on the product and the plant, movement may occur primarily through the xylem (upward with water) or, less commonly, through both the xylem and phloem. Systemic pesticides are available as insecticides, fungicides, and, in some cases, herbicides.
Because the active ingredient is inside the plant, systemic pesticides can control pests or pathogens that are difficult to reach with contact sprays, including sap-feeding insects such as aphids, mealybugs, scale insects, and whiteflies. They are generally applied as soil drenches, granules, trunk injections, or foliar sprays that are subsequently absorbed by the plant. Systemic activity develops over time as the product is taken up and distributed through new growth.
A systemic pesticide differs from a contact pesticide, which only affects pests or pathogens that are directly exposed to the product. Not all pesticides labelled as “systemic” move throughout the entire plant, and the extent of movement depends on the active ingredient, plant species, and method of application.
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