A contact pesticide is a pesticide that remains on the surface where it is applied and affects pests or pathogens only through direct exposure. Unlike systemic pesticides, it is not absorbed and transported through the plant’s vascular system. Contact pesticides are available as insecticides, fungicides, and herbicides.
Contact insecticides work when the active ingredient touches the insect or when the insect contacts a treated surface. Contact fungicides form a protective barrier on leaves and stems, preventing fungal spores from germinating or infecting plant tissue. Because they remain on the plant’s surface, they are often less effective against pests that feed inside leaves, stems, or roots, or insects protected by waxy coatings or hidden locations.
Most contact pesticides require thorough coverage of the plant and may need to be reapplied after new growth emerges, heavy rainfall, or irrigation removes the protective residue. Their effectiveness depends on the active ingredient, application quality, and the biology of the target pest or pathogen.
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