Horticulture seed treatment or seed dressing is a chemical, typically antimicrobial or fungicidal, with which seeds are treated (or "dressed") prior to planting. Less frequently insecticides are added. Seed treatments can be an environmentally more friendly way of using pesticides as the amounts used can be very small. It is usual to add colour to make treated seed less attractive to birds, and easier to see and clean up in the case of an accidental spillage. Specialist machinery is required to safely and efficiently apply the chemical to the seed. A seed coating is a thicker form of covering of seed and may contain fertilizer, growth promoters and or seed treatment as well as an inert carrier and a polymer outer shell. The term "seed dressing" is also used to refer to the process of removing chaff, weed seeds and straw from a seed stock.