A foam marking attachment to a lawn and garden tractor or tractor mounted agricultural implement spray apparatus attaches to a low voltage DC power supply of the tractor, applying a left or right side droplet of liquid marking foam to the outer edge of a traveled path, marking the traveled edge of application of a liquid spray from the spray apparatus, preventing over application to an area to be treated with the liquid spray and preventing non-application of the liquid spray the area to be treated with the liquid spray. The attachment may be used when applying liquid fertilizer, pesticide or herbicide to a golf course, yard, field, garden plot or other landscape area, and is used in place of colored spray or dyes which discolor the treated area and may be transferred to person, other objects or clothing. The attachment is best suited for golf courses and yards where people, clothing and pets often become discolored for an extended period after application of currently used dyes and colored sprays, which are difficult to remove from skin, hair and clothing.