Garden invader is a term used to describe two common pests that can invade gardens and cause damage to plants. The first is an APHID, which is a small insect that feeds on the sap of plants, causing them to become weak and stunted. The second is a WEED, which is a plant that grows in an unwanted place and competes with other plants for resources. Both of these garden invaders can be difficult to control and can cause significant damage to gardens if left unchecked.