Spotted lanternflies primarily feed on the sap of a wide variety of plants. Their preferred host is the Tree of Heaven (Ailanthus altissima), but they also feed on over 70 different plant species including fruit trees (such as apples, cherries, peaches, nectarines, plums), grapevines, walnuts, maples (especially silver and red maple), oaks, hops, and various hardwood trees. They also feed on vegetables, herbs, grains, and ornamental trees

. They use a specialized straw-like mouthpart called a proboscis to pierce the phloem tissue of leaves, stems, and trunks to suck sap. They do not chew leaves or fruit but extract nutrients directly from the plant's vascular system. This feeding causes damage to the plants, including "weeping" wounds from sap excretion, reduced photosynthesis due to mold growth encouraged by their sugary waste (honeydew), and can lead to weakened or even killed plants

. In summary, lanternflies eat sap from a broad range of plants, favoring Tree of Heaven, walnuts, grapevines, and many fruit and hardwood trees, making them a significant agricultural and ecological pest.