A versatile addition to your home’s landscape, maple trees (Acer) grow throughout U.S. Department of Agriculture plant hardiness zones 3 through 9, depending on the species. Worms can visit maples, using these stunning trees as a food source, home and shelter. Knowing which worms use maples as a host plant and the signs to look for can help protect the tree from damage. Flathead Borers Flathead borers are the larval stage of a metallic-colored beetle, which attacks various species of trees including maples. The most distinctive feature of flathead borers is the flattened enlargement behind its small head. These worm-like creatures infest trees stressed or injured by environmental conditions and create tunnels beneath the bark as they bore into the tree. The tunnels often cause a damp, sappy area to appear on the trunk that later crack. The damage can kill limbs or the entire tree. Chemical sprays are not usually warranted, so preventive measures prove the best defense against flathead borers. Avoid pruning when adult beetles are active (from spring through summer), remove dead limbs and destroy immediately, refrain from piling freshly cut wood near maple trees and provide adequate irrigation to prevent infestations. Carpenter worms Carpenter worms are the wood-boring larval stage of a large black and gray moth. These caterpillars feed on the inner bark of the maple tree’s sapwood. Darkened sap spots on the trunk are the first signs of carpenter worms. The excrement and sawdust carpenter worms expel are visible near entrance holes the larva create. In extreme infestations, carpenter worms can weaken branches, which increases the chance of breakage during high winds. Their feeding can also lead to branch dieback. Beneficial nematodes injected into the tunnel entrances can help control carpenter worms, but proper cultural care should be implemented before treating the maple tree with nematodes. Foliage-Feeding Caterpillars The larval stage of butterflies and moths -- commonly called caterpillars -- feed on the leaves of maple trees. Their feeding typically won’t cause long-term harm to healthy trees, but defoliation and branch dieback can occur in severe infestations. Control foliage-feeding caterpillars by treating the tree with Bacillus thuringiensis, handpicking the worms off the tree, keeping the tree properly watered and fertilized, and attracting beneficial predators -- such as spiders and birds -- to the area. Leaf rollers The larvae of tortricid moths -- called leaf rollers -- consume the foliage of maple trees and curl, roll or tie the leaves they are consuming with a webbing-like material. The adult tortricid moths lay their eggs on twigs and branches where the eggs overwinter until they hatch in the spring. A healthy maple tree can usually withstand a leaf roller infestation. In extreme cases, defoliation can occur, but healthy trees can usually recover. Control leaf rollers with Bacillus thuringiensis and beneficial predator insects, such as tachinid flies, assassin bugs and lacewings. Other Worms Other species of worms can visit maple trees. These worms include cankerworms (also known as inchworms), tent caterpillars and bagworms. Cankerworms are 1-inch long green worms that feed on the leaves, creating holes that have an appearance similar to a BB shot. The holes grow as the worms grow. Tent caterpillars are black with distinguishable hairs covering their bodies. They create a webbed housing in host trees where hundreds of worms congregate. Detected by their “bags” made from a silk-like material and plant debris that hang down from the host tree, bagworms feed on the leaves of evergreen and deciduous trees and shrubs. Insecticides containing carbaryl, permethrin or malathion as the active ingredient will kill cankerworms, tent caterpillars and bagworms but also pose a threat to beneficial insects. A safer option is the bacterium pesticide Bacillus thuringiensis, which is applied to the tree as a foliar spray. -Birdy [Sorry for sauch a lengthy answer, but it is necessary so that the asker can understand the problem -Birdy).