Maple trees are admired for their vibrant seasonal foliage. However, damage to their leaves is common. Understanding what causes this leaf consumption is a frequent concern for those who appreciate these trees. This article details the most common creatures that feed on maple leaves, providing insight into their feeding habits and the characteristic marks they leave behind.
Common Insect Herbivores of Maple Leaves
Insects are the most diverse and frequent group of maple leaf consumers. Caterpillars, the larval stage of moths and butterflies, are prominent defoliators. The forest tent caterpillar, a native insect, can cause significant defoliation across large areas, particularly favoring sugar maple trees. Their feeding can lead to reduced stem growth and an increased risk of decline, especially after repeated defoliation over several years. Another notable caterpillar is the spongy moth, an invasive species, whose larvae can consume a substantial amount of leaf tissue, sometimes stripping an entire tree of its leaves within days.
Aphids are tiny insects that feed by piercing leaf cells and sucking sap, often congregating on the undersides of leaves. This feeding can yellow, wrinkle, curl, or distort leaves, and may stunt new growth. Aphids also excrete a sticky, sugary substance called honeydew, which can attract black sooty mold. Mature maple trees often tolerate moderate aphid infestations, but young trees are more susceptible.
Leaf miners are the larvae of various insects, including certain flies, moths, and beetles, that tunnel and feed within the layers of a maple leaf. Their activity creates distinctive squiggly trails or blotches. Although the damage is primarily cosmetic and rarely leads to tree mortality, repeated infestations can weaken the tree over time.
Japanese beetles, characterized by their metallic copper and green bodies, are another common insect that feeds on maple leaves. Adult beetles consume the leaf tissue between the veins, leaving a lace-like, skeletonized appearance. Heavy infestations can cause leaves to brown and drop prematurely.
Spider mites, which are arachnids rather than insects, also feed on maple leaves. They pierce leaf cells and extract fluids, resulting in tiny speckles known as stippling. Extensive feeding can cause leaves to turn yellow or bronze and drop prematurely, and in severe cases, fine webbing may be visible.
Mammalian Browsers of Maple Leaves
Mammals also contribute to maple leaf consumption, though their impact often differs from insects. Deer are common browsers that feed on maple foliage, particularly targeting young shoots and saplings. Their browsing can concern newly planted or young maple trees, as extensive removal of tender growth impedes development.
Rabbits eat maple leaves, especially when other food sources are scarce. They may also gnaw on the bark of young trees. While some maple species, such as sugar and silver maples, are safe for rabbits in moderation, red maple leaves, especially when wilted or dried, can be toxic to them.
Squirrels primarily consume the winged seeds of maple trees, known as samaras. However, they can also chew on the bark of young maple trees, and may snap off small branches. The damage caused by mammalian browsers is more localized than widespread insect defoliation, but it can still be impactful, particularly for young or vulnerable maple trees.
Assessing Maple Leaf Damage
Identifying what is eating maple leaves involves examining damage patterns. Large, irregular holes or chewed edges indicate feeding by caterpillars or larger mammalian browsers like deer or rabbits. In contrast, Japanese beetles leave a distinctive lace-like pattern, consuming softer leaf tissue while leaving veins intact.
Tiny pinpricks or a stippled appearance, leading to yellowing or bronzing, suggest spider mites. Leaves that appear curled, distorted, or yellowed, accompanied by sticky honeydew and black sooty mold, are characteristic signs of aphid infestation. Squiggly trails or blotchy patterns within the leaf tissue point to leaf miners.
The severity of leaf consumption is important. Occasional leaf damage is common, and healthy, mature maple trees can withstand defoliation, often producing new leaves later in the growing season. However, extensive or repeated severe defoliation over multiple years can significantly stress a tree. This can lead to reduced growth, increased vulnerability to pests and diseases, and sometimes dieback or mortality. Careful observation of the type and extent of damage provides clues for evaluating tree health.