The sudden disappearance of seedlings or the unexpected shredding of leaves can be frustrating. To successfully address plant damage, a gardener must accurately interpret the physical signs left behind. Analyzing damage patterns provides the necessary foundation for pinpointing the specific culprit, whether it is a large mammal or a microscopic pest.
Analyzing the Evidence: Identifying Damage Patterns
The initial step in identifying the pest involves closely examining the type of cut and the height at which the damage occurs. Feeding by larger mammals results in either a clean slice or a ragged tear, a distinction based on the animal’s dental structure. A clean cut, often at a 45-degree angle on a stem or twig, indicates an animal with both upper and lower incisors, such as a rabbit or woodchuck.
In contrast, a ragged or ripped edge on foliage or woody stems points toward an animal that lacks upper incisors, forcing them to tear plant material against a dental pad. The location of the damage also offers a significant clue, as browsing that occurs above three feet high is almost exclusively the work of deer. Damage consistently found within a foot of the ground suggests smaller, ground-level feeders like rabbits or voles.
Below-ground damage presents a different set of evidence, requiring an inspection of the soil surface. Voles, which are herbivores, create small, open burrow holes, typically one to two inches wide, often connected by visible surface runways through the grass. Pocket gophers, however, rarely appear above ground and create fan-shaped or crescent-shaped mounds of soil, usually with the main entry hole plugged. Moles create volcano-shaped mounds and raised ridges in the soil, but these tunnels are made while foraging for insects, not for consuming plant roots.
Small invertebrates and insects leave damage that falls into distinct categories based on their mouthparts. Chewing insects create holes, consume entire sections of leaves, or skeletonize the foliage by eating the soft tissue between the veins. Sap-sucking pests, which pierce the plant tissue to extract fluids, leave behind characteristic stippling, or tiny pinprick marks, leading to yellowing or distorted growth.
Common Mammalian Consumers of Garden Plants
Deer are identified by ragged, uneven edges on bark, twigs, or foliage, a result of their lower incisors pulling against their upper dental pad. Since they can reach up to six feet, browsing damage above the height of a small shrub is a strong indicator of deer activity.
Rabbits prefer tender young plants and seedlings, leaving behind small stems cleanly severed with a sharp knife. This characteristic 45-degree cut occurs very close to the ground. Rabbits also consume the bark around the base of young trees and shrubs, which can girdle and kill the plant.
Woodchucks, also known as groundhogs, are herbivores that can consume entire sections of a vegetable garden quickly. They are known for “mowing down” large patches of leafy greens, such as beans and squash. Their presence is often confirmed by large, conspicuous burrow entrances nearby.
Smaller rodents that cause damage include voles, which target roots and bulbs. They often girdle the bark of trees and shrubs just above or below the soil line, leaving irregular gnaw marks that are roughly one-sixteenth to one-eighth of an inch wide. Moles are primarily insectivores and do not consume plant material, though their tunnels can indirectly damage roots by creating air pockets.
Insect and Mollusk Pests: The Smaller Eaters
Slugs and snails, which are mollusks, create irregularly shaped holes in leaves and fruit, often preferring soft, low-hanging tissue. The most conclusive evidence of their presence is the silvery, dried slime trails they leave behind as they move across surfaces.
Caterpillars and beetle larvae are chewing insects that cause defoliation, consuming large portions of the leaf tissue. Many species are known as skeletonizers because they eat the soft green material while avoiding the tougher veins, giving the leaf a lacy, window-like appearance. Finding small, dark, pellet-like droppings, known as frass, near the damage is a strong indicator of caterpillar activity.
Aphids, mites, and whiteflies use piercing-sucking mouthparts to feed on plant sap, resulting in a different type of damage entirely. This sap removal causes a loss of chlorophyll, manifesting as a fine, speckled stippling or yellowing on the leaves. Heavy infestations can lead to distorted or curled new growth, and many of these pests excrete a sticky substance called honeydew.
Japanese beetles are a common example of chewing insects that cause severe skeletonization damage, particularly on the leaves of favored hosts like roses and crape myrtles. Their feeding removes all the green material between the veins, severely limiting the plant’s ability to photosynthesize.