Marigolds, belonging to the genus Tagetes, are often planted because their pungent aroma is expected to repel garden pests. This fragrance comes from chemical compounds, including terpenes and thiophenes. While these chemicals deter many common herbivores, they do not make the plants completely immune to feeding pressure. Certain specialized feeders and generalist consumers have adapted to tolerate or even prefer the taste of these flowering annuals.
Small Garden Pests That Target Marigolds
Small invertebrate pests are the most frequent source of damage to marigolds, often focusing on the softer tissues. Mollusks, such as slugs and snails, are particularly attracted to delicate, newly emerged foliage and soft flower petals. These gastropods thrive in damp conditions and scrape away plant material, leaving behind large, ragged holes.
Other common offenders are chewing insects that consume the plant tissue directly, creating visible breaks in the leaf structure. Larvae from various moth and butterfly species, commonly called caterpillars, devour large sections of a leaf, sometimes skeletonizing it by eating the soft parts between the veins. Grasshoppers also clip and chew through the leaves, creating irregular holes along the edges and in the center.
A distinct category of tiny pests includes piercing-sucking feeders, such as spider mites and thrips. These organisms do not consume leaf tissue but instead puncture epidermal cells to extract internal plant juices. This feeding causes the leaves to develop a fine, speckled pattern known as stippling, which sometimes progresses into a bronze or yellow discoloration. Spider mites often feed on the undersides of leaves, causing widespread damage.
Larger Mammals That Graze on Marigolds
When entire plants or large sections of foliage disappear overnight, the damage is caused by larger mammalian herbivores. Rabbits are frequent culprits, especially targeting young marigold transplants. They use their sharp incisors to make a clean, diagonal cut through the stem, often consuming the plant down to the ground level.
Deer also readily browse on marigolds, preferring soft terminal buds and flowers over older, tougher leaves. Since deer lack lower canine and incisor teeth, they tear the plant material away, resulting in a distinctly ragged and uneven appearance on the remaining stems. This browsing occurs higher up on the plant canopy compared to the ground-level feeding of smaller animals.
Groundhogs, while more selective in their diet, will occasionally feed on marigolds when other preferred food sources are scarce. The damage from groundhogs resembles that of rabbits, involving the clipping of stems, but often involves consumption of a larger volume of plant material.
Distinguishing Pests by the Damage Left Behind
Identifying the specific organism responsible for marigold damage relies on examining the physical evidence left on and around the plant.
Mammalian Damage
When an entire young plant disappears or stems are severed with a precise, clean angle near the soil line, the cause is a ground-level mammal. Damage concentrated on the uppermost growth and flowers, with torn or shredded stem ends, indicates feeding by a taller browser.
Chewing Damage
Irregular holes within the leaves or large scalloped edges indicate feeding by organisms that chew and ingest the plant material. If the leaf tissue between the veins is eaten away, leaving only a translucent network of vascular structures, the damage points toward caterpillars. Missing flower heads, where the stem remains bare, are also a strong sign.
Piercing-Sucking Damage
Damage characterized by discoloration and surface markings, rather than holes, suggests piercing-sucking pests. Fine, pale speckling (stippling) across the upper surface of the leaves suggests minute organisms are withdrawing cell contents. This damage may also be accompanied by a fine, silken webbing.
Mollusk Damage
A tell-tale sign of molluscan activity is the combination of large, uneven holes in the foliage alongside a silvery, dried mucus trail. These translucent slime paths confirm that soft-bodied gastropods were responsible for the ragged tears.