Corn is one of the world’s most widely cultivated and nutritionally dense cereal grains. Its high content of starches, oils, and proteins makes it an appealing energy source for countless species. The kernels’ concentrated energy attracts a diverse array of organisms. This competition for the crop begins in the field and extends into the post-harvest environment.
Mammalian Eaters of Growing Corn
Raccoons are notorious for targeting corn ears when the kernels are in the highly palatable “milky” stage, before the starches fully harden. They often climb the stalk, pull the developing ear down, and peel the husk back to access the sweet, soft kernels. This feeding typically results in significant destruction to the top portion of the stalk and the ear itself.
White-tailed deer consume various parts of the corn plant depending on its maturity. Early in the season, deer browse on young stalks and leaves, often nipping off the growing points, which can severely stunt development. As the ears mature, they consume the kernels, typically tearing the ear from the stalk with a distinctive ragged edge.
Gray and fox squirrels attack ears throughout the growing season, gnawing through the tough husk to reach the soft kernels. They frequently clip the ear from the stalk and either carry it away for later consumption or feed on it directly at the base of the plant. Groundhogs, also known as woodchucks, primarily eat the lower leaves and tender stalks. They often create distinct burrows and tunnels near the field edges where they feed.
Avian and Insect Consumers
Avian species like crows and blackbirds pose a threat immediately after planting by digging up newly sown corn seeds for the stored energy. Later in the season, these birds perch on the stalks and feed on the exposed tips of ripening ears, particularly where the silk has dried. Wild turkeys may also graze on young seedlings and occasionally feed on downed or low-hanging ears.
Insects present a complex challenge by attacking the plant at different developmental stages. The corn earworm (Helicoverpa zea) larvae feed on the silks and kernels at the tip of the ear, often introducing mold spores that cause spoilage. The European corn borer (Ostrinia nubilalis) tunnels into the stalk and ear shank, which weakens the plant and can cause the stalk to break or the ear to drop prematurely.
Various rootworms and beetles, such as the Western corn rootworm, focus their damage underground. They feed on the plant’s roots, interfering with water and nutrient uptake. This root pruning makes the corn plant susceptible to lodging, where the stalk falls over due to strong winds or heavy rain. These activities often lead to significant yield loss.
Pests of Stored Corn
Once corn is harvested and moved into storage facilities, the consumers change to organisms adapted to dry grain. Rodents, specifically house mice and Norway rats, contaminate stored grain with urine, feces, and hair, in addition to consuming the kernels. They gnaw through sacks and wooden structures to access the high-energy food source, thriving in bins and silos.
Numerous species of small insects specialize in consuming dried grains and are referred to as stored product pests. The rice weevil (Sitophilus oryzae) and the granary weevil (Sitophilus granarius) are destructive because their larvae develop entirely inside individual kernels, making detection difficult until a large population emerges. Other common pests include the saw-toothed grain beetle and the confused flour beetle, which feed externally on broken kernels and grain dust.
Recognizing Specific Animal Damage
Identifying the specific culprit often requires examining the physical evidence left behind. Raccoon damage is characterized by ears stripped from the top down, with the husks pulled back neatly. Deer feeding leaves a ragged, torn appearance on the plant tissue, and telltale hoof prints may be visible nearby. Squirrels typically leave a partially gnawed ear, dropping the damaged portion near the base of the stalk.
Signs of insect infestation on growing corn include the presence of frass—a fine, sawdust-like excrement—near entry holes on the stalk or ear tip, indicating internal tunneling activity. In stored corn, rodent damage is identified by small, parallel teeth marks on the remaining kernels and the presence of small, dark droppings near the pile of grain. These visual clues provide growers with the necessary information to choose the appropriate management strategy.