Corn (maize) is a globally significant staple crop, and its widespread cultivation makes it a highly desirable food source for a diverse array of organisms. The plant provides energy and nutrients at various stages of its development, attracting everything from microscopic pests to large mammals. Understanding which organisms feed on the plant and at what stage they cause damage is the first step in protecting the crop. The plant’s structure, from its underground roots to its exposed ears, offers a continuous food source throughout the growing season, drawing in consumers from the soil, air, and surrounding habitats.
Insect Pests Targeting Corn
Insects often specialize in different parts of the corn plant, causing distinct types of damage. Pests that attack the roots are typically subterranean larvae that feed below the soil surface, hindering the plant’s ability to absorb water and nutrients. Corn rootworms are a major concern, as their larvae chew on root tissue, creating feeding scars and tunneling that can prune the roots back to the crown, leading to plant lodging.
Other pests, like the black cutworm, target young stalks at or just below the soil line during early vegetative stages, completely severing the plant (known as “cutting”). Certain insects are borers, tunneling into the main structure of the plant. The European corn borer, for instance, bores into the stalk, disrupting the flow of water and nutrients and making the stalk susceptible to breaking off, which can complicate harvest.
The leaves and ears are also heavily targeted, especially by caterpillars and aphids. The corn earworm typically feeds on developing kernels at the tip of the ear, often protected within the husk. Corn leaf aphids are small, sap-sucking insects that gather in the whorl and on the tassels, excreting honeydew that can lead to black sooty mold and interfere with pollination and grain development. Fall armyworms are another leaf-feeding threat, identified by the inverted Y-shape on their heads, causing extensive defoliation when feeding in the whorl.
Mammalian Consumers of Corn
Larger animals typically cause their most noticeable damage later in the season when the ears of corn are mature and full of soft kernels. Raccoons are common culprits, often pulling down the stalks to access the ears. They peel back the husk and chew on the kernels, leaving behind a characteristic muddy, masticated cob, with most damage occurring during the milk stage. Raccoons can be responsible for the majority of documented corn damage.
Deer also consume corn throughout the growing phase, with their feeding habits changing as the plant matures. In the early stages, deer browse on the leaves and young stalks, leaving a rough, torn appearance. Once the ears are mature, deer clip the ends of the husks and scrape the kernels off the cob using their lower incisors. Smaller rodents, including mice, voles, and squirrels, cause damage near field edges or wooded areas. They often dig up seeds before emergence or feed on mature kernels, usually consuming only the heart of the seed.
Avian and Ground-Dwelling Eaters
Birds and ground-dwelling organisms contribute to corn damage, particularly during the vulnerable early stages of growth. Flocking birds such as crows, blackbirds, and grackles target newly planted seeds or emerging seedlings. They pull up young plants to eat the sprouted kernel attached to the root, resulting in significant stand reduction. Birds also damage mature ears by pecking through the husks to reach the kernels, leaving a cup-like hole.
Slugs and snails are persistent pests that thrive in cool, wet conditions and no-till systems. These gastropods feed on seedlings, leaving behind slimy trails and scarifying the leaf surface or creating small holes. Slugs can feed on the seed or burrow into an improperly closed seed furrow, potentially damaging the growing point and causing the seedling to die or become deformed.
Vulnerability Based on Plant Stage
The susceptibility of a corn plant to various consumers is highly dependent on its growth stage, making the timing of the attack a key diagnostic factor.
Seedling and Emergence Stage
This first phase is marked by extreme vulnerability to ground-level pests. Wireworms, seedcorn maggots, and cutworms attack the seed or the newly emerged plant. Birds will pull up the seedlings to consume the high-energy seed. Rapid germination and growth during this stage help the plant quickly pass through this period of high risk.
Vegetative Stage
As the plant enters the Vegetative Stage, the threat shifts to borers and leaf feeders. Pests like the European corn borer and fall armyworm target the stalk and the whorl, where new leaves are emerging. This causes feeding damage that appears as ragged holes or shot-holes when the leaves unfurl. This stage is characterized by damage to the plant’s structural integrity and photosynthetic ability.
Reproductive and Maturity Stage
This final phase is when the ears develop and the kernels fill, drawing in larger consumers. Raccoons and deer are most attracted to the developing and mature ears, causing damage to the kernels and often knocking down stalks to feed. Corn earworms and sap beetles also target the ears, with the sap beetles often infesting ears that have already been damaged by earlier pests or birds.