Corn is a staple crop in many gardens, but it is highly susceptible to a wide variety of pests that can attack the plant from the moment the seed is sown until the kernels are ready for harvest. Recognizing the specific pattern of damage is the first step toward successful management and a bountiful yield. Identifying these threats quickly and accurately is essential for protecting the crop.
Insect Pests Attacking Roots and Stalks
Early-season insect pests primarily attack the plant’s structural components, leading to wilting, stunting, or plant death. Cutworms often sever young plants at or just below the soil line. The larva typically feeds at night and can be found curled up in the soil near the severed plant stub. This damage usually occurs when the corn is still a small seedling, before the plant reaches the V6 growth stage.
Corn Rootworms feed directly on the plant’s root system during early summer. This root pruning reduces the plant’s ability to absorb water and nutrients, resulting in stunted growth and a characteristic S-shaped bend in the lower stalk, called “goosenecking” or lodging. Severe root damage can cause the entire plant to fall over, especially during strong winds or heavy rain.
The European Corn Borer targets the stalk by tunneling into the stem, which disrupts the flow of water and nutrients. Entry and exit holes are often marked by a sawdust-like excretion called “frass” accumulating near the base of the leaves or at the entry point. This internal tunneling weakens the stalk, causing the plant to snap off, or “break over,” later in the season, often near the ear.
Insect Pests Targeting Kernels and Foliage
The Corn Earworm is a common pest of the kernels, with its larvae feeding on the silks and the soft kernels at the tip of the ear. This feeding activity creates a clear, localized patch of damage near the end of the cob, often accompanied by moist, dark frass.
Flea Beetles are tiny, jumping insects that attack the foliage of young plants, leaving behind small, circular holes that give the leaves a “shot-hole” or shredded appearance. While direct feeding damage is minor, these beetles can transmit the bacterium that causes Stewart’s wilt, leading to more serious plant disease. This leaf damage is typically observed in the early vegetative stages.
Aphids, often found clustered on the undersides of leaves or on the tassels, suck the plant sap, which can stunt plant growth. This feeding coats the leaves in honeydew, which then becomes a substrate for sooty mold that interferes with photosynthesis. Heavy infestations can compromise the plant’s overall health and ear development.
Vertebrate Pests: Raccoons, Deer, and Birds
Larger pests, including mammals and birds, inflict distinctive damage easily identified by its scale and timing. Raccoons, being nocturnal, typically raid corn patches just as the ears reach the milk or dough stage, which is the time of peak sweetness. Their signature damage involves pulling down the entire stalk to access the ear, resulting in stalks lying down in various, random directions.
These clever masked mammals strip the husk back with their paws and teeth, eating only a portion of the kernels, often leaving behind a muddy or shredded-looking cob. The large-scale destruction and pulled-down stalks differentiate their feeding from deer, which tend to browse. Deer lack upper incisors, resulting in a rough or torn appearance on the foliage they consume.
White-tailed deer graze on the upper foliage, silks, and developing ears, often leaving behind plants with a “decapitated” look where the tassel has been removed. Damage to the ears is characterized by kernels scraped off the cob using their lower teeth, or by a clean bite that removes the end of the ear. Birds, such as crows and blackbirds, cause damage in two distinct phases: pulling newly emerged seedlings to eat the planted seed, or pecking holes into the ripening kernels on the ear, leaving behind shredded husks.
Matching Damage Symptoms to Control Strategies
Effective pest management begins by confirming the identity of the culprit based on the observed damage symptoms, which dictates the appropriate control measure. For soil and stalk pests, such as Corn Rootworms, implementing a strict crop rotation schedule is highly effective because the larvae cannot survive on non-corn crops. Cutworm problems can be mitigated by keeping the area weed-free before planting, as the moths prefer to lay eggs on weedy ground.
Targeting foliage and ear-feeding insects requires a different approach, often focused on direct removal or exclusion. For the Corn Earworm, manually removing the larvae from the ear tip can be an effective strategy in small gardens. Planting varieties with tight, long husks can naturally deter earworms and birds, while reflective mulches or row covers can physically exclude Flea Beetles and other early-season leaf feeders.
Vertebrate pests necessitate the use of physical barriers and deterrents. The most reliable method for deterring raccoons is a two-strand electric fence, with one wire placed four to six inches above the ground and the second wire at about twelve inches. Deer damage can be minimized with tall physical fencing, generally at least eight feet high, or by using commercial repellents that simulate predator scents.