The term “corn bugs” refers to a wide array of insects that damage corn at different stages of its life cycle. These pests are categorized into two distinct groups: those that attack the growing plant in the garden or field, and those that infest harvested grain or processed corn products in storage. Addressing an infestation effectively requires first correctly identifying where the problem is occurring. This article provides strategies for managing and preventing these pest issues in both environments.
Pinpointing the Problem: Field Pests Versus Storage Pests
The location of the damage determines the type of insect involved. Field pests, such as the Corn Earworm and the European Corn Borer, target the living plant. Signs of their activity include small feeding holes on unfurling leaves, tunneling into the stalk, or larvae found inside the protective husk of the developing ear. Damage is often visible by the presence of moist, sawdust-like frass near the entry point.
Storage pests damage dried kernels, cornmeal, or decorative corn after harvest, commonly including species like the Granary Weevil or Indian Meal Moth. Infestations are noticed through the presence of small beetles crawling in or around containers, or finding fine silk webbing and larvae in the stored product itself. Kernels damaged by weevils exhibit a small, perfectly round exit hole where the adult insect emerged.
Immediate Eradication Methods for Garden Infestations
Eradicating pests from growing corn focuses on preventing larvae from entering the ears and stalks. For pests like the European Corn Borer, the microbial insecticide Bacillus thuringiensis (Bt) is effective as a targeted spray. Bt is a naturally occurring soil bacterium that paralyzes the digestive system of caterpillars upon ingestion. The spray must be applied into the whorl of the plant before the stalk is entered, or directly onto the silks to target hatching Corn Earworm larvae.
A physical method for Corn Earworm control involves applying a small amount of mineral or light vegetable oil directly onto the fresh silks of each ear. This application should happen just after the silks have begun to turn brown, suffocating the young caterpillar before it tunnels deep into the kernels. For severe infestations, commercial growers may use targeted chemical sprays. These often involve rotating active ingredients, such as Spinosad and a pyrethroid, to manage insect resistance.
Strategies for Clearing Stored Grain Pests
Clearing an infestation from a pantry or storage area begins with the immediate removal of all infested material. Any dried corn, cornmeal, or grain showing signs of pests must be sealed in a bag and discarded outside the home. The next step is a thorough cleaning of all storage shelves, cracks, and crevices using a vacuum cleaner to remove stray kernels, eggs, or larvae.
To salvage exposed grain, a temperature treatment is necessary to kill hidden eggs or larvae. Small quantities can be placed in a freezer at 0°F (-18°C) or below for a minimum of four days. Alternatively, a heat treatment in an oven at 130°F (54°C) for 30 minutes can be used. After cleaning, food-grade diatomaceous earth can be lightly dusted in empty cabinets and shelf seams, causing desiccation in insects.
Preventing Future “Corn Bug” Problems
Long-term prevention requires a strategy that addresses both the field and the storage environment. In the garden, preventing field pests starts with cultural controls like crop rotation, which breaks the life cycle of soil-dwelling pests. Removing and destroying crop residue immediately after harvest eliminates overwintering sites for borers and earworms, reducing the next season’s population. Timing planting to avoid the peak egg-laying period for Corn Earworm moths can also reduce damage.
For stored corn products, proper storage conditions are key. All dried goods susceptible to pests, including cornmeal and popcorn kernels, should be placed in heavy-duty airtight containers immediately after purchase. Containers made of glass, metal, or thick plastic prevent pests from entering or exiting. Ensuring the grain is dried to a moisture content of 13 to 15 percent or less creates an inhospitable environment for weevils. Storing these containers in a cool, dry area and conducting regular inspections maintains a pest-free pantry.