Companion planting is a method of pest management that uses the natural properties of certain plants to protect a primary crop like corn. This ecological approach relies on intercropping, the practice of growing two or more crops in close proximity. The goal is to create a diversified planting environment that naturally deters or diverts common corn pests, such as the corn earworm, European corn borer, and aphids. Strategically placing specific plant species around the corn allows gardeners to use scent, attraction, and physical barriers to reduce pest damage without heavy chemical intervention.
Companion Plants That Repel Pests
Many herbs and flowers actively repel corn pests by emitting strong volatile organic compounds (VOCs). These compounds interfere with an insect’s ability to locate the corn crop, masking the scent and preventing pests from laying eggs on the silks or stalks. This olfactory disruption is a key mechanism for natural pest control.
Basil is an aromatic herb often planted near corn to deter pests. Thyme specifically repels the corn earworm, a moth larva that feeds on the kernels. Planting these herbs interspersed among the corn rows creates a scent barrier.
Marigolds are widely recognized repellent flowers, effective against pests including aphids. Certain varieties also release root substances that suppress nematodes, microscopic roundworms that feed on corn roots. Mint, with its intense aroma, can repel aphids, but it is best managed in a container to prevent it from becoming invasive.
Utilizing Trap Crops and Beneficial Insect Attractors
An alternative strategy uses plants that lure pests away from the corn (trap crops) or plants that attract beneficial insects that prey on corn pests. Grain sorghum is an effective trap crop for the corn earworm moth, as females often prefer to lay eggs on the sorghum over corn silks. Planting a border of a more attractive plant draws pests away, concentrating the infestation in a manageable area that can be sacrificed.
Other plants attract natural predators, controlling the pest population through biological means. Flowering plants with shallow, exposed nectaries are most effective because they provide easily accessible food for beneficial insects with short mouthparts. Dill, fennel, and coriander, when allowed to flower, are excellent at attracting parasitic wasps and ladybugs.
Ladybugs and lacewings are voracious predators of aphids. Parasitic wasps, such as the minute Trichogramma wasp, lay their eggs inside the eggs of pest moths like the corn earworm and European corn borer, killing the pest before it hatches. Flowers like cosmos, sunflowers, and sweet alyssum provide the necessary nectar and pollen to sustain these beneficial insects, keeping them in the area to patrol the corn patch.
Physical Arrangement and Timing of Planting
The success of companion planting depends heavily on the strategic placement and timing of auxiliary plants. Repellent plants, such as aromatic herbs, should be interspersed throughout the corn rows or planted along the perimeter to maximize the diffusion of masking scents. This intercropping breaks up the corn monoculture, making it harder for pests to find their host plant.
Trap crops should be planted slightly earlier than the corn, or in a succession of plantings, to ensure they are at their most attractive stage when corn pests arrive. For instance, grain sorghum should be flowering when the corn earworm moths are migrating into the area. This timing ensures the trap crop is more appealing than the vulnerable young corn.
To maintain a steady population of beneficial insects, ensure a continuous bloom of attractor flowers throughout the growing season. Succession planting of flowers like sweet alyssum or dill, or planting varieties with different bloom times, provides a constant source of nectar and pollen. The physical arrangement must also account for light, ensuring that the tall corn does not completely shade out lower-growing companions.