In a garden setting, ‘corn flies’ refers to common pests like corn earworm moths and corn rootworm beetles. These insects reduce corn yields and quality. Protecting corn crops is important for a successful harvest.
Understanding Common Corn Pests
The corn earworm moth (Helicoverpa zea) is a common concern. Adult moths are grayish-brown, about 1.5 inches, with irregular lines and a dark spot near the wing tip. Female moths lay tiny, ribbed, milky-white eggs on fresh corn silks.
After hatching, larvae, which vary in color, move down the silk channel to feed on developing kernels. These larvae grow up to 1.5 inches long with alternating light and dark stripes. Damage appears as chewed kernels at the ear’s tip, often with frass (insect excrement).
Corn rootworm beetles threaten corn. Western corn rootworm adults are yellow to yellowish-green with black stripes; Northern adults are pale green to yellow. Both are about 0.25 inches long.
Larvae are slender, white, up to 0.5 inches long with brown heads. Eggs overwinter in the soil, hatching in early summer. Larvae feed on corn roots, reducing water and nutrient uptake and potentially causing plants to lodge. Adult beetles feed on corn silks and pollen, interfering with pollination and ear fill.
Proactive Prevention Techniques
Proactive prevention techniques reduce pest infestations. Crop rotation, growing corn in a different location each year, ideally after a non-grass crop, is effective. This disrupts pest life cycles, as corn rootworm larvae cannot develop without corn roots. Healthy soil, through proper fertilization and drainage, supports vigorous plant growth, making corn plants more resilient.
Proper plant spacing allows good air circulation and reduces plant stress, making plants less attractive to pests. Selecting pest-resistant corn varieties, such as Bt corn hybrids for earworms, provides a built-in defense. While some Bt varieties may show reduced effectiveness, newer hybrids offer good control. Planting early helps corn mature before pest populations peak, especially for earworms.
Physical barriers protect corn plants. Row covers or fine netting exclude flying insects from young plants, preventing egg-laying on silks or leaves. Remove these covers once pollination is necessary. For smaller infestations, hand-picking visible pests, like earworm larvae from silks, is effective early intervention. This removal prevents small problems from escalating.
Natural and Organic Control Methods
Natural and organic control methods manage pest populations without harsh chemicals. Companion planting involves growing plants alongside corn to deter pests or attract beneficial insects. Marigolds, for example, repel corn earworms and aphids due to their aroma, and attract beneficial predators. Thyme and borage also repel corn earworms.
Attracting beneficial insects is another strategy. Ladybugs, lacewings, and parasitic wasps are natural predators that feed on or parasitize corn pests, including earworms and aphids. A diverse garden environment with flowering plants offering nectar and pollen encourages these helpful insects to stay and reproduce. Dill and borage, in addition to repelling pests, also attract beneficial insects.
Organic sprays offer targeted intervention when pest numbers are higher. Bacillus thuringiensis (Bt) is a naturally occurring bacterium producing toxins harmful to specific insect larvae, including corn earworms. It is applied to corn silks, where larvae ingest it as they feed.
Neem oil, extracted from the neem tree, acts as a repellent and feeding deterrent, disrupting insect reproduction, effective against corn earworms and corn beetles. Apply neem oil early morning or late evening, avoiding full bloom to protect pollinators.
Spinosad, a bacterial-based insecticide, is effective against earworms. Applying a few drops of mineral or vegetable oil to corn silks after pollination can also suffocate earworms.
Implementing an Integrated Approach
Effective corn pest management involves an integrated approach, combining various strategies for long-term success. Integrated Pest Management (IPM) prioritizes understanding pest life cycles and using combined methods rather than a single solution. IPM emphasizes regular monitoring of your corn patch to identify pests early and assess population levels, including inspecting plants for damage and observing insect activity.
Understanding pest thresholds helps determine when intervention is necessary, preventing unnecessary treatments while protecting the crop. If only a few pests are present, natural predators or hand-picking might suffice. Combining cultural practices, physical barriers, and natural controls creates a robust defense system, making the corn patch less hospitable to pests.
Adapting strategies based on observations and pest pressure is a core principle of IPM. This flexible approach ensures management efforts are effective and sustainable, promoting a healthy garden ecosystem. Regular inspection and timely intervention are key to managing pests, ensuring a productive corn harvest.