The JoY of growing corn can be overshadowed by the challenges posed by reappearance of the European corn borer. European corn borers can cause lots of damage to your crop, so it’s important to learn how to control the corn borer and get the most from your garden!
This guide will delve into the hallmark signs of the European corn borer, its life cycle, and preventative measures to slow its impact on your corn harvest.
Join in as we explore the essential strategies to reclaim your garden and keep those pesky pests at bay!
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Introducing the European Corn Borer
The European Corn Borer (Ostrinia nubilalis) is more than just a pest; it’s a formidable adversary in the world of agriculture, particularly for corn growers.
The corn borer feeds mainly on all parts of the corn plant (stalks, ears, and silk), but it is also known to eat developing apples, peppers, beans, potatoes, tomatoes, spinach, and rhubarb.
Originating from Europe, this invasive moth has spread across North America, causing significant damage to corn crops and other plants.
The first reports of the borer in the United States were in 1914 and in Canada the first sightings were reported in 1920. It slowly made its way across our land to Alberta by 1956.
Its advancement was slowed in the late 1990s when Bacillus thuringiensis was infused into corn seed genetics.
Being highly adaptable and able to survive in various environments, the corn borer has become resistant to the bacillus and is now making a comeback as a crop menace threatening corn production on this continent once again.
The Life Cycle of the European Corn Borer
Understanding the life cycle of the European corn borer is important for effective management and control strategies. This knowledge empowers you to take proactive measures and protect your corn harvest.
This pest undergoes a complex life cycle that consists of four main stages: egg, larva, pupa, and adult. It typically has two generations per growing season and sometimes three.
The first generation lays eggs in late May to early June, and the second in mid-July to August.
The Adult Stage
The cycle begins when mature moths emerge to lay eggs in late May and early June, having developed from fully grown larvae that overwintered in cornstalks, corn ears, and field stubble.
Corn borer moths are typically light brown, measuring 2.5 cm (1″) in length and width. They have distinctive darker markings on their wings, and males have darker markings than females.
The Egg Stage
After mating, females lay clusters of eggs on the underside of corn leaves, usually in groups of 5-50.
These small, flat, and spherical eggs are initially pale yellow and turn darker as they mature. They are layered upon each other like shingles on a roof.
The eggs hatch within a week to 10 days, depending on environmental conditions.
The Larval Stage
The larval stage is the most destructive phase, lasting about two to three weeks. During this time, the larvae feed voraciously, creating tunnels that weaken the plant and make it susceptible to disease.
Initially, the newly hatched larvae are reddish brown, but as they grow, their hairless bodies with tiny dark markings on each segment become a whitish, translucent colour with dark eyes.
Once the larvae emerge, they plunge into the corn plant, burrowing into the stalks, young corn plant whorls, corn silk, and developing corn ears.
A telltale sign of their boring activity is pinholes in corn stalks and developing corn ears.
You may also see leaves wilting above the entry point, caused by damage to the plant’s xylem and phloem.
Corn borers leave behind frass (excrement) that looks like sawdust in the tunnels as they move through the corn plant and you will see it at tunnel entries.
Once the larvae have entered the corn plant, they are impossible to affect with pesticides.
The Pupal Stage
The pupal stage is a quiet period. After completing their feeding, these mature larvae either cease activity and overwinter in the stalk or pupate in the tunnel to produce second-generation moths.
Depending on temperature and humidity, this process can last from a few days to several weeks.
Finally, the adult moths emerge again, ready to start the cycle over.
Understanding this life cycle helps recognize when the corn borer is most active and informs the timing of preventive measures, such as applying insecticides or implementing cultural controls, which are practices that modify the environment to reduce pest populations.
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Strategies to Reduce Corn Damage and Control European Corn Borers
Let’s look at proactive strategies to deter infestations and foster a healthier growing environment for your corn plants:
1. Regular Crop Monitoring
The first step in spotting these invaders is to familiarize yourself with their distinctive signs. Be especially vigilant in early summer, when the moths are most active.
Begin by inspecting the undersides of the leaves for eggs.
Then, examine where the leaf whorls emerge near the base of the corn plant.
Check the base of the corn plants or developing corn ears, where the larvae typically enter the corn stalk or ear, looking for tiny holes or frass. Frass is a mixture of excrement and chewed plant material that looks like sawdust, and it can often be found at the base or along the stalk.
Another noticeable sign to watch for is the presence of silk that appears to be damaged, as the corn borer can also affect the corn’s ear.
Regularly monitoring your corn plants, especially during the early summer months when European Corn Borers are most active, is an essential part of sustainable gardening. This diligence will help you spot any signs of infestation early and take appropriate action.
2. Clean Garden Hygiene
Field hygiene is another critical gardening practice.
Keep your garden free of corn debris, such as old corn stalks, corn ears, weeds, or other plant materials that can harbour the overwintering larvae.
Cut cornstalks off at ground level, destroy them, or run them through a chipper. After harvest, be sure to remove any large residual corn plant matter from your garden.
Additionally, maintaining a clean, weed-free garden reduces the habitat for the moth, which likes to mate in tall weeds. It also reduces the likelihood of attracting other pests that could complicate your battle against the corn borer.
3. The Use of Bacillus Thuringiensis
Bacillus thuringiensis, or BT, is a safe microbial insecticide that can be sprayed on corn plants as the larvae first appear, but you must be watchful to catch them in time.
Products containing the active ingredients of Bt (Bacillus thuringiensis) are particularly effective against larvae and are less harmful to beneficial insects and birds.
Once the larvae have bored into the stalk, pesticides can’t reach them.
Bacillus thuringiensis products can be found in forms that are ready to use or in concentrates. Read and follow directions carefully for reconstitution.
It will wash off with sprinkler activity or rain, so be sure to reapply in those cases.
4. Physical damage to the Larvae
When you see a corn borer hole, you can split the corn stalk, trace the tunnel and impale the larvae with a wire or nail.
5. Companion Planting
Consider integrating companion planting into your garden design. Certain plants naturally repel pests or attract beneficial insects that prey on the European corn borer.
For example, planting Marigolds and Basil alongside your corn can deter these pests. Marigolds emit a strong scent that repels many pests, including the European corn borer, while Basil attracts beneficial insects that prey on the Corn borer, adding a vibrant splash of colour to your garden.
Related: The Best Vegetable Companion Planting Chart for Alberta and the Canadian Prairies
6. Crop Rotation
Crop rotation is another effective method to disrupt the life cycle of the European corn borer.
By changing the types of crops you plant in a particular area each season, you can reduce the incidence of their establishment. This is because the Corn borer’s life cycle is closely tied to the corn plant, so planting other crops in the same area can disrupt their life cycle and reduce their numbers.
For instance, if you planted corn in a specific plot last year, consider rotating it with legumes or other non-host plants. This shift not only confuses the corn borer but also enriches the soil, enhancing overall plant health.
Reducing the Damage of the European Corn Borer
In conclusion, the European Corn Borer poses a significant threat to corn crops.
By understanding its life cycle and behaviour, familiarizing yourself with the signs of infestation, and implementing proactive strategies, you can protect your corn harvest and promote healthier corn plants.
Stay vigilant and proactive, and your efforts will help safeguard your crops against the challenges posed by the European Corn Borer!
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© Sharon Wallish Murphy © Gardening with Sharon
