European corn borer facts for kids
Quick facts for kids European corn borer |
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The European corn borer (Ostrinia nubilalis) is a type of moth. It is also called the European corn worm. This moth is known for being a pest that harms maize (corn) plants. It originally came from Europe. There, it would infest plants like millet.
The European corn borer first appeared in North America in 1917. It was likely brought over from Europe earlier. Since then, it has spread across the United States and into Canada.
Adult European corn borers are about 1 inch (2.5 cm) long. Their wingspan is about 1 to 1.2 inches (2.6-3 cm). Female moths are light yellowish-brown. They have dark, wavy bands on their wings. Male moths are a bit smaller and darker.
The caterpillars of the European corn borer cause damage to corn. They chew tunnels through different parts of the plant. This makes the corn crop yield smaller.
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Where Do European Corn Borers Live?
The European corn borer is originally from Europe. It was brought to North America in the early 1900s. In Europe, these moths cause problems for corn crops in countries like France, Spain, Italy, and Poland.
In North America, you can find the European corn borer in eastern Canada. It is also found in every U.S. state east of the Rocky Mountains.
Life Cycle of the Corn Borer
The European corn borer goes through four main stages as it grows. These stages are the egg, larva (caterpillar), pupa, and adult moth. When it is a larva, it is called a "borer." When it is an adult, it is called a "moth."
Adult moths lay their eggs on corn plants. Tiny larvae hatch from these eggs. The larvae grow through five different sub-stages. After the larval stage, the borer enters a resting period called hibernation (diapause) as a pupa. During the pupal stage, the borer changes into an adult moth. This change is called metamorphosis.
The time it takes for a borer to become an adult moth depends on things like temperature and how much light there is. It also depends on what the larva ate.
Some groups of European corn borers have two pupal stages. One happens in May and June, and another in July and August. In winter, the European corn borer stays in its larval stage. They only move to other stages when temperatures are above 50 degrees Fahrenheit (10 °C). Corn grows during these warmer months, giving the borers food.
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Adult Moths
Adult European corn borers are about 1 inch (2.5 cm) long. Their wingspan is about 0.75 to 1 inch (1.9-2.5 cm). Female moths are light yellowish-brown with dark, wavy bands on their wings. Males are a bit smaller and darker. Their abdomen sticks out past their wings when closed. They are most active just before sunrise. Adult moths spend most of their time eating and mating.
Larva (Caterpillar)
A fully grown larva is about 0.75 to 1 inch (1.9-2.5 cm) long. Larvae can be light brown or pinkish-gray. They have small, round, brown spots on each part of their body. As they grow, they can reach between 0.08 and 0.8 inches (2 to 20 mm).
The larvae eat the corn plant's leaves and burrow into the stalk and ear. Many larvae die right after they hatch. But once they find a good place to eat, they have a better chance of surviving. It takes about 50 days for a larva to grow before it becomes a pupa.
Hibernation (Diapause)
European corn borers go into a resting state called diapause, or hibernation. This happens because of temperature changes and how long the days are. If it's warmer, shorter daylight hours are enough to make them hibernate. For example, if there are 13.5 hours of light and 10.5 hours of dark, all larvae will hibernate. This happens no matter the temperature between 64 and 84 degrees Fahrenheit (18 to 29 °C). If it's hot and the days are long, fewer larvae will hibernate.
Eggs
Female corn borer moths lay groups of eggs on corn leaves. They usually lay them on the underside of the leaves. These egg clusters are whitish-yellow and overlap each other.
As the caterpillars grow inside the eggs, the eggs become clearer. You can even see the tiny black heads of the caterpillars inside. The caterpillars hatch by chewing their way out of the eggs.
A female moth can lay two egg clusters each night for about 10 nights. The number of eggs in each cluster gets smaller each day. The eggs are white at first, then turn pale yellow, and finally clear before they hatch. The eggs usually hatch within three to seven days after they are laid.
How European Corn Borers Reproduce
Breeding Cycles
The first European corn borers brought to North America settled in New York. This group produced one generation of moths per year. A second group was brought to Massachusetts. This group spread to Long Island and the Hudson River Valley. This second group produces two generations of moths per year.
Egg Laying
During her adult life, which lasts about 18 to 24 days, a female moth can lay 400 to 600 eggs in total. Female European corn borer moths first lay eggs in June. They lay their eggs on the underside of corn leaves, usually near the main vein.
About 90% of the eggs are laid on the leaf just below the main ear of corn. An equal number of eggs are laid above and below this leaf. There is a slight tendency for more eggs to be laid on the lower leaves. All egg clusters are laid within five leaves of the central ear leaf. Each egg cluster has about 15 to 30 eggs and is about 0.24 inches (6 mm) wide. The egg-laying period lasts about 14 days. A female lays about 20 to 50 eggs per day.
What Do Corn Borers Eat?
The European corn borer mostly lives and feeds on field corn. But it also eats sweet corn, popcorn, and corn grown for seeds. The first generation of corn borers, which grows in late spring, eats the leaves and stalks of corn plants.
The second generation of borers eats the corn ear, the leaf sheath (the part of the leaf that wraps around the stalk), and the ear shank (the stem that holds the ear). If a third generation appears, it will also feed on these parts of the corn plant.
If there isn't much corn, or when the harvest season is ending, European corn borers will also infest other plants. These include lima beans, peppers, potatoes, and snap peas. Sometimes, but rarely, these moths will live on other grains, soybeans, or flowers.
Corn Borers as Crop Pests
The European corn borer gets its name because it bores holes into all parts of the corn plant. When they damage the leaves, it makes it harder for the plant to make food through photosynthesis. Damage to the corn stalk means the plant can't send enough water and nutrients to the ear.
European corn borers also eat the corn ear itself. This reduces how much corn farmers can harvest. They also eat the ear shank, which often causes the ear to fall to the ground. Then, it cannot be harvested.
How Farmers Control Corn Borers
Farmers use different methods to control corn borers. These include:
- Natural Enemies: Tiny wasps called Trichogramma are used. These wasps lay their eggs inside corn borer eggs, stopping them from hatching.
- Fungi: A fungus called Beauveria bassiana can infect and kill corn borer larvae.
- Microbes: A tiny organism called Nosema pyrausta can also infect corn borers.
Farmers also use a special type of corn called Bt corn. This corn has been changed to include a gene from a bacteria called Bacillus thuringiensis kurstaki. This gene makes the corn produce a protein that is toxic to corn borer larvae. When the larvae eat the Bt corn, the protein kills them.
Young corn plants naturally produce a substance called DIMBOA. This substance acts like a natural defense against many pests, including the European corn borer. This is why young corn is often more resistant to them.
Why Refuge Corn is Important
When farmers plant Bt corn, they also need to plant an area of "refuge corn." This refuge area is made of regular corn that does not have the special insect-killing gene.
This refuge area is very important. It helps prevent corn borers from becoming resistant to the Bt gene. Insects that eat the non-Bt corn will not develop resistance. They will then mate with any moths that might have survived after eating the Bt corn. It's rare for an insect to survive eating Bt corn. But if resistant individuals mate with moths from the refuge area, their offspring will still be affected by the toxin. Studies show that planting refuge corn within half a mile of Bt crops helps prevent resistance.
Corn Borers and Plant Health
When European corn borers are present on corn crops, and they cause damage, it makes the corn more likely to get stalk rot. This rot is caused by a fungus called Fusarium graminearum. The tunnels made by the corn borers make it easier for this fungus to infect the corn stalks. This also increases the amount of dead stalk tissue. When the fungus is present in corn infested by corn borers, it can also make the larvae develop faster.
Corn Borers and Climate Change
Scientists predict that as temperatures rise due to climate change, the areas where the European corn borer can live will expand. They also expect that there will be more generations of corn borers each year. A model that predicts how organisms respond to climate change suggests that the area of farmland affected by the European corn borer in Europe could increase by 61%.
Gallery
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Female, dorsal view
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Female, ventral view
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Male, dorsal view
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Male, ventral view
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Lateral view
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Dorsal view
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See also
In Spanish: Taladro del maíz para niños
