Cereal leaf beetle facts for kids
Quick facts for kids Cereal leaf beetle |
|
|---|---|
 |
|
| Oulema melanopus | |
| Scientific classification | |
| Genus: |
Oulema
|
| Species: |
melanopus
|
The cereal leaf beetle (Oulema melanopus) is a small insect that causes big problems for farmers. It was first described by Carl Linnaeus in 1758. This beetle loves to eat cereal crops like wheat, oats, and barley, which are important foods for people and animals.
Contents
Life Cycle of the Cereal Leaf Beetle
These beetles usually have one generation each year. Adult beetles eat before winter. They spend the cold months in safe spots like under tree bark or in old crop fields.
When the weather gets warmer (above 9–10 degrees Celsius), the adults mate. Female beetles lay eggs for a long time, about 45 to 60 days. They place their tiny eggs on the underside of plant leaves.
Eggs and Larvae
The eggs hatch in 7 to 15 days. The young beetles, called larvae, then start eating a lot. This is the time when they cause the most damage to crops. Larvae grow for 12 to 20 days. They eat the top layer of leaves. This makes it hard for the plants to make food using sunlight, a process called photosynthesis.
Cereal leaf beetle eggs are round and look like tiny cylinders. They are about 0.9 mm long. At first, they are bright yellow. They turn darker over time, becoming partly black just before the larvae hatch.
The larvae are white or yellow and have a black head. They have a special way to protect themselves. They cover their bodies with their own waste. This makes them look shiny and black. It helps them hide from predators and makes them look less tasty!
Pupae and Adults
After eating, the larvae go into the soil to become pupae. This is a resting stage. Pupae are rarely seen in fields. They are about 5 mm long and yellow, also darkening over time.
New adult beetles come out of the soil in 20 to 25 days. They are then ready to start the whole cycle again. Adult beetles are usually about 5 mm long. They have dark-blue wing covers and red legs. Their bodies (called the thorax) can be red, orange, or reddish-brown.
Where Cereal Leaf Beetles Live
The cereal leaf beetle first came from Europe and Asia. But now, it is found in many more places around the world. In North America, it was first seen in Berrien County, Michigan, in 1962. Since then, it has spread across the Midwest and to the East Coast of the United States. It is also moving westward. You can find many of these beetles in states like Virginia, North Carolina, Utah, and Missouri.
The weather greatly affects how many beetles there are each year. A cold spring helps the plants grow strong. But a warm spring helps the beetles. Scientists think that if the planet gets warmer, these beetles might spread even more, possibly into Canada. Recent studies show that the cereal leaf beetle has indeed reached Canada.
Within a field, the beetles are not spread out evenly. You might find many in one spot and very few in another.
What Cereal Leaf Beetles Eat
Cereal leaf beetles eat almost all cereal crops. They especially like oats, barley, and rye. Their favorite food is wheat. They can also eat corn, sorghum, and different types of grass.
When they eat, they make thin, long lines on the leaves. This happens because they eat only the top layer of the leaf. Since the beetles move around while eating, the damage is not the same across a whole field. In places like Michigan, entire fields are rarely destroyed. The plants might look worn out, but they are usually not completely ruined. Damage is often less than 40% of the crop.
When a plant is eaten by an insect, it releases certain smells. These smells can attract predators of the insect. Female cereal leaf beetles can sense these smells. They try to avoid plants that have been eaten. This helps keep them and their young safe.
Scientists have studied what these beetles like to eat. They found that if the beetles don't have their favorite food, they might eat less or stop eating. But if they have a mix of different plants, they might start eating again. This suggests that some plants might have a special chemical that makes the beetles want to eat them, especially when their usual food is scarce.
Controlling Cereal Leaf Beetles
Farmers and scientists use different methods to control cereal leaf beetles. The goal is to protect crops without harming the environment too much.
Biological Solutions
One way to control these beetles is by using other living things. This is called biological control.
- Nematodes: Scientists have used tiny worms called nematodes. These worms attack adult beetles that are resting in the soil during winter. This stops the adults from having babies in the spring. Some types of nematodes work better than others, depending on the temperature.
- Traps: Male beetles release a special smell (a hormone) that attracts other beetles. Scientists can use this smell to lure beetles into traps. Once in the traps, the beetles can be removed from the field.
- Parasitic Flies: A type of fly called Hyalomyodes triangulifer can help. This fly lays its eggs on adult cereal leaf beetles. The fly larvae then grow inside the beetle, eventually killing it.
- Parasitic Wasps: Several types of tiny wasps are very good at controlling cereal leaf beetles.
- Diaparsis carnifer and Lemophagus curtis are wasps that eat the cereal leaf beetle larvae.
- Tetrastichus julis is another wasp that lays its eggs inside the bodies of cereal leaf beetle larvae. This wasp is very effective and can kill about 90% of a beetle population. It usually does not harm the crops. Farmers can sometimes spray a sugar solution on fields. This helps the wasps grow strong so they can kill more beetles.
- Anaphes flavipes is a wasp that lays its eggs inside the cereal leaf beetle's eggs. This kills the beetle egg before it can hatch. This wasp is also very effective, killing about 90% of eggs. It is a strong helper because its life cycle matches the beetle's. However, it might also lay eggs in other bugs, which could upset the natural balance.
- Ladybugs: Ladybugs are known to eat the eggs and larvae of the cereal leaf beetle. They can be helpful in some areas.
Other Solutions
- Weather: Sometimes, natural weather conditions like droughts or too much rain can cause the beetle population to go down.
- Quarantine: In the past, some places like California tried to stop the beetles from entering by checking materials like hay. If hay was thought to have beetles, it was not allowed in. Compressing hay into tight bales can also help stop beetles from traveling.
- Genetically Modified Plants: Scientists are also working on special plants that are changed to resist the beetles. For example, some types of corn have been made to be harmful to the beetles when they eat them. These plants can make it harder for the beetles to lay eggs on them.
- Pesticides: Farmers can use special chemicals called pesticides to kill the beetles. However, they must be careful. If pesticides are sprayed too early, they might not affect the eggs. Also, pesticides can sometimes kill the good insects that eat the beetles, which might actually cause more beetles to survive. The best time to spray is when about half of the eggs have hatched, or when the adult beetles are laying their eggs.
