Have you ever noticed strange signs in your garden or field, as if someone came and ate the leaves at night? Or have you seen perfectly formed corn or rice ears suddenly falling to the ground? You might think that this is something that happened due to a strong wind. But the cause of this could be a special type of caterpillar called "Armyworm" because it invades the crops suddenly like an army. Let's talk about this in a little more detail today.
Who is this Armyworm?
Simply put, the armyworm is a pest. To be precise, it is the caterpillar stage of a nocturnal, meaning active at night, moth. These moths are the ones that damage our crops, especially grain crops like rice, corn, and sorghum, and grass crops.
These caterpillars are called "armies" for a very special reason. When food runs out in one place, thousands of these caterpillars, like an army, line up and "march" to a new place where there is food. This phenomenon is why they got their name.
Life cycle of the army caterpillar
There are four main stages in the life cycle of this moth.
1. Egg stage: The female moth lays hundreds of eggs in clusters on the underside of grass-like leaves. Each cluster can contain up to 200 eggs. Within a few days, these eggs hatch into caterpillars.
2. Larva stage: This is the most destructive stage for crops. The little caterpillars that hatch from the eggs are very voracious. They grow rapidly by constantly eating parts of the plant such as leaves and pods. There are several sub-stages in this larval stage. These stages are called `(instar)`. It is in the sixth and final `(instar)` stage that about 80% of the damage done in the entire life cycle is done.
3. Pupa stage: The fully grown caterpillar burrows underground and forms a cocoon around itself to become a pupa. At this stage, the internal changes necessary to become a moth take place.
4. Adult stage: After one to three weeks, a gray or brown adult moth emerges from the cocoon. These moths continue the cycle by laying eggs again.
How do you know if it is a caterpillar infestation?
Keep an eye out for these signs to see if your crops have been damaged by this caterpillar. Identifying these is very important to take quick action.
| Characteristic of damage | Description |
|---|---|
| Signs of leaf damage | The edges and tips of the leaves appear to be torn off. Sometimes, only the base of the leaf is left, and the rest is eaten away. |
| Fallen ears of corn | The ears of crops such as rice and corn have not fully separated, but are hanging on the tree or falling to the ground. This is different from damage caused by strong winds. |
| Caterpillar waste | Small, green or yellow, cylindrical particles (1-2 mm) are found on leaves or at the base of trees. These are the excreta of the caterpillars. |
| Seeing caterpillars | During the day, you can find caterpillars hiding in the plant's trunk, among the leaves, or at the base of the tree. They are more active at night. |
Does this pose a risk to our health?
Now you might be wondering if this caterpillar is poisonous to our bodies or if it causes disease.
Fortunately, the Sena caterpillar does not pose a direct threat to human health. This means that touching or touching the caterpillar is not a big problem. However, there are several indirect health and economic impacts .
- Pesticide use: Farmers and gardeners use pesticides to control this pest. If these are not used correctly and safely , the chemicals they contain can be absorbed into the body. This can cause various health problems.
- Economic loss: This is a huge economic loss for farmers. A crop that has been cultivated at great expense can be destroyed in a few days. The mental stress caused by this is also not insignificant.
Very important: If pesticides are used incorrectly or accidentally ingested, they can cause poisoning. If this happens to you or someone else, go to the nearest hospital Emergency Department (ETU) immediately . If you need further information or advice in this regard, you can call the National Poisons Information Centre at the Colombo National Hospital .
How can this threat be controlled?
Controlling a caterpillar infestation is a challenge, but early action can minimize the damage.
1. Quickly identify and monitor
Check the crop regularly, especially in the morning and evening. Look for the signs of damage mentioned above. Be on the lookout for caterpillars and egg clusters.
2. Natural control methods
If the damage is minimal, you can remove the caterpillars by hand. It is also a good idea to create an environment that encourages the caterpillars' natural enemies, such as birds and other insects, to visit the crop.
3. Use of insecticides
If the infestation is uncontrollable, you may need to use insecticides. There are organic (such as `(Bacillus thuringiensis)`, `(spinosad)`) and chemical (such as `(deltamethrin)`, `(bifenthrin)`) insecticides.
Warning: Before selecting and using an insecticide, always consult your local agricultural extension officer or official. Use only the type and amount they recommend, and follow proper safety procedures (such as wearing a face mask and gloves). Never use insecticides at your own discretion.
4. Weed control
Keep the cultivated land and surrounding areas free of weeds, especially grasses, as these are the places where moths prefer to lay their eggs. Removing weeds can reduce egg laying.
Take-Home Message
- The armyworm is the caterpillar stage of a moth. It is this caterpillar that damages crops.
- The main symptoms of this damage are broken leaves, fallen pods, and caterpillar debris.
- Early detection is very important for pest control. Monitor your crops regularly.
- Although these caterpillars do not pose a direct threat to human health, the improper use of pesticides used to control them is harmful to health.
- Always seek the advice of an agricultural expert before using pesticides and follow recommended safety practices.
- In the event of a pesticide-related health emergency, see your doctor immediately or go to the nearest hospital ETU .
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