Identification and Control of Fall Armyworm

Fall Armyworm

The fall armyworm, Spodoptera frugiperda (J.E.Smith), is an insect in the order Lepidoptera, family Noctuidae, and genus Spodoptera. Its common names include Fall Armyworm, Corn Leafworm, and Southern Grassworm.

The fall armyworm is a polyphagous and migratory pest originally from the tropical and subtropical regions of Central and South America. It invaded the United States and Canada in the mid-19th century. Its widely known name is “Autumn Cabbage Worm” because it primarily damages crops in late summer and early fall in North America. The larvae often move in groups, migrating to feed, hence the name “marching caterpillar.”

The fall armyworm is characterized by its ability to “eat,” “reproduce,” and “fly,” with the ability to cause damage very quickly and is particularly prone to spreading rapidly. The fall armyworm has over 300 host plants, with corn and rice being the most severely damaged crops. In Africa alone, the economic losses caused by this pest have reached $13 billion. It is highly reproductive, with a single female moth capable of laying 100 to 200 eggs per batch, and can lay 900 to 1,000 eggs in her lifetime. The eggs hatch within two to three weeks. It is also highly migratory, with female moths able to travel up to 500 kilometers before laying eggs. Reports show that fall armyworm adults migrated from Mississippi, USA, to southern Canada within 30 hours, a distance of 1,600 kilometers. Furthermore, the damage caused by fall armyworms is extremely fast, as they are voracious pests that work in groups. In just one day, they can devour an entire cornfield, and once finished, they migrate in an organized manner to the next field.

Main Control Measures

1. Ecological Regulation and Natural Enemy Protection

In areas with suitable conditions, intercropping with non-grass crops can be employed to protect natural parasitic and predatory enemies in the field environment. This approach takes advantage of biodiversity’s natural control benefits, forming ecological barriers.

2. Adult Moth Trapping

During the adult moth occurrence period, concentrated use of insecticidal lamps can be employed to trap the moths. The effectiveness of this control can be enhanced by using sex pheromones and food attractants.

3. Larval Control Techniques

The best time for controlling fall armyworm larvae is during the early stages. The application of pesticides is best carried out in the early morning or evening, and it is crucial to spray the insecticide on the corn heart leaves, male and female tassels, and other affected areas.

• (1) Biological Control: During the early egg-hatching period, spraying biological pesticides such as Beauveria bassiana, Metarhizium anisopliae, Bacillus thuringiensis, as well as fungicides like Polyoxin or natural insecticides such as Quassia, Neem, and Azadirachtin can help in managing the larvae.

• (2) Emergency Control: If the pest density in a cornfield reaches 10 caterpillars per 100 plants (based on the pest density guideline for controlling second-generation corn earworms), high-efficiency and low-toxicity insecticides for noctuid pests can be used. (According to the FAO guide for managing fall armyworm, registered chemical pesticides such as chlorantraniliprole, lambda-cyhalothrin, and indoxacarb can be effective in controlling this pest).