Anticarsia gemmatalis (soybean caterpillar) is a pest of great importance to agriculture, especially in soybean cultivation. The insect is responsible for high levels of defoliation and can significantly compromise productivity, especially in high populations.
Taxonomic classification:
- Domain: Eukaryota (eukaryotic organisms, with cells that have an organized nucleus)
- Kingdom: Animalia (multicellular, heterotrophic animals)
- Phylum: Arthropoda (arthropods, characterized by segmented body, exoskeleton and articulated appendages)
- Class: Insecta (insects, with three main body parts: head, thorax and abdomen, plus six legs)
- Order: Lepidoptera (Lepidoptera, a group that includes moths and butterflies, characterized by wings covered in scales)
- Family: Erebidae (formerly classified in the family Arctiidae. Includes moths with diverse patterns and often associated with host plants)
- Genre: Anticarsia
- Species: Anticarsia gemmatalis
Common names
Anticarsia gemmatalis It is primarily known as the soybean caterpillar. But it can also be referred to as the leafworm, due to its ability to cause severe damage to the leaves of host plants.
Crops attacked
Although it is predominant in soybeans, Anticarsia gemmatalis can attack other crops, especially legumes.
The damage is more significant in areas with soybean monoculture, where food availability is constant.
Biology
The life cycle of A. gemmatalis includes four stages: egg, larva, pupa and adult.
In the larval stage, the caterpillar goes through six instars. Instars are the intermediate stages of larval growth, which occur between the caterpillar's molts (ecdysis). With each instar, the caterpillar grows and increases in size, until it reaches the final stage of larval development, when it is ready to transform into a pupa.
The small caterpillars are green in color and have four pairs of abdominal legs, two of which are vestigial, which gives them a characteristic span-measurement movement.
Larger caterpillars, measuring more than 15 mm, can be green or dark, with three white longitudinal lines on their backs.
Adults are moths that vary in color from light gray to dark brown, with a reddish-brown diagonal line on the first pair of wings.
Females lay light green eggs, usually on the underside of leaves, petioles and branches. Hatching occurs in three days, and the caterpillars begin feeding soon after.
Ecology
The pest is favored by hot and humid weather conditions, common in soybean-producing regions of Brazil. Successive planting cycles and inadequate management favor the increase in the caterpillar population, especially in agricultural systems with low biological diversity.
Some of its natural enemies:
- Parasitoids: insects like Trichogramma pretiosum parasitize the eggs, preventing the development of larvae.
- Predators: Beetles, birds and other predatory insects attack larvae and adults.
- Pathogens: fungi such as Nomuraea rileyi and viruses such as nucleopolyhedrovirus (NPV) infect larvae, causing mortality.
Damage
Damage occurs mainly in the third to sixth larval instars.
Initially, the caterpillars pierce the leaves, preserving the veins. From the fourth stage onwards, they consume more than 95% of the total leaf consumed per cycle, which is equivalent to up to 120 cm² per caterpillar.
At high population densities, they can cause defoliation of more than 30%, compromising plant development and resulting in productivity losses.
Control
the management of Anticarsia gemmatalis must be integrated, involving cultural, biological and chemical practices:
- Biological control: use of natural enemies, such as parasitoids and predators, is an efficient strategy. Bioinsecticides based on Bacillus thuringiensis are widely recommended.
- Monitoring: Periodic inspection of crops is essential to identify the level of infestation and determine the appropriate time for intervention.
- Chemical control: The use of insecticides must be done with discretion, considering the level of economic damage and aiming to avoid pest resistance.
- Cultural practices: Proper crop management, including crop rotation and maintenance of plant diversity, contributes to reducing pest pressure.
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