Spodoptera exigua

(Hübner, 1808)

Beet Armyworm, Small Mottled Willow Moth, Asparagus Fern Caterpillar

, commonly known as the , is a highly agricultural pest to Asia that has been worldwide. The is a member of the and is particularly destructive in vegetable , though it occasionally damages soybean in the southern United States. are characterized by variable green coloration with pinkish or yellowish undersides and a stripe. The species has gained attention in molecular research due to its microbiome interactions and susceptibility, which have implications for strategies.

Spodoptera exigua (29683245587) by Donald Hobern from Copenhagen, Denmark. Used under a CC BY 2.0 license.

Spodoptera exigua (32504469731) by Donald Hobern from Copenhagen, Denmark. Used under a CC BY 2.0 license.

Spodoptera exigua? by Frank Falconer. Used under a CC BY-SA 2.0 license.

Pronunciation

How to pronounce Spodoptera exigua: /ˌspɒd.oʊˈtɪə.rə ɛɡˈzɪɡ.ju.ə/

These audio files are automatically generated. While they are not always 100% accurate, they are a good starting point.

Identification

can be confused with Spodoptera eridania (southern ) due to a dark spot. The critical distinguishing character is spot location: in S. exigua, when present, the spot occurs on the , whereas in S. eridania the spot is located on the first abdominal . This character allows reliable separation of large larvae. Conclusive identification of young larvae is often not possible due to similarity in appearance among Spodoptera .

Images

Habitat

Agricultural environments, particularly fields of vegetable and occasionally soybean. In the southern U.S., prefer foliage of seedling soybean plants but will feed on blossoms and small pods if present during reproductive stages. Laboratory colonies are maintained at 25±3°C with 60±5% and 16-hour light:8-hour dark .

Distribution

to Asia; worldwide and now found almost anywhere are grown. Established in North America, South America, Oceania, the Azores (São Miguel and Terceira), and the Middle East (United Arab Emirates). In the United States, regularly occurs in the southern states including Mississippi and Illinois. In the British Isles, present as an introduced but not known to breed.

Diet

Highly . feed on foliage of seedling plants; during reproductive stages of soybean, also feed on blossoms and small pods. Better known as a pest of vegetables than of soybean. In laboratory studies, reared on artificial diet or pepper (Capsicum) leaves. feed on sugar solution.

Host Associations

Capsicum - Used in laboratory assays; show reduced weight gain and delayed growth compared to artificial diet
Glycine max - Soybean; occasional pest in southern U.S., preferring seedling foliage but feeding on blossoms and pods when available

Life Cycle

with . Larval stage consists of multiple . undergoes dramatic changes after . In laboratory colonies, kmo gene mutation affects larval-to- development with visible phenotypic changes including , golden yellow pigmentation, and transparent and brain coloration. Specific details on , pupal stages, or time in field conditions are not provided in sources.

Behavior

Oral secretion (regurgitation) contains 8-hydroxyquinoline-2-carboxylic acid (8-HQA) and bacterial content derived from . These oral secretions influence - interactions. exhibit group feeding early in development, with groups hatching from single masses and skeletonizing nearby foliage before dispersing as they grow larger.

Ecological Role

Agricultural pest that causes direct damage through foliar feeding and pod damage in legume . influences nutrition, , and interactions with plants and . Enterococcus form part of core microbiota. Microbiota can shape trophic interactions with plants by producing toxin-degrading or modulating defense responses. Targeted for using ; understanding of caspase-mediated apoptosis provides insights for engineering improved viral .

Human Relevance

Significant agricultural pest causing to vegetable and occasional damage to soybean. Subject of extensive research on , including -based and microbiome manipulation. Laboratory studies have investigated mechanisms to and strategies to enhance baculovirus through of viral .

Similar Taxa

Spodoptera eridania can be confused due to similar coloration and presence of a dark spot. Distinguished by spot location: in S. exigua versus first abdominal in S. eridania.
Spodoptera frugiperdaBoth are pests of soybean with overlapping distribution in the Americas. S. frugiperda is distinguished by pinaculae with single stout on abdominal and an inverted Y-shaped mark on the .
Spodoptera ornithogalli have more uniform appearance with paired black triangular spots and prominent stripes, lacking the variable green-pink coloration of S. exigua.

More Details

Gut Microbiome and Kynurenine Pathway

The kynurenine KMO (kynurenine 3-monooxygenase) produces 8-HQA, an iron-chelating compound that regulates microbial . CRISPR/Cas9-mediated kmo deletion abolishes 8-HQA production, reduces bacterial diversity, collapses compartment-specific bacterial , and promotes Enterococcus dominance. Mutants show reduced and increased susceptibility to .

Baculovirus Interactions

Caspase-4 (SeCaspase-4) functions as an effector caspase in -induced apoptosis. Recombinant Autographa californica multiple (AcMNPV) expressing SeCaspase-4 shows increased against by promoting apoptosis, despite reducing viral production. This provides a strategy for enhancing efficacy.