Spodoptera eridania

Stoll, 1781

Southern Armyworm Moth, Southern Armyworm

Spodoptera eridania is a highly whose are significant agricultural pests in tropical and subtropical regions of the Western Hemisphere. The has emerged as one of the most important pests of soybean in Brazil and Argentina, particularly in cotton-growing regions, while remaining a sporadic pest in the southern United States. Larvae feed gregariously when young, skeletonizing leaves, and become solitary as they mature, often boring into fruit. The species has been to West Africa (Nigeria and Cameroon).

Spodoptera eridania by Eddie McGriff, University of Georgia, United States. Used under a CC BY 3.0 us license.

Spodoptera eridania (16767585604) by Donald Hobern from Copenhagen, Denmark. Used under a CC BY 2.0 license.

Spodoptera eridania (16767587044) by Donald Hobern from Copenhagen, Denmark. Used under a CC BY 2.0 license.

Pronunciation

How to pronounce Spodoptera eridania: /spɔˈdɒptɛrə ɛˈrɪdəniə/

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

Identification

are distinguished from other Spodoptera by the combination of gray- with variable pattern (including presence or absence of central bean-shaped spot) and opalescent hind . are distinguished from similar species by the position of the dark spot on the first abdominal (versus in S. exigua), the interruption of the light-colored by the black marking on the first abdominal segment (line is continuous in S. cosmioides), and the larger size of black spots on the first abdominal segment relative to those on the eighth when the line is absent (opposite pattern in S. cosmioides). The species rarely exhibits a black marking on top of the mesothoracic segment, which is almost always present in S. cosmioides.

Images

Habitat

Agricultural fields, particularly soybean, cotton, and vegetable ; also found on various weeds in disturbed . are typically found on the lower parts of leaves. In northern Florida, larvae occur only in summer months despite being present year-round.

Distribution

range: North America (southern United States as far west as Kansas and New Mexico), through the Caribbean and Central America into South America (Brazil to Argentina). to West Africa: Nigeria and Cameroon. Present in Belgium (status doubtful) and Denmark.

Seasonality

are on year-round in tropical and subtropical regions. In northern Florida, adults occur throughout the year (withstanding several days of freezing weather), while are present only in summer months. Approximately four per year occur in Florida, with one generation lasting 30–40 days.

Diet

Highly . feed on a wide range of vegetables (beet, cabbage, carrot, collard, cowpea, eggplant, okra, pepper, potato, sweet potato, tomato, watermelon), fruits (avocado, citrus), field (peanut, sunflower, velvet bean, , soybean), and various flowers. Preferred weed include Amaranthus and Phytolacca americana. Lima bean is a preferred host, possibly due to cyanogenic glycoside content. Grasses are rarely eaten.

Host Associations

Solanum lycopersicum - feeds onheavy feeder on tomato in Florida
Glycine max - feeds onmajor pest in Brazil and Argentina
Gossypium - feeds onassociated with cotton-growing regions
Amaranthus - preferred preferred weed
Phytolacca americana - preferred preferred weed
Phaseolus lunatus - preferred preferred , possibly due to cyanogenic glycosides

Life Cycle

with four stages: , , , . Eggs are flattened spheres measuring approximately 0.45 mm diameter and 0.35 mm height, green initially turning tan with age, laid in clusters covered with from the female's body; duration 4–6 days. Larvae have six , duration 14–20 days; feed gregariously when young, becoming solitary as they mature. Pupae are mahogany , 16–18 mm long and 5–6 mm wide, formed in soil at 5–10 cm depth; duration 11–13 days. occurs in pupae, with females larger due to an additional instar. Adult lifespan is positively correlated with pupal size in females but negatively in males. Total time approximately 30–40 days. Four generations estimated per year in Florida.

Behavior

Young feed gregariously, skeletonizing leaves. As they mature, larvae become solitary and , hiding on lower leaf parts during the day. When food-stressed, larvae will eat portions of branches, bore into stem tissue, and attack tubers near the soil surface. Larvae readily bore into fruit, particularly tomatoes. are nocturnal.

Ecological Role

function as primary consumers and significant in agricultural . The serves as for numerous (Campoletis flavicincta, Chelonus insularis, Cotesia marginiventris, Euplectrus platyhypenae, Meteorus autographae, Meteorus laphygmae, Ophion flavidus) and (Choeteprosopa hedemanni, Eucelatoria rubentis, Euphorocera claripennis, Gonia crassicornis, Lespensia sp., Winthemia quadripustulata, Winthemia rufopicta), contributing to complexity.

Human Relevance

Major agricultural pest causing significant to soybean, cotton, and vegetable . In Brazil and Argentina, has emerged as one of the most important pests of soybean. In Florida, heavy feeder on tomatoes causing fruit damage. Subject of extensive research on alternative , particularly -based products containing , which reduce feeding and disrupt growth and development. Bt corn expressing Cry1F and Cry1F + Cry1A.105 + Cry2Ab2 causes 100% mortality in . Management relies primarily on foliar insecticides applied when larvae are small; are generally ineffective.

Similar Taxa

Spodoptera cosmioides easily confused in South America; distinguished by presence of dark spot on mesothoracic (usually absent in S. eridania), continuous (interrupted in S. eridania), and smaller first abdominal segment spots relative to eighth when line absent (opposite in S. eridania)
Spodoptera exigua can be confused due to dark spot; distinguished by position on versus first abdominal in S. eridania
Spodoptera frugiperdaSimilar distribution and pest status; distinguished by presence of four pinaculae per abdominal with Y-shaped marking in S. frugiperda
Spodoptera ornithogalliSimilar distribution; distinguished by paired black triangular spots with uninterrupted stripes in S. ornithogalli