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Beet armyworm

The beet armyworm (Spodoptera exigua), a moth species in the family Noctuidae, is a highly destructive agricultural pest originating from Southeast Asia and widely distributed across the Americas, including the southern United States.^[1] Its larvae, known as armyworms due to their gregarious feeding behavior, are pale green to yellowish caterpillars with dark longitudinal stripes and spots, growing up to 1.25 inches (3 cm) long, and they voraciously defoliate a broad range of host plants.^[1] Adults are medium-sized moths with a wingspan of 1 to 1.25 inches (25–30 mm), featuring mottled gray-brown forewings with pale spots and white hindwings bordered in dark gray.^[1] This insect undergoes complete metamorphosis, with a life cycle of 24–40 days that allows multiple generations per year in warm climates, exacerbating its pest status.^[1]^[2] The beet armyworm's eggs are laid in fuzzy, greenish-white clusters of 50–150 on the undersides of leaves, hatching in 2–5 days into tiny larvae that initially skeletonize foliage before older instars consume entire leaves, leading to significant crop damage.^[1]^[2] Pupation occurs in shallow soil chambers, lasting 5–8 days, after which adults emerge to mate and oviposit, with females capable of laying around 80 eggs per cluster.^[2] It attacks over 80 host species, including economically vital crops such as tomatoes, cotton, soybeans, lettuce, alfalfa, peppers, and sugar beets, as well as weeds like pigweed that serve as alternative hosts.^[1]^[2] In severe infestations, even low densities—one larva per 20 plants—can cause substantial economic losses through defoliation and fruit scarring, particularly in tomato production and other vegetable and field crops.^[1] First detected in North America in Oregon in 1876 and reaching Florida by 1924, the beet armyworm has become established in subtropical regions and migrates northward annually via wind currents, posing recurring threats to temperate agriculture.^[1] Management relies on integrated pest strategies, including monitoring with pheromone traps, cultural practices like crop rotation, biological controls such as the nuclear polyhedrosis virus, and targeted insecticides when thresholds are exceeded.^[1] Recent outbreaks in 2024–2025 in the southeastern United States have shown control failures with certain insecticides like diamides and chlorantraniliprole due to resistance, highlighting the ongoing challenges.^[3]^[4] Its rapid reproductive rate and polyphagous nature make it a persistent challenge for growers worldwide, underscoring the need for vigilant scouting and resistant crop varieties.^[2]

Taxonomy and Identification

Taxonomy

The beet armyworm is scientifically classified as Spodoptera exigua (Hübner, 1808), a species within the order Lepidoptera and the family Noctuidae, which comprises the owlet moths.^[5] Its full taxonomic hierarchy places it in the kingdom Animalia, phylum Arthropoda, class Insecta, order Lepidoptera, family Noctuidae, subfamily Noctuinae, genus Spodoptera, and species S. exigua.^[5] The genus Spodoptera is characterized by moths whose larvae exhibit gregarious feeding behavior, earning them the common name "armyworms."^[6] Originally described as Noctua exigua by Jacob Hübner, the species was later reassigned to the genus Spodoptera based on morphological and phylogenetic alignments within the Noctuidae.^[7] Accepted synonyms include Laphygma exigua, Caradrina venosa Butler, 1880, Caradrina junceti Zeller, 1847, and Caradrina pygmaea Rambur, 1834, reflecting historical taxonomic revisions as lepidopteran classifications evolved.^[6]^[8] The etymology of the binomial name highlights key traits: "Spodoptera" combines the Greek spodos (wood ash) and ptera (wings), alluding to the pale, ash-like coloration of the adult moth's wings.^[9] The specific epithet "exigua" derives from Latin, meaning "scanty" or "meager," a reference to the relatively small size of the species compared to other armyworms. Within the genus Spodoptera, which includes approximately 30 species of polyphagous pests, S. exigua is closely related to species like the true armyworm S. exempta and shares superficial similarities with the fall armyworm S. frugiperda, though it is distinguished by its original description and specific nomenclatural history.^[10]

Description

The beet armyworm, Spodoptera exigua, is a moth species whose adult form measures 25–30 mm in wingspan and has a body length of approximately 19 mm.^[1]^[11] The forewings are mottled gray-brown with irregular dark banding and a pale, bean-shaped spot near the middle, while the hindwings are whitish with a narrow dark border.^[1]^[11] Eggs are laid in clusters of 50–150, typically numbering up to 300 in larger masses, on the lower surfaces of leaves; each egg is circular to slightly conical, about 0.5 mm in diameter, greenish-white, and covered in a fuzzy layer of whitish scales that give a ribbed appearance.^[1]^[11] Larvae reach maturity at 30–35 mm in length, progressing through five instars where early stages (1–2) are pale green or yellow with dark heads, and later stages (3–5) develop a darker green to pinkish-brown dorsal area with a prominent dark midline stripe, pale wavy lateral stripes, and a broader white stripe along each side.^[1]^[11]^[13] A key diagnostic trait is the presence of two black spots on the mesothorax just behind the head, above the second pair of true legs; mature larvae bear three pairs of prolegs and exhibit sparse hairs with dark spiracles bordered in black.^[11]^[1] The pupa measures 15–20 mm in length and is smooth, light to reddish-brown in color, typically formed in a shallow underground chamber of soil particles or within plant debris.^[1]^[11] Sexual dimorphism is subtle, with females generally larger than males and possessing more prominent abdominal tufts for pheromone dispersal.^[1] For field identification, the species is distinguished by larval morphology, including the thoracic spots, alongside brief observations of group marching behavior in dense infestations.^[11]^[1]

Distribution and History

Origin and Spread

The beet armyworm, Spodoptera exigua (Hübner), is native to Southeast Asia and first described in 1808 (type locality: Europe).^[1] This polyphagous moth species likely evolved in tropical environments conducive to its broad host range, including vegetables and field crops, before human activities facilitated its dispersal beyond Asia.^[14] Early records from Asia highlight its association with agricultural systems, setting the stage for its role as an invasive pest elsewhere.^[15] The species was introduced to North America in the late 19th century, with the first record occurring in Oregon in 1876, probably transported via imported produce or trade goods.^[1]^[16] From there, it gradually spread eastward and southward, reaching Florida by 1924, with early records in California dating to 1876, aided by suitable climatic conditions in agricultural areas.^[1] These initial introductions underscore the role of commerce in bridging continents, allowing the moth to exploit new host plants like beets, cotton, and tomatoes.^[14] Globally, S. exigua has established in Europe, particularly in Mediterranean regions, South America, and Africa through trade routes, shipping, and wind-assisted migration.^[10] Today, it is cosmopolitan in tropical and subtropical areas worldwide, except Antarctica, due to a combination of dispersal mechanisms including wind-assisted migratory flights covering up to 100 km or more, human-mediated transport on ships and aircraft, and favorable air currents that carry adults over long distances.^[10]^[17]^[18] Significant historical outbreaks in the United States during the 1940s, particularly in cotton fields, highlighted the pest's economic threat and spurred early research into control methods. For instance, a major infestation in Arizona in 1946 affected thousands of acres but was managed with DDT applications, marking a pivotal moment in integrated pest management development for armyworms.^[19] These events, driven by population surges following mild winters and agricultural expansion, emphasized the need for monitoring migratory patterns to mitigate spread.^[20]

Current Distribution

The beet armyworm, Spodoptera exigua, exhibits a broad global distribution, spanning the Americas (including the United States, Mexico, Central and South America, and the West Indies), Asia (from Afghanistan and India to China, Japan, and Vietnam), Europe (primarily Mediterranean countries such as Bulgaria, France, Greece, Italy, Portugal, and Spain), Africa (from Algeria and Egypt to South Africa and Madagascar), and Oceania (including Australia and Hawaii).^[21] This pest is absent from extreme cold regions, such as Antarctica and high northern latitudes, where persistent low temperatures prevent survival and reproduction.^[10] Within the United States, S. exigua persists year-round in southern states like Florida, Texas, and California, as well as Hawaii, where mild winters support continuous generations.^[22] In northern and midwestern states, populations rely on annual northward migration from southern breeding grounds, with moths and larvae dispersing via wind currents during spring and summer to reinvade temperate areas.^[22] The species favors warm, humid climates for optimal development, with temperatures between 25 and 30°C promoting rapid life cycle completion and high reproductive rates.^[23] It cannot overwinter successfully in regions where average winter temperatures drop below 10°C, as eggs, larvae, and pupae lack sufficient cold tolerance, resulting in die-off and dependence on seasonal recolonization from southern refugia.^[24] S. exigua holds regulated pest status in select countries, prompting biosecurity measures such as import inspections and restrictions on host materials; for instance, Australia maintains surveillance and quarantine protocols to mitigate risks from potential introductions or internal spread.^[25]

Life Cycle and Ecology

Life Cycle

The beet armyworm, Spodoptera exigua, undergoes complete metamorphosis, consisting of egg, larval, pupal, and adult stages.^[1] The entire life cycle typically spans 25–40 days under optimal conditions of around 27°C, though durations vary with temperature.^[26] Eggs are laid in clusters of 50–150 on the lower surfaces of leaves, with females producing 300–600 eggs over their lifetime in masses covered by scales from the ovipositor.^[1] Hatching occurs in 2–3 days in warm weather (25–30°C), extending to 3.5–6 days at slightly lower temperatures; the minimum temperature for egg hatch and development is approximately 13°C, below which no viable development proceeds.^[1]^[26] Larvae pass through 5–6 instars over 14–20 days at 25–30°C, with early instars pale green and later ones darker green to black with longitudinal stripes and a posterior dark spot.^[1]^[26] Development accelerates at higher temperatures, shortening to 9–14 days near 35°C, but ceases below 13°C.^[26] The pupal stage lasts 6–8 days in soil chambers at warm temperatures (25–30°C), forming reddish-brown pupae 15–20 mm long.^[1]^[26] Adults emerge after this period, with a lifespan of 7–10 days; they are grayish-brown moths with a 25–30 mm wingspan.^[1] Reproduction involves polyandrous mating, where females can mate multiple times to enhance fecundity, and is mediated by female sex pheromones that attract males, often beginning on the first night post-emergence for optimal reproductive success.^[27]^[28] Oviposition starts 2–3 days after mating and continues for 3–7 days.^[1] The species lacks a diapause mechanism, allowing continuous development in frost-free regions but resulting in slowed growth and high mortality in cooler conditions below 15°C.^[1]^[29] In warm climates like Florida or desert areas, 4–8 generations occur annually, while fewer (2–4) arise in temperate zones due to winter limitations.^[1] Population dynamics feature exponential growth during outbreaks, driven by rapid cycling and high reproductive output when host plants are abundant, leading to sudden increases in local densities.^[30]^[1]

Habitat and Hosts

The beet armyworm, Spodoptera exigua, primarily inhabits agricultural fields, vegetable gardens, and weedy areas, with a particular preference for irrigated crops in arid and subtropical regions. It thrives in environments supporting a variety of host plants, such as cotton fields, vegetable plots, and areas with off-season crops, where warm temperatures and moisture facilitate its development. In temperate zones like Colorado, it does not overwinter and relies on annual reinvasion, while in tropical and southern subtropical areas south of 25°N latitude, it can breed year-round.^[31]^[18]^[1] The species has a broad host range encompassing over 170 plant species across multiple families, enabling its proliferation in diverse agroecosystems. Primary hosts include solanaceous plants such as tomato (Solanum lycopersicum), potato (Solanum tuberosum), pepper (Capsicum spp.), and eggplant (Solanum melongena); cruciferous vegetables like cabbage (Brassica oleracea); malvaceous crops including cotton (Gossypium spp.); and others such as beets (Beta vulgaris), lettuce (Lactuca sativa), alfalfa (Medicago sativa), corn (Zea mays), beans (Phaseolus spp.), and onions (Allium cepa). Weedy hosts like pigweed (Amaranthus spp.) are particularly favored for oviposition due to higher nutritional quality, including elevated levels of beneficial amino acids.^[18]^[32]^[33] Larval feeding behavior begins gregariously, with young instars congregating near plant growth tips, spinning loose silk webbing to enclose foliage and creating small pinholes or "transparent windows" in leaves as they skeletonize tender tissues. As larvae mature into later instars, they become more solitary, dispersing to feed nocturnally on foliage, fruits, and preferring young, succulent leaves over tougher older ones. This shift supports efficient resource exploitation while minimizing exposure during daylight.^[31]^[32] Adult moths exhibit strong migratory capabilities, flying long distances to colonize new fields after harvest or in response to favorable winds, particularly northward in spring and southward in autumn. Overwintering occurs in the pupal stage within soil in mild climates of the southern United States, such as Arizona, Florida, and Texas, where frost does not eliminate host plants. Recent studies indicate evolving adaptations, with larvae showing avoidance and antifeedant responses to Bt maize, potentially driving shifts toward non-traditional or resistant hosts like certain weeds.^[31]^[1]^[34]

Natural Enemies

The beet armyworm, Spodoptera exigua, is regulated in natural ecosystems by a diverse array of predators, parasitoids, and pathogens that target various life stages, particularly eggs and larvae, contributing to population cycles observed in agricultural fields.^[35] These biotic factors often impose significant mortality, with natural enemies collectively accounting for substantial suppression in untreated environments, though their efficacy can vary by region, crop, and environmental conditions.^[1]^[36] Predators play a key role in consuming eggs and early instar larvae, preventing outbreaks from escalating. Common invertebrate predators include ground beetles (Carabidae), spiders (Araneae), big-eyed bugs (Geocoris spp.), minute pirate bugs (Orius spp.), damsel bugs (Nabis spp.), assassin bugs (Hemiptera: Reduviidae), and lacewings (Chrysopidae).^[35]^[1] Vertebrate predators such as birds (e.g., blackbirds and other ground-foraging species) and rodents also target larvae and pupae, with field observations indicating larval consumption rates by predators reaching up to 50% in some crop systems like alfalfa.^[36]^[37] Parasitoids, primarily hymenopteran wasps, attack eggs and larvae, often achieving high parasitism levels on vulnerable stages. Egg parasitoids like Trichogramma spp. lay eggs inside host eggs, halting larval development, while larval parasitoids such as Cotesia marginiventris (Braconidae), Hyposoter exiguae (Ichneumonidae), Chelonus insularis (Braconidae), and Meteorus autographae (Braconidae) develop internally, leading to host death.^[35]^[1] In field studies on alfalfa, parasitoids alone contributed 25–60% mortality to beet armyworm populations.^[36] Tachinid flies like Lespesia archippivora also parasitize larvae, adding to overall pressure.^[1] Pathogens, including viruses and fungi, induce epizootics during favorable humid conditions, causing rapid population declines. The nucleopolyhedrovirus (SeMNPV) is a primary viral pathogen, infecting larvae and leading to liquefaction and death; in natural outbreaks and lab assays, it can cause up to 90–100% mortality at high doses or under optimal conditions.^[1]^[38] Entomopathogenic fungi such as Beauveria bassiana and Nomuraea rileyi (syn. Metarhizium rileyi) penetrate larval cuticles, resulting in 70–93% mortality in exposed populations.^[38]^[39] In unsprayed fields, these natural enemies collectively suppress beet armyworm populations by 70–80%, maintaining low densities between outbreak years, as evidenced in diverse cropping systems.^[35]^[36] However, broad-spectrum insecticides disrupt this regulation by killing non-target predators and parasitoids, often exacerbating pest resurgence.^[1] Recent research (2024) has explored enhancing NPV efficacy through tank-mix formulations with adjuvants like UV protectants, improving field persistence and mortality under variable climate conditions for related spodopterans, with potential applications to S. exigua.^[40]

Economic Impact

Crop Damage

The larvae of the beet armyworm (Spodoptera exigua) primarily cause damage through foliar feeding, with young instars (first and second) feeding gregariously by scraping the lower leaf surfaces, resulting in skeletonization where only the veins remain intact.^[41] These early-stage larvae often spin loose silk webs over the foliage for protection, while feeding predominantly at night to avoid predation and sunlight.^[42] As larvae mature (third instar and older), they become solitary and more mobile, dispersing across plants to chew large, irregular holes in leaves, bore into terminal buds, stems, or developing fruits, and deposit frass (excrement) along with additional silk.^[1]^[42] Damage symptoms include progressive defoliation, which can reach up to 100% in severe infestations, leaving plants bare and exposing them to environmental stress.^[1] Feeding on buds and growing tips causes stunted plant growth and distorted development, while the presence of frass and silk webs contaminates foliage and produce, diminishing aesthetic and market quality.^[41]^[42] Economic injury levels are generally reached at 20–30% defoliation in susceptible field crops, though complete destruction of seedlings can occur when small larvae target tender tissues en masse.^[1]^[41] Secondary effects exacerbate the primary injury, as larval feeding wounds create entry points for opportunistic pathogens, increasing plant susceptibility to secondary infections and diseases.^[41] The silk mats and frass accumulations produced during gregarious feeding can also harbor fungal spores or other minor pests, further compromising plant health.^[42] During outbreaks, mature larvae exhibit "marching" behavior, moving in loose groups across fields to exploit new food sources, which enables rapid defoliation of entire areas within 1–2 weeks under favorable conditions.^[1]^[42]

Affected Crops

The beet armyworm (Spodoptera exigua) primarily impacts vegetable crops such as lettuce, celery, and tomato. Field crops including cotton and alfalfa are also frequently affected, particularly during seedling and vegetative stages, while ornamentals like chrysanthemum suffer defoliation that reduces aesthetic and market value.^[43]^[44] Soybean serves as an occasional host, with larvae feeding on foliage and pods, though infestations are typically sporadic in this crop.^[1]^[45] In 2024, outbreaks in peanut fields in the Florida Panhandle led to control failures due to insecticide resistance, increasing economic impacts in southeastern US field crops.^[4] As of 2025, resistance to Vip3Aa in Bt crops has been confirmed, posing challenges for management.^[46] In California's vegetable production belts, particularly the Central Valley and coastal regions, the pest causes notable damage to high-value crops like lettuce and broccoli, with annual pest management costs increasing by $1.3 to $2.1 million in alfalfa alone due to reliance on alternative insecticides following restrictions on older chemistries.^[47] Pre-2020 estimates indicate revenue losses of $0.5 to $1.0 million in cotton from potential yield declines of 15% in upland varieties without effective control.^[47] Untreated infestations can result in yield reductions of 20–50% in susceptible crops like tomato, where one larva per 20 plants exceeds the economic injury level and leads to significant fruit damage.^[29] Seedlings and flowering stages are most vulnerable, as young larvae skeletonize leaves and older ones bore into buds, amplifying losses in these critical growth phases.^[1] Recent data highlight rising impacts from climate-driven range shifts, with temperatures above 20°C accelerating development and survival, potentially expanding suitable habitats northward.^[48]

Management

Cultural Control

Cultural control methods for the beet armyworm (Spodoptera exigua) emphasize farm management practices that disrupt the pest's life cycle and reduce infestation risks without relying on chemical inputs. Crop rotation plays a key role by alternating susceptible host crops with non-host crops where possible, over 2–3 year cycles to limit the survival of soil pupae and prevent population buildup. This approach breaks the pest's generational continuity, particularly in regions with multiple overlapping generations, and integrates well with broader soil health strategies.^[41] Sanitation practices further mitigate infestations by targeting crop residues and alternative hosts. Destroying plant debris immediately after harvest through disking exposes and kills remaining larvae and pupae in the soil, while deep tillage buries pupae beyond their emergence depth, reducing overwintering survival.^[41] Additionally, removing weeds such as pigweed and lambsquarters along field borders prevents migration of moths and larvae into new plantings, acting as a barrier to reinfestation.^[41] Timing of planting and use of physical deterrents enhance prevention efforts. Early planting allows crops to mature before peak beet armyworm generations, which typically occur in late summer and fall, thereby minimizing exposure during vulnerable growth stages.^[41] Reflective mulches, such as aluminum or silver-colored plastics applied around seedlings, disorient adult moths and deter oviposition by altering light reflection, providing effective early-season protection especially in cucurbit and vegetable fields.^[49] Regular monitoring supports threshold-based decisions to implement these practices proactively. Pheromone-baited and sticky traps placed along field perimeters detect adult moth influx, signaling potential egg-laying and prompting intensified scouting for eggs and young larvae on plants and borders.^[50] Fields should be inspected twice weekly, focusing on undersides of leaves and weeds, with action thresholds typically set at 10–20% infested plants to guide timely cultural interventions.^[41]

Biological Control

Biological control of the beet armyworm, Spodoptera exigua, relies on the deployment of living organisms and biopesticides to suppress populations in an environmentally targeted manner. These strategies leverage natural enemies and microbial agents that are selective for the pest, minimizing impacts on beneficial insects and non-target species. Key approaches include augmentative releases of parasitoids and predators, as well as applications of bacteria, viruses, fungi, and nematodes, which have demonstrated efficacy in field and laboratory settings across vegetable and field crops.^[43] Parasitoids play a central role in egg and larval suppression. Releases of the egg parasitoid Trichogramma pretiosum target S. exigua eggs, which significantly reduces larval emergence and crop damage.^[51] For larval stages, braconid wasps such as Cotesia marginiventris and Cotesia ruficrus parasitize early instars, with field observations in clover crops showing substantial attack rates during peak infestation periods, contributing to natural population regulation.^[52]^[53] Predators provide augmentation and conservation opportunities for broader suppression. Lady beetles (Coccinellidae) and lacewings (Chrysopidae) are effective generalist predators that consume S. exigua eggs and small larvae, with their larvae exhibiting high voracity in crop fields; augmentative releases enhance control in high-value systems like cotton and vegetables.^[54]^[55] Native spiders, including orb-weavers and wolf spiders, conserve through habitat management and prey on wandering larvae, forming part of the natural enemy complex that maintains low pest densities in agroecosystems.^[54] Microbial agents offer foliar-applied options for larval control. Bacillus thuringiensis (Bt) toxins, particularly Cry1Ac, exhibit high toxicity to susceptible S. exigua larvae, with laboratory bioassays determining LC₅₀ values indicative of effective suppression prior to widespread resistance development in some populations.^[56] Nuclear polyhedrosis viruses (NPV), such as Spodoptera exigua NPV (SeNPV), are applied foliarly and cause liquefaction of infected larvae, providing up to 90% mortality in vegetable crop trials and serving as a host-specific biopesticide.^[57]^[58] Entomopathogenic fungi and nematodes target specific life stages under suitable conditions. Metarhizium anisopliae isolates show high virulence against S. exigua larvae in humid environments, with field applications in onion crops achieving over 90% mortality and effective integration into IPM programs.^[59]^[60] Entomopathogenic nematodes, such as Steinernema and Heterorhabditis spp., infect soil-dwelling prepupae and pupae, proving more effective against these stages than foliar larvae, with susceptibility highest when pests drop to the soil for pupation.^[1] Recent advancements in transgenic crops enhance biological control integration. The 2025 Bt maize event DBN3601T, expressing Cry1Ab and Vip3Aa proteins, demonstrated over 95% efficacy against S. exigua in field trials, significantly reducing larval survival and plant damage even against resistant strains, supporting sustainable management in maize systems. However, as of 2025, field-evolved resistance to Vip3Aa has been reported in U.S. populations, highlighting the need for resistance management strategies.^[34]^[46]

Chemical Control

Chemical control of the beet armyworm (Spodoptera exigua) primarily relies on insecticides from several classes, selected based on their efficacy against larval stages and integration with other pest management practices. Pyrethroids, such as lambda-cyhalothrin, target the nervous system by disrupting sodium channels and are commonly applied for foliar control in crops like cotton and vegetables.^[43] Organophosphates, including methomyl, inhibit acetylcholinesterase to cause paralysis and have been used historically, though their application is now limited due to regulatory restrictions. Neonicotinoids, like thiamethoxam, act systemically by binding to nicotinic acetylcholine receptors and can provide uptake protection in transplants through soil drenches or seed treatments, offering early-season suppression.^[61] Additionally, spinosyns such as spinosad and spinetoram, which affect nicotinic acetylcholine and GABA receptors, serve as alternatives with reduced environmental impact and are effective against small larvae.^[41] Application strategies emphasize timing and method to maximize efficacy while minimizing resistance development. Foliar sprays are recommended when monitoring detects small larvae (second or third instar), as larger larvae are more tolerant and cause greater damage; for instance, applications should occur before crop heading in cole crops to achieve over 90% control with products like chlorantraniliprole.^[41] Systemic uptake via drenches in transplants, using neonicotinoids or diamides, protects emerging plants from initial infestations without broad foliar exposure. Ground applications require at least 5 gallons of water per acre for thorough coverage, while aerial methods use a minimum of 1 gallon per acre, often with adjuvants to enhance penetration.^[43] Resistance poses a significant challenge, with beet armyworm populations exhibiting widespread resistance to multiple insecticide classes since the 1990s, including carbamates, organophosphates, pyrethroids, spinosyns, avermectins, benzoylureas, diacylhydrazines, and diamides.^[62] This resistance, documented in the US, Mexico, and Asia, often involves metabolic detoxification through enzymes like cytochrome P450 monooxygenases (e.g., CYP321A8) and glutathione S-transferases, with recent 2024-2025 studies confirming elevated metabolic resistance in US populations from peanut and cotton fields.^[62] Organophosphates and pyrethroids show particularly high resistance levels due to decades of consistent use.^[63] Integration into integrated pest management (IPM) is essential to sustain chemical efficacy, focusing on rotation of modes of action to prevent further resistance selection. Guidelines recommend limiting any single IRAC group to no more than two applications per season and avoiding prophylactic sprays, instead applying based on economic thresholds like one larva per 10 plants.^[41] This approach, combined with scouting via pheromone traps or sweep nets, preserves natural enemies and reduces overall insecticide reliance.^[43] Regulatory considerations have shifted options toward lower-risk materials, with the US EPA revoking tolerances for chlorpyrifos on food crops in 2021, eliminating its use for beet armyworm control due to neurotoxicity concerns.^[64] Emphasis is placed on low-residue insecticides like spinosad and Bacillus thuringiensis products for export-oriented crops, ensuring compliance with maximum residue limits (MRLs) in markets like the EU.^[41] Permits may be required for certain organophosphates, and all applications must avoid bloom periods to protect pollinators.^[43]

References

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Beet Armyworm, Spodoptera exigua (Hübner) (Insecta: Lepidoptera
The beet armyworm originated in Southeast Asia. It was first discovered in North America about 1876, when it was found in Oregon, and it reached Florida in 1924 ...
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Noctuoidea: Noctuidae: Noctuinae: Spodoptera exigua (Hübner). Common names: beet armyworm, small mottled willow. Synonyms: Caradrina venosa, Laphygma exigua.Missing: etymology historical
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Spodoptera exigua (Hübner, 1808) in GBIF Secretariat (2023). GBIF Backbone Taxonomy. Checklist dataset https://doi.org/10.15468/39omei accessed via GBIF.org on ...Missing: authoritative | Show results with:authoritative
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Names and sources ; Laphygma caradrinoides Walker, 1856 synonym. AFD ; Caradrina junceti Zeller, 1847 synonym. AFD ; Caradrina pygmaea Rambur, 1834 synonym. AFD.<|control11|><|separator|>
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The beet armyworm (Lepidoptera: Noctuidae) belongs to the genus Spodoptera and species exigua. Hübner. The eggs of the BAW are white to white with a green tinge ...
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Spodoptera exigua. [Distribution map]. - CABI Digital Library
A new distribution map is provided for Spodoptera exigua (Hb.) (Laphygma exigua[Spodoptera exigua] Hb.) (Lep., Noctuidae) (Beet Army Worm, ...
[22]
beet armyworm (Spodoptera exigua (Hübner, 1808)) - EDDMapS
This species is Native to certain parts of the United States but may be invasive to others. States Counties Points List Species Info · Distribution Record ...
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[PDF] development-parameters-and-population-life-table-of-beet ...
Dec 1, 2017 · The upper limit, lower limit and optimum temperatures for development of the entire generation are 38, 5.7 and 30 ℃, resepctively. Keywords ...
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Modeling climate change impacts on overwintering of Spodoptera ...
In the present study, results apparently showed that winter warming could shift the overwintering boundary of S. exigua in a northerly direction. Range ...
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The beet armyworm (Spodoptera exigua) - Cropaia
Mar 16, 2025 · Beet armyworm (Spodoptera exigua) is an averagely sized moth that was native to Southeast Asia before spreading to other parts of the world.The Beet Armyworm... · Life Cycle · Damage
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C.O.R.N. Newsletter: 2024-26 | Agronomic Crops Network
Aug 6, 2024 · This past week, fields in Wooster have been seeing damage that can be tied back to fall armyworm larvae (Figure 1). Less larvae were present ...
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[PDF] Army worms (Spodoptera spp.) - Plant Pest Factsheet
The caterpillars of these moths feed on a wide range of plants. Caterpillars of the genus Spodoptera are known as. "armyworms", because of the behaviour of the ...
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Interactive Effects of Temperature and Plant Host on the ...
The beet armyworm Spodoptera exigua (Hübner) (Lepidoptera: Noctuidae) is an economic pest that causes significant damage to various vegetables and field crops ...
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[PDF] Biotic Potential and Reproductive Parameters of <i>Spodoptera ...
Aug 15, 2019 · The fecundity, longevity of both sexes, and the duration of pre- and post-oviposition periods were correlated with the number of copulations ...
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[PDF] Relationship of flight and reproduction in beet armyworm ...
Adults were further tested to determine if they have enough flight capacity to pursue inter-ovipositional migratory flights by comparing flight performance of ...
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[PDF] impact of spodoptera exigua, beet armyworm on tomato
Aug 26, 2006 · It lacks a diapause mechanism and daytime ... level as large as a natural occurring population in the field in the summer of 2004 was not.
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[PDF] Response of Reproductive Traits and Longevity of Beet Webworm to ...
Peak daily and lifetime fecundity were highest at 22–26 C and declined at temperatures outside this range, suggesting that 22–26 C is the optimal thermal range ...Missing: lifespan | Show results with:lifespan
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Armyworms - Agricultural Biology - CSU College of Ag Sciences
The beet armyworm is native to Asia and an introduced species in North America. Caterpillars of beet armyworm are pale green or yellow when young but develop ...
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[PDF] Hawai'i Landscape Plant Pest Guide: Chewing Insects - CTAHR
Host range: ornamentals (chrysanthemum, rose) andvegetable crops (beets, beans, crucifers, carrot, corn, cotton, lettuce, onion, peas, pepper, potato, sorghum, ...Missing: list | Show results with:list<|separator|>
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Beet Armyworm Eggs: Not Just a Random Scramble
It's well documented in the literature that pigweed, cotton, peppers, sunflowers, and cabbage, among many other species, are used as host plants by beet ...
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Selection Behavior of the Beet Armyworm, Spodoptera exigua ... - NIH
Oct 17, 2025 · The beet armyworm, Spodoptera exigua (Hübner) (Lepidoptera: Noctuidae), is a southern Asian native and a major agricultural pest that breeds ...
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Beet Armyworm / Alfalfa / Agriculture: Pest Management ... - UC IPM
Armyworms are common pests in the Central Valley and desert valleys from June through September. There are at least 5 generations per year in the low desert and ...
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[PDF] Evaluation of Natural Enemies of Beet Armyworm on Alfalfa in ...
Eggs and small to medium-sized larvae of beet armyworm are exploited by a complex of natural enemies in hay alfalfa fields in northern California.Missing: parasitoids Beauveria
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Armyworms « VegNet - Oregon State University
Biological Control: Parasites (flies, wasps) and predators (ground beetles, assassin bugs, spiders, birds, rodents) are important regulators of armyworm ...Missing: beet | Show results with:beet
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Effect of the fungus, Beauveria bassiana (Balsamo) Vuillemin, on the ...
Aug 16, 2019 · A local isolate of the fungus Beauveria bassiana was tested against the beet armyworm Spodoptera exigua (Hübner) (Lepidoptera: Noctuidae) larvae ...
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Effects of Entomopathogenic Fungi on the Biology of Spodoptera ...
Jul 31, 2019 · Entomopathogenic fungi (EPFs), Isaria fumosorosea and Beauveria bassiana, are efficient biological agents in the management of multiple arthropod pests.
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A novel tank-mix formulation increases the efficacy of ...
Dec 26, 2024 · The tank-mix simple formulation of baculoviruses might be a great alternative for improved stability in nature, providing better control.
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Beet Armyworm / Cole Crops / Agriculture - UC IPM
Beet armyworms can kill seedlings, consume large portions of leaves, and stunt growth by feeding on buds. However, serious economic damage to cole crops is ...Missing: mechanisms symptoms injury levels effects outbreak patterns
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Beet armyworm - Biocontrol, Damage and Life Cycle - Koppert
Damage symptoms. Older caterpillars migrate to the top of the plant where they feed mainly on the growing tips. They produce large holes in the leaf, sometimes ...Missing: mechanisms economic injury levels outbreak
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Beet Armyworm / Cotton / Agriculture: Pest Management Guidelines ...
Beet Armyworm ; Cultural Control. A recently developed transgenic cotton, Bollguard II, offers suppression of a broader range of caterpillars, such as beet ...
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[PDF] The beet armyworm in floricultural crops - California Agriculture
We therefore conducted studies to de- termine the biology of beet armyworm on ornamentals such as chrysanthemum and to examine the possibility that this species.
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[PDF] 2025 Insect Control Guide for Agronomic Crops
The BEET ARMYWORM prefers to feed on foliage of seedling soybean plants. However, if they are present during fruiting, they will feed on bloom buds, blooms ...
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[PDF] Economic and pest management evaluation of the withdrawal of ...
Dec 10, 2019 · Beet armyworm (Spodoptera exigua) ... Monitoring for beet armyworms in weedy field margins helps keep them from moving into cotton crops.
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Fall Armyworm in Ohio Field Crops - Ohioline
Aug 25, 2023 · Fall armyworm is a tropical species, and in the United States it can overwinter in only the warmest places—southern Texas and South Florida.Missing: distribution | Show results with:distribution
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Off-season survival and life history of beet armyworm, Spodoptera ...
Jun 14, 2024 · The beet armyworm, Spodoptera exigua (Hubner) (Lepidoptera: Noctuidae), has become a significant pest of chickpea in recent years.
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Impact of Temperature Variation on the Biological Traits and ...
Feb 3, 2025 · Across all studies, elevated temperatures led to a reduction in the developmental period of fifth-instar S. exigua, with a combined mean effect ...Missing: preferences | Show results with:preferences
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Pest risk assessment of Spodoptera frugiperda for the European Union
Aug 31, 2018 · EFSA was asked for a partial risk assessment of Spodoptera frugiperda for the territory of the EU focussing on the main pathways for entry, ...
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Organic Insect Control for Commercial Vegetable Production
Use trap crops when feasible. Trap crops are crops planted to attract pests away from the main crop. For example, around cabbage, a border planting of collards ...
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Insect Management for Cucurbits (Cucumber, Squash, Cantaloupe ...
Beet armyworm, Spodoptera exigua (Hubner) (Figure 4), also feeds on many ... Reflective mulch may be helpful early in the season before plants cover it.
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[PDF] Beet Armyworm - IPM Florida
Although the beet armyworm is attacked by numerous natural enemies, they usually do not cause mortality soon enough to ... Natural enemies can be conserved by ...
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Vegetable IPM Reports - UNH Extension
Fall armyworm numbers were overall lower than 2024, but once the moths showed up in July, pressure remained relatively steady for the rest of the season. ...
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Biocontrol potential of Trichogramma species against Spodoptera ...
pretiosum were released, the parasitism rate on the egg masses ranged from 61.5 % to 87.5 %. The rate that the egg masses did not hatch were 41.7 %, 12.5 %, ...
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Cotesia marginiventris - UT Crops
This small parasitic wasp has no common name, but it still often plays an important role in helping suppress beet armyworm populations.
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Parasitism of Beet Armyworm (Spodoptera exigua) Larvae by ...
Aug 8, 2025 · This study revealed that C. ruficrus attacked the larvae of S. exigua in clover fields, particularly during April and May, with overall ...
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Common Beneficial Arthropods Found in Field Crops
There are hundreds of species of insects and spiders that attack arthropod pests found in cotton, corn, soybeans, and other field crops.Missing: birds | Show results with:birds
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Beneficial Insects - Mid-Florida Research and Education Center
Common predators include lady beetles, rove beetles, many ground beetles, lacewings, true bugs such as Podisus and Orius, syrphid fly larvae, mantids ...Missing: beet | Show results with:beet
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Efficacy of Cry1Ac toxin from Bacillus thuringiensis against the beet ...
Aug 21, 2019 · The present study was carried out to evaluate the efficacy of Cry1Ac toxin from Bt against the beet armyworm, S. exigua, under laboratory conditions.Missing: NPV viruses
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Biological Warfare Against Beet Armyworms - AgResearch Magazine
One recruit is a natural insect pathogen known as a Spodoptera exigua nuclear polyhedrosis virus (SeNPV). It liquefies the bodies of armyworms it infects but ...
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Spodoptera exigua Nuclear Polyhedrosis Virus as a Candidate Viral ...
The results of these tests confirm the efficacy of the SeMNPV for control of the beet armyworm on several vegetable crops. Issue Section: BIOLOGICAL AND ...
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[PDF] Control of beet armyworm with entomopathogenic fungi-metarhizium ...
The death percentage of beet armyworm was only 1.1∼1.7 for control, indicating the Metarhizium anisopliae control beet armyworn effectively in green onion.
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Virulence of Entomopathogenic Fungi Metarhizium anisopliae and ...
In this study, among various entomopathogenic fungal strains isolated from soil two isolates were selected as high virulence pathogens against larva of beet ...
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Seed Treatment with Diamide and Neonicotinoid Mixtures for ... - NIH
Jun 8, 2022 · Two independent field experiments showed that both binary mixtures resulted in above 68.00% control efficacy at 14 DAE, suggesting that these ...
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Beet armyworm Archives | Insecticide Resistance Action Committee
exiguais native to Southeast Asia but is now found in all continents, except Antarctica. It lacks a diapause mechanism and can only overwinter successfully in ...Missing: CABI | Show results with:CABI<|control11|><|separator|>
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Resistance of beet armyworm Spodoptera exigua (Lepidoptera
Organophosphates and pyrethroids were consistently used over the past three decades, and the resistance had been increasing to these insecticide classes.
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EPA Update on the Use of the Pesticide Chlorpyrifos on Food
Jan 16, 2025 · In a final rule issued in August 2021, EPA revoked all tolerances for chlorpyrifos, which establish an amount of a pesticide that is allowed on food.