The fall armyworm (''Spodoptera frugiperda'') is a species in the order
Lepidoptera and one of the species of the fall armyworm
moth
Moths are a paraphyletic group of insects that includes all members of the order Lepidoptera that are not butterflies, with moths making up the vast majority of the order. There are thought to be approximately 160,000 species of moth, many of w ...
s distinguished by their
larva
A larva (; plural larvae ) is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle.
...
l life stage. The term "armyworm" can refer to several species, often describing the large-scale invasive behavior of the species' larval stage. It is regarded as a
pest and can damage and destroy a wide variety of
crop
A crop is a plant that can be grown and harvested extensively for profit or subsistence. When the plants of the same kind are cultivated at one place on a large scale, it is called a crop. Most crops are cultivated in agriculture or hydropon ...
s, which causes large economic damage. Its scientific name derives from ''frugiperda,'' which is
Latin
Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through the power of the ...
for ''lost fruit'', named because of the species' ability to destroy crops.
Because of its propensity for destruction, the fall armyworm's habits and possibilities for crop protection have been studied in depth. It is also a notable case for studying
sympatric speciation, as it appears to be diverging into two species currently.
Another remarkable trait of the larva is that they consistently practice
cannibalism, despite its fitness costs.
The fall armyworm is active at a different time of year from the
true armyworm, another species in the order
Lepidoptera and family
Noctuidae, but of the genus
''Mythimna''. Outbreaks of the true armyworm usually occur during the early part of the summer; the fall armyworm does most damage in the late summer in the southern part of the United States, and early fall in the northern regions.
Description
![Spodoptera frugiperda2](https://upload.wikimedia.org/wikipedia/commons/5/5a/Spodoptera_frugiperda2.JPG)
The adult moths are wing tip to wing tip, with a brown or gray
forewing
Insect wings are adult outgrowths of the insect exoskeleton that enable insects to fly. They are found on the second and third thoracic segments (the mesothorax and metathorax), and the two pairs are often referred to as the forewings and hindwi ...
, and a white
hindwing
Insect wings are adult outgrowths of the insect exoskeleton that enable insects to fly. They are found on the second and third thoracic segments (the mesothorax and metathorax), and the two pairs are often referred to as the forewings and hindwi ...
. There is slight
sexual dimorphism
Sexual dimorphism is the condition where the sexes of the same animal and/or plant species exhibit different morphological characteristics, particularly characteristics not directly involved in reproduction. The condition occurs in most an ...
, with males having more patterns and a distinct white spot on each of their forewings. The first larval
instar
An instar (, from the Latin '' īnstar'', "form", "likeness") is a developmental stage of arthropods, such as insects, between each moult (''ecdysis''), until sexual maturity is reached. Arthropods must shed the exoskeleton in order to grow or ...
is light colored with a larger dark head. As they develop through instars, they become browner with white lengthwise lines. They also develop dark spots with spines.
Geographic range
Native range
The fall armyworm is widely distributed in eastern and central North America and in South America. It cannot overwinter in below freezing temperatures, so it only survives the winter in the most southern regions of the United States, namely Texas and Florida. Because of this, the fall armyworm is a more prominent pest in southeastern states. However, seasonally it will spread across the eastern United States and up to southern
Canada
Canada is a country in North America. Its ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, covering over , making it the world's second-largest country by tot ...
, inhabiting areas with suitable food supplies.
Introduced range
The potential global distribution of ''S. frugiperda'' has been modelled using CLIMEX. The modelled global potential distribution reflects the marked seasonal range dynamics experienced in North America, with much of the potential range in Europe, South Africa, China and Australia consisting of habitat that is only climatically suitable during the warmer months.. A more recent physiologically-based population dynamics model was developed for assessing the potential distribution of ''S. frugiperda'' in Europe. The model showed that the Mediterranean coastal areas of Southern Europe might be particularly suitable for the establishment of the species.
''S. frugiperda'' was first found on the
Africa
Africa is the world's second-largest and second-most populous continent, after Asia in both cases. At about 30.3 million km2 (11.7 million square miles) including adjacent islands, it covers 6% of Earth's total surface area ...
n continent in 2013 in
Sao Tome
SAO or Sao may refer to:
Places
* Sao civilisation, in Middle Africa from 6th century BC to 16th century AD
* Sao, a town in Boussé Department, Burkina Faso
* Saco Transportation Center (station code SAO), a train station in Saco, Maine, U. ...
,
then spread through
Nigeria
Nigeria ( ), , ig, Naìjíríyà, yo, Nàìjíríà, pcm, Naijá , ff, Naajeeriya, kcg, Naijeriya officially the Federal Republic of Nigeria, is a country in West Africa. It is situated between the Sahel to the north and the Gulf o ...
,
Benin
Benin ( , ; french: Bénin , ff, Benen), officially the Republic of Benin (french: République du Bénin), and formerly Dahomey, is a country in West Africa. It is bordered by Togo to the west, Nigeria to the east, Burkina Faso to the nort ...
,
Togo
Togo (), officially the Togolese Republic (french: République togolaise), is a country in West Africa. It is bordered by Ghana to the west, Benin to the east and Burkina Faso to the north. It extends south to the Gulf of Guinea, where its c ...
, and was found in
Ghana
Ghana (; tw, Gaana, ee, Gana), officially the Republic of Ghana, is a country in West Africa. It abuts the Gulf of Guinea and the Atlantic Ocean to the south, sharing borders with Ivory Coast in the west, Burkina Faso in the north, and To ...
in February 2017.
(Also see below
§Africa.) In December 2020 ''S. frugiperda'' was first found in
Syria in
Daraa
Daraa ( ar, دَرْعَا, Darʿā, Levantine Arabic: , also Darʿā, Dara’a, Deraa, Dera'a, Dera, Derʿā and Edrei; means "''fortress''", compare Dura-Europos) is a city in southwestern Syria, located about north of the border with Jord ...
on the
Jordan
Jordan ( ar, الأردن; tr. ' ), officially the Hashemite Kingdom of Jordan,; tr. ' is a country in Western Asia. It is situated at the crossroads of Asia, Africa, and Europe, within the Levant region, on the East Bank of the Jordan Rive ...
ian border and is believed to have arrived from there without human assistance, having just been found in that country also.
It was first reported in Africa in 2016, where it is causing significant damage to maize crops and has great potential for further spread and economic damage. It has since spread to 28 countries in Africa. In December 2018,
it began to spread widely in India. In January 2019, a heavy infestation of fall armyworm was recorded in corn plantations in
Sri Lanka.
The pest was first detected in China in the southwest province of
Yunnan
Yunnan , () is a landlocked province in the southwest of the People's Republic of China. The province spans approximately and has a population of 48.3 million (as of 2018). The capital of the province is Kunming. The province borders the C ...
in January 2019 (or June 2019).
Through 2019, the pest infested a total of 26 provinces. The armyworm is expected in 2020 to hit China's Northeast wheat belt. A report issued by the
Ministry of Agriculture and Rural Affairs
The Ministry of Agriculture and Rural Affairs of the People's Republic of China () is the cabinet-level executive department of the State Council which is responsible for agriculture and rural affairs in the country. The ministry is headqu ...
rates the situation as "very grave".
Also in June 2019 it was detected in
Southeast Asia
Southeast Asia, also spelled South East Asia and South-East Asia, and also known as Southeastern Asia, South-eastern Asia or SEA, is the geographical south-eastern region of Asia, consisting of the regions that are situated south of mainlan ...
.
In January 2020 ''S. frugiperda'' was detected on the
Torres Strait Islands
The Torres Strait Islands are a group of at least 274 small islands in the Torres Strait, a waterway separating far northern continental Australia's Cape York Peninsula and the island of New Guinea. They span an area of , but their total land ...
,
in February in
North Queensland,
and then continued into the rest of
Queensland
)
, nickname = Sunshine State
, image_map = Queensland in Australia.svg
, map_caption = Location of Queensland in Australia
, subdivision_type = Country
, subdivision_name = Australia
, established_title = Before federation
, establishe ...
,
and the
Northern Territory
The Northern Territory (commonly abbreviated as NT; formally the Northern Territory of Australia) is an Australian territory in the central and central northern regions of Australia. The Northern Territory shares its borders with Western Aust ...
,
Western Australia
Western Australia (commonly abbreviated as WA) is a state of Australia occupying the western percent of the land area of Australia excluding external territories. It is bounded by the Indian Ocean to the north and west, the Southern Ocean to th ...
,
and then in September was found in
New South Wales
)
, nickname =
, image_map = New South Wales in Australia.svg
, map_caption = Location of New South Wales in AustraliaCoordinates:
, subdivision_type = Country
, subdivision_name = Australia
, established_title = Before federation
, es ...
between
Moree and
Boggabilla
Boggabilla is a small town in the far north of inland New South Wales, Australia in Moree Plains Shire. At the , the town had a population of 551, of which 63% identified as Aboriginal or Torres Strait Islander descent.
The name Boggabilla c ...
(and later in
Narrabri
Narrabri ( ) is a locality and seat of Narrabri Shire local government area in the North West Slopes, New South Wales, Australia on the Namoi River, northwest of Sydney. It sits on the junction of the Kamilaroi Highway and the Newell Highw ...
,
Wee Waa
Wee Waa () is a town located on the north-western slopes of the New England region in New South Wales, Australia. The town is within the Narrabri Shire local government area and is on the Namoi River. Wee Waa is north-west of Narrabri and n ...
,
Dubbo,
Breeza
Breeza is a locality in New South Wales, Australia. It is about south of Gunnedah, in the Liverpool Plains
The Liverpool Plains are an extensive agricultural area covering about of the north-western slopes of New South Wales in Australia ...
,
and
Maitland
Maitland is an English and Scottish surname. It arrived in Britain after the Norman conquest of 1066. There are two theories about its source. It is either a nickname reference to "bad temper/disposition" (Old French, ''Maltalent''; Anglo Norm ...
).
''S. frugiperda'' is expected to severely impact Queensland's
wool
Wool is the textile fibre obtained from sheep and other mammals, especially goats, rabbits, and camelids. The term may also refer to inorganic materials, such as mineral wool and glass wool, that have properties similar to animal wool. ...
industry because it feeds on all major
grazing
In agriculture, grazing is a method of animal husbandry whereby domestic livestock are allowed outdoors to roam around and consume wild vegetations in order to convert the otherwise indigestible (by human gut) cellulose within grass and other ...
plants.
It was observed in traps baited with a male pheromone lure, firstly on
Darnley Island
Darnley Island or ''Erub'' in the native Papuan language, Meriam Mir, is an island formed by volcanic action and situated in the eastern section of the Torres Strait, Queensland, Australia. It is one of the Torres Strait Islands and is loc ...
and
Saibai islands in the
Torres Strait
The Torres Strait (), also known as Zenadh Kes, is a strait between Australia and the Melanesian island of New Guinea. It is wide at its narrowest extent. To the south is Cape York Peninsula, the northernmost extremity of the Australian mai ...
, and subsequently on the mainland near
Croydon
Croydon is a large town in south London, England, south of Charing Cross. Part of the London Borough of Croydon, a local government district of Greater London. It is one of the largest commercial districts in Greater London, with an extensi ...
. Within a week it was officially declared ineradicable. In April 2020, it was detected in
Papua New Guinea
Papua New Guinea (abbreviated PNG; , ; tpi, Papua Niugini; ho, Papua Niu Gini), officially the Independent State of Papua New Guinea ( tpi, Independen Stet bilong Papua Niugini; ho, Independen Stet bilong Papua Niu Gini), is a country i ...
, spreading across the Torres Strait.
Bangladesh
''S. frugiperda'' was first detected in
Bangladesh
Bangladesh (}, ), officially the People's Republic of Bangladesh, is a country in South Asia. It is the eighth-most populous country in the world, with a population exceeding 165 million people in an area of . Bangladesh is among the mos ...
in late 2018.
it has reached 37
districts.
As a result of the introduction of ''S. frugiperda'' and
Lumpy Skin Disease
Lumpy skin disease (LSD) is an infectious disease in cattle caused by a virus of the family ''Poxviridae'', also known as Neethling virus. The disease is characterized by large fever, enlarged superficial lymph nodes and multiple nodules (measuri ...
within a few months of each other, the FAO, the
World Food Programme
The World Food Programme; it, Programma alimentare mondiale; es, Programa Mundial de Alimentos; ar, برنامج الأغذية العالمي, translit=barnamaj al'aghdhiat alealami; russian: Всемирная продовольствен ...
,
Bangladesh Government officials, and others agreed to begin improving Bangladesh's agricultural emergency response capabilities.
The use of two
biopesticide
A Biopesticide is a biological substance or organism that damages, kills, or repels organisms seens as pests. Biological pest management intervention involves predatory, parasitic, or chemical relationships.
They are obtained from organisms inclu ...
s -
Spodoptera frugiperda nuclear polyhedrosis virus/SfNPV (the SNPV/
single nuclear polyhedrosis virus specific to ''S. frugiperda'') and ''
Habrobracon hebetor'' - is recommended.
Food resources
Caterpillars
![Witch Hazel (2996982386)](https://upload.wikimedia.org/wikipedia/commons/6/67/Witch_Hazel_%282996982386%29.jpg)
The armyworm's diet consists mainly of
grass
Poaceae () or Gramineae () is a large and nearly ubiquitous family of monocotyledonous flowering plants commonly known as grasses. It includes the cereal grasses, bamboos and the grasses of natural grassland and species cultivated in lawns a ...
es and grain crops such as
corn, but the species has been noted to consume over 80 different plants (50 non-economic and 30 economic plants).
Armyworms earned their common name by eating all plant matter they encounter in their wide dispersals, like a large army. A few sweet corn varieties have partial, but not complete, resistance to armyworms.
The resistance comes from a unique 33-kD
proteinase
A protease (also called a peptidase, proteinase, or proteolytic enzyme) is an enzyme that catalysis, catalyzes (increases reaction rate or "speeds up") proteolysis, breaking down proteins into smaller polypeptides or single amino acids, and spurri ...
that the corn produces when it is being fed on by fall armyworms or other larvae. This protein was found to significantly decrease fall armyworm larva growth.
Cannibalism
When possible, larvae will cannibalize the larvae of smaller instars. A 1999 study showed that cannibalism only benefits the caterpillar when other food is scarce. Despite this, the caterpillars will cannibalize others whenever they can, even though it was found to decrease their own
fitness in many cases. One known reason why cannibalism is detrimental to the fall armyworm is because of disease transmission to the cannibal. In nature, the negative effects of cannibalism may be balanced by the fact that cannibalism removes
competitors
Competition is a rivalry where two or more parties strive for a common goal which cannot be shared: where one's gain is the other's loss (an example of which is a zero-sum game). Competition can arise between entities such as organisms, indivi ...
, thereby making more resources accessible and indirectly increasing fall armyworms' fitness.
Adults
Adult moths sip nectar from flowers such as that of
witch hazel (''Hamamelis virginiana'').
Life history
The fall armyworm's
life cycle
Life cycle, life-cycle, or lifecycle may refer to:
Science and academia
*Biological life cycle, the sequence of life stages that an organism undergoes from birth to reproduction ending with the production of the offspring
* Life-cycle hypothesis ...
is completed within 30 days during summer, and 60 days during the spring and autumn seasons; during the winter, these caterpillars' life cycle lasts about 80 to 90 days.
">/sup> The number of generations a moth will have in a year varies based on climate, but in her life span a female will typically lay about 1,500 eggs. Because larvae cannot enter into diapause
In animal dormancy, diapause is the delay in development in response to regular and recurring periods of adverse environmental conditions.Tauber, M.J., Tauber, C.A., Masaki, S. (1986) ''Seasonal Adaptations of Insects''. Oxford University Press I ...
they cannot survive cold temperatures.
Egg
The armyworm's egg is dome-shaped, and measures around in diameter and in height. Females prefer to lay eggs on the underside of leaves, but in high populations they will lay them just about anywhere. In warm weather, the eggs will hatch into larvae within a few days.
Larva
The larvae go through six different instar
An instar (, from the Latin '' īnstar'', "form", "likeness") is a developmental stage of arthropods, such as insects, between each moult (''ecdysis''), until sexual maturity is reached. Arthropods must shed the exoskeleton in order to grow or ...
s, each varying slightly in physical appearance and pattern. The larva process lasts from 14 to 30 days, again depending on temperatures. The mature caterpillar is about in length. This is the most destructive life stage as the larvae have biting mouth parts. The larvae have a distinctive inverted Y suture on the forehead.
Pupa
The larvae then pupa
A pupa ( la, pupa, "doll"; plural: ''pupae'') is the life stage of some insects undergoing transformation between immature and mature stages. Insects that go through a pupal stage are holometabolous: they go through four distinct stages in thei ...
te underground for 7 to 37 days in a cocoon they form of soil and silk. Duration and survival of the pupal stage depend on the temperature of the environment.
Adults
Once emerged, the adults live for about 10 days, and sometimes up to 21 days, with the female laying most of her eggs early in life. Adults are nocturnal and fare best during warm and humid nights.
Migration
Adults are capable of flying long distances, so even though they are unable to overwinter
Overwintering is the process by which some organisms pass through or wait out the winter season, or pass through that period of the year when "winter" conditions (cold or sub-zero temperatures, ice, snow, limited food supplies) make normal acti ...
north of the southern region of the United States, the moths can migrate as far north as southern Canada in warm months. Their migration
Migration, migratory, or migrate may refer to: Human migration
* Human migration, physical movement by humans from one region to another
** International migration, when peoples cross state boundaries and stay in the host state for some minimum le ...
rate is remarkably fast, estimated at per generation. Some scientists speculate that this fast migration is aided by the movement of air in weather fronts.
Neurochemistry
Allatotropin and allatotropin+ allatostatin C - neuropeptide
Neuropeptides are chemical messengers made up of small chains of amino acids that are synthesized and released by neurons. Neuropeptides typically bind to G protein-coupled receptors (GPCRs) to modulate neural activity and other tissues like the ...
s - extracted from ''Manduca sexta
''Manduca sexta'' is a moth of the family Sphingidae present through much of the Americas. The species was first described by Carl Linnaeus in his 1763 ''Centuria Insectorum''.
Commonly known as the Carolina sphinx moth and the tobacco hawk mo ...
'' were both found to suppress feeding in all life stages, increase larval mortality, and reduce adult lifespan, by Oeh et al 2000.
Enemies
Predators
Fall armyworm caterpillars are directly preyed upon by many invertebrate
Invertebrates are a paraphyletic group of animals that neither possess nor develop a vertebral column (commonly known as a ''backbone'' or ''spine''), derived from the notochord. This is a grouping including all animals apart from the chordate ...
s and vertebrate
Vertebrates () comprise all animal taxa within the subphylum Vertebrata () (chordates with backbones), including all mammals, birds, reptiles, amphibians, and fish. Vertebrates represent the overwhelming majority of the phylum Chordata, with c ...
s. Common predators
Predation is a biological interaction where one organism, the predator, kills and eats another organism, its prey. It is one of a family of common feeding behaviours that includes parasitism and micropredation (which usually do not kill th ...
include bird
Birds are a group of warm-blooded vertebrates constituting the class Aves (), characterised by feathers, toothless beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a strong yet lightweig ...
s, rodent
Rodents (from Latin , 'to gnaw') are mammals of the order Rodentia (), which are characterized by a single pair of continuously growing incisors in each of the upper and lower jaws. About 40% of all mammal species are rodents. They are n ...
s, beetle
Beetles are insects that form the order Coleoptera (), in the superorder Endopterygota. Their front pair of wings are hardened into wing-cases, elytra, distinguishing them from most other insects. The Coleoptera, with about 400,000 describ ...
s, earwig
Earwigs make up the insect order Dermaptera. With about 2,000 species in 12 families, they are one of the smaller insect orders. Earwigs have characteristic cerci, a pair of forcep-like pincers on their abdomen, and membranous wings folde ...
s, and other insect
Insects (from Latin ') are pancrustacean hexapod invertebrates of the class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body ( head, thorax and abdomen), three ...
s. It has been shown that direct predation can cause significant losses to caterpillar populations. The larva's main defense against enemies is their ability to reach large numbers and migrate before seasonal conditions are suitable for predators.
Parasitoids
Fly and wasp parasitoids target the fall armyworm, most commonly '' Archytas marmoratus'', '' Cotesia marginiventris'', and '' Chelonus texanus''. The armyworm is also vulnerable to additional parasitoids, varying with location. In 2018, egg parasitoid wasps of the genera '' Telenomus'' and ''Trichogramma
''Trichogramma'' is a genus of minute polyphagous wasps that are endoparasitoids of insect eggs. ''Trichogramma'' is one of around 80 genera from the family Trichogrammatidae, with over 200 species worldwide.Consoli FL, Parra JRP, Zucchi RA (201 ...
'' were discovered to attack army worm eggs in East Africa.
''Cotesia icipe
''Cotesia icipe'' is a parasitoid species of wasp of the genus ''Cotesia''. Found in tropical Africa and the Arabian Peninsula, it was first discovered as a parasitoid of the Lepidopterans ''Spodoptera littoralis'' and beet armyworm (''Spodopter ...
'' is another African braconid wasp suitable for the biological control of this lepidoptera.
Parasites and disease
Fifty-three different parasite
Parasitism is a close relationship between species, where one organism, the parasite, lives on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The entomologist E. O. Wilson has ...
species have been discovered in fall armyworm larvae, spanning ten different families. Often larvae can survive through much of their crop consumption despite outbreaks of disease, because of the larva's fast life cycle. Despite this, parasites of the fall armyworm are being studied extensively as a means of fighting armyworm attacks on crops. One suggested approach would be to introduce parasites from South America to North American fall armyworms, and vice versa.
Fungi
In February 2021, it was reported that an Australian agronomist
An agriculturist, agriculturalist, agrologist, or agronomist (abbreviated as agr.), is a professional in the science, practice, and management of agriculture and agribusiness. It is a regulated profession in Canada, India, the Philippines, the ...
Georgia Rodger had found at a property near Beaudesert (southern Queensland) the tropical fungus
A fungus ( : fungi or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and molds, as well as the more familiar mushrooms. These organisms are classified as a kingdom, separately from t ...
''Nomuraea rileyi
''Metarhizium rileyi''Kepler, Humber, Bischoff, Rehner SA (2014) ''Mycologia'' 106(4): 824. is a species of entomopathogenic fungus in the family Clavicipitaceae
The Clavicipitaceae are a family of fungi within the order Hypocreales. A 2008 es ...
'' which was known to be effective in killing and consuming fall armyworms. Samples of this were sent to Maree Crawford, the insect pathologist at the Queensland Department of Agriculture for further analysis.[ Australian entomologists have said the finding is reassuring and that laboratory tests have been promising.] This is substantiated by various studies including a 2018 journal article which looked into the effectiveness of ''N. rileyi'' had on infestations of armyworms in Indian maize
Maize ( ; ''Zea mays'' subsp. ''mays'', from es, maíz after tnq, mahiz), also known as corn (North American and Australian English), is a cereal grain first domesticated by indigenous peoples in southern Mexico about 10,000 years ago. The ...
crops. The study concluded ''N. rileyi'' could potentially be a cost-effective tool in combating the pest, compatible with eco-friendly management practices, although further studies were required.[ Farmers in Australia have struggled to control the pest which has been destroying crops, prompting concerns about potential food shortages which could cause an increase in food prices for consumers.][ The ''N. rileyi'' research has given them hope that this can be avoided.][
]
Subspecies
The fall armyworm may be presently undergoing a divergence
In vector calculus, divergence is a vector operator that operates on a vector field, producing a scalar field giving the quantity of the vector field's source at each point. More technically, the divergence represents the volume density of t ...
into two separate species. These two strains have major genetic differences that are connected to the plants they feed on, even though both still exist in the same area ( sympatric speciation). These two strains can be loosely categorized into a rice strain and a corn strain. This separation is occurring because of differences in habitat
In ecology, the term habitat summarises the array of resources, physical and biotic factors that are present in an area, such as to support the survival and reproduction of a particular species. A species habitat can be seen as the physical ...
(preferred host plant
In biology and medicine, a host is a larger organism that harbours a smaller organism; whether a parasitic, a mutualistic, or a commensalist ''guest'' ( symbiont). The guest is typically provided with nourishment and shelter. Examples include ...
), and differences in reproductive behavior. The reproductive differences can be divided into two categories: difference in the timing of mating at night, and difference in female sex pheromone
A pheromone () is a secreted or excreted chemical factor that triggers a social response in members of the same species. Pheromones are chemicals capable of acting like hormones outside the body of the secreting individual, to affect the behavio ...
s.
Mating
Mate searching behavior and male–male conflict
A female attracts males by perching atop the host plant feeding area and releasing a sex pheromone
A pheromone () is a secreted or excreted chemical factor that triggers a social response in members of the same species. Pheromones are chemicals capable of acting like hormones outside the body of the secreting individual, to affect the behavio ...
as the signal that she wishes to mate. The pheromone has been studied and found to contain the components Z7-12 and Z9-14. Each female only mates once per night; this creates a physical conflict between the multiple males that will fly towards a ready female. There is an order to which the females call and mate: virgin females do first, females who have mated once next, and females who have already mated multiple times call and mate last during the night.
Interactions with humans
Research use
''S. frugiperda'' cells (Sf9
SF9 ( ko, 에스에프나인 ; shortened from Sensational Feeling 9) is a South Korean boy band formed by FNC Entertainment and the company's first dance boy group. Consisting of nine members, the group debuted on October 5, 2016 with the relea ...
and Sf21
Sf21 (officially called IPLB-Sf21-AE) is a continuous cell line developed from ovaries of the Fall Army worm, ''Spodoptera frugiperda'', a moth species that is an agricultural pest on corn and other grass species. It was originally developed in ...
cell lines) are commonly used in biomedical research for the purpose of recombinant protein
Recombinant DNA (rDNA) molecules are DNA molecules formed by laboratory methods of genetic recombination (such as molecular cloning) that bring together genetic material from multiple sources, creating DNA sequence, sequences that would not othe ...
expression using insect-specific viruses called baculovirus
''Baculoviridae'' is a family of viruses. Arthropods, among the most studied being Lepidoptera, Hymenoptera and Diptera, serve as natural hosts. Currently, 85 species are placed in this family, assigned to four genera.
Baculoviruses are known ...
es.
Pest of crop plants
Because of their food preferences, fall armyworm larvae can wreak havoc on a wide range of crop
A crop is a plant that can be grown and harvested extensively for profit or subsistence. When the plants of the same kind are cultivated at one place on a large scale, it is called a crop. Most crops are cultivated in agriculture or hydropon ...
s. The first historical account of the fall armyworm's destruction was in 1797 in Georgia. Destruction can happen almost over night, because the first stages of a caterpillar's life require very little food, and the later stages require about 50 times more. Because of this rapid change in food consumption, the presence of larvae will not be noticed until they have destroyed almost everything in as little as a night. Some examples of targeted crops include cotton
Cotton is a soft, fluffy staple fiber that grows in a boll, or protective case, around the seeds of the cotton plants of the genus '' Gossypium'' in the mallow family Malvaceae. The fiber is almost pure cellulose, and can contain minor pe ...
, tobacco
Tobacco is the common name of several plants in the genus '' Nicotiana'' of the family Solanaceae, and the general term for any product prepared from the cured leaves of these plants. More than 70 species of tobacco are known, but the ...
, sweet corn, rice
Rice is the seed of the grass species '' Oryza sativa'' (Asian rice) or less commonly ''Oryza glaberrima'' (African rice). The name wild rice is usually used for species of the genera '' Zizania'' and '' Porteresia'', both wild and domesticat ...
, peanut
The peanut (''Arachis hypogaea''), also known as the groundnut, goober (US), pindar (US) or monkey nut (UK), is a legume crop grown mainly for its edible seeds. It is widely grown in the tropics and subtropics, important to both small and ...
s, and even fruits such as apple
An apple is an edible fruit produced by an apple tree (''Malus domestica''). Apple trees are cultivated worldwide and are the most widely grown species in the genus ''Malus''. The tree originated in Central Asia, where its wild ancestor, ' ...
s, oranges
An orange is a fruit of various citrus species in the family Rutaceae (see list of plants known as orange); it primarily refers to ''Citrus'' × ''sinensis'', which is also called sweet orange, to distinguish it from the related ''Citrus × ...
, and many more. The list of possible food sources for the worms is extensive, so crop damage is wide-ranging. It is estimated that almost 40 percent of those species that armyworms target are economically important. Because the larvae eat so much of the plant, they are very detrimental to crop survival and yield. In corn, larvae will even burrow into the corn ear to eat the kernels.
The UN Food and Agriculture Organization
The Food and Agriculture Organization of the United Nations (FAO)french: link=no, Organisation des Nations unies pour l'alimentation et l'agriculture; it, Organizzazione delle Nazioni Unite per l'Alimentazione e l'Agricoltura is an intern ...
estimates that ''S. frugiperda'' will reduce maize/corn yields by /annum if not successfully controlled. The fall armyworm have proved to be a pest in many regions, and methods of control continue to be developed.
Africa
The fall armyworm was identified in Africa in 2016. In early 2017, armyworms infested large swathes of corn crops across southern Africa
Southern Africa is the southernmost subregion of the African continent, south of the Congo and Tanzania. The physical location is the large part of Africa to the south of the extensive Congo River basin. Southern Africa is home to a number o ...
, devastating the livelihoods of many farmers. It is thought they arrived as an invasive species from the Americas as eggs in imported produce. This is causing immense concern among agricultural experts, due to the potentially huge amount of damage this invasive species will do to African food crops if allowed to spread. Many African countries have agreed to take urgent actions against armyworms.
Sri Lanka
After being first reported in India in May 2018 in Tamil Nadu
Tamil Nadu (; , TN) is a state in southern India. It is the tenth largest Indian state by area and the sixth largest by population. Its capital and largest city is Chennai. Tamil Nadu is the home of the Tamil people, whose Tamil language ...
, then the Sri Lankan Ministry of Agriculture issued a warning notice to farmers in the northwestern and north central provinces about possible fall armyworm invasion. At the time of warning, crop destruction had already been reported from the Ampara, Anuradhapura
Anuradhapura ( si, අනුරාධපුරය, translit=Anurādhapuraya; ta, அனுராதபுரம், translit=Aṉurātapuram) is a major city located in north central plain of Sri Lanka. It is the capital city of North Central ...
, and Polonnaruwa
Poḷonnaruwa, ( si, පොළොන්නරුව, translit=Poḷonnaruva; ta, பொலன்னறுவை, translit=Polaṉṉaṟuvai) also referred as Pulathisipura and Vijayarajapura in ancient times, is the main town of Polonnaruwa Dis ...
areas. The larvae are known among the local people as ''Sena dalambuwa'' (armyworm caterpillar). Not only corn, but also sugarcane plantations were attacked by the caterpillars in Anuradhapura, Ampara, and Monaragala districts.
In December 2018, heavy infestations in corn cultivation were identified. The spread of the moth leads to attack corn all around the country within weeks.[ On 6 January 2019, caterpillars spread to the ]Monaragala
Monaragala ( si, මොනරාගල, translit=Monarāgala; ta, மொணராகலை, translit=Moṇarākalai) is a town located in Monaragala District, Uva Province, Sri Lanka. It is the largest town in Monaragala District and is locate ...
district and devastated corn crops. At the end of January 2019, the armyworm was present in all districts of Sri Lanka except Nuwara Eliya
Nuwara Eliya ( si, නුවර එළිය ; ta, நுவரெலியா) is a city in the hill country of the Central Province, Sri Lanka. Its name means "city on the plain (table land)" or "city of light". The city is the administrativ ...
and Jaffna.
On 29 December 2018, armyworms were recorded from paddy cultivations in the Sinhapura
Sinhapura ("Lion City" for Sanskrit; IAST: Siṃhapura) was the capital of the legendary Indian king Sinhabahu. It has been mentioned in the Buddhist legends about Prince Vijaya. The name is also transliterated as ''Sihapura'' or ''Singhapura' ...
area of Polonnaruwa. In January 2019, caterpillars were also recorded from paddy cultivations of the Nochchiyagama area in the Anuradhapura district.
The Sri Lankan Department of Agriculture recommended 12 pesticides under three categories, to be used alternately every seven days. Organic farming expert, Thilak Kandegama said that the threat can be overcome by sprinkling rice husk ashes as a repellent. Agricultural Ministry also decided to use drone technology for the spraying of insecticides to control the spreading of caterpillars.
Management and control
Because of the fall armyworms' great destructive power, farmers must go to great lengths to deter the larvae. Insecticide is a widely used form of protection; in southern regions, farmers may have to apply insecticide to corn every day. Agricultural drone An agricultural drone is an unmanned aerial vehicle used in agriculture operations, mostly in yield optimization and in monitoring crop growth and crop production. Agricultural drones provide information on crop growth stages, crop health, and soil ...
s have been used to apply pesticides, used in China, Vietnam, Zambia and other regions.
The CABI-led programme, Plantwise
CABI (legally CAB International, formerly Commonwealth Agricultural Bureaux) is a nonprofit intergovernmental development and information organisation focusing primarily on agricultural and environmental issues in the developing world, and the c ...
and partners have several recommendations for managing fall armyworm, these include: planting early, avoiding staggered planting, and inter-cropping with crops that are not susceptible to fall armyworm, such as cassava
''Manihot esculenta'', commonly called cassava (), manioc, or yuca (among numerous regional names), is a woody shrub of the spurge family, Euphorbiaceae, native to South America. Although a perennial plant, cassava is extensively cultivated ...
or yam. They also recommend conserving shelters and flowering plants on the edges for beneficial insects such as ground beetles and parasitoids.
Inter-cropping with the " push-pull" technique with crops such as ''Desmodium
''Desmodium'' is a genus of plants in the legume family Fabaceae, sometimes called tick-trefoil, tick clover, hitch hikers or beggar lice. There are dozens of species and the delimitation of the genus has shifted much over time.
These are mostly ...
'' and Napier grass
''Cenchrus purpureus'', synonym ''Pennisetum purpureum'', also known as Napier grass, elephant grass or Uganda grass, is a species of perennial tropical grass native to the African grasslands. arrell, G., Simons, S. A., & Hillocks, R. J. (2002). ...
can be used to control fall armyworm.
For some crops, including wheat
Wheat is a grass widely cultivated for its seed, a cereal grain that is a worldwide staple food. The many species of wheat together make up the genus ''Triticum'' ; the most widely grown is common wheat (''T. aestivum''). The archaeologi ...
, sorghum, millet and rice
Rice is the seed of the grass species '' Oryza sativa'' (Asian rice) or less commonly ''Oryza glaberrima'' (African rice). The name wild rice is usually used for species of the genera '' Zizania'' and '' Porteresia'', both wild and domesticat ...
, it is recommend by Plantwise partners to plant short maturing and varieties that are less preferred by ''S. frugiperda''.
Another strategy is to plant crops earlier to avoid the increase in armyworm numbers as the summer progresses.
In South Africa, farmers are using pheromone
A pheromone () is a secreted or excreted chemical factor that triggers a social response in members of the same species. Pheromones are chemicals capable of acting like hormones outside the body of the secreting individual, to affect the behavio ...
lures with a combination of Dichlorvos
Dichlorvos (2,2-dichlorovinyl dimethyl phosphate, commonly abbreviated as an DDVP) is an organophosphate widely used as an insecticide to control household pests, in public health, and protecting stored products from insects. The compound has b ...
blocks to trap and eliminate male armyworms, with the intention of disrupting mating cycles.
CIMMYT and its partners are using forward genetics
Forward genetics is a molecular genetics approach of determining the genetic basis responsible for a phenotype. Forward genetics provides an unbiased approach because it relies heavily on identifying the genes or genetic factors that cause a partic ...
to breed for better ''S. frugiperda'' resistance in maize. Genome-wide association studies
In genomics, a genome-wide association study (GWA study, or GWAS), also known as whole genome association study (WGA study, or WGAS), is an observational study of a genome-wide set of genetic variants in different individuals to see if any varian ...
(GWAS) are the most effective method for associating ''S. f.'' resistance to the responsible genomic region, especially used in maize/corn but also wheat
Wheat is a grass widely cultivated for its seed, a cereal grain that is a worldwide staple food. The many species of wheat together make up the genus ''Triticum'' ; the most widely grown is common wheat (''T. aestivum''). The archaeologi ...
, sorghum, millet, rice
Rice is the seed of the grass species '' Oryza sativa'' (Asian rice) or less commonly ''Oryza glaberrima'' (African rice). The name wild rice is usually used for species of the genera '' Zizania'' and '' Porteresia'', both wild and domesticat ...
, and legumes. The first uses of conventional breeding in the first decade of the 1900s were reported by Gernet 1917 and Hinds 1914, improving resistance in maize/corn, sorghum, millet, ''Cynodon dactylon
''Cynodon dactylon'', commonly known as Bermuda grass, is a grass found worldwide. It is native to Europe, Africa, Australia and much of Asia. It has been introduced to the Americas. Although it is not native to Bermuda, it is an abundant invasiv ...
'', and ''Arachis hypogaea
The peanut (''Arachis hypogaea''), also known as the groundnut, goober (US), pindar (US) or monkey nut (UK), is a legume crop grown mainly for its edible seeds. It is widely grown in the tropics and subtropics, important to both small and la ...
''.
In Australia, a caterpillar-specific virus
A virus is a submicroscopic infectious agent that replicates only inside the living cells of an organism. Viruses infect all life forms, from animals and plants to microorganisms, including bacteria and archaea.
Since Dmitri Ivanovsk ...
packaged as Fawligen biopesticide
A Biopesticide is a biological substance or organism that damages, kills, or repels organisms seens as pests. Biological pest management intervention involves predatory, parasitic, or chemical relationships.
They are obtained from organisms inclu ...
was approved under emergency regulations in 2020 to help control the armyworm, and the parasitoid wasp '' Trichogramma pretiosum'' is also used.
Directorate of plant protection Quarantine and storage, Ministry of Agriculture, Govt of India regularly issues advisories from time to time to manage the menace of Fall Army Worm in India.
See also
* African armyworm (''Spodoptera exempta'') (Africa)
* Common armyworm or true armyworm (''Mythimna unipuncta
''Mythimna unipuncta'', the true armyworm moth, white-speck moth, common armyworm or rice armyworm, is a nocturnal agricultural pest belonging to the family Noctuidae. This moth is also commonly referred to by the scientific name ''Pseudaletia ...
'') (North and South America)
* Northern armyworm, Oriental armyworm or rice ear-cutting caterpillar ('' Mythimna separata'') (Asia)
References
External links
fall armyworm
on the UF / IFAS Featured Creatures Web site
Fall armyworm Food and Agriculture Organization of the United Nations
*
*
*
*
*
*
*
*
*
*
{{Taxonbar , from=Q2715913
Spodoptera
Moths of North America
Moths of the Caribbean
Moths of Cuba
Lepidoptera of Jamaica
Agricultural pest insects
Moths described in 1797
Invasive agricultural pests
Insect pests of millets