''Spodoptera eridania'' (southern armyworm) is a moth that is known to be a pest. They are one of the most important defoliators in the tropical and subtropical regions of the western hemisphere that feed heavily on plants while they are young, often resulting in skeleton leaves on their food plants. They are also heavy feeders on tomato in Florida. There is a lot of development in producing pesticides against the ''S. eridania'', specifically a neem-based pesticide that can result in smaller and prolonged development. The
wingspan
The wingspan (or just span) of a bird or an airplane is the distance from one wingtip to the other wingtip. For example, the Boeing 777–200 has a wingspan of , and a wandering albatross (''Diomedea exulans'') caught in 1965 had a wingspan o ...
is 33–38 mm. Adults are on wing year-round. The larvae feed on various weeds but prefer ''
Amaranthus
''Amaranthus'' is a cosmopolitan genus of annual or short-lived perennial plants collectively known as amaranths. Some amaranth species are cultivated as leaf vegetables, pseudocereals, and ornamental plants. Catkin-like cymes of densely pac ...
'' species and ''
Phytolacca americana
''Phytolacca americana'', also known as American pokeweed, pokeweed, poke sallet, dragonberries, and inkberry, is a poisonous, herbaceous perennial plant in the pokeweed family Phytolaccaceae. This pokeweed grows . It has simple leaves on green ...
.''
Geographic range
The ''S. eridania'' is found in
North America (the southern US states as far west as
Kansas
Kansas () is a state in the Midwestern United States. Its capital is Topeka, and its largest city is Wichita. Kansas is a landlocked state bordered by Nebraska to the north; Missouri to the east; Oklahoma to the south; and Colorado to th ...
and
New Mexico
)
, population_demonym = New Mexican ( es, Neomexicano, Neomejicano, Nuevo Mexicano)
, seat = Santa Fe
, LargestCity = Albuquerque
, LargestMetro = Tiguex
, OfficialLang = None
, Languages = English, Spanish ( New Mexican), Navajo, Ke ...
), through the
Caribbean and
Central America
Central America ( es, América Central or ) is a subregion of the Americas. Its boundaries are defined as bordering the United States to the north, Colombia to the south, the Caribbean Sea to the east, and the Pacific Ocean to the west. ...
into
South America
South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere at the northern tip of the continent. It can also be described as the sout ...
(through
Brazil
Brazil ( pt, Brasil; ), officially the Federative Republic of Brazil (Portuguese: ), is the largest country in both South America and Latin America. At and with over 217 million people, Brazil is the world's fifth-largest country by area ...
to
Argentina
Argentina (), officially the Argentine Republic ( es, link=no, República Argentina), is a country in the southern half of South America. Argentina covers an area of , making it the second-largest country in South America after Brazil, th ...
). It has been introduced
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 ...
and
Cameroon
Cameroon (; french: Cameroun, ff, Kamerun), officially the Republic of Cameroon (french: République du Cameroun, links=no), is a country in west-central Africa. It is bordered by Nigeria to the west and north; Chad to the northeast; the C ...
.
Food resources
Host plants
The plants that the armyworm feeds on include a wide range of important vegetables, fruits, and crops. The vegetables include beet, cabbage, carrot, collard, cowpea, eggplant, okra, pepper, potato, sweet potato, tomato, and watermelon. Other crops damaged include avocado, citrus, peanut, sunflower, velvet bean, tobacco and various flowers. Grasses are rarely eaten. One of the more preferred host plants is the lima bean, probably due to contact of cyanogenic glycoside linamarin. The lima bean is known to contain up to 31 ppm cyanide in some varieties.
Glucosinolates
Glucosinolates are feeding deterrents and are toxic to non-adapted herbivores. With higher glucosinolate concentrations, there is reduced feeding by ''S. eridania'' on ''B. juncea,'' a host plant. There is relative unresponsiveness of ''S. eridania'' to variation in
myrosinase
Myrosinase (, ''thioglucoside glucohydrolase'', ''sinigrinase'', and ''sinigrase'') is a family of enzymes involved in plant defense against herbivores, specifically the mustard oil bomb. The three-dimensional structure has been elucidated and is ...
activity. This suggests that glucosinolates may have originated as defenses against
generalist herbivores. Insects selectively adapting to glucosinolates may have selected for stronger defense produced by their rapid hydrolysis by myrosinase.
Environmental impact
Larvae are defoliators and feed gregariously while young, often skeletonizing leaves. As they mature they become solitary, and also bore readily into fruit, often damaging tomatoes in Florida. It can result in significant yield losses if uncontrolled. When stressed by a lack of food they will eat the apical portions of branches, bore into stem tissue, and attack tubers near the surface of the soil.
Insecticides
Neem-based insecticide
A lot of research has been done on
neem
''Azadirachta indica'', commonly known as neem, nimtree or Indian lilac, is a tree in the mahogany family Meliaceae. It is one of two species in the genus '' Azadirachta'', and is native to the Indian subcontinent and most of the countries in Afr ...
-based insecticides. There has been growing interest in the agricultural sector in using plant and botanical insecticides as alternatives to restore a biologically base equilibrium in insect populations. Neem has been shown to be a feeding deterrent for insects. The primary active ingredient in neem is azadirachtin, a steroid-like tetranortriterpenoid, that exhibits a wide range of bioactivity to hundreds of phytophagous insect species from different orders. There has been shown evidence that neem based products interfere with the regulation of feeding and metabolism as well as with anatomy and function of midgut tissues. Neem-based formulations of pesticides reduced the amount of food ingest by ''S. eridania'' larvae. The growth that is disrupted by neem is determined not only by feeding inhibition but also by digestibility, as the ''S. eridania'' larvae showed reduced efficiency in converting ingested food. These setbacks in growth and food ingestion and digestion extend the development time of larvae. Neem-based pesticides are exceptional in having broad range of bioactivity against herbivores that include toxicity, growth regulation, repellency, feeding deterrency, and disruption of metamorphosis.
Pure
neem oil
Neem oil, also known as margosa oil, is a vegetable oil pressed from the fruits and seeds of the neem (''Azadirachta indica''), a tree which is indigenous to the Indian subcontinent and has been introduced to many other areas in the tropics. It i ...
has been found to be the most effective antifeedants by the third instar. Pure neem oil and azatrol are most effective feeding deterrent for the second and fourth instars of southern armyworm. Although these products worked in laboratory experiences, it was found that the magnitude of the negative effect on the larval mortality and pupal ecdysis varied considerably among neem-derived insecticides tested.
GMO soybean plants
Research has also been done with the
genetically modified
Genetic engineering, also called genetic modification or genetic manipulation, is the modification and manipulation of an organism's genes using technology. It is a set of technologies used to change the genetic makeup of cells, including ...
soybean plant. They are created with insect resistance genes from ''
Bacillus thuringiensis'' Berliner (Bt-plants) and increasingly being cultivated around the world. Research has shown that the Bt soybean does not affect pest foliage consumption but does reduce larval duration by around two days.
Field corn
Larvae fed on fresh ear of field corn that expressed the Bt proteins (Cry1F and Cry1F + Cry1A.105 + Cry2Ab2), showed a 100% mortality rate. Bt is found all over the world and they produce a protein crystal that is toxic to insects. It is also safer than synthetic pesticides, and is also selective towards specific insects. ''S. eridania'' larvae survived less than two days after consuming Bt corncobs, while larvae reared on non-Bt corn cobs showed higher larval development than other species in Lepidoptera family. They ended up having poor development when fed on maize leaves.
Soybean cultivars
In the
cerrado
The ''Cerrado'' (, ) is a vast ecoregion of tropical savanna in eastern Brazil, particularly in the states of Goiás, Mato Grosso do Sul, Mato Grosso, Tocantins, Minas Gerais, and the Federal District. The core areas of the Cerrado biome are the ...
region of
Brazil
Brazil ( pt, Brasil; ), officially the Federative Republic of Brazil (Portuguese: ), is the largest country in both South America and Latin America. At and with over 217 million people, Brazil is the world's fifth-largest country by area ...
, the ''S. eridania'' has high capacity of defoliation and high population densities. It is an important pest of soybean, causing damage and economic losses. The cultivar of monsoy 8757 had the most significant impact on the development of ''S. eridania''. There is an increase in duration of larval, pupal and total cycle, and a reduction in pupal mass. The consequences may be favorable to the producer since the extension of the duration of the life cycle can reduce the number of generations that cycle in the field, and decrease the number of pests in the field.
Plant phenols
Two classes of phenols were analyzed for their effect on the southern armyworm. Rutin and quercetin were found to cause some mortality. The larvae died about 2–4 days after the onset of trials. Rutin also reduced growth rates by decreasing the consumption and digestion efficiency of the larvae. Salicortin, a gut toxin, caused numerous lesions in the gut of larvae, and were large and abundant in every section. However, these results do show that toxicity is not an inherent trait of even a narrowly defined class of phytochemicals, as minor structural changes within the compound masked reactive sites, which changes solubility and susceptibility of the chemical.
Life history
Life cycle
The number of generations is estimated at four each year in Florida. In
northern Florida
North Florida is a region of the U.S. state of Florida comprising the northernmost part of the state. Along with South Florida and Central Florida, it is one of Florida's three most common "directional" regions. It includes Jacksonville and near ...
, moths can be found throughout the year, withstanding several days of freezing weather. ''S. eridania'' larvae are found in northern Florida only in the summer months, which is consistent with most other insects. One generation is about 30 to 40 days.
Egg
The shape of the eggs is a flattened sphere. Eggs measure about 0.45 mm in diameter and 0.35 mm in height. The eggs are green initially, turning tan as they age. Eggs are laid in clusters, and covered with scales from the body of the moth. Duration of the egg stage is four to six days.
Larvae
The armyworm has six instars as they grow to attain a length of about 35 mm. Larvae are green or blackish green with uniform light brown or reddish brown through the period of development. Each side has a broad yellowish stripe that has a dark spot on the first abdominal segment. Series of dark triangles are usually present dorso-laterally along the length of the body. Larvae are usually found on the lower part of leaves and are more active at night than during the day. The larval stage usually lasts around 14 to 20 days.
Pupae
Larvae pupate in the ground soil, at a depth of 5 to 10 cm; pupae are mahogany brown and are about 16–18 mm in length and 5-6mm in width; duration of the pupal period is about 11–13 days. Female pupae may have difficulty in transforming into adults. There is also sexual dimorphism between the female and male pupae. The larger size of the female may be attributed to the additional instar. Survival of males from large pupae tends to be shorter than males from small pupae.
[Specht, A., Montezano, D. G., Sosa-Gómez, D. R., Paula-Moraes, S. V., Roque-Specht, V. F., & Barros, N. M.. (2016). Reproductive potential of Spodoptera eridania (Stoll) (Lepidoptera: Noctuidae) in the laboratory: effect of multiple couples and the size. ''Brazilian Journal of Biology'', ''76''(2), 526-530. Epub March 08, 2016.https://dx.doi.org/10.1590/1519-6984.23114] Larger males and females that emerged from larger pupae tend to survive for shorter periods of time. Fecundity has also been found to be positively correlated with size.
Adults
The adult moth measures about 33 to 38 mm in wing span. The forewings are colored gray and brown. Its wing pattern is highly variable with some with bean-shaped spot near the center of the wing whereas others do not have the spot. The back or hind wings are opalescent white.
Predators
Parasitoid insects associated with southern armyworm caterpillars include:
[Tingle FC, Ashley TR, Mitchell ER. 1978. Parasites of ''Spodoptera exigua'', ''S. eridania'' (Lep.: Noctuidae) and ''Herpetogramma bipunctalis'' (Lep.: Pyralidae) collected from ''Amaranthus hybridus'' in field corn. Entomophaga 23: 343-347.]
Wasps
* ''
Campoletis flavicincta''
* ''
Chelonus insularis
''Chelonus'' is a wasp genus in the subfamily Cheloninae. Their larvae feed chiefly on larvae of moths in superfamilies Tortricoidea and Pyraloidea.Shaw, S.R. 1997. Subfamily Cheloninae.
Species
* '' Chelonus abditus''
* '' Chelonus abduc ...
''
* ''
Cotesia marginiventris
''Cotesia marginiventris'' is a species of parasitoid wasp that develops in Noctuidae caterpillars. It can be found in the Americas. The wasp finds caterpillar hosts to rear its young in by detecting the volatiles produced by the plants that th ...
''
* ''
Euplectrus platyhypenae''
* ''
Meteorus autographae
''Meteorus'' is a genus of parasitoid wasps in the family Braconidae. It comprises over 330 species worldwide.
''Meteorus'' wasps are distinguished from other braconid wasps by the presence of a second submarginal cell in the forewing and a pe ...
'' (the dominant parasitoid in Tingle et al. 1978)
[
* '' Meteorus laphygmae''
* '' Ophion flavidus''
]
Flies
* '' Choeteprosopa hedemanni''
* '' Eucelatoria rubentis''
* '' Euphorocera claripennis''
* ''Gonia crassicornis
''Gonia crassicornis'' is a species of fly in the family Tachinidae.
Distribution
United States, Cuba, Jamaica, Puerto Rico, Trinidad and Tobago, Honduras, Mexico, Nicaragua, Brazil, Colombia, Peru, Venezuela
Venezuela (; ), officiall ...
''
* '' Lespensia sp.''
* '' Winthemia quadripustulata''
* '' Winthemia rufopicta''
Interactions with humans
Management
The southern armyworm is best controlled with foliar insecticides when larvae are small. Insecticides vary considerably in their toxicity to larvae, which are difficult to control with botanical insecticides. Berger (1920) reported some success at southern armyworm suppression by application of bran bait containing insecticide. However, this is primarily useful for large, mobile larvae that have left the plant and are on the soil surface.
References
External links
List of Noctuidae: Spodoptera eridania
, ''INRA''.
Southern Armyworm, Spodoptera eridania (Cramer) (Insecta: Lepidoptera: Noctuidae)
, ''IFAS.UFL.edu''
{{Taxonbar, from=Q3398735
eridania
Moths of North America
Moths of the Caribbean
Moths of Central America
Moths of South America
Moths of Cuba
Lepidoptera of Brazil
Lepidoptera of Jamaica
Moths described in 1781