Southern armyworm | |
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Imago | |
Pupa | |
Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Arthropoda |
Class: | Insecta |
Order: | Lepidoptera |
Superfamily: | Noctuoidea |
Family: | Noctuidae |
Genus: | Spodoptera |
Species: | S. eridania |
Binomial name | |
Spodoptera eridania Stoll, 1781 | |
Synonyms | |
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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 is 33–38 mm. Adults are on wing year-round. The larvae feed on various weeds but prefer Amaranthus species and Phytolacca americana.
The S. eridania is found in North America (the southern US states as far west as Kansas and New Mexico), through the Caribbean and Central America into South America (through Brazil to Argentina). It has been introduced Nigeria and Cameroon. [1]
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. [2]
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 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. [3]
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. [4] 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.
A lot of research has been done on neem-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. [5] 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 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. [6]
Research has also been done with the genetically modified soybean plant. They are created with insect resistance genes from Bacillus thuringiensis Berliner (Bt-plants) and increasingly being cultivated around the world. [7] Research has shown that the Bt soybean does not affect pest foliage consumption but does reduce larval duration by around two days.
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.
In the cerrado region of Brazil, 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[ check spelling ] 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. [8]
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. [9]
The number of generations is estimated at four each year in Florida. In northern Florida, 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.
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.
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.
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. [10] 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. [11] 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.
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.
Parasitoid insects associated with southern armyworm caterpillars include: [12] [13]
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.
The Noctuidae, commonly known as owlet moths, cutworms or armyworms, are a family of moths. They are considered the most controversial family in the superfamily Noctuoidea because many of the clades are constantly changing, along with the other families of the Noctuoidea. It was considered the largest family in Lepidoptera for a long time, but after regrouping Lymantriinae, Catocalinae and Calpinae within the family Erebidae, the latter holds this title now. Currently, Noctuidae is the second largest family in Noctuoidea, with about 1,089 genera and 11,772 species. This classification is still contingent, as more changes continue to appear between Noctuidae and Erebidae.
Helicoverpa zea, commonly known as the corn earworm, is a species in the family Noctuidae. The larva of the moth Helicoverpa zea is a major agricultural pest. Since it is polyphagous during the larval stage, the species has been given many different common names, including the cotton bollworm and the tomato fruitworm. It also consumes a wide variety of other crops.
The cabbage looper is a medium-sized moth in the family Noctuidae, a family commonly referred to as owlet moths. Its common name comes from its preferred host plants and distinctive crawling behavior. Cruciferous vegetables, such as cabbage, bok choy, and broccoli, are its main host plant; hence, the reference to cabbage in its common name. The larva is called a looper because it arches its back into a loop when it crawls.
The beet armyworm or small mottled willow moth is one of the best-known agricultural pest insects. It is also known as the asparagus fern caterpillar. It is native to Asia, but has been introduced worldwide and is now found almost anywhere its many host crops are grown. The voracious larvae are the main culprits. In the British Isles, where it is an introduced species and not known to breed, the adult moth is known as the small mottled willow moth.
The African armyworm, also called okalombo, kommandowurm, or nutgrass armyworm, is a species of moth of the family Noctuidae. The larvae often exhibit marching behavior when traveling to feeding sites, leading to the common name "armyworm". The caterpillars exhibit density-dependent polyphenism where larvae raised in isolation are green, while those raised in groups are black. These phases are termed solitaria and gregaria, respectively. Gregaria caterpillars are considered very deleterious pests, capable of destroying entire crops in a matter of weeks. The larvae feed on all types of grasses, early stages of cereal crops, sugarcane, and occasionally on coconut. The solitaria caterpillars are less active and undergo much slower development. The species is commonly found in Africa, but can also be seen in Yemen, some Pacific islands, and parts of Australia. African armyworm outbreaks tend to be devastating for farmland and pasture in these areas, with the highest-density outbreaks occurring during the rainy season after periods of prolonged drought. During the long dry seasons ("off-season"), the population densities are very low and no outbreaks are seen.
The diamondback moth, sometimes called the cabbage moth, is a moth species of the family Plutellidae and genus Plutella. The small, grayish-brown moth sometimes has a cream-colored band that forms a diamond along its back. The species may have originated in Europe, South Africa, or the Mediterranean region, but it has now spread worldwide.
Spodoptera litura, otherwise known as the tobacco cutworm or cotton leafworm, is a nocturnal moth in the family Noctuidae. S. litura is a serious polyphagous pest in Asia, Oceania, and the Indian subcontinent that was first described by Johan Christian Fabricius in 1775. Its common names reference two of the most frequent host plants of the moth. In total, 87 species of host plants that are infested by S. litura are of economic importance. The species parasitize the plants through the larvae vigorous eating patterns, oftentimes leaving the leaves completely destroyed. The moth's effects are quite disastrous, destroying economically important agricultural crops and decreasing yield in some plants completely. Their potential impact on the many different cultivated crops, and subsequently the local agricultural economy, has led to serious efforts to control the pests.
Spodoptera littoralis, also referred to as the African cotton leafworm or Egyptian cotton leafworm or Mediterranean brocade, is a species of moth in the family Noctuidae. S. littoralis is found widely in Africa, Mediterranean Europe and Middle Eastern countries. It is a highly polyphagous organism that is a pest of many cultivated plants and crops. As a result, this species was assigned the label of A2 quarantine pest by the EPPO and was cautioned as a highly invasive species in the United States. The devastating impacts caused by these pests have led to the development of both biological and chemical control methods. This moth is often confused with Spodoptera litura.
Mythimna unipuncta, the true armyworm moth, white-speck moth, common armyworm, or rice armyworm, is a species of moth in the family Noctuidae. The species was first described by Adrian Hardy Haworth in 1809. Mythimna unipuncta occurs in most of North America south of the Arctic, as well as parts of South America, Europe, Africa, and Asia. Although thought to be Neotropical in origin, it has been introduced elsewhere, and is often regarded as an agricultural pest. They are known as armyworms because the caterpillars move in lines as a massive group, like an army, from field to field, damaging crops.
Helicoverpa punctigera, the native budworm, Australian bollworm or Chloridea marmada, is a species of moth in the family Noctuidae. This species is native to Australia. H. punctigera are capable of long-distance migration from their inland Australian habitat towards coastal regions and are an occasional migrant to New Zealand.
Mythimna separata, the northern armyworm, oriental armyworm or rice ear-cutting caterpillar, is a moth of the family Noctuidae. It is found in China, Japan, South-east Asia, India, eastern Australia, New Zealand, and some Pacific islands. It is one of the major pests of maize in Asia. The species was first described by Francis Walker in 1865.
The fall armyworm is a species in the order Lepidoptera and one of the species of the fall armyworm moths distinguished by their larval 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 crops, which causes large economic damage. Its scientific name derives from frugiperda, which is Latin 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.
Chloridea virescens, commonly known as the tobacco budworm, is a moth of the family Noctuidae found throughout the eastern and southwestern United States along with parts of Central America and South America.
Spodoptera is a genus of moths of the family Noctuidae erected by Achille Guenée in 1852. Many are known as pest insects. The larvae are sometimes called armyworms. The roughly thirty species are distributed across six continents.
Spodoptera cosmioides is an armyworm moth of the family Noctuidae found in Central America and South America.
Diabrotica speciosa, also known as the cucurbit beetle and in Spanish as vaquita de San Antonio is an insect pest native to South America. Its larvae feed on the roots of crops. The cucurbit beetle is also known to transmit several viruses such as comoviruses and different mosaic viruses. This is native to South America and is now distributed in Central America and other global areas.
Helicoverpa assulta, the oriental tobacco budworm, is a moth of the family Noctuidae. H. assulta adults are migratory and are found all over the Old World Tropics including Asia, Africa, and Australia.
Ascia is a genus of butterflies in the family Pieridae. It is monotypic, being represented by the single species Ascia monuste, commonly known as the great southern white, In this species the sexes may differ with the female being either light or dark colored. It is found from the Atlantic and Gulf coasts of the United States, and south to Argentina. It is migratory along the south-eastern coast of the United States, with strays to Maryland, Kansas, and Colorado.
Spodoptera mauritia, the lawn armyworm or paddy swarming caterpillar, is a moth of the family Noctuidae. The species was first described by Jean Baptiste Boisduval in 1833. Able to eat many types of food, it is a major pest throughout the world.
The Coconut black headed caterpillar, is a species of moth found in throughout East Asian countries including Bangladesh, India, Sri Lanka, Myanmar, as well as Indonesia. It is considered a pest of coconut palm trees, causing considerable damage to the trees, and reducing the plant's yield significantly and can be a major problem where coconuts contribute to the economy. The species exists on coconut palms through its life stages from larval to moth, and utilizes the tree fronds as a main source of nutrition. Various methods of control have been explored, yet the primary control method is the administration of pesticides directly to the root of the coconut palms.