Helicoverpa zea | |
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Scientific classification | |
Kingdom: | Animalia |
Phylum: | Arthropoda |
Class: | Insecta |
Order: | Lepidoptera |
Superfamily: | Noctuoidea |
Family: | Noctuidae |
Genus: | Helicoverpa |
Species: | H. zea |
Binomial name | |
Helicoverpa zea (Boddie, 1850) | |
Synonyms | |
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Helicoverpa zea, commonly known as the corn earworm, is a species (formerly in the genus Heliothis) in the family Noctuidae. [1] The larva of the moth Helicoverpa zea is a major agricultural pest. Since it is polyphagous (feeds on many different plants) 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. [2]
The species is widely distributed across the Americas with the exception of northern Canada and Alaska. It has become resistant to many pesticides, but can be controlled with integrated pest management techniques including deep ploughing, trap crops, chemical control using mineral oil, and biological controls.
The species migrates seasonally, at night, and can be carried downwind up to 400 km. Pupae can make use of diapause to wait out adverse environmental conditions, especially at high latitudes and in drought.
The corn earworm is found in temperate and tropical regions of North America, with the exception of northern Canada and Alaska as it cannot overwinter in these areas. [3] [4] Helicoverpa zea found in the eastern United States also does not overwinter successfully. [4] They live in Kansas, Ohio, Virginia, and southern New Jersey, but survival rate is mainly affected by the severity of the winter. [4] Corn earworm moths regularly migrate from southern regions to northern regions depending on winter conditions. [4] They are also found in Hawaii, the Caribbean islands, and most of South America, including Peru, Argentina, and Brazil. [5] [6]
Cotton earworms have also been reported from China in 2002. [7]
The taxonomy of Helicoverpa was poorly understood for a long time. Many older works referring to "Heliothis obsoleta", a synonym of H. armigera, are actually about H. zea. [8]
Eggs are individually deposited on leaf hairs and corn silks (not in reference given). [9] The eggs are initially pale green in color, but over time they turn yellowish and then grey. [9] Eggs are 0.5 mm in height and average about 0.55 mm in diameter. [9] They hatch after 66 to 72 hours of development. [10] Once larvae have breached the chorion, they spend up to 83% of eclosion making an exit hole larger than their heads. [10] Larvae spend the rest of the time making a silk meshwork around the exit hole; this both helps them escape the shell and helps them find the shell afterwards so they can feed on it. [10] After feeding on their shell, larvae rest about 3 minutes before they begin feeding on the plant material around them. [10]
Following hatching, larvae feed on the reproductive structures of the plant and usually develop through four to six instars. [3] Initially, the young larva feed together, and this stage is their most destructive stage. [12] Through maturation, older larvae become aggressive and cannibalistic, leaving one or two larvae per feeding site (See Interfamilial Predation). [13] They usually have orange heads, black thorax plates, and a body color that is primarily black. [14] Their bodies can also be brown, pink, green, and yellow with many thorny microspines. [14] Mature larvae migrate to the soil, where they pupate for 12 to 16 days. [15]
Larvae pupate 5 to 10 cm below the soil surface. [3] Pupae are brown in color; they measure 5.5 mm wide and 17 to 22 mm long. [3] The biggest environmental factor that affects the pupal developmental rate is temperature, primarily soil temperature. [15] This is because proper insulation facilitates development, and soil temperatures below 0 degrees Celsius correlate to higher pupal mortality. [15] Another factor that influences pupal development is soil moisture. Pupal mortality is high in wet soil, where the moisture level is between 18 and 25 percent. Dehydration can also lead to high death rates among pupae, if soil moisture is as low as 1 to 2 percent. [16]
Adults have forewings that are yellowish brown in color and have a dark spot located in the center of their body. [17] The moths have a wingspan ranging from 32 to 45mm, and live over thirty days in optimal conditions. [17] However, the life span ranges from five to fifteen days on average. [17] They are nocturnal and hide in vegetation during the day. [17] Adult moths collect nectar or other plant exudates from a large number of plants, and live for 12 to 16 days. Females can lay up to 2,500 eggs in their lifetime. [3]
The corn earworm is a major agricultural pest, with a large host range encompassing corn and many other crop plants. [18] H. zea is the second-most important economic pest species in North America, next to the codling moth. [8] [ dubious ] The estimated annual cost of the damage is more than US$100 million, though expenditure on insecticide application has reached up to $250 million. [19] The moth's high fecundity, ability to lay between 500 and 3,000 eggs, polyphagous larval feeding habits, high mobility during migration, and a facultative pupal diapause have led to the success of this pest. [19] [20]
Two kinds of control measures have been advocated since the 19th century. [8] One aims at total pest population reduction, while the other is aimed at protection of the particular crop. [8] As of 2013 [update] , integrated pest management (IPM), an array of techniques and approaches to control pests, was recommended. [8] Practices such as deep ploughing, mechanical destruction, and trap crops are also used to kill different instars. [8] Chemical control is widely successful, and includes the use of applying mineral oil inside the tip of each corn ear, which suffocates the young larvae. [8] [21] Pesticides are one method by which corn earworm populations are controlled; however, since they have been widely used, the insects have become resistant to many pesticides. [4] The use of biological controls, such as the bacterium Bacillus thuringiensis and various forms of nematodes, is also common, although not without their own problems. [1] [4] Corn earworm moths are not always vulnerable to the bacterium, and they are only afflicted by nematodes once the larvae have pupated and dropped to the ground. [4] [22] Strains of maize have been genetically modified to produce the same toxin as the bacterium, and are referred to as Bt-corn. [23]
More than 100 insect species prey on H. zea, usually feeding on eggs and larvae. [24] The insidious flower bug (Orius insidiosus), a pirate bug, feeds on the eggs of H. zea, thus acting as a biological control agent. [24] Some plants emit a blend of chemicals in response to damage from H. zea, which attract parasitic insects. [25] Cardiochiles nigriceps, a solitary endoparasitoid wasp, makes use of these volatile plant compounds to identify the presence of H. zea. [25] [26] When the wasps find damaged host plants, they hover around and then search for the host with their antennae. When the females find their prey, they use their antennae to position themselves and deposit eggs into the host. [25] [26] The braconid wasp Microplitis croceipes , which deposits its eggs inside a living caterpillar, is also an important parasitoid of both H. zea and the related species Heliothis virescens . [26] When larval densities are high, a fungal pathogen, Nomuraea rileyi , can cause an outbreak of disease. [26] However, pupal mortality is high not because of predators, but because of harsh weather conditions, collapsing pupal chambers, and disease. [26]
As the larvae mature, they become increasingly aggressive. [13] Although they have host plants surrounding them, H. zea larvae attack and eat other insects. [13] When presented with a second-instar larva of Urbanus proteus , the corn earworm larva grasps the insect, rolls onto its side to form a semicircle, and begins feeding on the insect's posterior end. [13] If the U. proteus begins to bite out of defense, H. zea rotates the larva 180° and uses its mandibles to puncture the head capsule, killing the insect. [13] Then, the H. zea larva rotates the U. proteus back to its original position and continues feeding until the insect is entirely consumed. [13] Even when presented with up to five U. proteus larvae, H. zea engages in the unique behavior, as the larvae have a higher affinity for lepidopterous prey over plant material. [13] H. zea raised in a low-moisture environment has a lower pupal weight and a longer developmental time than those raised in environments of high moisture, so a nutritional benefit exists to such aggressive feeding behavior under such conditions. [26]
Helicoverpa zea is a seasonal, nocturnal migrant, and adults disperse, weather permitting, when there are poor reproductive conditions. [27] In short-range dispersal, the moths move within the crop and low over the foliage. [27] This type of dispersal is mostly independent of wind currents. Long-range dispersal involves adults flying up to 10 meters above the ground and moving downwind from crop to crop. [27] Migratory flights occur up to 1–2 km above the ground and can last for hours. [28] Migration of 400 km is common for such flights as moths are carried downwind. [27] Helicoverpa zea caterpillars are usually intercepted on produce transported by air-freight transportation. [27] Most activity is restricted to the night-time. [20] Some moths display vertical take-off flight, which carries them above the flight boundary layer and allows them to undertake migratory movement in upper wind systems. [20] During mating, males engage in high-speed directed flight in search of pheromone plumes (See Pheromone Production). [20]
Pupae have the ability to enter facultative diapause, the state of arrested development and growth in response to a change in the environment. [29] By preparing themselves for a major change in environmental conditions, they can increase reproductive success. [30] Diapause increases with increasing latitude. In tropical conditions, populations breed continuously, and only 2-4% of pupae diapause. [30] In subtropical and temperate regions, most individuals diapause. Individuals who don't enter diapause in these areas emerge in late fall and die without reproducing. Drought-responsive diapause has also been observed in the summer. [30]
Helicoverpa zea has a wide host range, attacking vegetables that include corn, tomato, artichoke, asparagus, cabbage, cantaloupe, collards, cowpea, cucumber, eggplant, lettuce, lima bean, melon, okra, pea, pepper, potato, pumpkin, snap bean, spinach, squash, sweet potato, and watermelon. [31] However, not all of these are good hosts. While corn and lettuce are shown to be great hosts, tomatoes are less beneficial, and broccoli and cantaloupe are poor hosts. [31] Corn and sorghum are most favored by corn earworms. [31] Various signs reveal the presence of these moths. [32] Young maize crops have holes in their leaves, following whorl-feeding on the apical leaf. [32] Eggs can be found on silks on larger plants, and silks display grazing evidence. [32] The soft, milky grains in the top few centimeters of corn cobs are eaten as the corn ears develop. [32] One larva per cob can be observed. [32] Bore holes are observed in cabbage and lettuce hearts, flower heads, cotton bolls, and tomato fruits. Sorghum heads are grazed, and legume pod seeds are eaten. [32]
Helicoverpa zea earns its nickname the corn earworm for its widely known destruction of cornfields. [34] The corn earworm feeds on every part of corn, including the kernels. [34] Severe feeding at the tip of kernels allows entry for diseases and mold growth. [34] Larvae begin feeding on the kernels once they have reached third instar. [34] Larvae penetrate 9 to 15 cm into the ear, with deeper penetration occurring as the kernels harden. [34] Larvae do not eat the hard kernels, but take bites out of many kernels, lowering the quality of the corn for processing. [34]
Helicoverpa zea is the most common and destructive pest of soybean growth in Virginia. [35] About one-third of Virginia acreage is treated annually with insecticide, costing farmers around 2 million dollars. [35] The degree of damage varies on the size of the pest infestation, the timing, and the stage of the plant. [35] However, soybean plants are capable of withstanding a large amount of damage without substantial yield loss depending on soil moisture, planting date, and weather. [35] If the damage is early in the plants life, then damage will mostly be to the leaves. [35] Plants compensate for the damage by processes such as increasing seed size in remaining pods. [35] Most damage happens in August, when the plants are flowering. Attacks that happen after August do much less damage because many pods have developed tougher walls that H. zea can't penetrate. Infestations that affect pod formation and seed filling have the potential to reduce yields, and because this happens in the later stages of plants, they have less time to compensate. [35]
Female moths are attracted to flowering soybean fields. [35] The most severe infestations occur between flowering and when pods become fully developed. [35] Large-scale outbreak is associated with time of peak flowering, when most pods are developed, and peak moth flight, for giant. [35] Moths are also attracted to drought stressed soybeans or fields with poor growth. [35] Dry weather leads to quick drying of corn plants, compelling moths to leave and seek other hosts. [35] Heavy rainfall also decreases corn earworm populations because it drowns pupae in their soil chambers, limits moth flight, washes eggs from leaves, and creates favorable conditions for fungal diseases that kill caterpillars. [35]
A hormone produced in the brain of the female moths controls sex pheromones. The hormone is released into the hemolymph to stimulate pheromone production. [36] Pheromone biosynthesis-activating neuropeptide (PBAN) is a peptide that regulates pheromone production in moths. It acts on the pheromone gland cells using calcium and cyclic AMP. [37] Although the photoperiod regulates the release of PBAN to some extent, the chemical signals from the host plant supersede the effect from the time of day. [38] Female Helicoverpa zea in corn fields do not produce pheromones during the night until they encounter corn. Several natural corn silk volatiles like the plant hormone Ethylene as a plant hormone#ethylene induce H. zea pheromone production. [38] The presence of the silk from an ear of corn is enough to cause pheromone production, and physical contact between females and corn is unnecessary. [38] This evolutionary mechanism enables the moths to coordinate their reproductive behavior with the availability of food. [38] Female moths often become depleted of sex pheromone after mating within 2 hours of separation from the male. [39] The pheromonostatic peptide (PSP), a protein 57 amino acids long found in the male accessory gland, is what causes depletion of the female's sex pheromone. [40] This capability in males has been selected for because it increases the reproductive fitness of those that carry it, since other males will not be attracted to a female without a sex pheromone; thus, the female will bear only the first male's offspring. [41] The transfer of a spermatophore without accessory gland products does not stop female pheromone production, but does stop the female's calling behavior. [41] Intense selection acting on males to manipulate female reproductive physiology promotes rapid evolution of specific molecules, and male-derived pheromone suppressing factors exhibit positive selection. [41] When females are infected with the virus Helicoverpa zea nudivirus 2, they produce 5 to 7 times the amount of sex pheromone than uninfected females. [42]
Sperm competition and chemicals introduced to females through mating have a negative effect on females and their lifespan. [41] [44] In males, production of the spermatophore, sperm, and secondary chemicals reduces their lifespan. [44] As the number of copulations increase, the rate of mortality also increases in both sexes. [44]
Males must first wait to sense a female's pheromones before they can locate her. [39] Before males engage in flight to find a female, they warm-up by shivering the major flight muscles to reach thoracic temperature optimal to sustain flight, around 26 degrees Celsius. The thermoregulatory shivering activities of males were measured as they were exposed to different sex-related olfactory cues. [45] Males are found to heat up more quickly in the presence of a female pheromone and take-off at a lower thoracic temperature than males who are exposed to other chemical scents. [45] Since heating up to the right temperature leads to better flight performance than flying immediately, there is a trade-off between sub-optimal flight performance and rapid onset of directed flight. [45] Helicoverpa zea males exposed to an attractive pheromone blend thus spend less time shivering and increase their heating rate. [45] Thermoregulatory behavior of unrestrained moths is associated with competition for access to females, showing the ecological trade-off. [45]
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.
The Indianmeal moth, also spelled Indian meal moth and Indian-meal moth, is a pyraloid moth of the family Pyralidae. Alternative common names are weevil moth, pantry moth, flour moth or grain moth. The almond moth and the raisin moth are commonly confused with the Indian-meal moth due to similar food sources and appearance. The species was named for feeding on Indian meal or cornmeal, and does not occur natively in India. It is also not to be confused with the Mediterranean flour moth, another common pest of stored grains.
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.
Heliothis is a genus of moths in the family Noctuidae. It was first described by Ferdinand Ochsenheimer in 1816. Some of the species have larvae which are agricultural pests on crop species such as tobacco, cotton, soybean and pigeon pea. Some species originally in this genus have been moved to other genera, see Chloridea and Helicoverpa.
Helicoverpa armigera is a species of Lepidoptera in the family Noctuidae. It is known as the cotton bollworm, corn earworm, Old World (African) bollworm, or scarce bordered straw. The larvae feed on a wide range of plants, including many important cultivated crops. It is a major pest in cotton and one of the most polyphagous and cosmopolitan pest species. It should not be confused with the similarly named larva of the related species Helicoverpa zea.
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.
The European corn borer, also known as the European corn worm or European high-flyer, is a moth of the family Crambidae which includes other grass moths. It is a pest of grain, particularly maize. The insect is native to Europe, originally infesting varieties of millet, including broom corn. The European corn borer was first reported in North America in 1917 in Massachusetts, but was probably introduced from Europe several years earlier. Since its initial discovery in the Americas, the insect has spread into Canada and westward across the United States to the Rocky Mountains.
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.
The leek moth or onion leaf miner is a species of moth of family Acrolepiidae and the genus Acrolepiopsis. The species is native to Europe and Siberia, but is also found in North America, where it is an invasive species. While it was initially recorded in Hawaii, this was actually a misidentification of Acrolepiopsis sapporensis.
Agrotis ipsilon, the dark sword-grass, black cutworm, greasy cutworm, floodplain cutworm or ipsilon dart, is a small noctuid moth found worldwide. The moth gets its scientific name from black markings on its forewings shaped like the letter "Y" or the Greek letter upsilon. The larvae are known as "cutworms" because they cut plants and other crops. The larvae are serious agricultural pests and feed on nearly all varieties of vegetables and many important grains.
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 nocturnal agricultural pest belonging to the family Noctuidae. This moth is also commonly referred to by the scientific name Pseudaletia unipuncta. The species was first described by Adrian Hardy Haworth in 1809. Mythimna unipuncta is found in the Americas and in parts of Europe, Africa and Asia. Its original distribution is North and South America. It has been introduced to other places from there. 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.
Heliothis punctifera or the lesser budworm, is an Australian moth of the family Noctuidae; one of the most migratory families of insects. It is considered a pest species to agricultural crops, however, due to its inland habitat, is found to be less damaging to agricultural areas than other species of the genus.
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.
Heliothinae is a small, cosmopolitan subfamily of moths in the family Noctuidae, with about 400 described species worldwide. It includes a number of economically significant agricultural pest species, such as Helicoverpa armigera and Helicoverpa zea.
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.
Cadra figulilella, the raisin moth, is a moth of the family Pyralidae. The raisin moth is known most commonly as a pest that feeds on dried fruits, such as the raisin and date. It covers a range that includes much of the world, primarily situating itself in areas of California, Florida, the Eastern Mediterranean region, and some parts of Africa, Australia, and South America. The moth prefers to live in a hot, arid climate with little moisture and plentiful harvest for its larvae to feed on. Study of this species is important due to the vast amount of economic damage it causes yearly and worldwide to agriculture crops.
Cadra calidella, the dried fruit or date moth, is a species of snout moth in the genus Cadra and commonly mistaken for the species Cadra figulilella. It thrives in warmer conditions and is found primarily in Mediterranean countries, although it can also be found in Central Asia, Kazakhstan, Transcaucasia, Caucasus, and the western part of Russia. It feeds on dried fruits, carobs, nuts and seeds, hence earning its colloquial name. This diet damages the food industry, and it is a common storage pest. Because of this, much research has been done to study ways to limit its reproduction rate and population size. It was first described by Achille Guenée in 1845.
Ostrinia furnacalis is a species of moth in the family Crambidae, the grass moths. It was described by Achille Guenée in 1854 and is known by the common name Asian corn borer since this species is found in Asia and feeds mainly on corn crop. The moth is found from China to Australia, including in Java, Sulawesi, the Philippines, Borneo, New Guinea, the Solomon Islands, and Micronesia. The Asian corn borer is part of the species complex, Ostrinia, in which members are difficult to distinguish based on appearance. Other Ostrinia such as O. orientalis, O. scapulalis, O. zealis, and O. zaguliaevi can occur with O. furnacalis, and the taxa can be hard to tell apart.