diamondback moth
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The diamondback moth (''Plutella xylostella''), sometimes called the cabbage moth, is a moth species of the family
Plutellidae The Plutellidae are a family of moths commonly known as the diamondback moths, named after the diamondback moth (''Plutella xylostella'') of European origin. It was once considered to have three subfamilies: Plutellinae, Praydinae, and Scythropi ...
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 Europe is a large peninsula conventionally considered a continent in its own right because of its great physical size and the weight of its history and traditions. Europe is also considered a Continent#Subcontinents, subcontinent of Eurasia ...
,
South Africa South Africa, officially the Republic of South Africa (RSA), is the southernmost country in Africa. It is bounded to the south by of coastline that stretch along the South Atlantic and Indian Oceans; to the north by the neighbouring countri ...
, or the
Mediterranean The Mediterranean Sea is a sea connected to the Atlantic Ocean, surrounded by the Mediterranean Basin and almost completely enclosed by land: on the north by Western and Southern Europe and Anatolia, on the south by North Africa, and on the e ...
region, but it has now spread worldwide.AgroAtlas
/ref> The moth has a short life cycle (14 days at 25 °C), is highly
fecund Fecundity is defined in two ways; in human demography, it is the potential for reproduction of a recorded population as opposed to a sole organism, while in population biology, it is considered similar to fertility, the natural capability to pr ...
, and is capable of migrating long distances. Diamondback moths are considered pests as they feed on the leaves of cruciferous crops and plants that produce
glucosinolate Glucosinolates are natural components of many pungent plants such as mustard, cabbage, and horseradish. The pungency of those plants is due to mustard oils produced from glucosinolates when the plant material is chewed, cut, or otherwise damaged. T ...
s. However, not all of these plants are equally useful as hosts to the moth. Because of this, studies have suggested using wintercress as a trap crop around agricultural fields because diamondback moths are highly attracted to that plant but their
larvae 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. The ...
fail to survive when eggs are laid on it. Originally,
pesticides Pesticides are substances that are meant to control pests. This includes herbicide, insecticide, nematicide, molluscicide, piscicide, avicide, rodenticide, bactericide, insect repellent, animal repellent, microbicide, fungicide, and lampric ...
were used to kill the moths but diamondbacks have developed resistance to many of the common chemicals. For this reason, new biological and chemical controls, as well as different planting methods are being pursued to reduce the destruction caused by the moths.


Description

This small moth is colored gray and brown. It can potentially identified by a cream-colored band that may be present in the shape of a diamond on its back. The diamondback moth has a
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 of ...
of about 15 mm and a body length of 6 mm. The forewings are narrow, brownish gray and lighter along the anterior margin, with fine, dark speckles. A creamy-colored stripe with a wavy edge on the posterior margin is sometimes constricted to form one or more light-colored diamond shapes, which is the basis for the common name of this moth. The hindwings are narrow, pointed toward the apex, and light gray, with a wide fringe. The tips of the wings can be seen to turn upward slightly when viewed from the side. The antennae are pronounced. The adults of this species are visually identical to the adults of the New Zealand endemic moth ''
Plutella antiphona ''Plutella antiphona'', also known as the diamondback moth, is a moth of the family Plutellidae first described by Edward Meyrick in 1901. It is endemic to New Zealand. Description This species is very similar in appearance to ''Plutella xyl ...
.''


Geographic range

The diamondback moth has a global distribution and is found in Europe,
Asia Asia (, ) is one of the world's most notable geographical regions, which is either considered a continent in its own right or a subcontinent of Eurasia, which shares the continental landmass of Afro-Eurasia with Africa. Asia covers an area ...
,
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 ...
, the
Americas The Americas, which are sometimes collectively called America, are a landmass comprising the totality of North and South America. The Americas make up most of the land in Earth's Western Hemisphere and comprise the New World. Along with th ...
,
Australia Australia, officially the Commonwealth of Australia, is a Sovereign state, sovereign country comprising the mainland of the Australia (continent), Australian continent, the island of Tasmania, and numerous List of islands of Australia, sma ...
,
New Zealand New Zealand ( mi, Aotearoa ) is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and over 700 smaller islands. It is the sixth-largest island count ...
, and the
Hawaiian Islands The Hawaiian Islands ( haw, Nā Mokupuni o Hawai‘i) are an archipelago of eight major islands, several atolls, and numerous smaller islets in the North Pacific Ocean, extending some from the island of Hawaii in the south to northernmost Kur ...
. It is said by some experts to be the most widely distributed of all
Lepidoptera Lepidoptera ( ) is an order (biology), order of insects that includes butterfly, butterflies and moths (both are called lepidopterans). About 180,000 species of the Lepidoptera are described, in 126 Family (biology), families and 46 Taxonomic r ...
, but despite tremendous interest in limiting the damage it causes, the actual available data is inadequate.p.518, " Despite the pest status of DBM and assertions that it has the most extensive distribution of all Lepidoptera (168), current understanding of its global distribution and relative abundance is limited (187). The original distribution map (25) is a composite of incomplete distribution records, and this has recently been superseded by a version that simply records countries where DBM has been reported (16)." It probably originated in Europe, South Africa, or the Mediterranean region, but the exact
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 ...
path is not known. However, in
North America North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and the Car ...
it was observed in
Illinois Illinois ( ) is a U.S. state, state in the Midwestern United States, Midwestern United States. Its largest metropolitan areas include the Chicago metropolitan area, and the Metro East section, of Greater St. Louis. Other smaller metropolita ...
in 1854, and then found in
Florida Florida is a state located in the Southeastern region of the United States. Florida is bordered to the west by the Gulf of Mexico, to the northwest by Alabama, to the north by Georgia, to the east by the Bahamas and Atlantic Ocean, and to ...
and the Rocky Mountains by 1883. Although diamondback moths cannot
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 ...
effectively in cold climates, it was found in
British Columbia British Columbia (commonly abbreviated as BC) is the westernmost province of Canada, situated between the Pacific Ocean and the Rocky Mountains. It has a diverse geography, with rugged landscapes that include rocky coastlines, sandy beaches, ...
by 1905 and is now present in several Canadian regions.


Parental care


Oviposition

Diamondback moths prefer the cabbage plant, from the plant species ''
Brassica oleracea ''Brassica oleracea'' is a plant species from family Brassicaceae that includes many common cultivars used as vegetables, such as cabbage, broccoli, cauliflower, kale, Brussels sprouts, collard greens, Savoy cabbage, kohlrabi, and gai lan. Its ...
'', as their host plant. The females lay eggs only on the leaves of the cabbage and do not discriminate between young and more developed leaves. However, females are more likely to deposit their eggs on a host with larval infestation. It is not fully known why females do not choose the uninfested host, but it is thought that a specific, attractive odor is emitted by the infested host. Female diamondback moths use both
gustatory The gustatory system or sense of taste is the sensory system that is partially responsible for the perception of taste (flavor). Taste is the perception produced or stimulated when a substance in the mouth reacts chemically with taste receptor ...
and
olfactory The sense of smell, or olfaction, is the special sense through which smells (or odors) are perceived. The sense of smell has many functions, including detecting desirable foods, hazards, and pheromones, and plays a role in taste. In humans, it ...
stimuli to determine where to lay their eggs. When both stimuli are available, more eggs are deposited. If gustatory stimuli or both gustatory and olfactory signals are absent, female moths will not lay their eggs. However, if only olfactory signals are absent,
oviposition The ovipositor is a tube-like organ used by some animals, especially insects, for the laying of eggs. In insects, an ovipositor consists of a maximum of three pairs of appendages. The details and morphology of the ovipositor vary, but typical ...
will continue.


Host plant learning and selection for egg laying


Host plants

Host plant selection is crucial because diamondbacks spend the majority of their life near their host plant. The diamondback moth lays its eggs only on plants in the family
Brassicaceae Brassicaceae () or (the older) Cruciferae () is a medium-sized and economically important family of flowering plants commonly known as the mustards, the crucifers, or the cabbage family. Most are herbaceous plants, while some are shrubs. The le ...
. Nearly all cruciferous vegetable crops are attacked, but some are favored over others. These include *
Broccoli Broccoli (''Brassica oleracea'' var. ''italica'') is an edible green plant in the cabbage family (family Brassicaceae, genus ''Brassica'') whose large flowering head, stalk and small associated leaves are eaten as a vegetable. Broccoli is cl ...
*
Brussels sprout The Brussels sprout is a member of the Gemmifera cultivar group of cabbages (''Brassica oleracea''), grown for its edible buds. The leaf vegetables are typically 1.5–4.0 cm (0.6–1.6 in) in diameter and resemble miniature cabbages ...
s *
Cabbage Cabbage, comprising several cultivars of ''Brassica oleracea'', is a leafy green, red (purple), or white (pale green) biennial plant grown as an annual vegetable crop for its dense-leaved heads. It is descended from the wild cabbage ( ''B.&nb ...
*
Chinese cabbage Chinese cabbage (''Brassica rapa'', subspecies ''pekinensis'' and ''chinensis'') can refer to two cultivar groups of leaf vegetables often used in Chinese cuisine: the Pekinensis Group (napa cabbage) and the Chinensis Group (bok choy). These ...
*
Cauliflower Cauliflower is one of several vegetables in the species ''Brassica oleracea'' in the genus ''Brassica'', which is in the Brassicaceae (or mustard) family. It is an annual plant that reproduces by seed. Typically, only the head is eaten – the ...
*
Collard greens Collard is a group of certain loose-leafed cultivars of ''Brassica oleracea'', the same species as many common vegetables including cabbage ( Capitata group) and broccoli ( Italica group). Collard is a member of the Viridis group of ''Brassica ...
*
Kale Kale (), or leaf cabbage, belongs to a group of cabbage (''Brassica oleracea'') cultivars grown for their edible leaves, although some are used as ornamentals. Kale plants have green or purple leaves, and the central leaves do not form a head ...
*
Kohlrabi Kohlrabi (pronounced ; scientific name ''Brassica oleracea'' Gongylodes Group (horticulture), Group), also called German turnip or turnip cabbage, is a Biennial plant, biennial vegetable, a low, stout cultivar of wild cabbage. It is a cultivar o ...
*
Mustard Mustard may refer to: Food and plants * Mustard (condiment), a paste or sauce made from mustard seeds used as a condiment * Mustard plant, one of several plants, having seeds that are used for the condiment ** Mustard seed, seeds of the mustard p ...
*
Radish The radish (''Raphanus raphanistrum'' subsp. ''sativus'') is an Eating, edible root vegetable of the family Brassicaceae that was domesticated in Asia prior to Roman Empire, Roman times. Radishes are grown and consumed throughout the world, be ...
*
Watercress Watercress or yellowcress (''Nasturtium officinale'') is a species of aquatic flowering plant in the cabbage family Brassicaceae. Watercress is a rapidly growing perennial plant native to Europe and Asia. It is one of the oldest known leaf ve ...
Several wild species in the family also act as hosts, especially early in the season when cultivated crops are unavailable. The egg-laying females have been reported to recognize chemicals in the host plants,
glucosinolate Glucosinolates are natural components of many pungent plants such as mustard, cabbage, and horseradish. The pungency of those plants is due to mustard oils produced from glucosinolates when the plant material is chewed, cut, or otherwise damaged. T ...
s and
isothiocyanate In organic chemistry, isothiocyanate is the functional group , formed by substituting the oxygen in the isocyanate group with a sulfur. Many natural isothiocyanates from plants are produced by enzymatic conversion of metabolites called glucosinol ...
s, that are characteristic of the family Brassicaceae (but also occur in some related families). These chemicals were found to stimulate oviposition, even when applied to a piece of paper. One plant species that contains the egg-laying cues is wintercress, ''
Barbarea vulgaris ''Barbarea vulgaris'', also called wintercress (usual common name), or alternatively herb barbara, rocketcress, yellow rocketcress, winter rocket, yellow rocket, and wound rocket, is a biennial herb of the genus '' Barbarea'', belonging to the fa ...
''. Indeed, diamondback moth females lay eggs on this plant species, but the newly hatched larvae die due to the effects of additional natural plant chemicals called
saponin Saponins (Latin "sapon", soap + "-in", one of), also selectively referred to as triterpene glycosides, are bitter-tasting usually toxic plant-derived organic chemicals that have a foamy quality when agitated in water. They are widely distributed ...
s.


Odor

Different behaviors occur before a female diamondback moth deposits her eggs. While virgin and mated females both have the same sensitivity to a host plant's odor, pregnant diamondback females are more strongly drawn and sensitive to it because they are in search of a place to lay their eggs. Diamondbacks are
nocturnal Nocturnality is an animal behavior characterized by being active during the night and sleeping during the day. The common adjective is "nocturnal", versus diurnal meaning the opposite. Nocturnal creatures generally have highly developed sens ...
and use their olfactory system to discover the host plant odor. Additionally, in order to search for the host odor, they rotate their antennas. When the host odor is not present or in low concentrations the moth spends more time rotating its antennas. A moth has increased antennal rotation activity when it is near an uninfested host when compared to an infested host which indicates that the damaged host leaves emit a stronger odor.


Taste and touch

Antennation occurs when the moth hits its antennae on the leaf. This behavior is likely used to taste the host site. Only after antennation will the moth sweep its
ovipositor The ovipositor is a tube-like organ used by some animals, especially insects, for the laying of eggs. In insects, an ovipositor consists of a maximum of three pairs of appendages. The details and morphology of the ovipositor vary, but typical ...
across the site of deposition in order to gather more information about the host. Because the female moths lay their eggs one at a time and prefer crevices, they search for grooves on the leaves. The crevices may offer protection and easy access to food sources. However, grooves on leaves do not determine when oviposition occurs, but they may play a higher role in egg placement.


Life cycle


Eggs

The
eggs Humans and human ancestors have scavenged and eaten animal eggs for millions of years. Humans in Southeast Asia had domesticated chickens and harvested their eggs for food by 1,500 BCE. The most widely consumed eggs are those of fowl, especial ...
are oval and flattened, measuring 0.44 mm long and 0.26 mm wide. They are yellow or pale green at first, but darken later. They are laid singly or in groups of two to eight eggs in depressions on the surface of leaves. Females may deposit up to 300 eggs in total, but average production is probably half that amount. The larvae emerge from the eggs in about six to seven days.


Larvae

The
larvae 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. The ...
have four
instars 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 ass ...
, each with an average development time of about four days. The larval body form tapers at both ends. The larvae have a few short black hairs and are colorless in the first instar, but pale or emerald green with black heads in later instars. Of the five pairs of
prolegs A proleg is a small, fleshy, stub structure found on the ventral surface of the abdomen of most larval forms of insects of the order Lepidoptera, though they can also be found on other larval insects such as sawflies and a few other types of ins ...
, one protrudes from the posterior end, forming a distinctive "V". The larvae are quite active, and when disturbed, may wriggle violently, move backward, and spin a strand of silk from which to dangle. The feeding habit of the first instar is
leaf mining A leaf miner is any one of numerous species of insects in which the larval stage lives in, and eats, the leaf tissue of plants. The vast majority of leaf-mining insects are moths ( Lepidoptera), sawflies ( Symphyta, the mother clade of wasp ...
, although they are so small, the mines are difficult to detect. The larvae emerge from these mines to
moult In biology, moulting (British English), or molting (American English), also known as sloughing, shedding, or in many invertebrates, ecdysis, is the manner in which an animal routinely casts off a part of its body (often, but not always, an outer ...
and subsequently feed on the lower surface of the leaf. Their chewing results in irregular patches of damage, though the upper leaf
epidermis The epidermis is the outermost of the three layers that comprise the skin, the inner layers being the dermis and hypodermis. The epidermis layer provides a barrier to infection from environmental pathogens and regulates the amount of water rele ...
is often left intact. These irregular patches are called window panes.


Sex pheromone effect on larvae

When female diamondback moths lay their eggs, some of their
sex pheromone Sex pheromones are pheromones released by an organism to attract an individual of the same species, encourage them to mate with them, or perform some other function closely related with sexual reproduction. Sex pheromones specifically focus on ind ...
s are left behind on the leaves. Diamondback larvae are attracted to the major component of this species-specific pheromone, which is (Z)11-hexadecenal. For larvae, the sex pheromone is a foraging indicator, rather than a mating attractant so they use it to find a healthy source of food and avoid competition for food from other species on the host plant. After the fourth instar, larvae are no longer attracted to the sex pheromone for food sources.


Pupa

The yellowish
pupae 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 their ...
are about 8 mm long and are wrapped in a loose silk cocoon. They are usually found on the lower or outer leaves of the food plant, but on cauliflower and broccoli, pupation may occur in the florets. It is possible for a pupa to fall off of its host plant. The pupal stage lasts on average for about eight days, but ranges from five to fifteen days. Before emergence occurs, pupa will turn from a yellowish color to a browner color.


Adult

The lifespan averages three to four weeks for females, but less for males. These moths are weak fliers, seldom rising more than 2 m above the ground and not flying long distances. They are, however, passive migrants, being easily transferred by wind over long distances. Diamondback moths overwinter as adults among field debris of cruciferous crops, and active adults may be seen during warm periods at any time during the winter in temperate areas.Oklahoma State University
/ref> They do not survive cold winters and reinvade colder areas each spring, being carried there by the wind. Moths are active usually at twilight and at night, feeding on flowers of cruciferous plants, but they also fly in the afternoon during mass outbreaks.


Enemies


Predators and parasites

The agriculture industry has been trying to find biological and natural ways to eliminate the diamondback moth especially since the moths have become resistant to pesticides. Common enemies of the moth include the
parasitoids In evolutionary ecology, a parasitoid is an organism that lives in close association with its host at the host's expense, eventually resulting in the death of the host. Parasitoidism is one of six major evolutionary strategies within parasi ...
''Trichogramma chilonis'' and ''Cotesia plutella'' and the predator '' Chrysoperla carnea'', a lacewing. Lacewings feed on eggs and young larvae, while the parasitoids attack the eggs. These organisms can recognize diamondback sex pheromones, larval
frass Frass refers loosely to the more or less solid excreta of insects, and to certain other related matter. Definition and etymology ''Frass'' is an informal term and accordingly it is variously used and variously defined. It is derived from the ...
odors, and green leaf volatiles emitted from cabbage. Cabbage odors in combination with the sex pheromone are particularly capable of attracting the predators and parasitoids, which will then consume the diamondback larvae and eggs.


Mating


Pheromones

Female diamondback moths secrete a sex hormone that attracts males who have developed an olfactory system that can detect female sex hormones from a long distance. 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 ...
emission, courtship, and mating occur near the host plant and may be enhanced due to host cues. Climate plays a role in the body size of the diamondback both. However, regardless of the climate, even a few days of high temperatures can lead to lower reproductive success in females. It is possible that high temperatures can decrease the concentration of sex pheromones released by female, thereby delaying the time for mating.


Number of mates

Multiple mating can be beneficial to certain species because it allows for increased reproduction and a variety of genes in offspring. In some cases, females prefer multiple matings because it increases their lifespan as they receive nutrients from males during copulation. It is possible for diamondback moths to mate multiple times, but monogamy seems to be more common. When males have more than one mate, they do not receive any benefit. In fact, their fitness and lifespan decreases along with the success rate of reproduction. Additionally, females who mate with multiple mated males, experience decreased longevity and
fecundity Fecundity is defined in two ways; in human demography, it is the potential for reproduction of a recorded population as opposed to a sole organism, while in population biology, it is considered similar to fertility, the natural capability to pr ...
. Copulation duration has also been shown to increase when males mate multiple times. A longer mating time is disadvantageous to diamondback moths as it leaves the diamondback moth open to predation and injury from copulation. While male diamondbacks can mate multiple times, females show a clear preference for mating once. One of the reasons may be that female diamondback moths only need one mating event to fertilize all of her eggs. The females do this by securing extra sperm from the single mating and creates a
spermatophore A spermatophore or sperm ampulla is a capsule or mass containing spermatozoa created by males of various animal species, especially salamanders and arthropods, and transferred in entirety to the female's ovipore during reproduction. Spermatophores ...
. In addition, a female can deter disadvantageous multiple mating by forming a
mating plug A mating plug, also known as a copulation plug, sperm plug, vaginal plug, or sphragis (Latin, from Greek σφραγίς ''sphragis'', "a seal"), is gelatinous secretion used in the mating of some species. It is deposited by a male into a female ge ...
.


Interaction with humans


Pest of crops

DBM is the worst pest of ''Brassicas'' in the world, and an increasing problem in
canola Close-up of canola blooms Canola flower Rapeseed oil is one of the oldest known vegetable oils. There are both edible and industrial forms produced from rapeseed, the seed of several cultivars of the plant family Brassicaceae. Historically, i ...
.p.518, "Despite these advances, DBM has retained its status as the most destructive member of the different insect pest complexes that attack ''Brassica'' vegetable crops in various parts of the world (34, 147, 155, 161, 165, 167), and it is increasingly considered a significant, if sporadic, threat to canola production (45)." Larvae damage leaves, buds, flowers, and seed buds of cultivated cruciferous plants. Although the larvae are small, they can be very numerous and cause complete removal of foliar tissue except for the leaf veins. This is damaging to young seedlings and may disrupt head formation in cabbage, broccoli, and cauliflower. The presence of larvae in
florets This glossary of botanical terms is a list of definitions of terms and concepts relevant to botany and plants in general. Terms of plant morphology are included here as well as at the more specific Glossary of plant morphology and Glossary o ...
can result in complete rejection of the produce. The diamondback moth is considered a pest in areas that do not experience very cold winters, as these help to reduce adult activity and kill off overwintering moths. It is considered an especially significant issue in China, as it has been argued that Chinese cabbage represents the country's most significant vegetable crop.


Pesticide resistance

The diamondback's lack of natural enemies, such as parasitoids, may be accounted for by the widespread use of
insecticides Insecticides are substances used to kill insects. They include ovicides and larvicides used against insect eggs and larvae, respectively. Insecticides are used in agriculture, medicine, industry and by consumers. Insecticides are claimed to b ...
in the 1950s. The diamondback was not recognized as
DDT Dichlorodiphenyltrichloroethane, commonly known as DDT, is a colorless, tasteless, and almost odorless crystalline chemical compound, an organochloride. Originally developed as an insecticide, it became infamous for its environmental impacts. ...
-resistant until 1953, and broad-spectrum use of insecticides did not begin until the late 1940s. By the 1980s, resistance to
pyrethroid A pyrethroid is an organic compound similar to the natural pyrethrins, which are produced by the flowers of pyrethrums (''Chrysanthemum cinerariaefolium'' and ''Chrysanthemum coccineum, C. coccineum''). Pyrethroids are used as commercial and hou ...
s had developed. Limiting broad spectrum insecticide use and particularly elimination of pyrethroid use, can increase survival and propagation of diamondback
parasitoids In evolutionary ecology, a parasitoid is an organism that lives in close association with its host at the host's expense, eventually resulting in the death of the host. Parasitoidism is one of six major evolutionary strategies within parasi ...
, ''Microplitis plutellae'', ''
Diadegma insulare ''Diadegma insulare'' is a wasp first described by Ezra Townsend Cresson in 1865. No subspecies are listed.Walley, G.S. (1926) A new Sagaritis from western Canada (Hymen.)., Canadian Entomologist. 58:225.Viereck, H.L. (1925) A preliminary revisi ...
'', and ''Diadromus subtilicornis''. The diamondback moth was the first insect found to have become resistant to biological control by the Bt toxin (from '' Bacillus thuringiensis'') in the field. Bt toxin is poisonous when ingested by insects but not mammals, so it was used to target low infestation levels of the moth. Research has shown that the diamondback moth has an autosomal ressessive gene that provides resistance to four specific types of ''B. thuringiensis'' (Cry1Aa, Cry1Ab, Cry1Ac, and Cry1F). ''Trichoplusia ni'' (
cabbage looper The cabbage looper (''Trichoplusia ni'') 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 vegetable ...
) is the only other insect to have developed resistance to Bt toxin in agricultural systems, specifically in greenhouses.


Other controls

Rainfall and
irrigation Irrigation (also referred to as watering) is the practice of applying controlled amounts of water to land to help grow Crop, crops, Landscape plant, landscape plants, and Lawn, lawns. Irrigation has been a key aspect of agriculture for over 5,00 ...
can kill larvae. The cultural practice of
intercropping Intercropping is a multiple cropping practice that involves growing two or more crops in proximity. In other words, intercropping is the cultivation of two or more crops simultaneously on the same field. The most common goal of intercropping is ...
in China could serve to reduce the number of diamondback larvae on cruciferous plants. However, it does not always lead to a reduction of the damage. It has been suggested that sex pheromones and host odors could be manipulated to attract and trap diamondback moths as a means of chemical management.


Climate effects

Seasonal temperature changes lead to differences in body size of the diamondback moths. Warmer temperatures lead to smaller bodies whereas colder temperatures lead to the development of larger bodies. The larger moths have a greater flight ability, longevity, and reproductive performance when compared to the smaller moths. Therefore, long-distance migration tends to occur in the spring rather than midsummer as a greater number of large moths are available and capable of flying.


Integrated pest control


Potential cultural practices

Firstly, inter-cropping is good for reducing pests. Because of the biological diversity, two or more crops can be planted in one field, which can reduce fertilization or pesticide use, making planting the most profitable, and producing higher quality cabbage or increasing yield. High and low growing ''
Trifolium pratense ''Trifolium pratense'', the red clover, is a herbaceous species of flowering plant in the bean family Fabaceae, native to Europe, Western Asia, and northwest Africa, but planted and naturalized in many other regions. Description Red clove ...
'' was used to inter-plant cabbage and compared with cabbage alone. It was concluded that only inter-cropping with the high-growing red clover could reduce the number of eggs produced by the diamondback moth. Secondly, planting time can be considered, because pest populations are affected by seasonal factors. For example, during wet periods, the infection rate of the diamondback moth is very low. As a result, growing cruciferous plants during wet seasons can effectively reduce pesticide use. Thirdly, crop rotation could be used; cruciferous vegetables can be rotated with melons, fruits, onions and garlic resulting in a break in the food chain of the diamondback moth generations. In addition, maintaining clean cabbage field hygiene is a simple but important pest control and prevention measure. A clean growing environment can greatly reduce the likelihood of infection. Before farming, for example, the soil can be ploughed and exposed to the sun for at least a week. This helps to clear the diamondback moth and strengthen the quality of the soil.


Potential physical and mechanical practices

Blue-light traps can catch a lot of adult diamondback worms. dult worms? Clarify?Setting up a trap on top of the cabbage can effectively slow the encroachment of the resistant diamondback moth.


Potential biological control options

1. Introduction of natural enemies which feed on the larvae, thereby reducing numbers. Although they usually only have a noticeable effect in the later stages of crop growth and can kill up to 70% of their prey. Wasps and spiders are considered common predators. The introduction of natural predators can be one of the most effective ways of both stabilizing ecosystems and managing pests. 2. The homologous gene of ''Plutella xylostella'' was knocked out i.e. changed. This is a genetically-based approach that requires precise research to identify suitable genetic targets. Using the CRISPR/Cas9 system as a targeted gene to identify the abdominal segment, thus removing the harmful homologous gene (gene for cruciferous preference) in the diamondback moth. Field trials conducted by the UK
biotechnology Biotechnology is the integration of natural sciences and engineering sciences in order to achieve the application of organisms, cells, parts thereof and molecular analogues for products and services. The term ''biotechnology'' was first used b ...
company Oxitec, released between 1,000 and 2,500 genetically modified males to a crop in
New York state New York, officially the State of New York, is a state in the Northeastern United States. It is often called New York State to distinguish it from its largest city, New York City. With a total area of , New York is the 27th-largest U.S. stat ...
, during August and September 2017 on six occasions. When the male GM moths mated with wild females all the resulting female larvae died. Following pupation of the male larvae, the moths passed on their lethal gene to their offspring, with about half of GM males dying in each generation, resulting in the gene disappearing in a few years and not persisting in the wild.


Potential chemical control options

The method of chemical control is to use pesticides to prevent damage to cabbage fields when larva populations exceed economic thresholds. The pests are controlled during the germination period, and the crops ripen quickly, so the diamondback moth doesn't grow in large numbers. It is more effective to apply insecticide when larval population is high. Since pesticides are difficult to kill larvae and pupae, sufficient pesticides must be used. Make sure there is adequate coverage. The diamondback moth is most active at dusk or at night, when the insecticide is most effective. In addition, avoiding coverage of flowering crops can minimize damage to bees and other pollinated insects. Agdex 606-1. Ntonifor et al 2002 finds ''
Piper guineense ''Piper guineense'' is a West African species of ''Piper''; the spice derived from its dried fruit is known as Ashanti pepper, Benin pepper, Edo pepper, false cubeb, Guinea cubeb, and called locally ''kale'', ''kukauabe'', ''masoro'', ''etiñ ...
'' extract to be highly effective in ''Brassica'' crops. . .


References

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External links


diamondback moth
on the UF / IFAS Featured Creatures Web site
''Plutella xylostella'' (Linnaeus, 1758) Diamond Back or Cabbage Moth
Coffs Harbour Butterfly House, NSW, Australia. Updated January 2014 * R. Srinivasan; Anthony M. Shelton; Hilda L. Collins (1 April 2011)
The Sixth International Workshop on Management of the Diamondback Moth and Other Crucifer Insect Pests.
AVRDC-WorldVegetableCenter.
Download link
{{DEFAULTSORT:Diamondback Moth Plutellidae Agricultural pest insects Leaf miners Moths described in 1758 Moths of Africa Moths of Asia Moths of Australia Moths of Europe Moths of Iceland Moths of Japan Moths of Madagascar Moths of Mauritius Moths of the Middle East Moths of New Zealand Moths of Oceania Moths of Réunion Moths of São Tomé and Príncipe Taxa named by Carl Linnaeus