Cactoblastis cactorum Berg 1885

Die Kaktusmotte (Cactoblastis cactorum) ist eine Schmetterlingsart aus der Familie der Zünsler. Sie kommt ursprünglich in Südamerika vor, wo sie auf Opuntien lebt.

Merkmale

Die Kaktusmotte weist als Adultus ein charakteristisches Bandenmuster auf den braungrauen Vorderflügeln auf, das denjenigen anderer Arten der Familie ähnlich ist, sowie schwarze Streifen. Die Hinterflügel sind hell mit dunkleren Enden. Die Flügelspannweite liegt im Bereich zwischen gut 20 und knapp 40 mm. Die Raupen sind durch schwarze Flecken auf orangem bis rotem Grund gekennzeichnet. Sie werden bis zu ca. 30 mm lang. Die Art gilt als nur durch mikroskopische Untersuchung der abgetrennten männlichen Geschlechtsorgane bestimmbar.^[1][2]

Fortpflanzung

Nach dem Absondern von Pheromonen durch die Weibchen in den Abendstunden und der Antwort durch die Männchen erfolgt die Begattung sowie nach kurzer Inkubationszeit die Ablage von ca. 70–90, teils auch bis über 100 Eiern in kettenartigen Verbänden auf Kakteen. Nach einem knappen Monat schlüpfen die Larven und entwickeln sich im Kaktus, bevor sie außerhalb am Boden an Laubabfall einen Kokon bilden und sich verpuppen. Befallenes Pflanzengewebe verfärbt sich gelb.

Die australische Population weist zwei Lebenszyklen pro Jahr auf.^[1][3]

Wirtschaftliche Bedeutung

Die Art wurde 1925 bis 1930 in Australien erfolgreich eingesetzt, um die Ausbreitung eingeschleppter Kakteen-Arten unter Kontrolle zu bringen. Andernorts, unter anderem in Südafrika und auf Hawaii, wurde die Methode wiederholt. Heute ist sie nach einem lokalen Einsatz auch rund um die Karibik heimisch und stellt eine Bedrohung von Kaktusbeständen in Mexiko dar.^[1][4][5]

Adultes Weibchen

Quellen

1. ↑ ^{a b c} http://entnemdept.ufl.edu/creatures/bfly/cactus_moth.htm
2. ↑ Heinrich C. 1956. American moths of the subfamily Phycitinae. U.S. National Museum Bulletin 207. 581 p.
3. ↑ Dodd AP. 1940. The biological campaign against prickly-pear. Commonwealth Prickly-pear Board Bulletin, Brisbane, 177 p.
4. ↑ Simmonds FJ, Bennett FD. 1966. Biological control of Opuntia spp. by Cactoblastis cactorum in the Leeward Islands (West Indies). Entomophaga 11: 183–189.
5. ↑ Urania Tierreich, Urania Verlag 1994, Band „Insekten“, S. 659

Weblinks

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Cactoblastis cactorum, the cactus moth, South American cactus moth or nopal moth, is native to Argentina, Paraguay, Uruguay and southern Brazil. It is one of five species in the genus Cactoblastis that inhabit South America, where many parasitoids, predators and pathogens control the expansion of the moths' population. This species has been introduced into many areas outside its natural range, including Australia, the Caribbean, and South Africa. In some locations, it has spread uncontrollably and was consequently classified an invasive species.^[1] However, in other places such as Australia, it has gained favor for its role in the biological control of cacti from the genus Opuntia, such as prickly pear.

Interactions in native habitat

In South America, Cactoblastis cactorum has many natural predators, including ants and New World monkeys.^[1] Ants, the moths' main predators, consume its larvae. New World monkeys dig the larvae and pupae out from the flattened leaf-like stems, or "cladodes", of the cacti.^[1] The relationship between Cactoblastis cactorum and Opuntia cactus species is parasitic: the moth feeds on the host cactus. Recent work in South America has identified four genetically-structured^[2] ecotypes of C. cactorum that infest different hosts and possess different larval morphology.^[3][4] The mechanism driving this isolation and pattern of host-association in the field remains unexplored.

Anatomy

Adults of Cactoblastis cactorum are nondescript brownish-gray moths with long legs and long antennae. The moth can be identified only by a microscopic examination of dissected male genitalia. They generally appear as typical Pyralidae, with the pronounced labial palps of the female, thus the name "snout moths".

The forewings show a characteristic banding pattern similar to other related moths.^[5] The hindwings are whitish and semitransparent, and the wingspan of adult moths varies by age and sex. The average wingspan is 27–40 mm for females, and 23–32 mm for males.^[6]

The larvae of C. cactorum are caterpillars that start out with a pink-cream color and gradually become orange, with distinctive black spots or bands.^[6]

Reproduction and lifespan

Cactoblastis cactorum mating occurs before sunrise. Mates are found by scent rather than sight.^[7] Once a female finds a mate, she begins to release sex pheromones that signal to males her readiness. When the male responds, the mating process is initiated.

The initial process of mating begins when the female and male attach themselves at their abdomens.^[7] The male passes a sac, known as the "spermatophore", and the female stores the sac in her abdomen's reproductive center.^[7] After an incubation period, the female deposits an "egg stick" that contains 30–50 eggs.^[8] The eggs are laid on either the tip of the cactus spine, the cactus leaf, the cladode, or the cactus fruit.^[8]

Egg sticks that resemble cactus spines develop and hatch in 25–30 days. The gregarious larvae bore into the cactus pad through a single entry hole by chewing through the tough outer cuticle of the cladode.^[8] The external damage that results is characterized by yellowed plant tissue with plant fluid ooze and insect frass. The larvae feed inside the cactus and eventually hollow out the cactus pad, consuming everything but the vascular tissues.

Larvae will typically spend two months within the host cactus during the summer, and approximately four months during the winter.^[6] Mature larvae exit the cactus pad to form cocoons. They pupate under debris on the ground at the base of the plant. As soon as the moths emerge, they search for a mate,^[8] and usually reproduce three to four times within their lifetime.^[8] The average longevity is nine days for females and eleven days for males.^[5][9] During this time, the female moth does not eat; she uses all of her energy to travel up to 10 kilometres (6 mi) in search of dense cactus patches for reproduction. The male moth devotes his energy to maximizing his mating opportunities.^[9] Males mate between two and five times, and wait two to three days on average between mating events.^[9]

Effects and status

As a biological control agent

An Opuntia infested area in Australia, before Cactoblastis was introduced

Cactoblastis cactorum was first introduced to Australia in 1925 from Argentina, where it was successfully used as a biological control agent for Opuntia cacti.^[10] Due to this success, it was subsequently introduced into other countries, including South Africa in 1933 and the Caribbean in the 1950s.^[5]

Following introduction, Cactoblastis exerted an immediate effect on the agricultural community in South Africa, where it diminished the population of the spineless Opuntia species valued as "cattle fodder".^[11] In 1956, the moth was introduced to the Caribbean island of Nevis and successfully controlled a complex of native "prickly pear" cacti. In 1960 Cactoblastis was introduced into Montserrat and Antigua as a successful biological control agent.^[10]

Spread

Following its introduction into the Caribbean, Cactoblastis cactorum was able to spread across the Atlantic Ocean and throughout the Caribbean through an unknown mix of natural dispersal, intentional and unintentional human transport, and importation on infested livestock fodder.^[5] It has been spotted in Saint Kitts, the US Virgin Islands, Haiti, Cuba, the Dominican Republic, the Bahamas, the Cayman Islands, Puerto Rico and Barbados.^[10]

It eventually reached the Southeastern United States and was first detected in Florida in 1989. Cactoblastis cactorum likely entered Florida through importation of Opuntia from the Dominican Republic.^[10] It is estimated that Cactoblastis is currently expanding its range along both the Gulf and Atlantic coasts at a rate of 100 miles per year, with a constant increase in the rate of colonization along the Gulf Coast.^[5] As it spreads, it threatens the population of Opuntia cacti in Florida, in the Atlantic coast up to Charleston, South Carolina, and around the Gulf Coast up to New Orleans.^[5]

Cactoblastis distribution in the United States:

Prickly pear habitat

Cactus moth habitat

As the moth moves through the Southeastern United States, it endangers many cactus species and threatens many ecosystems. In Florida, the greatest concern is for the critically endangered semaphore cactus Consolea corallicola.^[12] Studies aim to identify the most efficient way to prevent the invasion of Cactoblastis cactorum in the semaphore cactus population. In addition to the semaphore cactus, the arrival of Cactoblastis cactorum to the United States caused concern for the ornamental cactus industry in Arizona, California, Nevada, New Mexico and Texas.^[10] Arizona has the largest economic stake in Cactoblastis; the retail value of its cactus industry is around $9.5 million.^[10]

Cactoblastis cactorum has spread across the Gulf to Mexico, where it was first discovered on Isla Mujeres, a small island off the northeast coast of the Yucatán Peninsula.^[10] It is unknown how the moth migrated to Mexico; speculated means of propagation include winds and hurricanes, unintentional transport by humans, or commercial trade.^[10] Cactoblastis cactorum began to attack Opuntia cacti on San Salvador Island in the Bahamas, where Opuntia cacti, especially the prickly pear cactus, are a major food source for the Cyclura iguanas. The decrease in Opuntia cacti population raises concern of severe damage to the iguana population.^[12]

In 2020 a study found that C. cactorum is unselective as to which Opuntia species it chooses to feed upon. This may result in even more widespread devastation than previously expected.^[13][14][15]

Projected spread

Researchers are projecting a westward expansion of Cactoblastis cactorum in North America.^[12] This threatens cactus industries in the Southwestern United States and inner parts of Mexico.^[12] In the Western United States, over sixty Opuntia species are a vital part of the ecosystem. In Mexico, Opuntia is a vital plant; its fruit and pads (nopal) are a staple food, chopped cacti are used to sustain cattle in times of drought, and some Opuntia species support the cochineal dye industry.^[12][16] Loss of these cacti would have a major environmental and economical impact on the country. Estimated stress factors in the moths' native community indicate that it is restricted to temperate climates, due to the incubation period of its larvae,^[10] but host associations may also play an important role in determining spread.^[17] Models based on environmental tolerances predict that its eventual range limits in the United States are bound by Charleston, South Carolina, to the north and by California to the west.^[6] However, the eventual extent of the western spread remains unclear because we know little about biotic interactions that will occur in this region.

Ecological interactions and mechanisms

Host selection

The ecological relationship between the Cactoblastis cactorum moth and the Opuntia cactus is a parasite–host relationship.^[18]

Cactoblastis larvae feeding on Opuntia cacti

Laboratory feeding studies suggest that Cactoblastis cactorum is one of the least selective moths in the genus Cactoblastis when it comes to host selection,^[1] but the observed patterns of infestation in the field suggest that host identity is important in determining which sites become infested.^[17] The moth selects its host by detecting CAM production in Opuntia cacti.^[18] They have a detection system that enables them to detect the carbon and nitrogen gradients in the air surrounding the host.^[18] The females have a superior detection system to that of the males because they use this to determine where to implant the larvae, which then destroy the cactus.^[18]

Competition

There have been no formal studies of competition between C. cactorum and other cactophagous species to date. This is an area of great potential interest in the Southwestern United States and Mexico because we know little about how of the diversity of cactophagous insects that are found in the region might influence the spread of C. cactorum.

Predation

Another factor that allows the moth to spread so easily in the United States is lack of predation. In South America, several parasitoid species as well as many diseases help to control the spread of the moth and its larvae.^[19] The parasitoids and diseases seem to be enough to control the spread of Cactoblastis cactorum.^[19] These parasitoids and diseases are not present in the areas where the moth has become a problem.^[19] This may be allowing the moth to spread more rapidly than normal. It has yet to be determined if these organisms that limit the growth of the Cactoblastis are host-specific enough to be introduced into affected areas as a method of biological control of the moth itself.^[19]

Life history strategy

Adult female moth in the process of laying an egg stick on a cladode.

Cactoblastis cactorum shows both r-selected and k-selected life history traits. Although the moth reproduces more than once in its lifetime (a more k-selected trait), it produces a large number of eggs at one time (a more r-selected trait).^[1] A female moth can lay up to 50 eggs per generation, and produce at least three generations.^[1] Multiple generations are a sign of iteroparous reproduction. However, large amounts of offspring during a single generation time is a trait of semelparous reproduction. In this particular case, the moth also has high adult mortality rates which tend to push organisms towards semelparous reproduction.^[1] Also, these generations occur over a short period of time, considering that an adult moth only lives for about nine days.^[1]

There are many different combinations and gradients between semelparity and iteroparity. However, it is clear in this case that the moth is closer to the semelparous side of the scale. Semelparity is an r-selected trait, whereas iteroparity is a k-selected trait. Other r-selected traits that the moth exhibits besides large breeds of offspring and short life span are: a small body structure, low adult investment in rearing offspring, and high dispersal ability.^[1] This shows that the moth is much more r-selected than it is k-selected. Most invasive species tend to be r-selected individuals because of their high growth rate and dispersal ability.^[20]

Control options

Many attempts are being made to halt the expansion of Cactoblastis cactorum in order to prevent further damage to Opuntia cacti across Central America and the Southeast United States, where the effect of the moth has been identified as the most dangerous to the native flora. Some attempts to control the population are biological in nature whereas others are more physical attempts to quarantine afflicted Opuntia.

Bacterial control

One option currently being explored is a bacterium, Bacillus thuringiensis, which would kill middle-aged larvae of Cactoblastis cactorum.^[21] The bacterium was discovered by a group of scientists working in a colonization facility in Tifton, Georgia, who were attempting to rear large colonies of the moth.^[21] In their efforts to produce a sterile variety of the moth to eradicate it from its introduced habitat, a unique strain of bacterium was discovered.^[21] A particularly virulent variety of the bacterium was cultured that killed 100% of developing Cactoblastis cactorum larvae.^[5] This bacterium, when raised with the developing moth larvae, caused 100% mortality due to a combination of excreted exotoxins.^[21] The primary lethal exotoxin found in the guts of Cactoblastis cactorum after being exposed to Bacillus thuringiensis is referred to commonly as BtCc.^[21] It is being explored as short-term pest suppression because the bacterium is currently unable to be transferred from generation to generation in the gut of the moth.^[21] BtCc disrupts the digestive process of the larvae and causes near immediate larvae death.^[21] In order for this to be a long-term solution to control the spread of Cactoblastis cactorum, the bacterium or exotoxin would have to be able to reproduce and sporulate within the moth for its effects to spread in the population.^[21]

Wasp predator control

Some researchers are also looking at using a parasitic wasp to curb the spread of Cactoblastis cactorum in the United States.^[12] These wasps, native to South America, lay their eggs in Cactoblastis larvae and eat the larvae from the inside out.^[12] Current concerns are that the wasp itself could become an invasive species, parasitizing native caterpillars and other native insect larvae.^[12]

Ant interaction control

Another possible control option being explored would utilize ants to serve in a mutually beneficial relationship with the Opuntia cacti. Many ant species in the natural world participate in mutualistic relationships with various species of cactus and it is hoped that this general trend of interaction can be exploited to protect the Opuntia cacti from the Cactoblastis moth.^[22] This relationship would offer Opuntia protection from the invader, Cactoblastis, and would offer the ants a place to rear their young and receive nourishment.^[23] In South Africa, a mutualism already exists between many species of cacti and ants to prevent the spread of Cactoblastis.^[22] Many cactus species throughout the world excrete an extrafloral nectar (ENF) that initially attracts the ants.^[23] The ants then feed on this nectar and attack anything that disturbs the cacti.^[23]

Researchers at Rice University in Houston and the Florida A&M University are collaborating in their research to explore such a beneficial relationship that could be reproduced in the United States.^[22] Initial lab experiments showed that the presence of ants living together with the cacti increased the mortality of Cactoblastis eggs laid on the cacti.^[22]

Quarantine in the United States

Currently in the United States, most populations of Cactoblastis cactorum have been discovered in Florida, Georgia, and most recently, in Louisiana. Many of these states have already begun their own programs to halt the progress of the moth in conjunction with the 2009 Strategic Plan.^[5][24]

The United States began a plan in 2009 through the Animal and Plant Health Inspection Service (APHIS) to quarantine afflicted Opuntia species and slow the migration of Cactoblastis cactorum across the United States. The APHIS hopes to create a permanent barrier across which colonization of the invasive moth would be impossible.^[5] This barrier includes not only colonization of new areas across land, but also by sea. By sea, new regulations by APHIS require livestock fodder in transit found with evidence of Cactoblastis cactorum to be destroyed, fumigated, or returned to its country of origin.^[5] By land, quarantining means creating a barrier of area over which the moth will be unable to reproduce across the gap; this has been accomplished by physically removing all cacti in swaths of area or by removing and replacing afflicted cacti.^[5]

One of the primary implementations proposed would be to create a sterile version of Cactoblastis cactorum that would serve to eliminate the westernmost population of the moth and push its current territory eastward.^[5] This method would create a generation of moths which is unable to reproduce and would slowly but effectively curb the spread of the species. However, the sterile version of the moth has had little success in spreading to the majority of the affected area.^[1]

Other methods include identifying infected areas and then mechanically destroying all cacti in that area. Crude methods such as these are being used in Louisiana to eliminate the presence of the moth in swampy areas and generally involve the heavy use of removal by chainsaw, hacksaw, or other mechanical chopping device. Chemical pesticides in most areas have proven to be ineffective due to the large quantity and frequency of treatment of pesticide needed to limit the population and also the effective protection the moth is allotted by the cactus leaves.^[5]

Uncertainties

There is still much to be learned about Cactoblastis cactorum. Its native habitat of South America remains a mostly-unexplored area of scientific research. The moths' interactions with other species are not well understood. Although it is well known that the moth is capable of switching hosts, the full range of host plants susceptible to the moth is unknown. How the moth will affect agriculture in North America will be seen in the next few years, and the effectiveness of many of the control tactics may be seen in even less time. Lastly, a big unknown in the study of Cactoblastis cactorum is how various Opuntia species may develop defenses in response to its invasion. More studies need to be done both to understand the biological mechanisms of the moth and to halt its spread as an invasive species.

Queensland monuments and memorials

Monument to the Cactoblastis cactorum moth in Dalby, Queensland, Australia

There is a monument commemorating eradication of Opuntia by the moth in a park by Myall Creek, in Dalby, Queensland, Australia. ().^[25] It was erected on the Queensland Women's Historical Association on Thursday 27 May 1965.^[25]

The Cactoblastis Memorial Hall is located at Boonarga, 10 kilometres (6 mi) east of Chinchilla in Queensland () and purports to be "the only building dedicated to an insect."^[26] It was erected in 1936, and was one of the first insect memorials ever built, following the 1919 Boll Weevil Monument in Alabama.^[27]

References

Cactoblastis cactorum, comúnmente conocido como polilla de cacto, gusano de la tuna o polilla de nopal, es un insecto de la familia de los pirálidos nativo de Argentina, Paraguay, Uruguay, y Brasil del sur. Es una de las cinco especies del género Cactoblastis que habita en América del Sur, donde muchos parasitoides y patógenos controlan la expansión de su población. Esta especie ha sido introducida a muchas áreas fuera de su distribución natural, como Australia, el Caribe, y Sudáfrica. En algunas ubicaciones, se ha extendido sin control por lo que se ha clasificado como especie invasora.^[1]​ En Australia ha sido introducida intencionalmente para el control biológico de cactos del género Opuntia, como la pera espinosa, que son especies invasoras en esa región.

Interacciones en hábitat nativo

En América del Sur, Cactoblastis cactorum tiene muchos depredadores naturales, incluyendo hormigas y monos de Nuevo Mundo.^[1]​

Las larvas del gusano de la tuna recién nacidas son de color gris verdoso, mientras que los últimos estadios tienen un color que va del salmón naranja saturado al rojo, con puntos negros formando bandas transversales, estas están divididas en cuatro bloques y nunca se unen en la línea media.

Referencias

Cactoblastis cactorum, parfois appelé Pyrale du cactus ou Mite des cactus, est une espèce de lépidoptères (papillons) originaire d’Amérique du Sud de la famille des Pyralidae. Il est devenu invasif^[1] dans de nombreux pays du monde, particulièrement en Amérique du Nord, après y avoir été introduit pour lutter contre le figuier de Barbarie. Quelle que soit sa forme, papillon ou chenille, il se nourrit de cactus de la famille des Opuntia.

De son utilisation à son invasion

Il a été utilisé avec succès comme un agent de lutte biologique en Australie dans les années 1920 pour le contrôle de plusieurs espèces introduites d'Opuntias. Fort de ce succès australien il a été introduit dans d'autres parties du monde, dont l'Afrique du Sud en 1933, et Hawaï en 1950, puis dans les Caraïbes, sur Niévès en 1957 où il s'est pérennisé. Il a finalement réussi à gagner par voie aérienne ou sur des figuiers de Barbarie importés des Caraïbes, les Keys et le Mexique, où il menace les autres espèces de cactus. Il a été aperçu pour la première fois aux Keys en 1989, puis a agrandi son territoire vers le nord, le long des côtes de Floride, le long de l'Atlantique et du Golfe bien que des mesures de lutte aient été engagées.

Alimentation

L'espèce peut se nourrir de tous les Opuntias. Ainsi aux États-Unis, 31 espèces dont 9 endémiques comme Opuntia corallicola en Floride sont menacées. L'insecte s'attaque aux 38 espèces de figuier de Barbarie mexicain qui couvre une superficie de 3 millions d’hectares. Or ces cactus nourrissent un très grand nombre d'espèces d'invertébrés, d'oiseaux, de chauve-souris ou de petits mammifères. En outre ces cactus offrent un refuge pour de nombreuses espèces. S'implantant dans des zones sèches au sol fragile, ces cactus contribuent au maintien des sols. Ces faits font de l'insecte un fléau. En effet la culture de certaines de ces espèces de cactus comme supplément alimentaire se classe au septième rang des cultures agricoles au Mexique, elle est jugée importante aussi bien économiquement que culturellement^[2]. Plus anecdotiquement, ces lépidoptères ravagent les cactus cultivés pour l'aménagement paysager, ce qui aurait coûté 14 millions d'USD par an à l'état d'Arizona. Le Mexique et les États-Unis collaborent donc pour empêcher l'extension de son aire de répartition vers l'ouest.

En 2006, la présence de l’insecte a été détectée à Isla Mujeres, au Mexique ce qui a donné lieu à une grande campagne d'éradication.

Description

Larve de Cactoblastis cactorum.

Les imagos sont des papillons de nuit brun-gris typiques des Pyralidés. La chenille est très facilement reconnaissable avec des bandes noires alternant avec des bandes orange à rouges sur le corps.

Cycle de vie

Avant le coucher du soleil, la femelle commence à libérer des phéromones sexuelles pour signaler aux mâle qu'elle est disposée à s'accoupler. Les mâles répondent et effectuent l'accouplement très rapidement. Après une période d'incubation, la femelle dépose 70 à 90 œufs en forme d'épine de cactus. Ces œufs se développent en 25 à 30 jours. Ils restent grégaires. Les larves se nourrissent, se développent, et finalement se laissent tomber sur le sol pour se métamorphoser. Les plantes infectées se repèrent par des stries jaunâtres et les dépôts d'excréments laissés par les larves.

Cactoblastis cactorum et culture

À Dalby dans le Queensland en Australie, un monument a été élevé à la gloire de cet insecte dans un parc de la ville nommé parc de Myall Creek. Plusieurs autres bâtiments célèbrent l'insecte, comme à Chinchilla toujours dans le Queensland.

Notes

Voir aussi

Références taxonomiques

• (fr) Référence Catalogue of Life : Cactoblastis cactorum Berg, 1885
• (en) Référence NCBI : Cactoblastis cactorum (taxons inclus)

La farfalla del cactus (Cactoblastis cactorum Berg, 1885) è un lepidottero della famiglia Pyralidae, originario dell'Argentina, parassita di differenti specie di Cactaceae del genere Opuntia .

Storia

Il C. cactorum deve la sua notorietà al fatto di essere stato usato con successo come agente di lotta biologica in Australia negli anni venti per il controllo di alcune specie di Opuntia (O. stricta) che si erano diffuse oltre ogni previsione, invadendo alcuni milioni di ettari di pascoli. Dopo il successo ottenuto in Australia fu utilizzato in altre parti del mondo tra cui il Madagascar nel 1925, il Sudafrica nel 1933, le isole Hawaii nel 1950, e i Caraibi nel 1957. Di recente l'insetto è stato segnalato in Florida e in Messico, dove è visto come una potenziale minaccia alla biodiversità delle cactacee locali.

Descrizione

Larve di Cactoblastis cactorum.

Le forme adulte di Cactoblastis cactorum sono delle farfalle poco appariscenti, grigio brunastre, facilmente confondibili con altre specie della famiglia delle Pyralidae, a cui le accomunano i palpi labiali pronunciati della femmina. Le ali anteriori mostrano un caratteristico disegno a bande, simile comunque a quello di altre specie di Phycitinae.

Le larve di C. cactorum sono invece facilmente distinguibili per la loro colorazione rosso-arancio con strie nere.

Ciclo vitale

La femmina segnala la sua disponibilità all'accoppiamento secernendo ferormoni sessuali che richiamano il maschio. L'accoppiamento avviene in genere al tramonto ed è molto breve. Dopo un periodo di incubazione, la femmina deposita una pila di uova (egg stick) contenente 70-90 uova. Gli egg sticks, che richiamano la forma delle spine dei cactus, si schiudono in 25-30 giorni e le larve al primo stadio penetrano nello spessore dei cladodi attraverso le areole. Le larve si nutrono e sviluppano internamente talora perforando la superficie dei cladodi. Il danno esteriore prodotto dalla infestazione è rappresentato dall'ingiallimento dei tessuti della pianta, con stillicidio di fluidi e di feci delle larve. Le larve mature fuoriescono dal cladode per formare i bozzoli e quindi dare vita alle pupe, sotto i detriti del terreno alla base della pianta. Dopo l'emergenza le farfalle adulte si disperdono in nuove aree.

• Femmina in fase di ovodeposizione

• Fuoriuscita delle larve da un egg stick

• Larve

• Pupe (femmina a sn e maschio a dx) e bozzolo

Tributi alla farfalla del Cactus

• La città di Dalby in Queensland (Australia) ha dedicato un monumento al C. cactorum in un parco cittadino. [1] Archiviato il 14 maggio 2007 in Internet Archive.
• L'isola di Ascension ha dedicato al C. cactorum un francobollo

Bibliografia

Cactoblastis cactorum is een vlinder uit de familie snuitmotten (Pyralidae). De vlinder heeft cactussen uit het geslacht Opuntia als waardplant. Het wijfje zet op deze planten staafjes met 70 tot 90 eitjes af op de cactus, die doen denken aan de stekels van een cactus. Na 25 tot 30 dagen komen de eitjes uit. De rupsen boren zich in de cactus en vreten hem van binnen helemaal leeg. Als de rupsen volgroeid zijn, komen ze weer uit de cactus, en verpoppen op de grond tussen de plantenresten. De nieuwe imagines gaan op zoek naar een nieuwe plant.

De vlinder komt oorspronkelijk voor in Zuid-Amerika, maar heeft zich verspreid over het Caribisch gebied en heeft ook Mexico en Florida bereikt.

Biologische bestrijder

Cactoblastis cactorum is in Australië in de jaren 1920 met succes ingezet om geïntroduceerde cactussen uit het geslacht Opuntia ("Prickly pears") onder controle te krijgen. Dit succes werd herhaald in Zuid-Afrika in 1933, in Hawaï in 1950 en in Nevis in 1957.

Monument

In Dalby, in Queensland, Australië, is een monument opgericht voor Cactoblastis cactorum^[1], terwijl bij Chinchilla, ook in Queensland, de "Boonarga Cactoblastis Memorial Hall"^[2] ook is opgedragen aan C. cactorum. De vlindertjes en vooral de rupsen hebben daar succesvol een plaag van de Prickly pears bestreden. Deze monumenten behoren tot de weinige grote eerbetonen aan insecten.

• Cactus Moth, University of Florida

Cactoblastis cactorum syn. Zophodia cactorum – gatunek nocnego motyla z rodziny omacnicowatych (Pyralidae), powszechnie znany jako zjadacz opuncji. Pochodzi z Ameryki Południowej (Argentyna i Brazylia). Gąsienice Cactoblastis cactorum żyją i żerują na opuncjach skutecznie ograniczając ich populację, z tego powodu gatunek introdukowano w wielu regionach świata.

Larwy Cactoblastis cactorum

Cactoblastis cactorum é um inseto, nativo da Argentina, parasita dos cactos do gênero Opuntia, largamente utilizado em ambientes exóticos, como a Austrália para o controle biológico daquele vegetal, através de sua introdução artificial.^[1]

Referências

Cactoblastis cactorum je nočni metulj iz družine vešč (Pyralidae), ki v naravi zajeda kaktuse, predvsem opuncije. Izhaja iz Južne Amerike, vendar se je na tak ali drugačen način razširil po področjih, kjer rastejo opuncije. Preplah med znanstveniki je povzročilo odkritje tega škodljivca na Floridi, kjer raste nekaj ogroženih vrst opuncij, obstaja pa tudi nevarnost širjenja tega škodljivca v notranjost Severne Amerike.

Opis

Odrasla žival je sivkast molj z razponom kril od 22 do 35 mm. Predkrilca so sivkasto rjava, na robu svetlejša. Na krilcih ima prečne črnikaste proge. Podkrilca so bela s sivimi progami. Gosenica je 25 do 30 mm dolga, svetlo rdeča z velikimi črnimi pikami, ki tvorijo kolobarje.

Na Floridi so na opuncijah našli več vrst ličink: Cactioblastis cactorum (Berg), Melitara prodenialis (Walker), Rumatha glaucatella (Hulst), Ozamia lucidalis (Walker) in Laetilia coccidivora (Comstock). Cactoblastis se od ostali loči po tipični barvi in po tem, da se hrani v tkivu. Ozamia lucidalis (Walker) se hrani le s popki in plodovi, Laetilia coccidivora (Comstock) pa se najde le v mrtvem tkivu, pogosto pa se hrani tudi s košenilkami.

Življenjski krog

Samica zaleže jajčeca v verigo, ki posnema bodice. Prvo jajčece odloži na konec bodice, ostale (poprečno 75 jajčec) pa eno na drugo v zaporedje, ki na ta način oblikuje paličico. Po razvitju se gosenice odplazijo na površino kaktusa in se nekaj centimetrov proč zavrtajo v tkivo. Hranijo se v notranjosti rastline, se hitro premikajo iz veje na vejo in v kratkem času uničijo precej tkiva.

Polno razvita gosenica običajno zapusti rastlino in oblikuje bel kokon na listnih steblih, v lubju dreves ali v podobnih skrivališčih. Bube se oblikujejo v tkivu rastline. Razvit molj lahko potem ponovi življenjski ciklus. V krajih z dolgo sezono lahko nastaneta dve generaciji letno, v hladnejših le ena.

Cactoblastis cactorum je razširjen v srednjem delu Južne Aamerike (Argentina, Čile, Paragvaj...) in se hrani tudi s cvetovi in plodovi drugih vrst kaktusov. Kljub temu, da je bil z uvoženimi kaktusi zagotovo že prenešen v Evropo, se v rastlinjakih ni razširil.

Zgodovina

Rezultat uporabe Cactoblastis cactorum proti opuncijam v Avstraliji (slika iz 1930. let)

Populacija Cactoblastis cactorum je bila prenešena v Avstralijo leta 1925. Uporabili so jo za zmanjšanje in kontrolo divje razširjenih opuncij, ki so se razrastle po deželi. Samo v Queenslandu so s tem pridobili 16 miljonov akrov kmetijskih površin. Ta uspeh je bil povod za uporabo molja za uničenje opuncij na Havajih, Indiji in po južni Ameriki. Leta 1957 so jo zanesli na Karibske otoke v Nevis za zožanje rastišč Opuntia currasavica in drugih vrst naravnih opuncij. Učinek je bil tako hiter, da so jajca, larve ali pa okužene dele rastlin leta 1962 poslali še v Monserrat in Antiguo, leta 1970 pa še na Kajmanske otoke. Leta 1963 se je naravno razširila iz Malih Antilov v Puerto Rico. Zdaj je razširjena tudi na Haitiju, Dominikanski republiki in na Bahamih.

V oktobru 1989 so odkrili Cactoblastis cactorum tudi na Floridi. Njeno območje postaja zdaj tudi obala Atlantskega oceana in Mehiški zaliv. Gosenice so sicer leta 2000 našli v okuženih rastlinah v vrtnariji Wal-Mart v Pensacoli, vendar odkritja populacij na območju St. Marka kažejo na naravno razširjanje molja. Sicer zaenkrat ni evidentirano razširjanje molja v notranjost, vendar se biologi bojijo tega, saj že na Floridi raste nekaj ogroženih vrst opuncij, Opuntia spinosissima (Martyn) Mill. in Opuntia tricantha (Willdenow) Sweet. Zajedavec ogroža tudi druge naravne vrste opuncij, Opuntia cubensis Britton & Rose, Opuntia stricta Haw. in Opuntia humifusa (Raf.) Rafinesque.

Zdaj obstaja možnost, da se Cactoblastis cactorum razširi preko Teksasa v Mehiko, predvsem s plodovi opuncij, ki jih uporabljajo v prehrani in z rastlinami, ki jih v sušnih obdobjih uporabljajo za prehrano goveda.

Nadzor škodljivca

Zaradi nevarnosti razširitve potekajo raziskave, s katerimi bi našli načine za omejitev tega škodljivca. Kemijsko uničevanje zaradi razprostranjenosti škodljivca in zaradi nevarnosti, da uničijo tudi ogrožene in koristne vrste žuželk, ne pride v poštev. Raziskave potekajo bolj na področju biološkega nadzora, s plenilci. Nakazana je možnost uporabe parazita Brachymeria sp. na bubah, vendar opazovanja ne kažejo najboljših rezultatov. Večje možnosti so z uporabo naravnih plenilcev, ki so avtohtoni v Južni Ameriki. V poštev pridejo Apanteles alexanderi Brethes (Braconidae), Phyticiplex doddi (Cushman) in Phyticiplex eremnus (Porter) (Ichneumonidae), Brachymeria cactoblastidis Blanchard (Chalcididae) in Epicoronimyia mundelli (Blanchard) (Tachinidae). Vsekakor se mora pred uporabo in razširjanjem teh organizmov preveriti vpliv na okolje in posledice uporabe.

Nevarnost razširitve v Evropi

Čeprav je bil Cactoblastis cactorum pogosto prenešen z rastlinami v Evropo, se zaradi hladnejšega podnebja ni razširil. Prav tako ni znana nobena okužba v rastlinjakih, tako v gojilnicah kot v botaničnih vrtovih, zato na evropskih tleh razširjanje tega škodljivca ni možno.

Пам'ятник Cactoblastis cactorum у Квінсленді, Австралія.

У місті Далбі в Квінслендц, Австралія, споруджено пам'ятник кактусовій молі.

Посилання

• USDA
• Smithsonian
• Center for Plant Conservation
• Species Profile- Cactus Moth (Cactoblastis cactorum), National Invasive Species Information Center, United States National Agricultural Library. Lists general information and resources for Cactus Moth.

Гусеницы кактусовой огнёвки, питающиеся на опунции

Памятник гусеницам кактусовой огнёвки в штате Квинсленд, Австралия.

Интродуцированные виды кактусов стали опасными сорняками в известном случае с Австралией. В 1832 году кактусы рода Platyopuntia использовались в качестве живых изгородей к северу от Сиднея, а в 1839 году одиночный экземпляр опунции вида Opuntia stricta был ввезён в Сидней в качестве декоративного растения. Данный вид натурализовался и распространялся кусками кладодий в том числе и при вспашке земель. Птицы также распространяли семена. В 1914 году коллекция различных опунций была завезена в Австралию. К 1925 году заросли кактусов-опунций видов Опунция крупноколючковая, Opuntia stricta и Opuntia vulgaris занимали площадь до 24 миллионов гектаров пастбищ и стали настоящим бедствием для местных фермеров. Для борьбы с ними в Австралию был завезён естественный враг опунций — кактусовая огнёвка (Cactoblastis cactorum). Вид был завезён в 1925 году из Аргентины^[6]. Программа по биологической борьбе с кактусами была начата в австралийском городке Бунарге, где в 1926 году на опытной станции «Cactoblastis» была начата интродукция кактусовой огнёвки. Благодаря данным мерам популяцию опунции удалось взять под контроль. Опунция полностью не уничтожена в Австралии, благодаря гусеницам кактусовой огнёвки возникло экологическое равновесие^[7].

В 1938 году в долине реки Дарлинг, в городе Далби (англ. Dalby) штата Квинсленд австралийские фермеры поставили памятник гусеницам, «спасшим» Австралию от засилья опунции^[8].

Борьба с кактусовой огнёвкой в Северной Америке

Синим отмечены места произрастания кактусов опунции, красным — ареал интродуцированной кактусовой огнёвки

После интродукции в Карибском бассейне, кактусовая огнёвка была непреднамеренно завезена с морскими судами и грузами в Сент-Китс, американские Виргинские острова, Гаити, Куба, Доминику, Багамские острова, Каймановы острова, Пуэрто-Рико и Барбадос. Это создало предпосылки для возможности расселения вида на юго-востоке США, где он был впервые обнаружен в штате Флориде в 1989 году. Кактусовая огнёвка вероятно была завезена во Флориду вместе с кактусами рода опунция (Opuntia) из Доминиканской Республики. В настоящее время бабочка активно расселяется движется по обе стороны Мексиканского залива и вдоль американского побережья Атлантического океана со скоростью около 160 километров за год, а скорость колонизации вдоль побережья Мексиканского залива увеличивается с каждым годом^[3]. В США кактусовая огнёвка угрожает кактусам-опунциям во Флориде, на побережье Атлантического океана, в Южной Каролине и в Новом Орлеане^[3].

Распространяясь на юго-востоке США, она ставит под угрозу многие виды кактусов и многие экосистемы. Во Флориде наиболее уязвимыми является несколько видов исчезающих кактусов^[9]. Современные исследования делаются с целью выявления наиболее эффективных способов предотвращения вторжения вида в популяции местных кактус. Кактусы выращивают в США для продажи в качестве декоративных растений в Аризоне, Калифорнии, Неваде, Нью-Мексико и Техасе.

Кактусовая огнёвка также распространилась по всему побережью Мексиканского залива в Мексике, где она была впервые обнаружена на острове Isla Mujeres у северо-восточного побережье полуострова Юкатан. Неизвестно, как вид был способен мигрировать в Мексику. Однако предположительно, это стало возможным благодаря ветрам, ураганам и непреднамеренному завозу. В последнее время кактусовая огнёвка стала вредить кактусам на острове Сан-Сальвадор на Багамах. Здесь опунция являются основным источником пищи для рода игуан Cyclura^[9].

В будущем исследователи прогнозируют расширение на запад ареала вида в Северной Америке^[9]. Эта экспансия на запад угрожает промышленности, связанной с кактусами, в юго-западе США и во внутренних частях Мексики. В Северной Америке произрастает более шестидесяти видов опунции, которые являются жизненно важной частью экосистемы. Также плоды опунции служат основной частью диеты местного населения, в основном в Мексике. Кроме того, в Мексике, кактусы служат альтернативой пищей для скота во время засухи, и многие из различных видов опунции являются основой для промышленности, связанной с разведением кошенили^[9][10]. Уничтожение этих кактусов оказало бы серьёзное влияние на экономику и экологию Мексики^[9].

Источники