Cactoblastis cactorum
Cactoblastis cactorum | |
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Female moth | |
Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Arthropoda |
Class: | Insecta |
Order: | Lepidoptera |
Family: | Pyralidae |
Genus: | Cactoblastis |
Species: | C. cactorum
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Binomial name | |
Cactoblastis cactorum (Berg, 1885)
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Synonyms | |
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Cactoblastis cactorum, the cactus moth, South American cactus moth or nopal moth, is native to
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
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
Reproduction and lifespan
Cactoblastis cactorum mating occurs before sunrise. Mates are found by scent rather than sight.[7][unreliable source?] 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
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
Larvae will typically spend two months within the host cactus during the summer, and approximately four months during the winter.
Effects and status
As a biological control agent
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
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]
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.
Ecological interactions and mechanisms
Host selection
The ecological relationship between the Cactoblastis cactorum moth and the Opuntia cactus is a parasite–host relationship.[18]
Laboratory feeding studies suggest that Cactoblastis cactorum is one of the least selective moths in the
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.
Life history strategy
Cactoblastis cactorum shows both
There are many different combinations and gradients between
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,
Wasp predator control
Some researchers are also looking at using a
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.
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.[citation needed]
Queensland monuments and memorials
There is a monument commemorating eradication of Opuntia by the moth in a park by Myall Creek, in Dalby, Queensland, Australia. (27°11′00″S 151°15′59″E / 27.1832°S 151.2665°E).[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 (26°47′43″S 150°42′55″E / 26.7953°S 150.7154°E) 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
- ^ a b c d e f g h i j Zimmermann, H., Bloem, S., Klei, H., "Biology, History, Threat, Surveillance and Control of the Cactus Moth, Cactoblastis cactorum", April 10, 2004.
- S2CID 36621465.
- PMID 22624321.
- S2CID 16392106.
- ^ a b c d e f g h i j k l m "Plant Health: Cactus Moth (Cactoblastis cactorum)". United States Department of Agriculture. Retrieved 7 March 2010.
- ^ a b c d Materson, J., "Cactoblastis cactorum. Smithsonian Marine Station at Fort Pierce", March 10, 2007.
- ^ a b c Everlyn, K. (2011). "How Does a moth reproduce? "[self-published source?]
- ^ S2CID 24558217.
- ^ .
- ^ a b c d e f g h i Capinera, John L., Encyclopedia of Entomology, Springer, April 10, 2008.
- S2CID 196651099.
- ^ a b c d e f g h Stiling, P., "A Worm That Turned", Natural History, 109(5), 40-43, March 5, 2000.
- S2CID 226339523.
- ^ "Invasive Cactus Moth Likely to Spread and Destroy Native Prickly Pear". College of Natural Sciences, University of Texas at Austin. 2021-03-07. Retrieved 2021-03-07.
- ^ Currie, Kristen (2021-03-05). "Invasive moth species poses serious threat to Texas' prickly pear cactus". KXAN-TV Austin. Retrieved 2021-03-07.
- ^ Robyn, R., W., Shaharra U., "Cactus Moth, Cactoblastis cactorum", 2011 Survey Plan for PPQ and State Cooperators, March 5, 2011.
- ^ JSTOR 23268477.
- ^ PMID 15647464.
- ^ JSTOR 2673383.
- ^ Davis, Heather G., "r-Selected Traits in an Invasive Population", "Evolutionary Ecology 19.3 255-274", April 14
- ^ JSTOR 20787586.
- ^ S2CID 14135662.
- ^ JSTOR 40205388.
- ^ "Texas Invasives". Texas Invasive Plant and Pest Council. Retrieved 27 September 2011.
- ^ a b "Cactoblastis Memorial". Monument Australia. Archived from the original on 2020-12-26. Retrieved 2020-12-26.
- ^ "Chinchilla Gateway: Tourism and Economic Development: Boonarga Hall". Chinchilla.org.au. Archived from the original on 2011-09-30. Retrieved 2011-10-07.
- ^ Patterson, Ewen K. 1936. The World's First Insect Memorial. "The Review of the River Plate", December, pp.16/17.
External links
- Indian River Lagoon Species Inventory, Smithsonian Marine Station at Fort Pierce.
- Species Profile- Cactus Moth (Cactoblastis cactorum), National Invasive Species Information Center, United States National Agricultural Library. Lists general information and resources for Cactus Moth.
- Cactus moth on the UF / IFAS Featured Creatures websites .