NOTE: this pest is not known to spread in or on firewood. It is included in the Gallery of Pests for general information purposes only.
The cactus moth, Cactoblastis cactorum, is native to northern Argentina and parts of Perú and Paraguay. It was introduced into the Caribbean islands in the 1960’s to control several (native) prickly pear cactus (Opuntia) species (Simonson 2005).
In 1989 the cactus moth was discovered to have spread to southern Florida. The moth probably entered the United States more than once (Simonsen et al. 2008) – either on winds from nearby Caribbean islands or on imported cactus plants. Over the next 25 years, the cactus moth spread up the peninsula as far north as coastal South Carolina and west along the shore of the Gulf of Mexico as far as southern Louisiana. There are both native prickly pear cacti and ornamental cacti throughout the Southeast. The outbreak in the swamps and bayous southwest of New Orleans detected in May 2009 were more than 50 miles farther West than the Mississippi islands (USDA APHIS 2009a).
Still, in the absence of a USDA-led slow-the-spread program (see below), the moth was predicted to have reached Texas by 2007 (Enkerlin at Entomological Society Symposium, 2010).
The cactus moth has also been introduced to Mexico. Small outbreaks on islands off Mexico’s Caribbean coastline – detected in 2006 and 2007 were eradicated (APHIS 2009) through application of several techniques: host plant removal, sanitation (removal of eggsticks, pads and plants infested with larvae and pupae), and release of sterile males to disrupt mating. While the survey and control tactics had been developed in the U.S., Mexico’s success can be attributed to a public awareness campaign and willingness to commit sufficient resources, as well as the small size of the outbreaks due to their early detection (Mengoni Goñalons et al. 2014).
The cactus moth can kill most prickly pear cacti (genus Opuntia), in particular those species that have flat pads. In Florida, the cactus moth has caused considerable harm to the six species of vulnerable prickly pears (Garrett 2004), three of which are listed by the state as endangered or threatened. In some places, 75% of the prickly pear cacti have been attacked by the moth, with small individuals at greatest risk of death from these attacks (Johnson and Stiling 1998, Baker and Stiling 2009).
The greatest threat is to nearly two million square miles of arid lands in the American Southwest – from Texas to California – and Mexico. These deserts are home to 114 native species of Opuntia (APHIS 2009b), about 80 of which are flat-padded species vulnerable to the cactus moth (Simonson et al. 2005). Mexico is a center of endemism for Opuntia.
These cacti support a great diversity of pollinators. They provide a nutritious and reliable food supply for many wildlife species, including deer, javelina (peccaries), Texas and desert tortoises, and spiny iguana. Prickly pears provide shelter for packrats – which in turn are eaten by raptors, coyotes, and snakes; and for nesting birds including the cactus wren and curve-billed thrasher. The cacti also are nurse plants, under which other desert plants’ seedlings may start life. Finally, the prickly pears’ root systems hold the highly erodible soils (Simonson 2005).
The economic consequences of loss of prickly pear cacti will fall most heavily on Mexico, where prickly pears provide food to both people and livestock. Prickly pears are cultivated for both the fruits (tunas) and pads (nopales). Fruits and pads are also collected from the wild.
Another associated commercial crop is the natural deep-red dye extracted from the cochineal beetle (Dactylopius coccus) – which feeds on prickly pear cacti. In Mexico, cochineal dye production is a significant agricultural crop (Simonson 2005). The dye, as a natural product, is considered by some to be preferable for use in foods and cosmetics (https://www.botgard.ucla.edu/html/botanytextbooks/economicbotany/Cochineal/index.html).
There would be smaller potential economic losses in the U.S. Depending on what species, if any, expand into areas where the prickly pear cacti were formerly abundant, losses could include reduced revenue from licensed hunting opportunities. In South Texas, higher rents are received for ranchland leased for hunting than for cattle production (Garrett 2004). Ecotourism in the Southwest would probably also be harmed by widespread death of prickly pear cacti.
The U.S. Department of Agriculture began trying to slow the spread of the cactus moth in 2005 – 15 years after it was first detected in Florida (Mengoni Goñalons et al. 2014). The USDA Agricultural Research Service (ARS) and APHIS relied on a program that combines release of sterile moths to disrupt mating and removal of the cactus hosts on the leading edge of the invasion. In cooperation with state departments of agriculture, APHIS also funded surveys in western states to detect any outbreaks in those most vulnerable areas when they could still be eradicated.
For several years, the program was a cooperative U.S.-Mexican program coordinated through a SAGARPA/USDA agreement implemented through the North American Plant Protection Organization (NAPPO). Through this mechanism, Mexico even provided funds and personnel to support efforts within the U.S. to monitor and suppress moth populations – for example, in Louisiana.
Other participants in the program were the Florida Department of Agriculture Department of Plant Industry’s quarantine laboratory at Gainesville, which is the facility where cactus moths are reared for a variety of purposes – research to improve the lure used in traps; providing sterile males for release; and – now – biocontrol host specificity testing. A volunteer network managed by Mississippi State University managed a volunteer network that monitored federal, state, and private lands along the Gulf Coast for the presence of cactus moth.
The USDA program was never funded adequately. Congress never appropriated funds. Mexico provided at least $1.4 million over several years. As noted, the Florida Department of Agriculture and Consumer Services, Mississippi State University, and the U.S. Geological Survey (Department of Interior) helped in cactus moth detection and control work.
As its budget declined after 2010, APHIS halted its regional management program in the U.S. (Mengoni Gonfalons et al. 2014).
The focus of the program is now on biocontrol. Biocontrol is considered the only viable control measure once the cactus moth reaches arid regions of Texas and the Southwest where cacti are plentiful.
Over four years (2007 – 2011), USDA ARS and Argentine collaborators conducted field surveys in Argentina for possible biocontrol agents (Mengoni Goñalons et al. 2014). Those surveys determined that the parasite exclusively found on the cactus moth in its native range is a previously undescribed wasp, Apanteles opuntiarum Martínez & Berta. This wasp is in the same genus as but distinct from the wasp Apanteles alexanderi Brèthes that had previously been thought to be the parasite. Collection records to date have revealed that A. opuntiarum attacks only C. cactorum and another moth, C. doddi Heinrich (Mengoni Goñalons et al. 2014).
Scientists have collected Apanteles opuntiarum wasps from 393 sites across nine provinces in Argentina. The wide ecological conditions in which the wasp has been found – including dry and humid regions, high elevations to sea level – shows promising adaptability, important for the wasp’s use as a biocontrol agent (Mengoni Goñalons et al. 2014).
Wasps have been taken to the FL-DACS DPI laboratory where scientists are now learning how to rear them in preparation for necessary host specificity testing (Mengoni Goñalons et al. 2014).
In 2009 APHIS amended its regulations to prohibit movement of Opuntia cactus nursery stock from infested states in the southeastern United States would not spread the cactus moth (Federal Register Vol. 74 No. 108 [June 8, 2009], pp. 27071-27076). However, a regulation to limit importation of prickly pear cacti to prevent additional introductions of the moth, in 2011(USDA APHIS 2011), has never been finalized.
Sources
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Garrett, L. 2004. USDA APHIS PPQ CPHST. White Paper: Economic Impact from spread of Cactoblastis cactorum in the United States.
Johnson, D. M. and P. D. Stiling. 1998. Distribution and dispersal of Cactoblastis cactorum (Lepidoptera: Pyralidae), an exotic Opuntia-feeding moth in Florida. Florida Entomol. 81: 12-21
Mengoni Goñalons, C., L. Varone, G. Logarzo, M. Guala, M. Rodriguero, S.D. Hight, and J.E. Carpenter. 2014. Geographical range & lab studies on Apanteles opuntiarum (hymenoptera: braconiDae) in AR, a candidate for BC of Cactoblastis cactorum (Lepidoptera: Pyralidae) in North America. Florida Entomologist 97(4) December 2014
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Simonsen, T.J., R.L. Brown, and F.A. H. Sperling. 2008. Tracing an Invasion: Phylogeography of Cactoblastis cactorum (Lepidoptera: Pyralidae) in the United States Based on Mitochondrial DNA. Ann. Entomol. Soc. Am. 101(5): 899-905 (2008)
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