Species Description: The cactus moth, Cactoblastis cactorum is a species not native to Florida but whose numbers in the state have been increasing since its first appearance in 1989. Adults are non-descript gray-brown moths with faint dark dots and wavy transverse lines marking the wings. The rear margins of the hindwings are whitish and semitransparent and the antennae and legs are long. Larvae are caterpillars that are pink-cream colored at first and become orange with age. Black and red dots on the dorsal surface of each body segment coalesce with age to form dark bands (APHIS 2005, Floyd 2007, ISSG).
Potentially Misidentified Species: Habeck and Bennet (2002) indicate there are at least five moths in the same subfamily (phycitinae) as Cactoblastis cactorum that are associated with prickly pear (Opuntia spp.) cacti in Florida. The species are very difficult to positively identify from adult individuals, and identification typically involves dissection and microscopic examination of the anatomy of the male genitalia. Positive identification of the highly distinctive C. cactorum larvae is easier.
A key to the Florida phyticine larvae associated with Opuntia species can be found here.
Regional Occurrence: The highly specialized diet of Cactoblastis cactorum limits its habitat and distribution to coincide with that of its food source, prickly pear cacti of genus Opuntia. The species is native to South America, but since the mid-1920s it has been intentionally introduced elsewhere as a biocontrol agent, including Australia, South Africa, Hawaii, and the Caribbean. In the continental U.S., C. cactorum presently occurs along both Florida coasts as well as in Alabama, Georgia, and South Carolina (APHIS 2005).
IRL Distribution: Cactoblastis cactorum can be found in all coastal Florida counties including the 6 counties of the IRL watershed. The species may be established in all 6 IRL counties.
Age, Size, Lifespan: Adult females have a wingspan of 27-40 mm and males are slightly smaller, with a wingspan of 23-32mm. Larvae reach a length of up to 1.5 cm. The average longevity of the adult is 9 days.
Abundance: Cactoblastis cactorum likely occurs in all coastal Florida counties where suitable Opuntia spp. populations exist. The species may also occur inland as well (e.g., around Lake Okeechobee) although the extent of occurrence in the interior of the state is unclear.
Reproduction: Floyd (2007) provides reproductive details for Cactoblastis cactorum. Females release pheromones in the pre-dawn hours that signal mating readiness. Males respond and mating ensues. After a period of internal incubation, females deposit a stick-like chain of 70-90 eggs cemented to a prickly pear spine.
Embryology: The external incubation period for the eggs is typically 23-28 days, but can occur in as little as 18 days and is temperature-dependent. Larvae hatch out and bore into the cactus pad to assume a gregarious existence within. The larvae persist inside the cactus pad through several instars, consuming the cactus from the inside as they mature, eventually hollowing out the cactus pad (ISSG, Floyd 2007).
Mature larvae emerge from the cactus pad to form cocoons and pupate on the ground at the base of the host cactus. Adult moths emerge from cocoons to disperse into new areas and repeat the reproductive process (Floyd 2007).
Temperature: Pemberton (1995) examined mean low temperature data from the native South American range of Cactoblastis cactorum and predicted the species could survive in the eastern U.S. as far north as Charleston, SC. Current distribution of the species validates these predictions. Similar predictions by the author suggest that westward spreading populations of C. cactorum wouldl be able to survive as far north as San Antonio, TX, and in the lower-altitude areas of New Mexico, Arizona, and California north to Sacramento.
C. cactorum is fairly broad in its tolerance to mean low temperatures. It currently occurs within three USDA plant hardiness zones (zones 8, 9, 10), and predictive models indicate it has the potential to survive in three additional zones (Simonson et al. 2005).
Hydrology: Cactoblastis cactorum may be incapable of surviving in extremely arid desert environments (Simonson et al. 2005).
Trophic Mode: The caterpillars of Cactoblastis cactorum feed on the flat pads of Opuntia spp. cacti. They live communally within the pads and feed on the internal biomass, destroying the pads from the inside out (USDA APHIS 2005).
C. cactorum has been found to eat most Opuntia species with flat pads. Cholla cacti of genus Cylindropuntia (formerly contained within genus Opuntia) appear not to be preferred hosts/food of this species. (USDA APHIS 2005).
Associated Species: There is an obligate habitat/dietary relationship between Cactoblastis cactorum and the prickly pear cactus species of genus Opuntia.
Invasion History: The native range of Cactoblastis cactorum includes northern Argentina, Uruguay, Paraguay, and southern Brazil. It was introduced to Queensland, Australia in the 1920s as a biological control for prickly pear (Opuntia stricta) which had become a major pest plant. This introduction (2,000,000 eggs) proved successful in controlling prickly pear and C. cactorum was subsequently released for biocontrol purposes in South Africa (1933), Hawaii (1950), and the Caribbean island of Nevis (1957).
C. cactorum was first discovered in the United States on Big Pine Key, Florida, in 1989 (Habeck and Bennet 1990). There is uncertainty as to whether the spread to Florida is the result of natural dispersal from the introduced Caribbean population or from the importation of infected prickly pear nursery stock (USDA). Since its initial discovery, C. cactorum has steadily spread up both coasts of Florida and beyond. On the Atlantic coast it is now found north of Charleston, SC, and on the Gulf Coast it occurs as far west as Dauphin Island, AL. Adult moths have moderate dispersal abilities and may travel up to 24 km (APHIS 2005, Floyd 2006).
Bloem (2003) indicates the spread rate of C. cactorum has accelerated to 158 kms/year.
Potential to Compete With Natives: The feeding activities Cactoblastis cactorum larvae are capable of destroying entire stands of cacti. The species threatens native landscapes and agricultural industries (USDA APHIS 2005). There is substantial concern over the potential westward spread of C. cactorum to the western United States and Mexico where it could threaten more than 80 native Opuntia species and the economic resources (e.g., food, medicine, and emergency fodder) they provide (Simonson et al. 2005). Opuntia species are cultivated as a food product in Mexico, and are major community components in some western U.S. ecosystems (Solis et al 2004).
Possible Economic Consequences of Invasion: The feeding activities Cactoblastis cactorum larvae are capable of destroying entire stands of cacti. The species threatens native landscapes and agricultural industries (USDA APHIS 2005). There is substantial concern over the potential westward spread of C. cactorum to the western United States and Mexico where it could threaten more than 80 native Opuntia species and the economic resources (e.g., food, medicine, and emergency fodder) they provide (Simonson et al. 2005). Opuntia species are cultivated as a food product in Mexico, and they are major community components in some western U.S. ecosystems (Solis et al 2004).
Bloem K.A. 2003. Overview of the cactus moth problem. Paper presented at the Cactus Moth Cactoblastis cactorum Planning Meeting, December 9-10, 2003, in Miami, Florida (abstract).
Floyd J. 2007. USDA Plant Pest Information: Cactus moth Cactoblastis cactorum.
Habeck D.H. and F.D. Bennett. 1990. Cactoblastis cactorum Berg (Lepidoptera: Pyralidae, a phycitine new to Florida. Entomology Circular No. 333, Florida Department of Agriculture and Consumer Services.
Habeck D. H. and K. A. Bennett. 2002. Cactoblastis cactorum (Berg) (Insecta: Lepidoptera: Pyralidae). Featured Creatures: University of Florida Institute of Food and Agricultural Sciences. Available online.
Johnson D.M. and P.D. Stiling. 1996. Host specificity of Cactoblastis cactorum (Lepidoptera: Pyralidae), an exotic Opuntia-feeding moth, in Florida. Population Ecology 25:743-747.
Possley J., Fellows M., Lane C, Wright S.J., and Maschinski J. 2004. Conservation Action Plan, Opuntia corallicola. Conservation of South Florida Endangered and Threatened Flora, Research Department, Fairchild Tropical Garden.
Simonson S.E., Stohlgren T.J. Tyler L., Gregg, W.P., Muir R., and L.J. Garrett. 2005. Preliminary assessment of the potential impacts and risks of the invasive cactus moth, Cactoblastis cactorum Berg, in the U.S. and Mexico. Final Report to the International Atomic Energy Agency, April 25, 2005.
Solis M.A. and S.D. Hight. 2004. Taxonomy and identification of Cactoblastis cactorium. ARS Meeting Proceedings (Abstract). Available online.
Solis M.A., Hight S.D, and D.R. Gordon. 2004. Alert: tracking the cactus moth as it flies and eats it way westward in the U.S. News of the Lepidopterist's Society 46:3-4.
Stiling P. 2002. Potential non-target effects of a biological control agent, prickly pear moth. Cactoblastis cactorum (Berg) (Lepidoptera: Pyralidae), in North America, and possible management actions. Biological Invasions 4:273-281.
USDA Animal and Plant Health Inspection Service (APHIS). 2005. Pest Alert (Cactoblastis cactorum). Program Aid No. 1834.