Jeffrey W. Lotz, Florida Department of Agriculture and Consumer Services

Class: Insecta

Order: Lepidoptera

Family: Pyralidae

Synonym(s): Argentine cactus moth, prickly pear moth, nopal moth

Adult Description: Adult cactus moths are non-descript, gray-brown moths with faint dark spots and wavy transverse lines marking the wings. The rear margins of the hindwings are whitish, and semitransparent; and the antennae and legs are long. The wing span of the adults ranges from 22 to 35 mm.

Larva Description: The larvae of Cactoblastis cactorum are caterpillars that are pink-cream colored at first. As they age, black and red dots on the dorsal surface of each body segment coalesce to form dark bands. Mature larvae are 25 to 30 mm long. Nothing else looks like these. The larvae are much easier to identify than the non-descript adults.

Host Plant: Prickly pear cacti of the genus Opuntia

Symptoms: Oozing wounds at the base of spines (where the larvae entered), yellowing and damage of pads, hollowed out pads that are translucent, pads infested with colony of larvae. See for more information and photos.

History: Cactoblastis cactorum was introduced into Australia as a means to control introduced Opuntia cacti. The cactus moth was so successful at controlling the cacti in Australia, (Aussies even erected a monument for the moth), that it was subsequently introduced to South Africa, the Caribbean, and Hawaii to control cacti populations there. The moth was first observed in the Florida Keys in 1989 and has established a breeding population in parts of Florida. The moth has also spread to other states including as far north as South Carolina and as far west as Louisiana. The moth was discovered breeding in south Texas in 2018.

Biology: Female moths lay on average 70-90 eggs in a distinctive stick-like formation that protrudes from the cactus pad. 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, bore into the cactus pad, and persist inside the cactus pad through several instars. While consuming the cactus from the inside as they mature, they may eventually hollowing out the pad. Larvae are gregarious, which leads to an almost communal destruction of the cactus. Cacti riddled with C. cactorum have a low survival rate.

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. Adults only live for 9 days on average, but, as airborne organisms, can spread fair distances in a short time.

Ecological Threat: The cactus moth is so efficient at eliminating Opuntia cacti species that it is used as a biological control agent in areas where Opuntia are invasive. Thus, the cactus moth are a considerable threat to the native Opuntia cactus population and the ecosystem it supports. Native Lepidoptera, such as the endangered Schaus swallowail, Papilio aristodemus ponceanus, birds, reptiles, and other insects rely on the cactus as a source of food and shelter. With the decimation and collapse of the native cacti, the surrounding ecosystem could follow suit.

US Habitat: 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.

Distribution

Native Origin: South America: specifically northern Argentina, Uruguay, Paraguay, and southern Brazil.

US States: The cactus moth has established breeding populations from Florida north to South Carolina, and west to Texas.
***Also of note, the moth has a successful breeding population in Hawaii, but was introduced intentionally.

Texas: Currently (April 2020), occurs in Brazoria (2018), Calhoun, Colorado, and Matagorda (2019) counties.

If you believe you have found cactus moth, please report this species.

Texas:

Resembles: Adult cactus moths are non-descript and look similar to other Pyralid moths, especially those of the subfamily Phycitinae. However, the larvae are very unique in appearance.

Management: As of 2010, a management plan has not been established. Currently, the best method of control is by manual removal of the "egg sticks". Insecticides are not used to control the cactus moth because of the potential to poison and kill indigenous endangered species such as the Schaus swallowtail butterfly, Papilio aristodemus ponceanus.

Text References

Hight, S. D., J. E. Carpenter, and K. A. Bloem. 2002. Expanding geographical range of Cactoblastis cactorum (Lepidoptera: Pyralidae) in North America. Florida Entomologist. 85(3): 527-529.

Higgins, A. 2001. Cactus Caretakers 101: Monitoring the Endangered Semaphore Cactus, Opunita corallicola. The Nature Conservancy, Key West, FL. 10 pp.

Moran, V. C. and H. G. Zimmermann. 1984. The biological control of cactus weeds: achievements and prospects. Biocontrol News and Infor. 5:297–320.

Solis, M. A., Hight, S. D., Gordon, D. R., & Florida, P. O. 2004. Tracking the cactus moth, Cactoblastis cactorum Berg., as it flies and eats its way westward in the US. News of the Lepidopterists' Society, 46:3-5.

Zimmermann, H. G., Moran, V. C., & Hoffmann, J. H. 2000. The renowned cactus moth, Cactoblastis cactorum: its natural history and threat to native Opuntia floras in Mexico and the United States of America. Diversity and Distributions 6(5):259-269.

Data Source

http://www.sms.si.edu
http://entomology.ifas.ufl.edu
http://www.invasivespeciesinfo.gov
http://pest.ceris.purdue.edu
http://www.aphis.usda.gov
http://www.invasive.org
http://www.galvbayinvasives.org

Last Updated: 2020-04-23 by Hans Landel, Lady Bird Johnson Wildflower Center.
Original: Amber Bartelt - Sam Houston State University