Cactoblastis cactorum (Berg) (Lepidoptera: Pyralidae) use of Opuntia host species in Argentina

Authors: VARONE, LAURA - Fuedei; LOGARZO, GUILLERMO - Fuedei; BRIANO, JUAN - Fuedei; Hight, Stephen; Carpenter, James

Submitted to: Biological Invasions
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/4/2014
Publication Date: 5/19/2014
Publication URL: http://DOI 10.1007/s10530-014-0670-9
Citation: Varone, L., Logarzo, G., Briano, J.A., Hight, S.D., Carpenter, J.E. 2014. Cactoblastis cactorum (Berg) (Lepidoptera: Pyralidae) use of Opuntia host species in Argentina. Biological Invasions. 16(11):2367-2380.

Interpretive Summary: Caterpillars of the Argentine cactus moth feed on prickly pear cactus and have become an invasive pest to cactus in the southeastern U.S. Moths were introduced from eastern Argentina and appear to be associated with only a few of the prickly pear species in Argentina. Other groups of the cactus moth in Argentina feed on different prickly pear species. Little is known about which species of prickly pear across Argentina are attacked by the different cactus moth groups. Scientists with USDA, Agricultural Research Service, Center for Medical, Agricultural and Veterinary Entomology, Gainesville, Florida, and the Argentine Foundation for the Study of Invasive Species have studyied the patterns of prickly pear attack by the different Argentine cactus moth groups. In the laboratory, females laid eggs on any prickly pear cactus species, including new species they find in North America. Field studies revealed that cactus moths in the different areas attacked the cactus species that was the most abundant. Each group of cactus moths had the capability of attacking all the species of prickly pears in Argentina. This represents a worst-case scenario for North America because, the invading moths attack the full breadth of prickly pears species in the insects’ native land and the insect’s new homeland. Results of this study suggested that the moth’s continued spread across North America threatens the prickly pear cactus rich environments of the southwestern U.S. and Mexico.

Technical Abstract: A central aspect in biology and ecology is to determine the combination of factors that influence the distribution of species. In the case of herbivorous insects, the distribution of herbivorous species is necessarily associated with their host plants, a pattern often referred to as “host use”. Novel interactions that arise during a biological invasion can have important effects on the dynamics of that invasion, especially if it is driven by only a subset of the genetic diversity of the invading species. This is the case of the well-known South American cactus moth, Cactoblastis cactorum, a successfully used biological control agent of non-native Opuntia cacti in Australia and South Africa, but now threatening unique cactus diversity and agriculture in North America. We studied the patterns of host plant usage by and host plant availability for C. cactorum under field conditions in Argentina, covering the geographical range of the four C. cactorum phylogroups and the recently documented southern distribution. We also assessed female preference and larval performance under laboratory conditions. Cactoblastis cactorum showed a geographical pattern of host use in its native range that was related to host availability. Laboratory assays of female preference showed some degree of preference to oviposit on O. ficus-indica, O. leucotricha and O. quimilo, but it was not positively correlated with the performance of larvae. These findings contribute to the further comprehension of the host use dynamics of C. cactorum in the insects’ native range, and could provide useful information for assessing the risk and future spread of this insect in North America.