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Surveys of patterns of genetic variation in natural sympatric and allopatric populations of recently diverged species are necessary to understand the processes driving intra- and interspecific diversification. The South American moths Cactoblastis cactorum, Cactoblastis doddi and Cactoblastis bucyrus are specialized in the use of cacti as host plants. These species have partially different geographic ranges and differ in patterns of host plant use. However, there are areas that overlap, particularly, in northwestern Argentina, where they are sympatric. Using a combination of genome-wide SNPs and mitochondrial data we assessed intra and interspecific genetic variation and investigated the relative roles of geography and host plants on genetic divergence. We also searched for genetic footprints of hybridization between species. We identified three well delimited species and detected signs of hybridization in the area of sympatry. Our results supported a hypothetical scenario of allopatric speciation in the generalist C. cactorum and genetic interchange during secondary geographic contact with the pair of specialists C. bucyrus and C. doddi that probably speciated sympatrically. In both cases, adaptation to new host plants probably played an important role in speciation. The results also suggested the interplay of geography and host plant use as drivers of divergence and limiting gene flow at intra and interspecific levels.

As part of sterile insect technique (SIT) programs, irradiation can effectively induce sterility in insects by damaging germline genomic DNA. However, irradiation also induces other off‐target side effects that reduce the quality and performance of sterilized males, including the formation of damaging free radicals that can reduce sterile male performance. Thus, treatments that reduce off‐target effects of irradiation on male performance while maintaining sterility can improve the feasibility and economy of SIT programs. We previously found that inducing a form of rapid, beneficial plasticity with a 1‐hr anoxic‐conditioning period (physiological conditioning hormesis) prior to and during irradiation improves male field performance in the laboratory while maintaining sterility in males of the cactus moth, Cactoblastis cactorum. Here, we extend this work by testing the extent to which this beneficial plasticity may improve male field performance and longevity in the field. Based on capture rates after a series of mark release–recapture experiments, we found that anoxia‐conditioned irradiated moths were active in the field longer than their irradiated counterparts. In addition, anoxia‐conditioned moths were captured in traps that were farther away from the release site than unconditioned moths, suggesting greater dispersal. These data confirmed that beneficial plasticity induced by anoxia hormesis prior to irradiation led to lower postirradiation damage and increased flight performance and recapture duration under field conditions. We recommend greater consideration of beneficial plasticity responses in biological control programs and specifically the implementation of anoxia‐conditioning treatments applied prior to irradiation in area‐wide integrated pest management programs that use SIT.

The sterile insect technique (SIT), an environmentally friendly means of control, is currently used against plant, animal, and human pests under the area-wide integrated pest management. It consists in the mass production, sterilization, and release of insects in an affected area where sterile males mate with wild females leading to no reproduction. Here, we review SIT in the Neotropics and focus on particular recent successful cases of eradication of the Mediterranean fruit fly, Ceratitis capitata (Wiedemann), as well as effective programs used against the Mexican fruit fly Anastrepha ludens (Loew), the New World screwworm fly Cochliomyia hominivorax (Coquerel)), and the Cactus moth Cactoblastis cactorum (Berg). We examine when SIT does not work and innovations that have made SIT more efficient and also highlight complimentary techniques that can be used in conjunction. We address potential candidate species that could be controlled through SIT, for example Philornis downsi Dodge & Aitken. Finally, we consider the impact of climate change in the context of the use of the SIT against these pests. Given the recent dramatic decline in insect biodiversity, investing in environmentally friendly means of pest control should be a priority. We conclude that SIT should be promoted in the region, and leadership and political will is needed for continued success of SIT in the Neotropics.

The pre-excavation activity of the neonate larvae of Cactoblastis cactorum (Lepidoptera: Pyralidae) is typically confined to an arena that encircles the base of their egg stick. If the caterpillars are unable to penetrate the host plant within the arena, they strike off en masse in search of a more favorable site, marking their pathway with secretions from their mandibular glands. One component of this secretion, 4-hydroxy-2-oleoylcyclohexane-1,3-dione (an acylcyclohexanedione, ACHD), has been previously shown to function as a trail pheromone. In this paper, we report the characterization, synthesis, and bioassays of a family of 3-acyl fatty acid methyl esters (which we named cactoblastins), a chemically distinct group of mandibular gland compounds that also elicit trail following behavior. The relative effectiveness in eliciting trail following of the ACHD and six, chemically distinct, synthetic cactoblastins was determined. The most bioactive of the cactoblastins was also compared to whole mandibular gland extract to assess its ability to disrupt the aggregative behavior of the neonates and to serve as a biorational alternative to pesticides for managing invasive populations of the caterpillar.

Fil: Varone, Laura. Fundacion para el Estudio de Especies Invasivas; Argentina. Consejo Nacional de Investigaciones Cientificas y Tecnicas; Argentina

The study was conducted in the laboratory to observe the effect of the colony on the establishment of feeding activity and development responses of Cactoblastis cactorum (Berg) (Lepidoptera: Phycitidae) on two cactus species namely and Opuntia lindheimeri. The main objective was to establish the minimum number of C. cactorum larvae needed to facilitate a successful attack on a cactus cladode. We also examined the effect of cladode age on the larva establishment. In order to get this information replicates of cactus cladodes collected from different levels of cactus plants were infested with 5, 10, 15, 20, and 25 egg batches. All the different levels of egg batches placed on the cladodes hatched well. It was observed that the neonate larvae initially kept together while attempting to enter the cladode. Successful entrance into O. ficus indica cladode was observed on those cladode infested 15 were 20 and 25 eggs were placed. Those larvae fed, developed and eventually pupated and the adults emerged normally. On the other hand, larvae which hatched on O. lindheimeri larvae were unable to establish on this cactus species. When the neonate larvae attempted to penetrate into the cladode they drowned in the exudates produced at the point of entrance. As a result all larvae on O. lindheimeri did not complete their developmental cycle.

The spectacular success of the cactus moth, Cactoblastis cactorum (Berg), in controlling invasive Opuntia species has been cited often in biological control literature. This insect is highly damaging to plants of the Cactaceae family and has been regarded as one of the most successful classical weed biological control agents. In Australia, the cactus moth effectively controlled approximately 25 million hectares of non-native Opuntia species that had invaded cattle grazing lands. In Mexico, however, the Cactaceae are native, where they have their greatest diversity, and have major ecological and socio-economic importance. In the 1950s, 562the cactus moth was introduced into several Caribbean islands for management of Opuntia spp. on grazing lands. The moth arrived accidentally in Florida by 1989, and concerns were raised that this highly mobile moth could spread into the south-western USA and reach Mexico. Therefore, a cactus moth surveillance programme was established in Mexico in 2002 to detect and prevent the introduction and establishment of this invasive pest. Through this detection trapping network, two localized but large outbreaks of C. cactorum were detected off the coast of the Peninsula of Yucatan, Mexico; on Isla Mujeres, 10 August 2006, and Isla Contoy, 4 May 2007, both in the municipality of Isla Mujeres in the state of Quintana Roo. An eradication programme was immediately implemented by the National Service for Health, Safety and Food Quality (SENASICA) of the Ministry of Agriculture, Livestock, Rural Development, Fisheries and Food (SAGARPA) of Mexico, in close collaboration with other national and international organizations. An area-wide integrated pest management (AW-IPM) approach was implemented that included regulatory actions, outreach activities, surveillance, intensive sanitation and the release of sterile moths. Eradication was achieved in 2008 and officially declared in 2009. A surveillance network is currently maintained for detecting early pest incursions, allowing for a rapid response to any future incursion of the pest. This successful programme has resulted in the protection of the high value commercial Opuntia cacti industry in Mexico, as well as native Opuntia species in natural arid and semi-arid ecosystems where they are an essential element in maintaining biodiversity and soil conservation.

886The rapid expansion of international travel and trade are facilitating the spread of non-native species, while climate change is creating new ecological niches enabling the establishment of pests in previously inhospitable regions. The temporary large-scale application of insecticides and “scorched earth” approaches are often indispensable to deal effectively with such outbreaks of invasive pests. However, even when the political will is there to implement the required systematic eradication efforts, they often result in public resistance to drastic actions such as the destruction of infested crops, herds, and orchards, and the indiscriminate insecticide spraying that raises concerns about damage to the environment and human health. Furthermore, such campaigns can still fail to achieve final eradication of all remnants of incipient populations. Therefore, and also in response to the enactment of environmental laws and regulations, increased efforts are needed to develop new and effective early detection and eradication tools that can prevent the establishment of a new pest in a less disruptive and more environment-friendly way. The sterile insect technique (SIT) is a proven method to prevent, contain, and eradicate outbreaks of invasive insect pest populations. It is an effective and ecology-friendly method that, unlike insecticides and other control methods, acts in an inversely density-dependent manner, and as a result increases its efficiency with decreasing population density. Therefore, it is particularly well-suited to eliminate incipient invasive-pest introductions and outbreaks when applied as part of an area-wide integrated pest management (AW-IPM) approach. When flooding a target pest population with sterile males, the wild virgin females (that are not controlled with other methods) are actively located and mated by the sterile males, producing no offspring. Some examples of eradication include incipient invasive populations of the painted apple moth Teia anartoides Walker in New Zealand, and the cactus moth Cactoblastis cactorum (Berg) in Mexico; major outbreaks (Cochliomyia hominivorax (Coquerel) in Libya); and all the way to fully established invasive pest populations (pink bollworm Pectinophora gossypiella (Saunders) in the southern USA and northern Mexico, and melon fly Zeugodacus cucurbitae (Coquillett) in the archipelagos of southern Japan). The SIT is also being used to contain invasive pest populations, such as Ceratitis capitata (Wiedemann) in southern Mexico, and preventively by releasing sterile insects over areas with a historically high risk of invasive pest incursions (C. capitata in California and Florida). There is great potential to expand the SIT application to similar situations against other major invasive insect pests. This chapter compares some eradication campaigns in the pre-SIT era with those integrating the SIT to eradicate, contain or prevent the establishment of non-native insect pests, and discusses the constraints and needs for contingency planning, including a proactive approach to develop the SIT package for other potential major invasive insect pests.

Cactoblastis cactorum, a species of moth native to Argentina, feeds on several prickly pear cactus species (Opuntia) and has been successfully used as a biological control of invading Opuntia species in Australia, South Africa and native ruderal Opuntia species in some Caribbean islands. Since its introduction to the Caribbean its spread was uncontrolled, invading successfully Florida, Texas and Louisiana. Despite this long history of invasion, we are still far from understanding the factors determining the patterns of invasion of Cactoblastis in North America. Here, we explored three non-mutually exclusive explanations: a) a stepping stone model of colonization, b) long distance colonization due to hurricanes, and/or c) hitchhiking through previously reported commercial routes. Genetic diversity, genetic structure and the patterns of migration among populations were obtained by analyzing 10 nuclear microsatellite loci. Results revealed the presence of genetic structure among populations of C. cactorum in the invaded region and suggest that both marine commercial trade between the Caribbean islands and continental USA, as well as recurrent transport by hurricanes, explain the observed patterns of colonization. Provided that sanitary regulations avoiding humanmediated dispersal are enforced, hurricanes probably represent the most important agent of dispersal and future invasion to continental areas. Fil: Andraca Gómez, Guadalupe. Universidad Nacional Autónoma de México. Instituto de Ecología; México Fil: Lombaert, Eric. Université Côte d'Azur; Francia. Centre National de la Recherche Scientifique; Francia Fil: Ordano, Mariano Andrés. Fundación Miguel Lillo; Argentina. Universidad Nacional de Tucumán. Instituto de Ecología Regional. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto de Ecología Regional; Argentina Fil: Pérez Ishiwara, Rubén. Universidad Nacional Autonoma de Mexico. Departamento de Ecología Evolutiva; México Fil: Boege, Karina. Universidad Nacional Autonoma de Mexico. Departamento de Ecología Evolutiva; México Fil: Domínguez, César A.. Universidad Nacional Autonoma de Mexico. Departamento de Ecología Evolutiva; México Fil: Fornoni, Juan. Universidad Nacional Autonoma de Mexico. Departamento de Ecología Evolutiva; México

The cactus moth, Cactoblastis cactorum (Berg) (Lepidoptera: Pyralidae), is an invasive species in North America where it threatens Opuntia native populations. The insect is expanding its distribution along the United States Gulf Coast. In the search for alternative strategies to reduce its impact, the introduction of a natural enemy, Apanteles opuntiarum Mart&iacute, nez and Berta (Hymenoptera: Braconidae), is being pursued as a biological control option. To identify promising areas to intentionally introduce A. opuntiarum for the control of C. cactorum, we estimated the overlap of fundamental ecological niches of the two species to predict their common geographic distributions using the BAM diagram. Models were based on native distributional data for both species, 19 bioclimatic variables, and the Maxent algorithm to calculate the environmental suitability of both species in North America. The environmental suitability of C. cactorum in North America was projected from Florida to Texas (United States) along the Gulf coastal areas, reaching Mexico in northern regions. Apanteles opuntiarum environmental suitability showed a substantial similarity with the calculations for C. cactorum in the United States. Intentional introductions of A. opuntiarum in the actual distribution areas of the cactus moth are predicted to be successful, A. opuntiarum will find its host in an environment conducive to its survival and dispersal.

Herbivory has long been recognized as a significant driver of plant population dynamics, yet its effects along environmental gradients are unclear. Understanding how weather modulates plant–insect interactions can be particularly important for predicting the consequences of exotic insect invasions, and an explicit consideration of weather may help explain why the impact can vary greatly across space and time. We surveyed two native prickly pear cactus species (genus Opuntia) in the Florida panhandle, USA, and their specialist insect herbivores (the invasive South American cactus moth, Cactoblastis cactorum, and three native insect species) for five years across six sites. We used generalized linear mixed models to assess the impact of herbivory and weather on plant relative growth rate (RGR) and sexual reproduction, and we used Fisher's exact test to estimate the impact of herbivory on survival. Weather variables (precipitation and temperature) were consistently significant predictors of vital rate variation for both cactus species, in contrast to the limited and varied impacts of insect herbivory. Weather only significantly influenced the impact of herbivory on Opuntia humifusa fruit production. The relationships of RGR and fruit production with precipitation suggest that precipitation serves as a cue in determining the trade‐off in the allocation of resources to growth or fruit production. The presence of the native bug explained vital rate variation for both cactus species, whereas the invasive moth explained variation only for O. stricta. Despite the inconsistent effect of herbivory across vital rates and cactus species, almost half of O. stricta plants declined in size, and the invasive insect negatively affected RGR and fruit production. Given that fruit production was strongly size‐dependent, this suggests that O. stricta populations at the locations surveyed are transitioning to a size distribution of predominantly smaller sizes and with reduced sexual reproduction potential.

Apanteles opuntiarum Martínez & Berta (Hymenoptera: Braconidae) is a native natural enemy of the cactus moth, Cactoblastis cactorum Berg (Lepidoptera: Pyralidae) in Argentina, where the 2 species are believed to have co-evolved. Cactoblastis cactorum is an established invasive pest in the US that is rapidly spreading throughout the southeast. Apanteles opuntiarum was imported from Argentina, and reared at the Division of Plant Industry containment facility in Gainesville, Florida, for study as a possible biocontrol agent for release in the US to control C. cactorum. A DNA barcode was developed to enable the identification of the reared parasitoid population. The mitochondrial cytochrome oxidase I (COI) gene of the A. opuntiarum reared in Florida containment was found to be identical to its Argentine founders, but distinctly different from the COI sequences of all other reported Apanteles species in the NCBI (National Center for Biotechnology Information) GenBank. Additionally, the AoF1 and AoR1 primer pair developed in this study specifically amplified the COI gene of A. opuntiarum, but did not amplify the COI gene of the host C. cactorum. Therefore, the COI gene fragment identified in this study has the potential to be used as a DNA barcode specific to A. opuntiarum that can aid in tracking and identifying this parasitoid inside hosts. Apanteles opuntiarum Martínez & Berta (Hymenoptera: Braconidae) es un enemigo natural de la polilla de la tuna Cactoblastis cactorum Berg (Lepidoptera: Pyralidae) en Argentina, su rango nativo, donde han co-evolucionado. Cactoblastis cactorum es una especie invasora establecida en Estados Unidos, que se está dispersando rápidamente hacia el sudeste de este país. Apanteles opuntiarum fue importado desde Argentina y es criado en la cuarentena de Gainesville, Florida (Division of Plant Industry), donde está siendo evaluado como posible agente de control de C. cactorum, para ser liberado en Estados Unidos. Se desarrolló un código de barras de ADN para permitir la identificación de la población de parasitoides criada. Se encontró que el gen de la citocromo oxidasa mitocondrial I (COI) de los A. opuntiarum criados en Florida fue idéntico al de sus fundadores argentinos, y claramente diferente de las secuencias de COI de todas las demás especies de Apanteles reportados en el GenBank del NCBI (Centro Nacional de información sobre biotecnología). Además, el par “primer” AoF1 y AoR1 desarrollado en este estudio amplificó específicamente el gen COI de A. opuntiarum, y no amplificó el gen de la COI del hospedador C. cactorum. Por lo tanto, el fragmento del gen COI identificado en este estudio tiene el potencial para ser utilizados como un código de barras de ADN específico para A. opuntiarum que puede ayudar en el seguimiento y la identificación de este parasitoide dentro de los hospedadores Fil: Srivastava, Mrittunjai. Florida Department of Agriculture and Consumer Services; Estados Unidos Fil: Srivastava, Pratibha. Florida Department of Agriculture and Consumer Services; Estados Unidos Fil: Karan, Ratna. Florida Department of Agriculture and Consumer Services; Estados Unidos Fil: Jeyaprakash, Ayyamperumal. Florida Department of Agriculture and Consumer Services; Estados Unidos Fil: Whilby, Leroy. Florida Department of Agriculture and Consumer Services; Estados Unidos Fil: Rohrig, Eric. Florida Department of Agriculture and Consumer Services; Estados Unidos Fil: Howe, Amy C.. Florida Department of Agriculture and Consumer Services; Estados Unidos Fil: Hight, Stephen D.. United States Department of Agriculture. Agriculture Research Service; Estados Unidos Fil: Varone, Laura. Fundación para el Estudio de Especies Invasivas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina

A bi-national program was established by Mexico and the United States to mitigate the threat of the cactus moth, Cactoblastis cactorum (Berg) (Lepidoptera: Pyralidae)—an invasive herbivore from South America—to native Opuntia spp. (Caryophyllales: Cactaceae) biodiversity and Opuntia-based industries. Mass-rearing, sterilization, and transport and release technologies assisted with the development of several control tactics including the sterile insect technique. Following the successful eradication of C. cactorum from Mexico and the elimination of C. cactorum from Alabama barrier islands, the bi-national program established an additional mass-rearing insectary for the production of sterile moths. Laboratory and field bioassays were conducted on sterile moths from both insectaries. Bioassays and assessments included moth mass, moth longevity, percentage of female moths mated at time of collection from the insectary, percentage of female moths mated 24 h after collection, flight ability, percentage recaptured after release in the field, and mean distance dispersed from release site. Data from the quality assessments and comparisons between the 2 insectaries were used as feedback mechanisms to make protocol changes in both rearing and handling that improved sterile moth quality and performance. ResumenUn programa bi-nacional fue establecido por Mexico y los Estados Unidos para mitigar la amenaza de Cactoblastis cactorum (Berg) (Lepidoptera: Pyralidae)—un herbivoro invasivo de America del Sur—a la biodiversidad de las especies de Opuntia (Caryophyllales: Cactaceae) nativas y las industrias basadas en el Opuntia. La cria masiva, la esterilizacion y la tecnologia del transporte y liberacion ayudaron con el desarrollo de varias tacticas de control, incluyendo la tecnica del insecto esteril. Tras el exito en la erradicacion de C. cactorum de Mexico y la eliminacion de C. cactorum de islas barreras del estado de Alabama, el programa bi-nacional establecio un insectario adicional de cria en masa para la produccion de polillas esteriles. Se realizaron bioensayos de laboratorio y de campo en las polillas esteriles de ambos insectarios. Los bioensayos y evaluaciones incluyeron la masa y la longevidad de las polillas, el porcentaje de las polillas hembra apareadas en el momento de su recoleccion en el insectario, el porcentaje de las polillas hembra apareadas 24 horas despues de la recoleccion, la capacidad de vuelo, el porcentaje recapturadas despues de la liberacion en el campo, y el promedio de la distancia del sitio de la liberacion de las polillas capturadas. Los datos de las evaluaciones de la calidad y ls comparacion entre los 2 insectarios fueron utilizados como una mecanismo de retroalimentacion para hacer cambios en el protocolo, tanto en la cria como en el manejo que mejoran la calidad de la polilla esteril y el rendimiento. View this article in BioOne

One of the most important components of a program that has a sterile insect technique (SIT) component is an appropriate irradiation dose. Knowing the organismal dose-response enables the selection of a dose that induces the highest level of sterility while preserving the sexual competitiveness and other desired qualities of the sterile insect. Finding this balance in Lepidoptera is crucial because of the use of inherited (F1) sterility, where the irradiated parent must be competitive enough to mate while its offspring must be sterile. Manipulations of atmospheric oxygen content have been shown to be an effective way of lowering post-irradiation somatic damage while preserving sterility and improving sterile insect performance, particularly in fruit flies. In this study we tested the irradiation dose response of adults of the cactus moth, Cactoblastis cactorum (Berg) (Lepidoptera: Pyralidae), and the effects of those doses on sterility, longevity, and F1 performance, and whether a nitrogen conditi...

Governments across the globe use public–private partnerships to foster entrepreneurship while limiting their risk. ThePrickly Pear Destruction Act 1912enabled the Queensland government to enter contracts with private entities for land heavily covered with prickly pear (OpuntiaandNopaleaspecies). The story of Cactus Estates Ltd, the first negotiation under the Act, provides an opportunity to analyse this response to local ecologies changed by nineteenth-century plant transfers. Most scholarship on the invasion of prickly pear focuses on the science of entomology due to the spectacular success of the introduction ofCactoblastis cactorumin 1926. This article examines an earlier period in the history of applied science in Queensland. The Queensland government, along with scientific and business communities, pursued poisons for controlling the density of plant growth as the preferred mechanism for eliminating plants. Cactus Estates Ltd experimented with arsenic-based poisons for this purpose. An examination of Cactus Estates Ltd provides evidence of the state's willingness to produce a multifaceted approach to dealing with invasive species in Australia in the early twentieth century.

Cactoblastis cactorum Berg (Lepidoptera: Pyralidae) has been extensively studied since its initial use as a biological control agent for invasive populations of Opuntia Mill. The moth is native to several South American countries including Argentina where the exotic Opuntia ficus-indica (L.) Mill. (Cactaceae) is grown as a commercial crop. Recently C. cactorum has attracted considerable attention following its non-intentional establishment in Florida, because it now threatens the highly diverse and economically important Opuntia taxa of the southern USA and Mexico. To elucidate several aspects of this system, we recorded phenological data and parasitoid activity from Argentina across an annual cycle. We reared several generations of moths to better document the life cycle, described several formerly unpublished larval stages and morphological characters, and compared developmental parameters from samples collected from different sites. We found that C. cactorum has 3 overlapping generations across a 9 mo growth period with winter quiescence at the larval VI instar or pupal stage. The most common natural enemy of larvae was the parasitoid Apanteles opuntiarum (Martínez and Berta) (Hymenoptera: Braconidae). Information is given on its development and percentages of parasitism throughout the year. No egg parasitoids were found in field-collected eggsticks or on experimental eggsticks. There were no significant differences between developmental stages and times of C. cactorum from Tucumán and Córdoba in Argentina. We found intermediate C. cactorum damage on low-density cultivated Opuntia, but much lower damage in commercial plantations with high densities of plants. Surprisingly, we found that a “black spot” fungal infection (Alternaria Nees) (Pleosporaceae) produced a higher level of damage in commercial plantations in Córdoba, as well as in natural settings in Tucumán. Cactoblastis cactorum Berg (Lepidoptera: Pyralidae) ha sido extensamente estudiada desde su uso incial como un agente de control biológico de las poblaciones invasoras de Opuntia Mill. Su larva es nativa de Sud América, incluyendo la Argentina, donde el cactus exótico Opuntia ficus-indica (L.) Mill (Cactaceae) se cultiva comercialmente. C. cactorum ha atraído la atención recientemente, después de su establecimiento accidental en Florida, dado que amenaza a la gran diversidad de especies de Opuntia que son económicamente importantes y nativas de Estados Unidos y México. Con el objeto de dilucidar varios aspectos de este sistema hemos registrado datos fenológicos y la actividad de parasitoides en el campo a lo largo de un año. Hemos criado varias generaciones de polillas para documentar mejor el ciclo de vida, para describir estadios larvales y caracteres morfológicos previamente no publicados, y para comparar parámetros de desarrollo de muestras colectadas de diferentes sitios. Hemos encontrado que C. cactorum tiene 3 generaciones superpuestas a lo largo de 9 meses de crecimiento con una quiescencia invernal de la larva VI o pupa. El enemigo natural más común fue el parasitoide de larvas Apanteles opuntiarum (Martínez and Berta) (Hymenoptera: Braconidae). Se presenta información sobre su desarrollo y porcentaje de parasitismo a lo largo del año. No se hallaron parasitoides de huevo en muestras de campo ni en ristras de huevo colocadas experimentalmente. No se encontraron diferencias significativas en los estadios de desarrollo ni en sus tiempos entre muestras provenientes de los sitios de Córdoba y Tucumán. Registramos intermedio daño por C. cactorum en la especie de Opuntia cultivada en baja densidad pero mucho menor daño en plantaciones comerciales con alta densidad de plantas. Sorpresivamente, encontramos un alto nivel de daño producido por un hongo que genera la “mancha negra”, tanto en plantaciones comerciales de Córdoba como en situaciones naturales de Tucumán. Fil: Folgarait, Patricia Julia. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnología. Laboratorio de Hormigas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Albioni Montenegro, Gloria. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnología. Laboratorio de Hormigas; Argentina Fil: Plowes, Robert. University of Texas; Estados Unidos Fil: Gilbert, L. E.. University of Texas; Estados Unidos

Summary Field exploration in Argentina for cactophagous lepidopteran hosts parasitized by the recently described braconid parasitoid Apanteles opuntiarum Martinez & Berta (Hymenoptera: Braconidae) revealed a host range restricted to Cactoblastis cactorum (Berg) (Lepidoptera: Pyralidae) and C. doddi. Field collections of cactophagous larvae parasitized by the congeneric and sympatric parasitoid A. alexanderi included the host species C. bucyrus, Sigelgaita nr. chilensis, Tucumania sp., Tucumania tapiacola and Salambona sp. If a narrow host range for A. opuntiarum is confirmed in quarantine with North American cactus-feeding species, then this parasitoid could be released as a biological control agent for C. cactorum with little or no risk to non-target species.

Caterpillars of Cactoblastis cactorum secrete onto the surface of host cactuses droplets of an oily fluid that issues from the orifices of their paired mandibular glands. The fluid contains a series of 2-acyl-1,3-cyclohexanediones that, collectively, have been shown to elicit trail-following behavior from the caterpillars. This study reports the results of bioassays to determine the ability of two specific compounds, previously shown to be prominent components of the mandibular glands of pyralid caterpillars, 4-hydroxy-2-oleoyl-1,3-cyclohexanedione and 2-oleoyl-1,3-cyclohexanedione, to elicit trail-following behavior from the larvae of C. cactorum. Additionally bioassayed were structural fragments of these molecules. The relative effectiveness of the chemicals in eliciting trail following, the effect of varying concentration on the trail-following response, the importance of specific functional groups to the trail-following response, and the threshold sensitivity of the caterpillar to the pheromone were determined. The study showed that while all the tested compounds elicited some degree of trail following, they differed significantly in their effectiveness. The most effective of the compounds was 4-hydroxy-2-oleoyl-1,3-cyclohexanedione, which, on a per unit volume basis, was as effective as whole gland extract. Caterpillars secreted large quantities of fluid from the glands, and the threshold response to 4-hydroxy-2-oleoyl-1,3-cyclohexanedione occurred at a relative high application rate compared to trail pheromones of other social caterpillars and eusocial insects. This and the observation that the trail marker is secreted from the mandibular glands suggests that the use of 2-acyl-1,3-cyclohexanediones as trail markers is secondary, and that these compounds function primarily in some other, as yet undetermined, context.

Sensory organs that detect CO2 are common in herbivorous moths and butterflies, but their function has been unclear until now. As the CO2 gradients in the vicinity of a host plant depend on its physiological condition, CO2 could provide a sensory cue for the suitability of the plant as a larval food source. This study investigated whether changing the atmospheric CO2 concentration affected oviposition by Cactoblastis cactorum on its host, the cactus Opuntia stricta. On host plants exposed to rapid fluctuations in CO2 concentration, the frequency of oviposition was reduced by a factor of 3.2 compared to the control. As the fluctuations mask the much smaller CO2 signals generated by the plants, this suggests that those signals constitute an important component of the host identification process. On host plants exposed to a constant background of doubled CO2, oviposition was also reduced, by a factor of 1.8. An increased background reduces host signal detectability, partially as a consequence of a general principle of sensory physiology (Weber-Fechner's law), and partially due to other factors specific to CO2-receptor neurons.

La polilla de la tuna, Cactoblastis cactorum (Berg) (Lepidoptera: Pyralidae), es una plaga que amenaza las Opuntia spp. nativas de América del Norte. Se han implementado varias estrategias para su control, erradicándola de México pero no de los Estados Unidos, donde ha continuado incrementando su distribución geográfica con éxito. Por lo tanto, se propone un enfoque integrado que incluya al control biológico para regular las poblaciones de C. cactorum en América del Norte. Se realizaron relevamientos de campo del parasitoide recientemente descrito, Apanteles opuntiarum Martínez & Berta, dentro del área de distribución nativa de C. cactorum en Argentina, y se realizaron estudios de laboratorio para desarrollar un protocolo de cría del parasitoide. Apanteles opuntiarum fue el parasitoide más común de C. cactorum y sus distribuciones en el campo coincidieron ampliamente. En el laboratorio, el éxito reproductivo del parasitoide se maximizó cuando una o dos avispas estuvieron expuestas a 30 larvas dentro de un recipiente de 500 ml. Hembras criadas en laboratorio fueron menos exitosas parasitando hospedadores que hembras provenientes del campo. A pesar del éxito logrado en la cría de los parasitoides, obtuvimos una proporción de sexos sesgada hacia machos en los experimentos. Como este sesgo podría estar relacionado a la presencia del parásito reproductivo Wolbachia, tanto la colonia de laboratorio como individuos provenientes del campo fueron analizados y poseían Wolbachia. El presente estudio proporcionó información útil de campo y laboratorio para (1) estandarizar una técnica de cría en laboratorio; (2) realizar estudios de especificidad de hospedadores en condiciones de cuarentena; y (3) seleccionar las poblaciones de parasitoides que mejor coinciden con el clima de las áreas invadidas por C. cactorum en América del Norte. The cactus moth, Cactoblastis cactorum (Berg) (Lepidoptera: Pyralidae), is a pest that threatens native Opuntia spp. in North America. Control tactics developed and implemented against this invasive pest successfully eradicated the moth in Mexico and on barrier islands in the United States. However, with the cancellation of the regional management program in the United States, no control tactics are being implemented to mitigate the expansion of the moth's geographical range. Hence, an integrated approach including biological control is proposed to regulate the population of C. cactorum in North America. Field surveys of the recently described parasitoid, Apanteles opuntiarum Martínez & Berta, were carried out within the C. cactorum native range in Argentina, and laboratory studies were conducted to develop a parasitoid rearing protocol. Apanteles opuntiarum was the most common parasitoid of C. cactorum and their field distributions were similar. In the laboratory, the parasitoid's reproductive success was maximized when one or two female wasps were exposed to 30 host larvae within a 500 ml container. Laboratory reared females were less successful at parasitizing hosts than field collected females. In spite of the success achieved with laboratory rearing, male bias was observed throughout the experiments. Because this bias might be related to the presence of the reproductive parasite Wolbachia, both laboratory colony and field collected individuals were screened and Wolbachia was detected. This study provides useful field and laboratory information on (1) laboratory rearing techniques for A. opuntiarum; (2) developing host specificity test protocols for studies under quarantine conditions; and (3) selecting parasitoid populations that best match the climatic conditions present in the C. cactorum invaded areas of North America. Fil: Mengoni Goñalons, Carolina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Fisiología, Biología Molecular y Neurociencias. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Fisiología, Biología Molecular y Neurociencias; Argentina Fil: Varone, Laura. Fundación para el Estudio de Especies Invasivas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Logarzo, Guillermo Alejandro. Fundación para el Estudio de Especies Invasivas; Argentina Fil: Guala, Mariel. Fundación para el Estudio de Especies Invasivas; Argentina Fil: Rodriguero, Marcela Silvina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Ecología, Genética y Evolución de Buenos Aires; Argentina Fil: Hight, Stephen D.. United States Department Of Agriculture. Agriculture Research Service; Estados Unidos Fil: Carpenter, James E.. United States Department Of Agriculture. Agriculture Research Service; Estados Unidos

In July 1926, the science behind biological control transitioned from an experimental method to a trusted policy tool in invasive species management. In local storytelling, historical writing and scientific analysis, the ‘lucky’ discovery of the South American Cactoblastis cactorum moth was a watershed moment for scientists concerned with prickly pear, Opuntia and Nopalea spp. Within 10 years, Queensland declared itself pest free. Overnight success is the climax in this tale's narrative arc. Articulating this introduction as a ‘lucky break’ worked to stabilize the narrative of human control in the agricultural environments of post-colonial Queensland, and, in doing so, consolidated biological control as critical management technique. I argue that ‘luck’ elides the assemblage of elements and actors necessary to enable this change, allowing settlers to distance themselves from the responsibility for disruptions associated with nineteenth-century plant transfers. To challenge the rhetorical function of luck, three episodes of contingency are discussed: (1) transnational mobility of things and knowledge, (2) the unpredictable adaptation of insect diet, and; (3) human vectors in industrialized insect–plant complexes. There are important distinguishing differences between luck and contingency, which I frame as a critical analytical tool for understanding the political role of non-humans, in the storied worlds of science in prickly pear land.

Summary This study compared several biological parameters of native cactus moth, Melitara prodenialis, reared on an artificial versus the natural diet of Opuntia spp. cladodes. Results suggest that the current artificial diet developed for mass rearing C. cactorum can provide nutritional value for the rearing of Melitara spp. native cactus moths. Overall, rearing M. prodenialis on the artificial diet was more successful than on Opuntia cladodes and required less time and labor. Mass rearing of M. prodenialis using artificial diet should improve once sub sequent generations become adapted to laboratory rearing conditions.

The cactus moth, Cactoblastis cactorum (Berg) (Lepidoptera: Pyralidae), spends most of its larval life feeding within the cladodes of Opuntia cactuses, but the gregarious caterpillars begin their life outside the plant, and in the later instars make intermittent excursions over plant surfac- es to access new cladodes and to thermoregulate. The study reported here showed that when the caterpillars move en masse , they mark and follow trails that serve to keep the cohort together. Artificial trails prepared from hexane extracts of the caterpillar’s paired mandibular glands were readily followed by the caterpillars. The glands are remarkably large, and their fluid contents, which constitute approximately 1% of the total wet mass of a caterpillar, are secreted onto the substrate as they move. Although the caterpillars also lay down copious quantities of silk, the ma- terial in itself neithxer elicits trail following nor is it a requisite component of pathways that elicit trail following. Previous analyses of the mandibular glands of other species of pyralid caterpillars showed that they contain a series of structurally distinct 2-acyl-1,3 cyclohexane diones. Chemical analysis indicates that the glands of C. cactorum contain structurally similar compounds, and bio- assays indicate that trail following occurs in response to these chemicals. While the mandibular glands’ fluids have been shown to act as semiochemicals, effecting both interspecific and intra- specific behavior in other species of pyralids, the present study is the first to report their use as a trail pheromone.

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 wellknown 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.

Newly eclosed larvae of Cactoblastis cactorum Berg (Lepidoptera: Pyralidae) contain their activity to an arena formed at the base of their eggstick, marked with a mandibular gland pheromone. Laboratory and field studies were undertaken to determine if these pre-excavation aggregations, essential to their successful penetration of the host plant, could be disrupted with mandibular gland extract causing the incipient colonies to perish. Cladodes or whole plants were sprayed with the pheromone, obtained by extracting macerated caterpillars in hexane, hexane only, or left unsprayed, and the survivorship of caterpillars that eclosed from eggsticks attached to the cladodes recorded at a later date. In 4 separate experiments, the average survivorship of C. cactorum larvae from cohorts on cladodes sprayed with the extract (15%) differed markedly from survivorship of caterpillar cohorts on cladodes treated with the solvent only (84%) or left untreated (80%). This differential mortality was attributed to the elicitation of the independent dispersal of the caterpillars by the mandibular gland pheromone and their failure to reaggregate in numbers sufficient to mount a successful attack on the host plant. The potential for managing pest populations of caterpillars employing this target-specific alternative to conventional pesticides is discussed.

The cactus moth, Cactoblastis cactorum (Berg) (Lepidoptera: Pyralidae), is an invasive species in North America, where it poses a threat to species of Opuntia Mill. of economic and ecological importance. The parasitoid Apanteles opuntiarum Martinez & Berta (Hymenoptera: Braconidae) is currently under evaluation as a potential biological control agent. This study was conducted to develop a parasitoid rearing protocol, with special attention to laboratory sex ratio and the effects of inbreeding. The parasitoid rearing method used a natural cactus host diet for culture of the moths. Female wasps were mated with siblings, non-siblings, or a combination. Clutch size, clutch number, and offspring sex ratios were recorded. The effects of sibling mating on these factors were analyzed. Offspring of sibling-mated parasitoids exhibited a significant increase in female sex ratio. The rearing method produced 6 successive generations in captivity with no additional introductions of genetic material. Hence, the protocol appears suitable for long-term maintenance of quarantine colonies. The effects of inbreeding suggest that natural populations of A. opuntiarum are subject to local mate competition. Therefore, some amount of inbreeding is recommended for maintenance of an optimal sex ratio of A. opuntiarum in laboratory colonies.

Cactoblastis cactorum (Berg) (Lepidoptera: Pyralidae) is a non-native moth attacking prickly pear cactus, Opuntia spp., in southeastern U.S. The insect is also an important threat to ecological systems and to native and endangered Opuntia spp. in southwestern USA. The egg parasitoid Trichogramma fuentesi Torre (Hymenoptera: Trichogrammatidae) was discovered attacking wild C. cactorum in Florida. To evaluate the potential effect of inundative releases of T. fuentesi against C. cactorum, the host searching behavior of T. fuentesi on C. cactorum eggs and host suitability of selected lepidopteran eggs were studied in the laboratory. Host suitability was studied on the native blue cactus moth, Melitara prodenialis Walker, and 6 selected species of butterfly eggs [Danaus plexippus (L.), Dryas iulia (Hubner), Junonia coenia (Hubner), Papilio glaucus (L.), Papilio polyxenes (F.), and Vanessa cardui (L.)] to assess the potential for non-target effects from T. fuentesi. The proportion of parasitism of the ...

Despite their recognized importance in the literature, the contribution of native-range species interactions to invasion success has been inadequately studied. Previous authors have suggested that biases in the sampling of propagules from the native range might influence invasion success, but most contemporary invasion hypotheses focus on the development of novel interactions or a release from native consumers and competitors. When ecotypic variation exists in native host-consumer associations, the specific pattern of sampling across ecotypes could determine invasion success, especially when the genetic diversity among exotic propagules is low. The South American cactus moth, Cactoblastis cactorum (Berg), is an oligophagous consumer whose larvae feed on prickly pear cacti (subfamily Opuntioideae). The moth was collected from a small geographic area along the Argentina-Uruguay border in 1925 and was introduced to multiple continents as a biological control species, which has subsequently invaded North America. Here we show that groups defined by genetic structure in this species’ native range are concordant with distinct patterns of host association and larval morphology. Furthermore, in Florida populations, morphological traits have diverged from those found in the native range, and patterns of host association suggest that strong biases in host preference also occur in invasive populations. The documented history of C. cactorum introductions confirms that multiple attempts were made to export the moth, but that only a single ecotype was exported successfully. Additional work will be necessary to determine whether the observed host biases in North America reflect a rapid adaptation to naive hosts or a conservation of traits related to specific aspects of the host-consumer association.

The behavioral biology of the first instar larva of Cactoblastis cactorum was studied from the time of eclosion until the colony penetrated and initiated excavation of the host plant. Hatching from an egg stick was asynchronous, requiring 20 h for the entire cohort to eclose at 50%–70% RH and significantly longer at a lower range of RHs. On eclosion, neonates aggregated in an arena at the base of their egg stick and did not attempt to excavate the cladode until an average of 25 caterpillars had collected, approximately 15 h after the onset of egg hatch. Typically only a single entrance hole was formed, limiting the active process of excavating to one or a few individuals at-a-time until the host was fully penetrated and enlarged internally. Olfactometer tests showed that the neonates are strongly attracted to volatile chemicals released when caterpillars chewed into the cladode, accounting for the strong fidelity of the whole cohort to the initial site of penetration. In one instance, the caterpillars were observed to deal with an explosive release of mucilage by imbibing the liquid until the flooded zone was drained and the caterpillars could reenter the plant through the original entrance hole. Once inside the cladode, marked individuals adopted a regular cycle of defecating at the surface at a mean interval of approximately 10 min when followed for 35 successive cycles. Blanket spraying cladodes with a mandibular gland extract prior to hatching led to the independent dispersal of neonates and a failure to form an arena. When the cladode was impenetrable at the site of eclosion, the active cohort of unfed neonates set off together in search of a new site, marking and following a persistent trail that allowed late-to-eclose caterpillars to join their departed siblings. The adaptive significance of these observations is discussed in the context of the life history of the caterpillar.

Associational susceptibility has been predicted to arise when a target plant's neighbor is more palatable to an herbivore than the target plant itself, resulting in attraction and spill-over of the herbivore onto the target plant. This prediction was tested on two hosts of the invasive pyralid moth Cactoblastis cactorum Berg. A combination of observational surveys and experimental plantings were used to test for differences in herbivore damage and plant size on isolated Opuntia humifusa (Raf.) Raf. plants, O. humifusa paired with O. stricta (Haw.) Haw., and O. humifusa in conspecific pairs. Based on general patterns of associational effects and specific C. cactorum behavior, it was predicted that O. humifusa would have higher levels of C. cactorum damage when growing near O. stricta, as compared with isolated plants or those growing near conspecifics. However, little support for associational resistance or susceptibility was found. Surveys revealed that isolated O. humifusa plants had on average ...

The cactus moth, Cactoblastis cactorum (Berg), is native to South America. Since its unintentional arrival to the United States in 1989 and to Mexican islands in 2006, it has become a serious threat to the diversity of both wild and cultivated species of Opuntia Mill, in North America. The native ecological host range of C. cactorum has not been directly ascertained and host acceptance is unclear. Taxonomic nomenclature of Opuntia spp. has been confusing, contradictory, and rapidly changing, leading to inaccurate conclusions about host plant use by C. cactorum in its native South American range. This study was conducted to better understand the biology and ecology of C. cactorum in Argentina by evaluating, under laboratory conditions, the insects’ performance (survivorship, development time, potential fecundity) on 8 Opuntia spp. occurring in Argentina. Feeding trials were conducted on 5 Opuntia spp. native to Argentina and 3 Opuntia spp. native to Mexico. Cactoblastis cactorum larvae failed to f...

The invasive cactus borer Cactoblastis cactorum (Berg) (Lepidoptera: Pyralidae) now cooccurs with a species of borer native to North America, Melitara prodenialis Walker (Lepidoptera: Pyralidae), in the southeastern United States. Because C. cactorum damages native species of pricklypear (Opuntia) often through population outbreaks, it is necessary to distinguish this species from the native cactus borer that has reduced impact on pricklypear populations. Cactoblastis cactorum and M. prodenialis eggs are laid one on top of another to form eggsticks that resemble cactus spines. Both moth species utilize the same host plant species in the Opuntia genus, and during larval life stages it is easy to distinguish the two species. Determining species identification based on eggs alone, however, has been difficult. Yet, it is impractical to wait for eggs to hatch and larvae to develop to determine species identification for research or monitoring purposes. Several objective, quantitative differences were ...

We examined the association between the exotic South American cactus moth, Cactoblastis cactorum (Berg) (Lepidoptera: Pyralidae), and its host plants (prickly pear cacti, subfamily Opuntioideae) in Florida to assess the role of host plant identity and local host community on the prevalence of this invasive moth. From May to September 2008, we surveyed 4,243 plants across 165 sites throughout Florida for C. cactorum. The probability of C. cactorum presence at a particular site was best explained by the presence of either Opuntia humifusa var. ammophila (Small) L. D. Benson or O. stricta (Haworth) Haworth. Within infested sites, only O. stricta individuals were significantly more infested than other host plants. Our results suggest that understanding patterns of C. cactorum infestation, both in Florida and as it spreads towards the western United States relies, at least in part, on determining the mechanism by which O. stricta influences the suitability of specific host communities.

Some species have insufficient defenses against climate change, emerging infectious diseases, and non-native species because they have not been exposed to these factors over their evolutionary history, and this can decrease their likelihood of persistence. Captive breeding programs are sometimes used to reintroduce individuals back into the wild; however, successful captive breeding and reintroduction can be difficult because species or populations often cannot coexist with non-native pathogens and herbivores without artificial selection. In captive breeding programs, breeders can select for host defenses that prevent or reduce pathogen or herbivore burden (i.e., resistance) or traits that limit the effects of parasitism or herbivory on host fitness (i.e., tolerance). We propose that selection for host tolerance may enhance the success of reintroduction or translocation because tolerant hosts generally have neutral effects on introduced pathogens and herbivores. The release of resistant hosts would have detrimental effects on their natural enemies, promoting rapid evolution to circumvent the host resistance that may reduce the long-term probability of persistence of the reintroduced or translocated species. We examined 2 case studies, one on the pathogenic amphibian chytrid fungus (Batrachochytrium dendrobatidis (Bd)) and the other on the herbivorous cactus moth (Cactoblastis cactorum) in the United States, where it is not native. In each case study, we provide recommendations for how captive breeders and managers could go about selecting for host tolerance. Selecting for tolerance may offer a promising tool to rescue hosts species from invasive natural enemies as well as new natural enemies associated with climate change-induced range shifts.

Opinions about the value of biological control are often extreme. Colloquially, biological control most often refers to classical biological control, in which one species is introduced from another region to control pests such as arthropod herbivores in agricultural systems, or weeds in managed and natural systems.1 As such, biological control has the potential to be a low-cost, chemical free, means to control pests. Numerous biological control programs have been unqualified successes (Bellows 2001), such as the control of cacti in Australia with the moth Cactoblastis cactorum (Raghu and Walton 2007), of cottony-cushion scale (Icerya purchasi) in California with the vedalia lady beetle, Rodolia cardinalis (Caltagirone and Doutt 1989), and of glassy-winged sharpshooters in French Polynesia with the egg parasitoid Gonatocerus ashmeadi (Grandgirard et al. 2009). Yet, classical biological control, as with any introduction of a species into a new area, necessarily involves the unknown and therefore carries some inherent risk (Simberloff and Stiling 1996) – what will these organisms actually do in a novel ecosystem? The most unpredictable element in biological control is the extent to which the realized niche is modified in the new environment. This effect has been responsible for some disastrous outcomes of classical biological control, many of which occurred during an era when vertebrates were being introduced around the world by Europeans for a variety of reasons (e.g., introducing the birds of Shakespeare to America, Mirsky 2008), including for biological control (Howarth 1991). The introductions as biological control agents of cane toad to Australia (Crossland et al. 2000) and mongoose to Hawaii (Hays and Conant 2007) are notorious. Introductions of generalist invertebrate agents also have had dire consequences, such as the introduction of predatory snails to French Polynesia (Murray et al. 1988; Coote 2007). In retrospect, some of the unintended consequences of biological control could have been avoided with more ecological knowledge (McEvoy and Coombs 2000) or more societal appreciation for native species (which has developed with time, Henneman and Memmott 2001), but with other introductions, it would have been impossible to know ahead of time what the risks would be (e.g., gall fly agents of knapweeds providing supplementary food to mice that harbor hantavirus, Pearson and Callaway 2006). Many of the unknown outcomes of biological control are purely ecological – what is the risk that a wasp, introduced to parasitize an agricultural pest, will also be able to feed on a native insect? Other unknowns involve evolution – will a herbivore adapt over time to be able to feed on a new nontarget host or hybridize with a closely related species? This volume explores the evolutionary aspects of biological control. Although often overlooked, evolutionary considerations are critical to all stages of classical biological control, from agent selection, to quarantine, release, establishment, and ultimately success in pest control (Ehler et al. 2004). Many questions are unresolved. For example, should agents be chosen that have a long history with the host or are ‘new associations’ more likely to succeed (Hokkanen and Pimentel 1989)? Can one improve effectiveness through artificial selection (Hopper et al. 1993)? Will postcolonization adaptation of the agent increase the likelihood of success, and/or are hosts equally likely to evolve resistance over time (Roderick 1992; Holt and Hochberg 1997; Hufbauer 2001)? Are generalist consumers more likely to survive in novel environments or are specialists more effective (Murdoch et al. 1985; Waage 1990; Brodeur 2012)? More recently, concern for the environment, as well as theory examining the reasons for success of generalist predators, prompted a shift to the release of specialized consumers typically preceded by extensive testing aimed at delimiting the host range of candidate biological control agents. While this approach has clearly made biological control more predictive ecologically, research focused on host range currently lacks measures of genetic variation in host use and responses of those hosts, and thus evolutionary uncertainties remain.

Cactoblastis cactorum is known for being both a biological control agent and an invasive pest of opuntioid cacti. The spread of C. cactorum in the southeastern United States may threaten the biological and physical integrity of desert, scrub, and coastal habitats. However, the effects of invasive species are known to vary spatially and temporally, and C. cactorum’s efficacy as a biological control agent varies considerably from region to region. Therefore, the long term effects of C. cactorum within its U.S. range are still uncertain. Marked Opuntia stricta (n = 253) and O. humifusa (n = 327) plants along the west coast of Florida were censused for 6 years to determine the effects of C. cactorum attack on survival and growth rate of plants, and to examine host species differences and the effects of plant size. 78.1 % of the Opuntia plants were attacked by C. cactorum during the 6 year study and the overall survival rate was 75.8 %. Plants attacked by C. cactorum were more likely to die than unattacked plants and a plant’s odds of surviving the 6 year period decreased as C. cactorum attack frequency increased. However, plants that survived the 6 year period showed, on average, positive growth and there was no significant difference in growth rates between surviving attacked and unattacked plants. O. stricta plants were more likely to be attacked at least once, were attacked more frequently, and were more likely to die after being attacked than were O. humifusa plants. Plant size did not predict plant survival, but larger surviving plants lost proportionally more pads over the 6 years than smaller surviving plants. Although C. cactorum should still be considered a threat, particularly for rare opuntioids, overall survival along the west central Florida coast is currently high and plants that are able to survive C. cactorum attack are not being reduced in size, possibly because they possess traits that render them more tolerant of C. cactorum damage. Our findings suggest that an assumption of severe negative effects of an invasive species, based on its effects in other regions or over short periods of time, may not always be justified.

Trichogramma fuentesi Torre was identified attacking Cactoblastis cactorum (Berg), a serious pest of Opuntia spp. in North America, raising the possibility of using this egg parasitoid as an inundative biological control agent. Studies were conducted to assess the biological parameters of this parasitoid under laboratory conditions. Nutritive quality influence of the rearing supplement on the parasitoid's longevity, mating, and age was evaluated based on the level of parasitism. The presence and type of food source had a positive impact on female longevity, and female parasitoids given a diet composed of pure honey lived the longest; an average of 11 d. Mated females parasitized a greater number of C. cactorum host eggs than did unmated females. Percent parasitism significantly decreased with female age. Two- to 3-day old female parasitoids had the highest level of parasitism. Two-day old host eggs were the optimal host egg age for parasitization by T. fuentesi. In the context of implementing an ...

Opuntia ficus-indica (L.) Miller is a globally important cactus species with a long history of human use. In addition to the importance of O. ficus-indica as a food for humans and livestock, it also has long served a role in the production of cochineal, a once important textile dye. This cactus also is intimately interwoven into the story of Cactoblastis cactorum (Berg) (South American cactus moth), one of the best-known examples of biological weed control. In this regard, O. ficus-indica has been a target weed as well as an unintended host in C. cactorum invasion. Although the distribution and human-assisted movement of this cactus throughout much of the world is well documented, surprisingly little has been written about its history and movement within the Americas. Literature associated with Opuntia and their phytophagous pests in North and South America was examined in an attempt to determine the history of O. ficus-indica in the Americas. Available information suggests with some certainty t...

The legume Chamaecrista fasciculata attracts ants to its extrafloral nectar (EFN) which can lead to reduced herbivory and increased fecundity for the plant. In Florida, Opuntia stricta and O. humifusa, hosts of the invasive moth Cactoblastis cactorum, are often found growing in close association with C. fasciculata. We tested the hypotheses that O. stricta and O. humifusa individuals have higher ant abundance, lower levels of herbivore damage, and increased growth when growing in close association with C. fasciculata compared with individuals not growing near the plant. We also experimentally placed C. cactorum eggsticks and pupae on Opuntia individuals to see if ant predation of these stages occurred, and if so, whether predation rates were higher on individuals growing close to C. fasciculata. Opuntia plants near C. fasciculata were less likely to be attacked by C. cactorum and had higher ant abundance than plants far from C. fasciculata. Field surveys showed that Opuntia plants near C. fasciculata had a lower proportion of cladodes with C. cactorum damage of any type. Proportions of cladodes with damage from five native herbivores were not significantly different between treatments. In addition, Opuntia individuals growing near C. fasciculata added proportionately more pads during the growing season. We found evidence of ant predation on 15.9% of C. cactorum eggsticks and 17.6% of pupae. In August and October of 2008, there was significantly more evidence of predation on eggs and pupae placed on Opuntia individuals near C. fasciculata. No effect of distance to C. fasciculata was seen in November of 2008, potentially because plants were no longer producing EFN at this time. Our finding that Opuntia plants close to C. fasciculata show reduced herbivory from invasive C. cactorum, but not from the native herbivores examined, suggests that patterns of associational resistance may be influenced by the co-evolutionary history of the organisms in question.

Interest in the natural enemies of Cactoblastis cactorum (Berg) has increased since the moth was found in Florida in 1989. Previous surveys for natural enemies in Argentina identified egg parasitoids in the family Trichogrammatidae as potentially important control agents of C. cactorum. A study was conducted in north Florida to identify and to assess occurrence of egg parasitoids attacking this invasive moth in its new homeland. Surveys undertaken at 6 locations in north Florida from Jul 2008 to Dec 2009 revealed that eggsticks of C. cactorum were attacked by egg parasitoids from the Trichogramma genus: T. pretiosum Riley, T. fuentesi Torre, and an additional unidentified Trichogramma species belonging to the T. pretiosum group. In order to assess the importance of these egg parasitoids, the fate of individual C. cactorum eggsticks was determined during weekly visits to each site. This assessment showed that the combined level of parasitism of C. cactorum eggsticks was very low with less than 0.2...

Cactoblastis cactorum Berg (Lepidoptera: Pyralidae), the cactus moth, is a well-known biological control agent of prickly pear cactus (Cactaceae: Opuntia Miller). The arrival of the moth in Florida and its subsequent spread through the southeastern United States poses a threat to opuntioid diversity in North America. Of particular concern are the ecological and economic impacts the moth could have in the southwestern United States and Mexico, where both native and cultivated Opuntia species are important resources. It is unknown which species would best support larval development if the moth were to spread further westward in North America. This study aimed to determine if ovipositing females demonstrate preferences for any of 14 common opuntioids native to or naturalized in Mexico and the southwestern United States; which of these opuntioids best support larval development; and if oviposition preference correlates with larval performance, as predicted by simple adaptive models. Results from a field experiment showed that female moths preferred O. engelmannii Salm-Dyck ex Engelmann variety linguiformis (Griffiths) Parfitt and Pinkava and O. engelmannii variety engelmannii for oviposition. A generalized linear model showed number of cladodes and degree of spininess to be significant predictors of oviposition activity. Results from a no-choice larval survival experiment showed Consolea rubescens (Salm-Dyck ex de Candolle.) Lemaire and O. streptacantha Lemaire to be the best hosts. Epidermal toughness was a significant predictor of most larval fitness parameters. In general, oviposition preference was not correlated with larval performance. A lack of co-evolutionary history between C. cactorum and North American opuntioid species may help explain this disconnect.

Spread of the invasive cactus-feeding moth Cactoblastis cactorum has been well documented since its export from Argentina to Australia as a biocontrol agent, and records suggest that all non-native populations are derived from a single collection in the moth’s native range. The subsequent global spread of the moth has been complex, and previous research has suggested multiple introductions into North America. There exists the possibility of additional emigrations from the native range in nursery stock during the late twentieth century. Here, we present mitochondrial gene sequence data (COI) from South America (native range) and North America (invasive range) to test the hypothesis that the rapid invasive spread in North America is enhanced by unique genetic combinations from isolated portions of the native range. We found that haplotype richness in the native range of C. cactorum is high and that there was 90% lower richness in Florida than in Argentina. All Florida C. cactorum haplotypes are represented in a single, well-defined clade, which includes collections from the reported region of original export from Argentina. Thus, our data are consistent with the documented history suggesting a single exportation of C. cactorum from the eastern region of the native range. Additionally, the presence of geographic structure in three distinct haplotypes within the same clade across Florida supports the hypothesis of multiple introductions into Florida from a location outside the native range. Because the common haplotypes in Florida are also known to occur in the neighboring Caribbean Islands, the islands are a likely source for independent North American colonization events. Our data show that rapid and successful invasion within North America cannot be attributed to unique genetic combinations. This suggests that successful invasion of the southeastern US is more likely the product of a fortuitous introduction into favorable abiotic conditions and/or defense responses of specific Opuntia hosts, rapid adaptation, or a release from native enemies.

The roles of biotic interactions in determining invasion success emerge from the set of traits possessed by the invader and those present in the community being invaded. Identifying traits important for governing invader distributions is challenging, but systems in which invaders specialize on hosts or resources may facilitate narrowed focus on particular suites of traits. Most examples of specialist consumers that become successful invaders are escaped biological control species. One example is the South American cactus moth (Cactoblastis cactorum), an escaped biological control agent that infests prickly-pear cacti (primarily taxa in the genus Opuntia). Here we quantify tissue macronutrient traits (crude fiber, lipid, crude protein, and carbohydrate by difference) and evaluate C. cactorum infestation of several North American Opuntia taxa as a function of those traits. We then evaluate whether a common, native cactus moth (Melitara prodenialis) infests plants that are similar to those used by C. cactorum to evaluate the likelihood that the species compete for hosts. Our results generally suggest that Opuntia tissue macronutrients may be important traits in mediating cactus moth-Opuntia associations. While the range of macronutrients that are suitable for M. prodenialis are largely similar to those for C. cactorum in the east, M. prodenialis tend to infest plants with higher crude fiber content than C. cactorum. Tissue crude fiber content may thus play an important role in both constraining infestation of host plants by C. cactorum in its current invasive range as well as determining its future spread in North America.

Conseola corallicola is a rare cactus that is known from just two islands in Florida, Little Torch Key and Swan Key. The appearance of the cactus-eating moth, Cactoblastis cactorum, in the 1980s, threatened its survival. Outplantings at various locations were made in the 1990s and early in the 21st century to try to boost population sizes in the field and to determine optimal outplanting conditions. Here, I examine the survival of these cacti and compare it to the survival of volunteers around the bases of parent plants at Little Torch Key. I correlate percent survival in all locations with soil nutrients. Survival of recruits in outplantings was lower than that of volunteers around parent plants. Transplant experiments showed the physical act of replanting did not reduce survival. Cacti planted close to individuals of prickly pear cactus, Opuntia stricta, suffered from attack by Cactoblastis as they spilled over from O. stricta onto C. corallicola outplantings. Survival of cacti planted far away...

Understanding the influence of resident species on the success of invaders is a core objective in the study and management of biological invasions. We asked whether facultative food-for-protection mutualism between resident, nectar-feeding ants and extrafloral nectar-bearing plants confers biotic resistance to invasion by a specialist herbivore. Our research focused on the South American cactus-feeding moth Cactoblastis cactorum Berg (Lepidopetra: Pyralidae) in the panhandle region of Florida. This species has been widely and intentionally redistributed as a biological control agent against weedy cacti (Opuntia spp.) but arrived unintentionally in the southeast US, where it attacks native, non-target cacti and is considered a noxious invader. The acquired host-plants of C. cactorum in Florida secrete extrafloral nectar, especially on young, vegetative structures, and this attracts ants. We conducted ant-exclusion experiments over 2 years (2008 and 2009) at two sites using potted plants of two vulnerable host species (O. stricta and O. ficus-indica) to evaluate the influence of cactus-visiting ants (total of eight species) at multiple points in the moth life cycle (oviposition, egg survival, and larval survival). We found that the presence of ants often increased the mortality of lab-reared C. cactorum eggsticks (stacks of cohered eggs) and larvae that we introduced onto plants in the field, although these effects were variable across sites, years, host-plant species, ant species, and/or between old and young plant structures. In contrast to these “staged” encounters, we found that ants had little influence on the survival of cactus moths that occurred naturally at our field sites, or on moth damage and plant growth. In total, our experimental results suggest that the influence of cactus-visiting ants on C. cactorum invasion dynamics is weak and highly variable.