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Landscape heterogeneity and the host plant use are factors suggested to play determinant roles in shaping the evolutionary history of herbivorous insects. However, the role of the reconfiguration of host plants distributions linked to Quaternary climate oscillations as drivers of contemporary population genetic structure is still poorly understood. Here, we formally examine the relative contribution of such factors on intraspecific diversification using the South American cactus moth, Cactoblastis cactorum, an herbivore insect specialized in the use of cacti as host plants. We assessed genomic variation using genome-wide SNPs and mitochondrial data in populations sampled across a broad geographical gradient where moths feed on different cactus species. We integrated demographic simulations and ecological niche modeling into a landscape genomics framework, to test alternative hypotheses of past and current population connectivity for both C. cactorum and its host plants. Regions exhibiting higher genomic diversity were evaluated for congruence with areas where suitable climatic conditions remained stable through time. Our results revealed that past spatial configuration of suitable habitat conditions and shifts of host plants distributions are the factors that better explain the intraspecific diversification. Genomic data also supported the hypothesis that areas of long-term habitat stability served as refugia for C. cactorum, enabling the maintenance of high levels of genetic diversity over time. Overall, our study highlights the importance of integrating inter-specific interactions and their spatio-temporal dynamics to better understand the relative importance of abiotic and biotic factors driving the diversification processes in herbivorous insects with broad geographical and restricted host ranges.

Aeolian sand dunes on the Broughton Island are heavily disturbed by nesting birds and invaded by Opuntia stricta (Prickly Pear). Biological control agents do not establish well on exposed coastal systems and thus herbicide treatment is currently the main control, but it is expensive in terms of resource allocation. Invasive species are generally considered by many to be controlled at all cost but in many situations, they are benign or even beneficial. We test if O. stricta causes significant change to the vegetation on aeolian sands on Broughton Island. 40100 m2 plots were placed randomly over areas of differing cover of O. stricta. Within these plots additional six subplots of 4 m2 were placed. All flora species were scored for cover. Univariate and multivariate analyses were performed testing the effects of O. stricta on floristic composition and species density and turnover. Regression models showed a non-significant (r2 = 0.95; P = 0.0557) negative effect of O. stricta cover on species density at the 100 m2 plot size and at the 4 m2 scale (r2 = 0.013; P = 0.0858). Global comparison of species density between plots with and without O. stricta at the 4 m2 scale was non-significant. Homogenisation occurred (lowered beta diversity) across plots with O. stricta presence at the 4 m2 scale. More species had their average cover reduced by O. stricta presence than those that were benefited. The scale at which the investigation was undertaken (4 or 100 m2; species density and beta diversity) affected the magnitude and significance of O. stricta on the results obtained. The scale at which investigations are made was found to be of importance. Overall, although negative changes were noted in flora species diversity and homogenisation was apparent the negative impact may not be sufficient to justify the costs and resources needed to control the species which is unlikely to be eradicated from the site. Opuntia stricta was found to be associated with homogenisation within the dunal communities in which it commonly dominated. However, the magnitude of these effects on diversity and the inability to eradicate the species may not constitute effective use of labour, funds and time and the potential detrimental effects of long-term use of herbicides. There are limited resources available and such resources need more specific targeting to maximise the chances of reducing biodiversity loss. [ABSTRACT FROM AUTHOR]

1. Relationships between prickly pear cactus (Cactaceae: Opuntia) and specialist moth larvae (Lepidoptera: Pyralidae) are exemplar of exclusive interactions between herbivorous insects and host plants. 2. We measured nutritional and defensive factors indicative of Opuntia quality to native and invasive host‐specialised moth larvae. Our goals were to investigate whether host qualities varied among and within Opuntia species, use that information to test whether host quality axes predicted occupancy by larvae in two focal O. engelmannii populations, and draw conclusions about whether these herbivores were resource limited. 3. There were minimal differences in protein, carbohydrate, fatty acid, fibre, water, and cuticular thickness, among four Opuntia species distributed throughout Texas. Macronutrient content did not differ between most species. Mucilage exudation was an induced response to herbivory. Field experiments compared pairs of O. engelmannii in which one individual hosted native Melitara doddalis or invasive Cactoblastis cactorum larvae, and the other did not; host quality and nutritional space did not predict herbivore occupancy. Moreover, ordination of host quality traits did not reveal spatial aggregation of cacti with and without herbivores. 4. These results demonstrated that neither moth species was resource limited. An overall lack of variation among and within Texas Opuntia indicate that these species were suitable resources to invasive C. cactorum that recently established in Texas. 5. Outcomes of this study have serious implications for Opuntia, native moths, and associated food webs, that will soon interact with an expanding C. cactorum population as it spreads inland from the Texas Gulf Coast. [ABSTRACT FROM AUTHOR]

We report on a long‐term evaluation of biological control of an invasive cactus, Opuntia stricta, in the Kruger National Park, South Africa. By forming large impenetrable thickets, this weed species posed a major threat to the integrity and biodiversity of the park, and to agroecosystems more widely.Over 22 years, from 1992 to 2013, counts were made along fixed transects at four different sites to measure the abundance of O. stricta and the prevalence of two of its biological control agents: (a) Cactoblastis cactorum, whose larvae feed in the plants' cladodes and (b) a sap‐sucking cochineal insect, Dactylopius opuntiae. With only C. cactorum present, the numbers of O. stricta cladodes and fruit remained unchanged at two of the sites but increased annually at the other two. Within 5 years of the introduction of D. opuntiae, the numbers of cladodes and fruit decreased substantially at all the sites and the residual cactus populations have been held at inconsequentially low levels ever since.Both the C. cactorum and D. opuntiae populations on O. stricta in South Africa were sourced from founder stocks in Australia. This allows direct comparisons of biological control of O. stricta in South Africa with the world‐famous program against O. stricta, in Queensland and in New South Wales, that peaked in the 1920s and 1930s.Synthesis and applications. Almost all accounts acclaim Cactoblastis cactorum as the dominant contributor to the sustained decline of populations of prickly pears in Australia in the 1930s. Our results provide evidence that this now widely accepted conclusion is incorrect and that cochineal was and is the key role player. Managers and biological control practitioners concerned with the apparent underperformance of C. cactorum in the suppression of invasive Opuntia cacti should interpret the entrenched reports in the literature with circumspection. There may also be less cause for concern about the anticipated devastation of native Opuntia prickly pear species in the southern United States where C. cactorum has become an invasive pest species. [ABSTRACT FROM AUTHOR]

Cactoblastis cactorum (Berg) (Lepidoptera: Pyralidae) is native to South America and has been used successfully as a biocontrol agent against invasive species of Opuntia (Cactaceae). After its release in the Caribbean, it entered North America, dispersed to southeastern USA, and may reach Mexico threatening native cacti biodiversity and industry based on Opuntia spp. Identifying mortality factors acting on insect populations is central to develop pest management programs. The objective of this study was to estimate mortality causes of C. cactorum in its native range through life table experiments conducted on the exotic O. ficus-indica (L.) Miller and the native species O. quimilo K. Schum. and O. megapotamica Arechav., to detect vulnerable stages and natural enemies. The main mortality factors were generalist predators and native plant defenses. Apanteles opuntiarum Martínez & Berta (Hymenoptera: Braconidae) was found to be the parasitoid with the highest potential as a biocontrol agent. [ABSTRACT FROM AUTHOR]

Four species of Consolea have been reported from the Cuban archipelago, each of which has been considered under threat of extinction. During the last three years various expeditions were carried out to try to update existing information about the conservation status of populations of the different species and their primary threats. Likewise, we revised and identified herbarium specimens from HAC, HAJB, HMC, MNHN, and NY to put together distribution maps for each species on Cuba. All native species of Consolea on Cuba are under threat of extinction/extirpation. Consolea moniliformis is the species with the largest populations on Cuba, while C. macracantha displays the widest range of any other species on the island. Two new localities of C. macracantha were found during this study, but likewise, showed the only signs to date of attack by the invasive moth, Cactoblastic cactorum. Among the principle threats detected for species of Consolea on Cuba are exotic, invasive plant species, livestock grazing and development. We provide a key to the species on Cuba. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The genus Opuntia is worldwide known for its ecological, ornamental and agronomic importance. Some species became pests in the countries in which they where introduced, and as biological control, Cactoblastis cactorum (Lepidoptera: Pyralidae) larvae, originary from Argentina, were used. However, the effect of the attack of this piralid on native cactus has yet not been elucidated. The objective of this study was to detect and to quantify the predation of C. cactorum on Opuntia monacantha. The study was carried out from September to November of 2004, along pre-defined tracks, on a sand bank vegetation area, between the Mole and Galheta beaches in the Santa Catarina island (27º35’83.1’’S e 48º25’70.6’’W). All the studied plants (n = 20) presented some damage caused by C. cactorum. The proportion of unpredated cladodes (68%) and fruits (85%) was higher than the predated ones. Terminal cladodes were highly predated structures and presented the highest number of larvae inside. Seed loss in the predated fruits was high. The remaining areole of the predated cladodes and fruits differentiated into sprouts and routs and formed new plants. O. monacantha, despite of being predated by C. cactorum larvae, apparently possess defense mechanisms which assure the maintenance of its populations.

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. [ABSTRACT FROM AUTHOR]

The cactus moth, Cactoblastis cactorum mainly distributed throughout central and northeastern Argentina was intentionally introduced in the Caribbean region in 1957 as a biological control agent of cacti species of the genus Opuntia. This moth invaded during the last 20-30 years the North American continent, threatening the major center of biodiversity of native Opuntia species. Although human induced and natural dispersal have been invocated to explain its expansion in the non-native distribution range, there is still no evidence to support natural dispersal. In particular, hurricanes are one of the major environmental factors affecting species dispersal in the region. In this study we used mitochondrial DNA to examine whether the spatial distribution of haplotype variation of C. cactorum is at least partially explained by hurricane trajectories within the Caribbean region. DNA sequences for the mitochondrial gene cytochrome oxidase I were obtained for a sample of 110 individuals from the Antillean islands. This information was combined with existing sequences in the GenBank for the same gene for the Caribbean and Florida (N = 132 sequences). Genetic diversity descriptors, a haplotypic network, a spatial analyses of molecular variance and a landscape genetic analysis of migration conditioned by hurricane tracks were conducted to test our hypothesis. Our results revealed a significant spatial grouping of haplotypes consistent with the more frequent hurricane trajectories in the Caribbean region. Significant isolation by distance conditioned by hurricane tracks was detected. Populations of Florida were genetically closer to those of Cuba than to the rest of the population sampled. Within the region, Cuba appears as a reservoir of genetic diversity increasing the risk of invasion to Mexico and the US. Despite commercial transportation of Opuntia promoted dispersal to Florida, our results support the hypothesis that natural disturbances such as hurricanes played a role dispersing this invasive insect. Future conservation programs of North American Opuntia species requires taking into account hurricane mediated dispersal events and permanent whole regional monitoring and international control policies to prevent future range expansions of C. cactorum. [ABSTRACT FROM AUTHOR]

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.

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 subsequent generations become adapted to laboratory rearing conditions. [ABSTRACT FROM AUTHOR]

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 naïve hosts or a conservation of traits related to specific aspects of the host-consumer association. [ABSTRACT FROM AUTHOR]

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 (Hübner), Junonia coenia (Hübner), 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 native cactus moth (M. prodenialis) was 98%; significantly higher than the non-native cactus moth, C. cactorum (11% average parasitism rate). The high proportion of parasitism for all native non-target species tested and the lowest proportion of parasitism for the exotic target species suggested that T. fuentesi not be considered for inundative releases in a biological control approach against C. cactorum. [ABSTRACT FROM AUTHOR]

The gregarious species of Apanteles that attack cactus-feeding phycitine moths (Lepidoptera : Pyralidae) from Argentina are identified using DNA barcodes and morphological data. Sequences of specimens from 10 different populations were generated. Corrected genetic divergences showed two clusters of specimens separated by COI divergences higher than 6%. Our morphological examinations were congruent with the molecular evidence and therefore two species were confidently identified: Apanteles alexanderi Bêgrave;thes and a new species, Apanteles opuntiarum Martínez & Berta, sp. nov., which we describe and illustrate. Despite these two taxa being considered to represent a single polyphagous species for at least 50 years, they can be easily distinguished by the length of their ovipositor sheaths. A key to the species of microgastrine parasitoids of cactus-feeding Lepidoptera in South America is provided. The recognition of the new species reveals a narrower host range for the species involved in this system, making it necessary to re-evaluate their potential as biocontrol agents of the prickly pear moth. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The unintentional introduction of the cactus moth, Cactoblastis cactorum, a successful biological control agent formerly employed in the control of invasive prickly pear cactus species ( Opuntia spp.) in Australia, Hawaii, South Africa, and various Caribbean islands, has posed great concern as to the possible threat to native, endangered species of cactus in the southeastern USA as well as with the potential to cause a major infestation of commercial and agricultural cactus crops in Mexico. A number of control measures have been investigated with varying degrees of success including, field exploration for cactus moth-specific parasitoids, insecticides, fungal, bacterial, and nematode agents. Current tactics used by the USA-Mexico binational program to eradicate cactus moth from Mexico and mitigate its westward movement in the USA include host plant removal, the manual removal and destruction of egg sticks and infected cacti stems, and the Sterile Insect Technique. One other approach not taken until now is the development of a cactus moth cell line as a tool to facilitate the investigation of baculoviruses as an alternative biocontrol method for the cactus moth. Consequently, we established C. cactorum cell lines derived from adult ovarian tissue designated as BCIRL-Cc-AM and BCIRL-Cc-JG. The mean cell population doubling time was 204.3 and 112 h for BCIRL-Cc-AM and BCIRL-Cc-JG, respectively, with weekly medium change, while the doubling time was 176.6 and 192.6 h for BCIRL-Cc-AM and BCIRL-Cc-JG, respectively, with a daily change of medium. In addition, the daily versus weekly change in medium was reflected in the percentage viability with both cell lines showing higher levels with a daily medium change. Of the three baculoviruses tested, only the recombinant AcMNPV-hsp70Red and GmMNPV at a multiplicity of infection (MOI) of 1.0 were able to demonstrate significant production of extracellular virus (ECV) in each of the cell lines, whereas both cell lines were refractive to an HzSNPV challenge at an MOI of 10. In this study, we have demonstrated both the successful development of a C. cactorum cell line and its ability to support a complete baculovirus infection. The potential is also there to pursue further investigations to determine the susceptibility of the cactus moth cell line to other viruses. Additionally, the availability of a cactus moth cell line will facilitate the analysis of viruses prior to using the more expensive bioassay test. Finally, it is hoped with the knowledge presented here that baculoviruses may also be considered as an alternative biocontrol method for the cactus moth. [ABSTRACT FROM AUTHOR]

Environmental niche models (ENMs) have gained enormous popularity as tools to investigate potential changes in species distributions resulting from climate change and species introductions. Despite recognition that species interactions can influence the dynamics of, invasion spread, most implementations of ENMs focus on abiotic factors as the sole predictors of potential range limits. Implicit in this approach is the assumption that biotic interactions are relatively unimportant, either because of scaling issues, or because fundamental and realized niches are equivalent in a Species' native range. When species are introduced into exotic landscapes, changes in biotic interactions relative to the native range can lead to occupation of different regions of niche space and apparent shifts in physiological tolerances. We use an escaped biological control organism, Cactoblastis cactorum (Berg.), to assess the role of the environmental envelope as compared with patterns, of host-herbivore associations based on collections made in the native range. Because all nonnative populations are derived from a single C. cactorum ecotype, we hypothesize' that biotic interactions associated with this ecotype are driving the species' invasion dynamics. Environmental niche models constructed from known native populations perform poorly in predicting nonnative distributions of this species, except where there is an overlap in niche space. In contrast, genetic isolation in the native range is concordant with the observed pattern of host use, and strong host association has been noted in nonnative landscapes. Our results support the hypothesis that the apparent shift in niche space from the native to the exotic ranges results from a shift in biotic interactions, and demonstrate the importance of considering biotic interactions in assessing the risk of future spread for species whose native range is highly constrained by biotic interactions. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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% of host eggs attacked at any one of the 6 sites. While parasitoids attacked smaller eggsticks, there was no correlation between the numbers of eggs in an eggstick attacked with increasing number of eggs/eggstick. Comparing the mean number of eggs/eggstick, there was no difference between the 3 flight periods of C. cactorum , but there was a difference between the 6 sites. Based on these results, the use of Trichogramma wasps as an inundative biological control agent, complementary to the Sterile Insect Technique application , is discussed. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Invasive pests, such as the cactus moth, Cactoblastis cactorum (Berg) (Lepidoptera: Pyralidae), have not reached equilibrium distributions and present unique opportunities to validate models by comparing predicted distributions with eventual realized geographic ranges. A CLIMEX model was developed for C. cactorum. Model validation was attempted at the global scale by comparing worldwide distribution against known occurrence records and at the field scale by comparing CLIMEX "growth indices" against field measurements of larval growth. Globally, CLIMEX predicted limited potential distribution in North America (from the Caribbean Islands to Florida, Texas, and Mexico), Africa (South Africa and parts of the eastern coast), southern India, parts of Southeast Asia, and the northeastern coast of Australia. Actual records indicate the moth has been found in the Caribbean (Antigua, Barbuda, Montserrat Saint Kitts and Nevis, Cayman Islands, and U.S. Virgin Islands), Cuba, Bahamas, Puerto Rico, southern Africa, Kenya, Mexico, and Australia. However, the model did not predict that distribution would extend from India to the west into Pakistan. In the United States, comparison of the predicted and actual distribution patterns suggests that the moth may be close to its predicted northern range along the Atlantic coast. Parts of Texas and most of Mexico may be vulnerable to geographic range expansion of C. cactorum. Larval growth rates in the field were estimated by measuring differences in head capsules and body lengths of larval cohorts at weekly intervals. Growth indices plotted against measures of larval growth rates compared poorly when CLIMEX was run using the default historical weather data. CLIMEX predicted a single period conducive to insect development, in contrast to the three generations observed in the field. Only time and more complete records will tell whether C. cactorum will extend its geographical distribution to regions predicted by the CLIMEX model. In terms of small scale temporal predictions, this study suggests that CLIMEX indices may agree with field-specific population dynamics, provided an adequate metric for insect growth rate is used and weather data are location and time specific. [ABSTRACT FROM AUTHOR]

Long term trapping studies of the invasive moth Cactoblastis cactorum (Berg) were conducted at various latitudes from Puerto Rico to South Carolina. Three flight periods per year were identified at the 5 temperate sites studied, which covered the majority of the infested range on mainland United States. In general, the 3 flight periods across a latitudinal gradient from south Florida to central, coastal South Carolina were a spring flight during Feb- May, a summer flight during Jun-Aug, and a fall flight during Sep-Nov. At any 1 site, each flight period lasted about 2 months. In the tropical areas of the Florida Keys and a Caribbean Island, the insect exhibited overlapping generations. Previous studies of this insect (as a biological control agent) report 2 flight periods per year in its native range of Argentina and its introduced range of Australia and South Africa. A synthetic pheromone-baited trap was a good indicator of generational time, and we suggest that trapping assays in these areas will likely identify 3 generations rather than 2. Initiation and timing of the 3 generational flights has importance in the current United States and Mexico monitoring program for presence and expansion of this invasive pest, development of mapping programs to identify monitoring windows and management efforts with the Sterile Insect Technique. [ABSTRACT FROM AUTHOR]

Environmental conditions during egg and larval development may influence the dispersal ability of insect pests, thus requiring seasonal adjustment of control strategies. We studied the longest single flight, total distance flown, and the number of flights initiated by wild Cactoblastis cactorum (Berg) (Lepidoptera: Pyralidae) to determine whether the flight performance of overwintered cactus moths with a prolonged feeding phase during development differs from nonoverwintered cactus moths. Pupae of field-collected and laboratory-reared moths were transported together from the United States to Switzerland, and flight mills were used to characterize the flight capacity of 24- to 48-h-old adults during their most active period of the diel cycle. The lack of seasonal variation in flight performance of those moths that developed under controlled environment but were fed with field-collected Opuntia cacti showed that seasonal changes in host plant quality did not affect flight. This consistent flight performance in the mass-reared laboratory population throughout the year is beneficial for sterile insect technique programs, which aim to limit the dispersal of this pest. For field-collected C. cactorum, the larger overwintered females performed similarly to nonoverwintered females, indicating that longer feeding time at lower temperature increases body size but does not influence female flight capacity. Young mated females had a similar flight capacity to unmated ones, suggesting that gravid females may play an important role in invading new habitats. For males, overwintering increased the proportion of long-distance flyers, suggesting that they are well-adapted to locate the more sparsely dispersed females in the spring. [ABSTRACT FROM AUTHOR]

The adventive cactus moth Cactoblastis cactorum (Berg) (Lepidoptera: Pyralidae), a widely used biological control agent for Opuntia Mill. cacti, was detected in Florida in 1989. Since then, it has spread along the Atlantic and Gulf Coasts of southeastern United States, threatening native Opuntia populations. We examined the phylogeography of 20 C. cactorum populations from Australia, South Africa, Hawaii, the Caribbean, Mexico, and the southeastern United States based on 769 bp of cytochrome oxidase subunit 1. Five distinct haplotypes were discovered, three of which occur in the United States. Cactoblastis cactorum in the United States falls into two distinct lineages: a western haplotype along the Gulf Coast and an eastern lineage with two haplotypes along the Atlantic Coast, with one of the eastern haplotypes identified as occurring at a single locality on the Gulf Coast. The two lineages have nontrivial genetic divergence (0.5%), and both are more closely related to populations outside the United States than they are to each other. This leads us to conclude that C. cactorum has been introduced to the United States at least twice. The isolated eastern haplotype on the Gulf Coast may indicate that C. cactorum has been introduced a third time, either from the Atlantic Coast or from outside the United States. Evidence from analysis of haplotypes and other information indicates that dispersal by commercial import action and human transport may be more important than flight ranges of ovipositing females for determining long range expansion of the species. Interestingly, the east-west pattern mirrors other coastal species distributions that have been interpreted as being due to Pleistocene vicariance. [ABSTRACT FROM AUTHOR]

Having gained some understanding of the consequences of the CO2-concentrating mechanisms in crassulacean acid metabolism (CAM) that internalize the photosynthetic environment of the Cretaceous on a daily basis, it may be time to consider potential long-term effects of the planetary CO2-concentrating mechanism on growth and ecology of these plants in the Anthropocene. This paper emphasizes our limited understanding of the carbohydrate economy of CAM in relation to growth processes and briefly reviews recent studies of the diel cycles of growth in these plants. An inadvertent long-term, regional-scale experiment from the past is revisited in which an Opuntia monoculture grew to occupy >25 million hectares of farmland in central eastern Australia, producing a total biomass of about 1.5 billion tonnes in about 80 years. Although at the time it does not seem to have been recognized that this invasion involved CAM, a botanist from the University of Melbourne, Jean White-Haney emerges as a heroic pioneer in the control of the invader by poison and pioneered its biological control. The Opuntia population was expanding at 10–100 ha h−1 when it was brought to a halt within a decade by the voracious appetite of Cactoblastis cactorum larvae. It is now known that the female parent moth of this predator detects CAM in O. stricta prior to oviposition by deploying the most sensitive CO2 detector system yet found in the Lepidoptera. The O. stricta invasion is a dramatic demonstration of the capacity of CAM plants to attain and sustain high biomass; to sequester and retain atmospheric CO2. In conclusion, experiments are reviewed that show stimulation of CO2 assimilation, growth, and biomass of CAM plants by elevated atmospheric [CO2], and the proposition that these plants may have a role in atmospheric CO2 sequestration is re-examined. This role may be compromised by predators such as Cactoblastis. However the moth CO2 sensors are adapted to pre-industrial atmospheric [CO2] and FACE (free-air CO2 enrichment) experiments show this exquisite system of biological control is also compromised by rising global [CO2] in the Anthropocene. [ABSTRACT FROM PUBLISHER]

The applied ecological discipline of classical biological control (CBC) has a long history, bolstered by some spectacular successes in the management of pea insect and plant species. A major poster child of CBC is the control of prickly pear (Opuntia spp.) in Australia by the moth Cactoblastis cactorum. In this article we investigate the idiosyncrasies of this CBC program and relate it to contemporary CBC, highlighting the intensive rearing and spatially extensive distribution effort critical to the rapid success of this project. We also emphasize the importance of the sociopolitical and economic context of the Opuntia CBC program and its role in its success. We use these historical clarifications to temper the expectations of equivalent successes in future CBC projects. Cactoblastis cactorum has recently invaded North America, and its threat to native cacti is of concern. We examine the global use of this moth as a biocontrol agent to clarify the nature of the hazard that it may pose as an invader in North and Central America. [ABSTRACT FROM AUTHOR]

Abstract: Opuntia stricta (Cactaceae), an alien weed, has invaded an area of more than 35 000 ha in the Skukuza region of the Kruger National Park [KNP]. The distribution of the plant and features of the environment were used to identify biotic and abiotic factors which may be affecting the distribution and density of the plant. A Canonical Community Analysis revealed that none of the environmental factors that were monitored influenced the distribution or abundance of O. stricta in KNP. There were no apparent natural barriers that might limit the occurrence of O. stricta within the KNP. The study provides insight into the relationship between the invader and host environment, showing that there is a high probability that, unless there is appropriate intervention, O. stricta will eventually colonise the entire KNP. [Copyright &y& Elsevier]

The morphological sensillum types on the antennae of male and female Cactoblastis cactorum were visualized by scanning electron microscopy. Electrophysiological recordings were performed for the first time on single olfactory sensilla of C. cactorum. The male sensilla trichodea house a receptor cell responding to the putative pheromone component (9Z,12E)-tetradecadienyl acetate. The sensilla trichodea of the females were much shorter than those of the males and contained specialized receptor cells responding to certain terpenoids, the most frequent being the nerolidol-sensitive cell. The sensilla auricillica and sensilla basiconica of both sexes contained cells responding less specifically to terpenoid compounds as well as to green leaf volatiles. Cells of the sensilla coeloconica responded to aliphatic aldehydes and acids. Eight volatile organic compounds emitted by Opuntia stricta, a host plant of C. cactorum, were identified using gas chromatography–mass spectrometry, β-caryophyllene being the major compound. Five compounds identified by gas chromatography in the headspace of O. stricta elicited responses in olfactory receptor cells of C. cactorum, nonanal being the most active compound and therefore a candidate attractant of C. cactorum. [ABSTRACT FROM AUTHOR]

The moth Cactoblastis cactorum (Berg), the poster child of weed biological control in Australia, has recently invaded the United States and threatens native cacti. Concern is greatest for the endangered semaphore cactus, Opuntia corallicola, of which only two known populations exist in the wild. We made three separate outplantings of 0. corallicola, designed to bolster the number of extant cacti and to test the effectiveness of three different treatments to protect the cacti from Cactoblastis. In one outplanting, we tested the associational susceptibility hypothesis and found that cacti planted more than 20 in away from the common prickly pear cactus, Opuntia stricta, which act as a reservoir of Cactoblastis, were just as frequently attacked and killed by Cactoblastis as cacti planted within S m. In addition, Cactoblastis attack was greater in the shade than in the sun. In the second outplanting, we minimized the attack from Cactoblastis by using protective cages planted at least 500 m from 0. stricta in areas not inhabited by cacti. Cages attracted the attention of local animals, which destroyed the cages and trampled the cacti inside to death. Crown rot caused high mortality in this outplanting. In the third outplanting, again conducted at least 500 m away from 0. stricta, fertillzation did not reduce crown rot mortality. We suggest that increasing populations of 0. corallicola in florida, by means of outplantings, will remain a challenge because of death from Cactoblastis when planted in areas where cacti normally grow and because of death from crown rot in areas where they do not. Because Cactoblastis is moving rapidly northward and westward and has already reached Charleston, South Carolina, rare cacti in the rest of the U.S. Southeast may be in danger. Eventually, many cactus species in the U.S. South, Southwest, and Mexico will likely be threatened by this moth. [ABSTRACT FROM AUTHOR]

Cactoblastis cactorum (Berg) (Lepidoptera: Pyralidae), the poster child of biological control, has recently invaded the United States. The first US record was at Big Pine Key, Florida, in 1989. Since then it has moved rapidly northward into South Carolina. Fears are high that it will disperse, either on its own, or with human help, into the US desert southwest and Mexico. There are at least 31 species of prickly pear in the US that are likely to be attacked by Cactoblastis and 56 species in Mexico. As well as the threat to wild cacti, there are over 250,000 ha of Opuntia plantations in Mexico that support a thriving agricultural industry, most of which is centered on harvesting fruits or pads. Possible control measures include classical biological control using parasitoids or pathogens from South America, chemical control or F1 sterility, as has been used successfully for the codling moth. However, most of these options appear to have insurmountable difficulties. Classical biological control raises the fear of further non-target effects of natural enemies on native cactus herbivores. Chemical control has potential non-target effects on other (rare) insects and is expensive. F1 sterility is also expensive and is not self-sustaining, requiring considerable and continual human input. Nevertheless, research on control options is vital as is further work on the rate of spread and impact of Cactoblastis in the United States Southeast, so that we can be as well prepared as possible to deal with this threat when it arrives in Arizona, California, and Mexico. [ABSTRACT FROM AUTHOR]