Thaumastocoris peregrinus is a recently introduced invertebrate pest of non-native Eucalyptus plantations in the Southern Hemisphere. It was first reported from South Africa in 2003 and in Argentina in 2005. Since then, populations have grown explosively and it has attained an almost ubiquitous distribution over several regions in South Africa on 26 Eucalyptus species. Here we address three key questions regarding this invasion, namely whether only one species has been introduced, whether there were single or multiple introductions into South

A phylogeographic analysis inferred from the partial mitochondrial cytochrome oxidase subunit I gene (433 bp) was performed with 22 populations of Diaphorina citri Kuwayama collected in the Americas and one in the Pacific. Eight populations from four countries in South America, 14 from four countries in North America, and one from Hawaii were analyzed. Twenty-three haplotypes (hp) were identified and they fell into two groups: hp1–8 were identified in South America (group 1) and hp9–23 were identified in North America and Hawaii (group 2). Hp1 and nine were present in the highest frequencies within each population and within their group, 81 and 85% for group 1 and group 2, respectively. A diagnostic nucleotide at position 48 was identified that allowed for the discrimination of the two groups; in addition, no haplotypes were shared between the two groups. An analysis of molecular variance uncovered significant genetic structure (φCT = 0.733; P < 0.001) between the two groups of the Americas. Two haplotype networks (ParsimonySplits and Statistical Parsimony) discriminated the two groups and both networks identified hp1 and nine as the predicted ancestral or founding haplotypes within their respective group. The data suggest that two separate introductions or founding events of D. citri occurred in the Americas, one in South America and one in North America. Furthermore, North America and Hawaii appear to share a similar source of invasion. These data may be important to the development of biological control programs against D. citri in the Americas.

Biological control has traditionally simplified the view of trophic relationships between herbivorous pests and their natural enemies in agriculture. The success or failure of this pest management strategy is still mainly attributed to the ability of a few key natural enemies to suppress the pest density. For example, successful regulation of the California red scale (Aonidiella aurantii), a key citrus pest, is generally credited to specific parasitoids of the Aphytis genus. Currently, research is revealing how herbivore regulation in agroecosystems can be alternatively achieved with a greater number of trophic associations within the system. The goals of the present study were as follows: i) to unravel species‐specific trophic links between A. aurantii and its natural enemies in citrus agroecosystems, and ii) to assess their contribution to control of A. aurantii. Predation and parasitism of this herbivorous pest were assessed through exclusion experiments. Species‐specific trophic links between this herbivorous pest and its natural enemies were studied using gut‐content analysis of field‐collected predators employing prey‐specific DNA molecular markers. Relative predation rates of the species involved in A. aurantii regulation were estimated. Predation was found to be the main biotic component of A. aurantii mortality, causing reductions of more than 75% in recently settled cohorts. Aonidiella aurantii DNA was detected in the digestive system of 11 species of predators. Generalist and stenophagous predators, mainly associated with other citrus pests such as aphids, proved to be the most important biological control agents of this pest. Complex trophic relationships, such as apparent competition between two key citrus pests, were revealed. The present study highlights the role of predation as biotic mortality factor of key pests in perennial agroecosystems, wherein it is a rich complex of indigenous or naturalized generalist predators that are primarily responsible for this mortality. The results herein presented may therefore offer another perspective on the biological control of one of the key world‐wide citrus pests, at least in those regions where specific parasitoids are not able to successfully regulate the scale populations.

Sexual maturation of Anastrepha fraterculus is a long process. Methoprene (a mimic of juvenile hormone) considerably reduces the time for sexual maturation in males. However, in other Anastrepha species, this effect depends on protein intake at the adult stage. Here, we evaluated the mating competitiveness of sterile laboratory males and females that were treated with methoprene (either the pupal or adult stage) and were kept under different regimes of adult food, which varied in the protein source and the sugar:protein ratio. Experiments were carried out under semi-natural conditions, where laboratory flies competed over copulations with sexually mature wild flies. Sterile, methoprene-treated males that reached sexual maturity earlier (six days old), displayed the same lekking behaviour, attractiveness to females and mating competitiveness as mature wild males. This effect depended on protein intake. Diets containing sugar and hydrolyzed yeast allowed sterile males to compete with wild males (even at a low concentration of protein), while brewer´s yeast failed to do so even at a higher concentration. Sugar only fed males were unable to achieve significant numbers of copulations. Methoprene did not increase the readiness to mate of six-day-old sterile females. Long pre-copulatory periods create an additional cost to the management of fruit fly pests through the sterile insect technique (SIT). Our findings suggest that methoprene treatment will increase SIT effectiveness against A. fraterculus when coupled with a diet fortified with protein. Additionally, methoprene acts as a physiological sexing method, allowing the release of mature males and immature females and hence increasing SIT efficiency.

1 The avoidance of parasitized or infested hosts, which is a common phenomenon in parasitic wasps and phytophagous insects, may act both intra-and interspecifically. Most studies on chemically-mediated avoidance of interspecific competition in insects have been conducted at the individual level. The role of this behaviour on the spatial distribution of offspring of sympatric species with overlapping host ranges has been overlooked. 2 In the present study, two analytical approaches were used to investigate the co-infestation patterns of the fruit flies Anastrepha fraterculus (Wiedemann) (Diptera: Tephritidae) and Ceratitis capitata (Wiedemann) (Diptera: Tephritidae), aiming to unravel the importance of cross-species infestation recognition in nature. 3 Guava fruit were sampled in an area of coexistence of these two fruit flies and individually categorized as non-infested, infested by one of the species or infested by both species. The frequency of each type of fruit was compared with the frequency distributions expected under two models: an independent oviposition model and a competition avoidance model. As an alternative approach, co-occurrence patterns were evaluated using null models. 4 The results showed that avoidance of competition could be occurring in nature, although only in a few cases in which infestation levels are moderate. The two approaches revealed that the spatial scale has significant impact on the resulting co-occurrence patterns, such that opposite behaviours towards infested fruit are inferred at the largest (mainly aggregated oviposition pattern) versus the smallest scale (mainly independent oviposition pattern). 5 For the system under investigation, our findings suggest that the avoidance of infested fruit does not contribute, or at least not strongly, to the coexistence of the two species.

The Spirea citrus aphid, Aphis spiraecola Patch, and the cotton aphid, Aphis gossypii Glover (Hemiptera: Aphididae), are key pests of clementine mandarines in the Mediterranean basin. Severity of aphid infestations is determined by environmental variables, host plant phenology patterns, and the biological control exerted by their associated natural enemies. However, there is no information about the role these limiting and regulating factors play. Aphid densities, citrus phenology, and associated predators that overwinter in the crop were monitored weekly throughout two flush growth periods (February to July) in four clementine mandarin groves; relationships between these parameters and environmental variables (temperature and precipitation) were studied. Our results show exponential increase in aphid infestation levels to coincide with citrus phenological stages B3 and B4; shoots offer more space and nutritional resources for colony growth at these stages. Duration of these phenological stages, which was mediated by mean temperature, seems to importantly determine the severity of aphid infestations in the groves. Among those studied, the micro-coccinellids, mostly Scymnus species, were the only group of predators with the ability to efficiently regulate aphid populations. These natural enemies had the highest temporal and spatial demographic stability. Aphid regulation success was only achieved through early presence of natural enemies in the grove, at the aphid colonization phase. Our results suggest that conservation strategies aimed at preserving and enhancing Scymnus sp. populations may make an important contribution to the future success of the biological control of these key citrus pests.

Predator-prey interactions are not static, but spatially and temporally dynamic. In addition to the climatic conditions and the prey density, the dynamics of predator populations may be influenced by the suitability of their diet. Therefore, to better understand aphid predator-prey relationships within food webs, it is necessary to know how their life history traits are affected by diet quality. In this research, under laboratory conditions, the suitability of the two most abundant aphid species in citrus agroecosystems of the Western Mediterranean basin, Aphis gossypii and A. spiraecola were evaluated for two of their principle natural enemies, the coccinellid predators Scymnus subvillosus and S.interruptus. The intrinsic rate of increase of S. subvillosus was found to be higher than that of S. interruptus regardless of the type of prey consumed. Some biological parameters of S. interruptus were lower when they were exclusively fed A. spiraecola; as opposed to when only fed A. gossypii. These differences were not found with S. subvillosus. When a mixed diet of both aphids was offered, the fitness of both predators was higher than when they were each fed only a single aphid species. These laboratory observations were further confirmed under field conditions, wherein S. subvillosus abundance was greater in those colonies where A. spiraecola was predominant. On the other hand both, S. subvillosus and S. interruptus were found equally in A. gossypii colonies. Implications of these results for the biological control of aphids in this crop are discussed.

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