The South American tomato pinworm, Tuta absoluta (Meyrick), is native to the western Neotropics. After invading Spain in 2006, it spread rapidly throughout Afro-Eurasia and has become a major threat to world tomato production. Integrated pest management (IPM) strategies have been developed, but widespread insecticide use has caused selection for insecticide resistance as well as undesirable effects on key beneficial arthropods. Augmentation and conservation biological control relying on omnivorous mirid predators has proved successful for management of T. absoluta, where implementation is dependent on abiotic, biotic (e.g., alternative prey), and anthropogenic factors (e.g., pesticides). Research has been carried out on larval parasitoids, showing potential for further development of sustainable control. The development of resistant tomato varieties is ongoing, but they are not commercially available yet. Knowledge gaps remain to be filled to optimize IPM packages on tomato crops and to help prevent furth...

Ecology, Worldwide Spread, and Management of the Invasive South American Tomato Pinworm, Tuta absoluta: Past, Present, and Future

The South American tomato leafminer, Tuta absoluta Meyrick (Lepidoptera: Gelechiidae), is an invasive Neotropical pest. After its first detection in Europe, it rapidly invaded more than 30 Western Palaearctic countries becoming a serious agricultural threat to tomato production in both protected and open-field crops. Among the pest control tactics against exotic pests, biological control using indigenous natural enemies is one of the most promising. Here, available data on the Afro-Eurasian natural enemies of T. absoluta are compiled. Then, their potential for inclusion in sustainable pest control packages is discussed providing relevant examples. Collections were conducted in 12 countries, both in open-field and protected susceptible crops, as well as in wild flora and/or using infested sentinel plants. More than 70 arthropod species, 20 % predators and 80 % parasitoids, were recorded attacking the new pest so far. Among the recovered indigenous natural enemies, only few parasitoid species, namely, some eulophid and braconid wasps, and especially mirid predators, have promising potential to be included in effective and environmentally friendly management strategies for the pest in the newly invaded areas. Finally, a brief outlook of the future research and applications of indigenous T. absoluta biological control agents are provided.

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Natural enemies of the South American moth, Tuta absoluta, in Europe, North Africa and Middle East, and their potential use in pest control strategies

Deep leaning approach with colorimetric spaces and vegetation indices for vine diseases detection in UAV images

To support management decisions, molecular characterization of data and geo-reference of incidence records of Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) were combined with data on the biology and ecology of the pest to estimate its climatic suitability and potential spread at regional and global scale. A CLIMEX model was developed and used for the global prediction of current and future climate-induced changes in the distributional shifts of T. absoluta. Results revealed that temperature and moisture characterized T. absoluta population growth while the pest ability to survive the cold, hot, wet and dry stress conditions are the primary characteristics defining its range frontiers. Simulated irrigation also played an important role in the model optimization. Model predictions suggest that T. absoluta represents an important threat to Africa, Asia, Australia, Northern Europe, New Zealand, Russian Federation and the United States of America (USA). Under climate change context, future predictions on distribution of T. absoluta indicated that the invasive nature of this pest will result in significant crop losses in certain locations whereas some parts of Africa may witness diminution in ranges. The following scenarios may occur: 1) T. absoluta damage potential may upsurge moderately in areas of Africa where the pest currently exists; 2) a range diminution in temperate to Sahel region with moderate upsurge in damage potential; 3) a range expansion in tropical Africa with reasonable upsurge of damage potential. These possible outcomes could be explained by the fact that the continent is already warm, with the average temperature in majority of localities near the threshold temperatures for optimal development and survival of T. absoluta. Outputs from this study should be useful in helping decision-makers in their assessment of site-specific risks of invasion and spread of T. absoluta with a view to developing appropriate surveillance, phytosanitary measures and management strategies.

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Identification and Risk Assessment for Worldwide Invasion and Spread of Tuta absoluta with a Focus on Sub-Saharan Africa: Implications for Phytosanitary Measures and Management

The African citrus psyllid (AfCP), Trioza erytreae (Del Guercio) (Hemiptera, Triozidae), recently has been found in northwestern Iberian Peninsula (Spain and Portugal). The insect is an important citrus pest because it transmits the phloem-limited bacteria Candidatus liberibacter spp., the causal agents of huanglongbing (HLB), the most devastating disease affecting citrus. The bacteria can be acquired by both AfCP nymphs and adults, but only adults can spread the pathogen. HLB has been detected neither in the Iberian Peninsula nor in Madeira and the Canary Islands, where the psyllid was recorded more than a decade ago. In the latter European islands, the eradication programmes of AfCP failed. Chemical-based control strategies are costly, could trigger increases of other pests and may have negative impact on the environment. The adoption of rigorous quarantine measures is extremely important for areas free of the psyllid. These measures likely represent the most effective prevention strategies for psyllid containment, because the geographic expansion of psyllids in citrus is mainly due to human activities, especially by the transport of plants and freshly harvested fruits from infested to uninfested areas. Many natural enemies may contribute to the reduction of its populations and consequent spread; hence, conservation biological control should be emphasised, especially in areas where the psyllid is not abundant. Classical biological control programmes should also be implemented in HLB-free areas by introducing effective AfCP parasitoids. In areas where HLB is detected, biological control is difficult to apply, and a rigorous chemical control program targeting the psyllid could complement this strategy. This report is an updated review of AfCP and strategies for its control in anticipation of its possible further spread in Europe and the Mediterranean Basin.

A review on Trioza erytreae (African citrus psyllid), now in mainland Europe, and its potential risk as vector of huanglongbing (HLB) in citrus

Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) is a serious threat to tomato (Solanum lycopersicum L.) crops in South America. In Europe, after its first detection in Spain in 2006, it rapidly spread through the Mediterranean basin, reaching Italy 2 yr later. The aim of our work was to find indigenous effective biological control agents and to evaluate their potential role in the control of larval populations of T. absoluta in controlled conditions. Nine species of larval parasitoids emerged from field-collected tomato leaves infested by T. absoluta. The most abundant, Necremnus near artynes (Walker) and Necremnus near tidius (Walker) (Hymenoptera:Eulophidae), were tested in laboratory parasitism trials. Furthermore, because the species N. artynes and N. tidius are each reported in literature as an ectoparasitoid of Cosmopterix pulchrimella Chambers (Lepidoptera: Cosmopterigidae) on upright pellitory plants, olfactometer bioassays were performed to assess the response of our parasitoids to th...

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Adaptation of indigenous larval parasitoids to Tuta absoluta (Lepidoptera: Gelechiidae) in Italy

Torymus sinensis Kamijo (Hymenoptera: Torymidae) has been released throughout Italy for biological control of the chestnut gall wasp. In response to concern about non-target impacts associated with the introduction of this exotic biological control agent, this study aimed at investigating T. sinensis’s host range. In total, 1371 non-target galls were collected in north-central Italy in a two-year period, representing nine different species. Collections were carried out on common oak, downy oak, sessile oak, Turkey oak, and wild rose. A total of five native torymid species were recorded from the non-target galls (Megastigmus dorsalis, Torymus affinis, T. auratus, T. flavipes, and T. geranii), and three ♂♂ T. sinensis individuals emerged from Biorhiza pallida galls collected in the field. Under controlled conditions, most of the non-target galls tested were not suitable hosts for oviposition. T. sinensis females only laid eggs on Andricus curvator. In olfactometer bioassays, higher numbers of T. sinensis females showed more interest to the chestnut galls compared to non-target hosts. This data highlights how T. sinensis has a broader ecological host range than reported in the literature and that it is attracted by non-target hosts other than D. kuriphilus.

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Non-target host risk assessment for the parasitoid Torymus sinensis

A post-release study was performed to assess the impact of Torymus sinensis (Hymenoptera: Torymidae), the biological control agent of Dryocosmus kuriphilus (Hymenoptera: Cynipidae), on native cynipid gall inducers in Italy. In total, 14,512 non-target galls were collected, corresponding to seven genera: Andricus, Aphelonyx, Biorhiza, Cynips, Diplolepis, Neuroterus, and Synophrus, and 8708 chalcid parasitoids were recorded. The Torymidae family accounted for about 30%, and Bootanomyia (=Megastigmus) dorsalis, Torymus affinis and T. flavipes were the most represented species. A total of 116 T. sinensis emerged from 15 different oak galls, mainly Andricus curvator and A. inflator. In controlled conditions, oviposition was recorded on A. cydoniae, A. grossulariae and A. lucidus, while no mating with native congeneric species occurred. This paper confirms the realised host-range expansion by T. sinensis. Even if it were extremely difficult to evaluate its magnitude, the impact appears minimal, and an occasional feeding with no changes in the distribution or abundance of non-target hosts is expected.

Post-release evaluation of non-target effects of Torymus sinensis , the biological control agent of Dryocosmus kuriphilus in Italy

Torymus sinensis Kamijo (Hymenoptera: Torymidae) is a biological control agent of the chestnut gall wasp Dryocosmus kuriphilus Yasumatsu (Hymenoptera: Cynipidae). It is reported in the literature as univoltine, but in NW Italy it exhibits a prolonged diapause mainly as late instar larva. Diapause is extended for 12 months, and adults emerge in April as usual, showing a two-year life cycle. Second year emergence individuals are able to mate, and the presence of mature eggs was confirmed in females which parasitised fresh chestnut galls, showing the same parasitism behaviour as first year emergence individuals. Both sexes of second year emergence individuals proved to be smaller than the univoltine ones according to ovipositor sheath length, pronotum width, and hind tibia length. Proving evidence of the extended diapause plays an important role for the establishment of T. sinensis especially in the first years after its release. Future studies are needed to clarify the factors which trigger off this response.

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Novel insight in the life cycle of Torymus sinensis, biocontrol agent of the chestnut gall wasp

The biocontrol agent Torymus sinensis has been released into Japan, the USA, and Europe to suppress the Asian chestnut gall wasp, Dryocosmus kuriphilus. In this study, we provide a quantitative assessment of T. sinensis effectiveness for suppressing gall wasp infestations in Northwest Italy by annually evaluating the percentage of chestnuts infested by D. kuriphilus (infestation rate) and the number of T. sinensis adults that emerged per 100 galls (emergence index) over a 9-year period. We recorded the number of T. sinensis adults emerging from a total of 64,000 galls collected from 23 sampling sites. We found that T. sinensis strongly reduced the D. kuriphilus population, as demonstrated by reduced galls and an increased T. sinensis emergence index. Specifically, in Northwest Italy, the infestation rate was nearly zero 9 years after release of the parasitoid with no evidence of resurgence in infestation levels. In 2012, the number of T. sinensis females emerging per 100 galls was approximately 20 times higher than in 2009. Overall, T. sinensis proved to be an outstanding biocontrol agent, and its success highlights how the classical biological control approach may represent a cost-effective tool for managing an exotic invasive pest.

Ester Ferrari

Papers

Adaptation of indigenous larval parasitoids to Tuta absoluta (Lepidoptera: Gelechiidae) in Italy

Non-target host risk assessment for the parasitoid Torymus sinensis

Post-release evaluation of non-target effects of Torymus sinensis , the biological control agent of Dryocosmus kuriphilus in Italy

Novel insight in the life cycle of Torymus sinensis, biocontrol agent of the chestnut gall wasp

Effectiveness of Torymus sinensis: a successful long-term control of the Asian chestnut gall wasp in Italy