Homobrassinolide Delays Huanglongbing Progression in Newly Planted Citrus (Citrus sinensis) Trees.

Huanglongbing (HLB), or citrus greening, is a devastating disease impacting citrus trees worldwide, with severe effects particularly noted in Florida. Current strategies to combat HLB focus on aggressive replanting, despite the high susceptibility of young trees to infection. In this context, it is critical to explore agronomic practices that can enhance the health and resistance of young citrus trees to HLB. Here, we demonstrate that treatment with homobrassinolide (HBr), a type of brassinosteroid, in newly planted citrus (Citrus sinensis) trees can delay HLB infection and improve tree health amidst the high psyllid pressure conditions endemic to Florida. Our study reveals a significant reduction in HLB infection rates in HBr-treated trees compared to control trees, with only 25% of treated trees testing positive for HLB by six months, in contrast to 100% infection in untreated trees. This delay in infection may be attributed to HBr inducing an immune response and negatively impacting psyllid performance, as subsequently demonstrated in a greenhouse experiment. Our findings suggest that HBr applications could serve as a viable strategy to enhance the resilience of citrus production against HLB, underscoring the need for further investigation into their mechanisms of action and potential role in a comprehensive pest and disease management strategy.

RNAi-mediated silencing of Mediterranean fruit fly (Ceratitis capitata) endogenous genes using orally-supplied double-stranded RNAs produced in Escherichia coli.

BACKGROUND: The Mediterranean fruit fly (medfly), Ceratitis capitata Wiedemann, is a major pest affecting fruit and vegetable production worldwide, whose control is mainly based on insecticides. Double-stranded RNA (dsRNA) able to down-regulate endogenous genes, thus affecting essential vital functions via RNA interference (RNAi) in pests and pathogens, is envisioned as a more specific and environmentally-friendly alternative to traditional insecticides. However, this strategy has not been explored in medfly yet. RESULTS: Here, we screened seven candidate target genes by injecting in adult medflies gene-specific dsRNA hairpins transcribed in vitro. Several genes were significantly down-regulated, resulting in increased insect mortality compared to flies treated with a control dsRNA targeting the green fluorescent protein (GFP) complementary DNA (cDNA). Three of the dsRNAs, homologous to the beta subunit of adenosine triphosphate (ATP) synthase (ATPsynbeta), a vacuolar ATPase (V-ATPase), and the ribosomal protein S13 (RPS13), were able to halve the probability of survival in only 48 h after injection. We then produced new versions of these three dsRNAs and that of the GFP control as circular molecules in Escherichia coli using a two-self-splicing-intron-based expression system and tested them as orally-delivered insecticidal compounds against medfly adults. We observed a significant down-regulation of V-ATPase and RPS13 messenger RNAs (mRNAs) (approximately 30% and 90%, respectively) compared with the control medflies after 3 days of treatment. No significant mortality was recorded in medflies, but egg laying and hatching reduction was achieved by silencing V-ATPase and RPS13. CONCLUSION: In sum, we report the potential of dsRNA molecules as oral insecticide in medfly. © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

The Dual Benefit of Plant Essential Oils against Tuta absoluta.

Plant essential oils (PEOs) are being studied as a potential alternative to synthetic pesticides in agriculture. PEOs have the potential to control pests both directly, by being toxic or repellent to pests, and indirectly, by activating plant's defense mechanisms. In this study, the effectiveness of five PEOs (Achillea millefolium, Allium sativum, Rosmarinus officinallis, Tagetes minuta, and Thymus zygis) on controlling Tuta absoluta and their impact on the predator Nesidiocoris tenuis was examined. The study revelead that PEOs from A. millefolium and A. sativum-sprayed plants significantly reduced the number of T. absoluta-infested leaflets and did not affect the establishment and reproduction of N. tenuis. Additionally, the spraying of A. millefolium and A. sativum increased the expression of defense genes in the plants, triggering the release of herbivory-induced plant volatiles (HIPVs), such as C6 green leaf volatiles, monoterpenes, and aldehydes, which can be messengers in tritrophic interactions. The results suggest that PEOs from A. millefolium and A. sativum can provide a dual benefit for controlling arthropod pests, as they can directly exhibit toxicity against these pests while also activating plant defense mechanisms. Overall, this study provides new insights into using PEOs as a sustainable solution for controlling pests and diseases in agriculture, by reducing synthetic pesticides and promoting the use of natural predators.

Induction of Glandular Trichomes to Control Bemisia tabaci in Tomato Crops: Modulation by the Natural Enemy Nesidiocoris tenuis.

Whitefly-transmitted viruses are one of the biggest threats to tomato (Solanum lycopersicum) growing worldwide. Strategies based on the introgression of resistance traits from wild relatives are promoted to control tomato pests and diseases. Recently, a trichome-based resistance characterizing the wild species Solanum pimpinellifolium was introgressed into a cultivated tomato. An advanced backcross line (BC5S2) exhibiting the presence of acylsugar-associated type IV trichomes, which are lacking in cultivated tomatoes, was effective at controlling whiteflies (Hemiptera: Aleyrodidae) and limiting the spread of whitefly-transmitted viruses. However, at early growth stages, type IV trichome density and acylsugar production are limited; thus, protection against whiteflies and whitefly-transmitted viruses remains irrelevant. In this work, we demonstrate that young BC5S2 tomato plants feeding-punctured by the zoophytophagous predator Nesidiocoris tenuis (Hemiptera: Miridae) displayed an increase (above 50%) in type IV trichome density. Acylsugar production was consistently increased in N. tenuis-punctured BC5S2 plants, which was more likely associated with upregulated expression of the BCKD-E2 gene related to acylsugar biosynthesis. In addition, the infestation of BC5S2 plants with N. tenuis effectively induced the expression of defensive genes involved in the jasmonic acid signaling pathway, resulting in strong repellence to Bemisia tabaci and attractiveness to N. tenuis. Thus, through preplant release of N. tenuis in tomato nurseries carried out in some integrated pest management programs, type IV trichome-expressing plants can be prepared to control whiteflies and whitefly-transmitted viruses at early growth stages. This study emphasizes the advantage of reinforcing constitutive resistance using defense inducers to guarantee robust protection against pests and transmitted viruses.

Sesame as an Alternative Host Plant to Establish and Retain Predatory Mirids in Open-Field Tomatoes.

The silverleaf whitefly (Bemisia tabaci) and the South America tomato pinworm (Tuta absoluta) are two of the most destructive pests of tomato. Open-field tomato production frequently relies on chemical treatments, which has been shown to lead to pesticide resistance. The integration of biological control using predatory mirid bugs is an effective alternative method for managing these pests. However, methods to establish and maintain populations of zoophytophagous mirids are not adequately described. We explored the potential use of two mirids naturally occurring in Florida, Nesidiocoris tenuis and Macrolophus praeclarus. We conducted 6 field experiments over 4 consecutive years to develop a strategy to maintain the mirids. Pre-plant inoculation of tomato plants did not lead to their establishment, likely due to the low prevalence of prey. We explored the use of sesame (Sesamum indicum) to retain the mirids. Intercropping sesame maintained the populations of N. tenuis throughout the duration of the crop. Macrolophus praeclarus never established in any of the open-field experiments. Nesidiocoris tenuis damage was minimal (<1 necrotic ring/plant) and mirid damage was reduced in the presence of sesame. Our results show that intercropping sesame may provide a means to utilize mirids to manage B. tabaci, an established pest, and provide options to tomato growers should T. absoluta invade USA.

Insights into the origin of the invasive populations of Trioza erytreae in Europe using microsatellite markers and mtDNA barcoding approaches.

The African citrus psyllid Trioza erytreae is one of the major threats to citrus industry as the vector of the incurable disease known as huanglongbing (HLB) or citrus greening. The psyllid invaded the northwest of the Iberian Peninsula 6 years ago. The invasion alarmed citrus growers in the Mediterranean basin, the largest citrus producing area in Europe, which is still free of HLB. Before our study, no research had been carried out on the genetic diversity of T. erytreae populations that have invaded the Iberian Peninsula and the archipelagos of the Macaronesia (Madeira and the Canary Islands). In this study, combining microsatellites markers and mtDNA barcoding analysis, we characterize the genetic diversity, structure and maternal relationship of these new invasive populations of T. erytreae and those from Africa. Our results suggest that the outbreaks of T. erytreae in the Iberian Peninsula may have derived from the Canary Islands. The populations of T. erytreae that invaded Macaronesia and the Iberian Peninsula are likely to have originated from southern Africa. We anticipate our results to be a starting point for tracking the spread of this invasive pest outside of Africa and to be important for optimizing contingency and eradication plans in newly invaded and free areas.

Changes in plant responses induced by an arthropod influence the colonization behavior of a subsequent herbivore.

BACKGROUND: Plants in nature can be sequentially attacked by different arthropod herbivores. Feeding by one arthropod species may induce plant-defense responses that might affect the performance of a later-arriving herbivorous species. Understanding these interactions can help in developing pest-management strategies. In tomato, the sweet-potato whitefly Bemisia tabaci and the two-spotted spider mite Tetranychus urticae are key pests that frequently cohabit on the same plant. We studied whether colonization by one species can either facilitate or impede later colonization of tomato plants by conspecific or heterospecific individuals. RESULTS: B. tabaci females showed a strong preference for and increased oviposition on plants previously colonized by conspecifics. In contrast, plants infested with T. urticae repelled B. tabaci females and reduced their oviposition rate by 86%. Although females of T. urticae showed no preference between conspecific-infested or uninfested plants, we observed a 50% reduction in the number of eggs laid on conspecific-infested plants. Both herbivorous arthropods up-regulated the expression of genes involving the jasmonic acid and abscisic acid pathways, increasing emissions of fatty-acid derivatives, but only B. tabaci increased the expression of genes related to the salicylic acid pathway and the total amount of phenylpropanoids released. Terpenoids were the most abundant compounds in the volatile blends; many terpenoids were emitted at different rates, which might have influenced the arthropods' host selection. CONCLUSION: Our results indicate that B. tabaci infestation facilitated subsequent infestations by conspecifics and mites, while T. urticae infestation promoted herbivore-induced resistance. Based on both the molecular and behavioral findings, a novel sustainable pest-management strategy is discussed.

Biological traits of the predatory mirid Macrolophus praeclarus, a candidate biocontrol agent for the Neotropical region.

The predatory mirid Macrolophus praeclarus is widely distributed throughout the Americas, and is reported to prey upon several horticultural pest species. However, little is known about its biology, thermal requirements, crop odour preferences, phytophagy, and capability to induce defensive responses in plants. When five temperatures studied (20, 25, 30, 33 and 35°C) were tested and Ephestia kuehniella was used as prey, the developmental time from egg to adult on tomato, was longest at 20°C (56.3 d) and shortest at 33°C (22.7 d). The ability of nymphs to develop to adults decreased as the temperature increased, with the highest number of nymphs reaching the adult stage at 20°C (78.0%) and lowest at 35°C (0%). The lower and upper developmental thresholds were estimated at 11.2° and 35.3°C, respectively. The maximum developmental rate occurred at 31.7°C and the thermal constant was 454.0 ± 8.1 degree days. The highest predation rate of E. kuehniella eggs was obtained at 30°C. In Y-tube olfactory choice tests, M. praeclarus selected tomato, sweet pepper and eggplant odours more frequently than no plant control treatment. Macrolophus praeclarus feeding did not damage tomato plants compared to another zoophytophagous mirid, Nesidiocoris tenuis, which caused necrotic rings. The phytophagy of M. praeclarus induced defensive responses in tomato plants through the upregulation of the jasmonic acid metabolic pathway. The implications of the findings for using M. praeclarus in tomato biological control programmes in the Americas are discussed.

Use of zoophytophagous mirid bugs in horticultural crops: Current challenges and future perspectives.

In recent years, the use of predatory mirid bugs (Hemiptera: Miridae) in horticultural crops has increased considerably. Mirid bugs are zoophytophagous predators, that is, they display omnivorous behavior and feed on both plants and arthropods. Mirid bugs feed effectively on a wide range of prey, such as whiteflies, lepidopteran eggs and mites. In addition, the phytophagous behavior of mirid bugs can activate defenses in the plants on which they feed. Despite the positive biological attributes, their use still presents some constraints. Their establishment and retention on the crop is not always easy and economic plant damage can be caused by some mirid species. In this review, the current strategies for using zoophytophagous mirid bugs in horticultural crops, mainly Nesidiocoris tenuis, Macrolophus pygmaeus and Dicyphus hesperus, are reviewed. We discuss six different approaches which, in our opinion, can optimize the efficacy of mirids as biocontrol agents and help expand their use into more areas worldwide. In this review we (i) highlight the large number of species and biotypes which are yet to be described and explore their applicability, (ii) present how it is possible to take advantage of the mirid-induced plant defenses to improve pest management, (iii) argue that genetic selection of improved mirid strains is feasible, (iv) explore the use of companion plants and the use of alternative foods to improve the mirid bug management, and finally (vi) discuss strategies for the expansion of mirid bugs as biological control agents to horticultural crops other than just tomatoes. © 2020 Society of Chemical Industry.

Biological Control Potential and Drawbacks of Three Zoophytophagous Mirid Predators against Bemisia tabaci in the United States.

Miridae (Hemiptera) of the tribe Dicyphini are important zoophytophagous predators use to control pest arthropods in vegetable crops. However, the risk that their herbivory may cause economic damage could hinder their application as useful biocontrol agents and may limit the likelihood they would meet regulatory requirements for importation. We conducted field cage studies to assess the predation capacity and tomato plant damage of three mirid species established in south USA, a known biocontrol agent (Nesidiocoris tenuis), and two native species (Macrolophus praeclarus and Engytatus modestus). All three species significantly reduced the number of whiteflies (Bemisia tabaci) on tomato plants compared to tomato plants without mirids. More damage, evaluated as the number of necrotic rings, was observed on tomato plants with E. modestus and N. tenuis compared to M. praeclarus. In our experiments that included sesame plants (Sesamum indicum) with tomato plants, mirid numbers increased despite a low number of prey, thus showing a benefit of the plant-feeding habit of these predators. USA's established mirids may therefore prove to be immediately available biological agents for the management of present and future tomato pests.

Genetic Variation in the Feeding Behavior of Isofemale Lines of Nesidiocoris tenuis.

Zoophytophagous predators provide biocontrol services in various major crops of modern horticulture due to the combination of its predatory capacity and the induction of plant defenses derived from its phytophagy. However, under certain conditions of prey scarcity, these natural enemies can inflict plant damage. Exploitation of genetic variation and subsequent selective breeding on foraging traits is a potential alternative to overcome this inconvenience. In this study, we quantified the genetic variation of phytophagy and zoophagy of Nesidiocoristenuis (Reuter) (Hemiptera: Miridae), a zoophytophagous predator widely used in tomato crops to suppress key pests. We compared nine isofemale lines on their capacity to produce necrotic rings and wilting on tomato plants as a proxy for phytophagy, as well as their efficacy to prey on Ephestia kuehniella Zeller (Lepidoptera: Pyralidae) eggs, as a proxy for zoophagy. Differences between isofemale lines in phytophagy and zoophagy indicated a genetic basis. Variation found in the zoophagy levels was larger than that in phytophagy levels. Our results showed that there is a genetic basis for the variation observed in the feeding behavior of isofemale lines of N.tenuis, highlighting the potential importance of selective breeding for such traits of biocontrol interest.

Next-generation biological control: the need for integrating genetics and genomics.

Biological control is widely successful at controlling pests, but effective biocontrol agents are now more difficult to import from countries of origin due to more restrictive international trade laws (the Nagoya Protocol). Coupled with increasing demand, the efficacy of existing and new biocontrol agents needs to be improved with genetic and genomic approaches. Although they have been underutilised in the past, application of genetic and genomic techniques is becoming more feasible from both technological and economic perspectives. We review current methods and provide a framework for using them. First, it is necessary to identify which biocontrol trait to select and in what direction. Next, the genes or markers linked to these traits need be determined, including how to implement this information into a selective breeding program. Choosing a trait can be assisted by modelling to account for the proper agro-ecological context, and by knowing which traits have sufficiently high heritability values. We provide guidelines for designing genomic strategies in biocontrol programs, which depend on the organism, budget, and desired objective. Genomic approaches start with genome sequencing and assembly. We provide a guide for deciding the most successful sequencing strategy for biocontrol agents. Gene discovery involves quantitative trait loci analyses, transcriptomic and proteomic studies, and gene editing. Improving biocontrol practices includes marker-assisted selection, genomic selection and microbiome manipulation of biocontrol agents, and monitoring for genetic variation during rearing and post-release. We conclude by identifying the most promising applications of genetic and genomic methods to improve biological control efficacy.

Development and Validation of Real-Time PCR Method to Estimate Stored Sperm in the Spermathecae of Ceratitis capitata (Diptera: Tephritidae).

The development of polymerase chain reaction (PCR) markers to identify the Y chromosome of Ceratitis capitata Wiedemann has permitted the detection of sperm transferred to females during mating. However, a molecular technique to quantify the sperm transferred has not yet become available. The current method to quantify the amount of sperm has been the direct counting of sperm heads. Thus, the purpose of this research was to develop and validate an accurate molecular method of diagnosis based on the application of an absolute quantitative real-time PCR, which allows the assessment of the quantity of sperm stored in the spermathecae. For this, Y-specific sequences were used to re-design and test distinct sperm markers. From the amplification product of samples detected as strong positives in conventional PCR, a cloning process of the target sequence was carried out to build the required standard curve. A series of known dilutions of this standard material was prepared for the absolute quantification process. A Roche Lightcycler 480 Real-Time PCR System and SYBRGreen fluorescent dye were used to quantify the sperm contained in the spermathecae of 4-d-old mated females and virgins. Wild-type and Vienna-8 strain sterile males were used to quantify the sperm transferred at four mating durations (10, 30, 60, and 90 min) under laboratory conditions. To validate the reported quantitative method, our results were compared by counting sperm heads under a fluorescent microscope using the same experimental design. In addition, DNA samples were also evaluated and compared by conventional PCR.

Zoophytophagous predator-induced defences restrict accumulation of the tomato spotted wilt virus.

BACKGROUND: The use of zoophytophagous predators in protected crops has been widely adopted to manage pests in southern Europe. We hypothesized that plant defence responses would be induced by zoophytophagous predators and this induction could affect plant virus occurrence; the phytophagy of these predators induces plant defences similarly to that of viral infection. Therefore, we evaluated whether or not mirid predator-activated plant defences limited the accumulation of Tomato Spotted Wilt Virus (TSWV) in mechanically infected sweet pepper. RESULTS: Our results revealed TSWV accumulation in mirid-punctured plants to be significantly lower than in intact plants. This is most likely associated with the upregulation of the jasmonate acid pathway triggered by mirid phytophagy. CONCLUSION: Activation of induced defences by mirid predators has been demonstrated for the first time to limit the accumulation of TSWV in sweet pepper. This novel approach can offer new control strategies for the management of plant diseases. © 2019 Society of Chemical Industry.

Contribution of predation to the biological control of a key herbivorous pest in citrus agroecosystems.

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.

Persimmon orchards harbor an abundant and well-established predatory mite fauna.

Traditionally persimmon cultivation has been considered a minor crop in Spain, but in recent years this crop has experienced an important increase in both cultivated area and production. This increase has been mainly attributed to the widespread adoption of a new postharvest treatment which considerably extends the fruit commercialization period. The sudden expansion of this crop has not allowed time to correctly develop an integrated pest management (IPM) program. Consequently, chemical treatments have become the main strategy to lessen the impact of pests. Given the importance of phytoseiids in other Mediterranean fruit crops, where they are the basis of IPM, we sought to determine whether they could be similarly employed in persimmon crops. For this, we studied the predatory mite complex, the phytoseiid population dynamics and the potential prey for them during three consecutive seasons in four persimmon orchards, two of which managed conventionally, and two organically. Phytoseiids were abundant throughout the season, found on average at a density of more than 1 predatory mite per leaf. The most abundant species was Euseius stipulatus (57.3%) followed by Typhlodromus phialatus (24.8%), Amblyseius andersoni (17.1%) and Paraseiulus talbii (0.8%). Persimmon leaves provided a diversity of prey for predatory mites throughout the year, the most abundant being mealybugs, coccids, whiteflies and thrips. The abundance of predatory mites was significantly correlated to the abundance of potential prey available. From our results we anticipate that phytoseiids will be key actors in the development of persimmon IPM. Their role in this crop is discussed, as well as how to conserve their populations.

Zoophytophagous mites can trigger plant-genotype specific defensive responses affecting potential prey beyond predation: the case of Euseius stipulatus and Tetranychus urticae in citrus.

BACKGROUND: Zoophytophagous predators can trigger plant defenses affecting prey populations beyond predation. Euseius stipulatus is a presumed zoophytophagous phytoseiid common in citrus. The response of citrus to one of its potential prey, Tetranychus urticae, is genotype dependent, with Citrus reshni and C. aurantium exhibiting extreme susceptibility and resistance, respectively. Volatile blends produced upon infestation affected the behavior of these two mites. We wondered whether E. stipulatus could trigger similar responses. RESULTS: Euseius stipulatus triggered genotype-dependent defense responses in citrus. Whereas C. aurantium upregulated the Jasmonic Acid, Salicylic Acid and flavonoids defensive pathways, C. reshni upregulated JA only. Likewise, different volatile blends were induced. These blends were exploited by E. stipulatus to select less-defended plants (i.e., those in which higher pest densities are expected) and, interestingly, did not prevent T. urticae from choosing E. stipulatus-infested plants. To the best of our knowledge, this is the first time that this type of response has been described for a zoophytophagous phytoseiid. CONCLUSION: The observed responses could affect herbivore populations through plant-mediated effects. Although further research is needed to fully characterize them and include other arthropods in the system, these results open opportunities for more sustainable and effective pest control methods (i.e., combining semiochemicals and biological control). © 2018 Society of Chemical Industry.

Induced Tomato Plant Resistance Against Tetranychus urticae Triggered by the Phytophagy of Nesidiocoris tenuis.

The zoophytophagous predator Nesidiocoris tenuis (Reuter) (Hemiptera: Miridae) is capable of inducing plant defenses in tomato due to its phytophagous behavior. These induced defenses, which include the release of herbivore-induced plant volatiles (HIPVs), have been proven to affect the oviposition behavior and reduce the subsequent performance of some tomato pests. However, the effect of induction of plant defenses by N. tenuis on the preference, development, and reproduction of the two-spotted spider mite Tetranychus urticae Koch (Acari: Tetranychidae) remains unknown. In this research, T. urticae did not show preference for the odor source emitted by intact tomato plants when compared with N. tenuis-punctured plants and jasmonic acid (JA) deficient mutant tomato plants. Furthermore, the number of eggs laid by T. urticae on intact tomato plants or on N. tenuis-punctured plants was similar. However, in a greenhouse experiment conducted to evaluate whether the defense induction mediated by N. tenuis had an effect on T. urticae the infestation of T. urticae was significantly reduced by 35% on those plants previously activated by N. tenuis when compared to the control. The expression of a JA-responsive gene that was upregulated and the transcription of the plant protein inhibitor II was higher on activated plants relative to the control. These results can serve as a basis for the development of new management strategies for T. urticae based on plant defense mechanisms induced from the phytophagous behavior of N. tenuis.

Combined Use of Predatory Mirids With Amblyseius swirskii (Acari: Phytoseiidae) to Enhance Pest Management in Sweet Pepper.

The combined release of Orius laevigatus (Fieber) (Hemiptera: Anthocoridae) with Amblyseius swirskii (Athias-Henriot) (Acari: Phytoseiidae) provides effective control of sweet pepper key pests, such as thrips and whiteflies. However, the management of the aphids can still be improved. Recently, the predatory mirids Nesidiocoris tenuis (Reuter) (Hemiptera: Miridae) and Macrolophus pygmaeus (Rambur) (Hemiptera: Miridae) have been found to be effective in the control of aphids, thrips and whiteflies when tested alone. Hence, integrating one of these two mirids with A. swirskii might enhance sweet pepper pest management. In this work, we began by investigating the co-occurrence of both mirid species when released together with A. swirskii. This was compared to the standard release of O. laevigatus with A. swirskii. N. tenuis and A. swirskii were involved in a bidirectional intraguild predation (IGP). On the contrary, this interaction (IGP) was apparently unidirectional in the case of M. pygmaeus with A. swirskii and O. laevigatus with A. swirskii. Both, M. pygmaeus and O. laevigatus significantly reduced the abundance of A. swirskii. Secondly, in a greenhouse experiment, where the same release combinations were tested (either N. tenuis, M. pygmaeus or O. laevigatus combined with A. swirskii), IGP seemed to be neutralized. Mirids with A. swirskii significantly suppressed thrips, whitefly, and aphid infestations. Contrarily, the combined use of O. laevigatus with A. swirskii did not reached a satisfactory control for aphids, despite the reduction in thrips and whitefly densities. Therefore, our results suggest that the use of mirids combined with A. swirskii could result in more efficient and robust biological control programs in sweet pepper crops.

Expression of two barley proteinase inhibitors in tomato promotes endogenous defensive response and enhances resistance to Tuta absoluta.

BACKGROUND: Plants and insects have coexisted for million years and evolved a set of interactions which affect both organisms at different levels. Plants have developed various morphological and biochemical adaptations to cope with herbivores attacks. However, Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) has become the major pest threatening tomato crops worldwide and without the appropriated management it can cause production losses between 80 to 100%. RESULTS: The aim of this study was to investigate the in vivo effect of a serine proteinase inhibitor (BTI-CMe) and a cysteine proteinase inhibitor (Hv-CPI2) from barley on this insect and to examine the effect their expression has on tomato defensive responses. We found that larvae fed on tomato transgenic plants co-expressing both proteinase inhibitors showed a notable reduction in weight. Moreover, only 56% of these larvae reached the adult stage. The emerged adults showed wings deformities and reduced fertility. We also investigated the effect of proteinase inhibitors ingestion on the insect digestive enzymes. Our results showed a decrease in larval trypsin activity. Transgenes expression had no harmful effect on Nesidiocoris tenuis (Reuter) (Heteroptera: Miridae), a predator of Tuta absoluta, despite transgenic tomato plants attracted the mirid. We also found that barley cystatin expression promoted plant defense by inducing the expression of the tomato endogenous wound inducible Proteinase inhibitor 2 (Pin2) gene, increasing the production of glandular trichomes and altering the emission of volatile organic compounds. CONCLUSION: Our results demonstrate the usefulness of the co-expression of different proteinase inhibitors for the enhancement of plant resistance to Tuta absoluta.