Temperature-Driven Selection of Predatory Mirid Bugs for Improving Aphid Control in Sweet Pepper Crops

Recent studies have suggested that predatory mirid bugs may be an effective alternative for controlling aphids in sweet pepper greenhouses. This study examined the effect of three constant temperatures (18, 24, and 30 °C) on the life history traits of predatory mirid species Nesidiocoris tenuis, Macrolophus pygmaeus, and Dicyphus bolivari, preying on the aphid Myzus persicae nicotianae in sweet pepper plants. As the temperature increased, the survival rate decreased for M. pygmaeus and D. bolivari, while for N. tenuis, it was the opposite, and their survival increased. When considering all the biological traits studied together, the estimated intrinsic rate of increase (rm) decreased as the temperature increased for M. pygmaeus and D. bolivari. In contrast, the rate increased as the temperature increased for N. tenuis. These results suggest that M. pygmaeus and D. bolivari are better adapted to lower temperatures than N. tenuis, which is more adapted to warm temperatures. The implications of these results for improving the biological control of aphids in sweet pepper greenhouses through the use of mirid bugs are discussed in relation to different temperature regimes

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

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

Garlic and peppermint essential oils elicit plant defensive responses in sweet peppers

Exploiting plant defense mechanisms is a promising tool for pest management in modern agriculture. Plant Essential Oils (EOs) are used for the sustainable control of agricultural pests; however, their impact on plant defense has been scarcely investigated. In this work, we study for the first time whether the spraying of EOs can activate plant defense mechanisms in sweet pepper. The olfactory capacity of Encarsia formosa (Hymenoptera: Aphelinidae) to respond to defense-activated plants was used to select garlic and peppermint EOs among nine EOs sprayed on sweet peppers. The expression level of defense-related genes in plant tissues and the phytotoxicity were measured in response to EO foliar applications. Moreover, the olfactory responses of the herbivores, Bemisia tabaci (Hemiptera: Aleyrodidae) and Frankliniella occidentalis (Thysanoptera: Thripidae), and their natural enemies, Orius laevigatus (Hemiptera: Anthocoridae) and Nesidiocoris tenuis (Hemiptera: Miridae), to EO induced plant volatiles were also investigated. The gene expression analysis revealed activated jasmonic and salicylic acid defense signaling pathways in EO sprayed sweet pepper plants and a negligible phytotoxic effect was recorded. Choice tests revealed varying behavioral responses in selected insect models when plants were treated with garlic and peppermint EOs in different concentrations. Our results suggest that garlic and peppermint EO spray applications can enhance the defense mechanisms of sweet peppers and have a cascading bottom-up effects on the associated food chain. These initial findings provide a foundation for the future development of Integrated Pest Management strategies to protect solanaceous crops

Covert infection with an RNA virus affects medfly fitness and the interaction with its natural parasitoid Aganaspis daci

With the advent of high-throughput sequencing, large sets of insect-infecting RNA viruses producing apparent asymptomatic infections are being discovered. In the Mediterranean fruit fly (medfly) Ceratitis capitata, an agricultural key pest of a wide range of fruits, 13 different RNA viruses have been described so far. Recent analysis demonstrated a wide distribution of these viruses in different medfly strains collected worldwide, but little is known about the interactions between those viruses and the medfly host. Previous studies suggested that a higher abundance of Ceratitis capitata nora virus (CcaNV) correlated with a shorter lifespan in adults. Here, we investigated the effect of CcaNV on a broad range of parameters related to host fitness and its interaction with other trophic levels. CcaNV purified from a naturally infected medfly strain was added to the larval diet. Pupal weight, adult emergence, flying ability, and longevity were monitored after oral infections. Our results revealed detrimental effects associated with a CcaNV infection in the medfly, in terms of reduced pupal weight and reduced adult longevity. Moreover, we tested the influence of a CcaNV infection in medflies on the parasitism performance of Aganaspis daci, an endoparasitoid used in biological control programs against medflies. Our results showed that A. daci progeny increased when parasitizing on CcaNV-infected larvae. Overall, we proved that covert RNA viruses can impact the insect ecology, directly affecting its insect host biology and indirectly influencing multitrophic interactions

Un nuevo enfoque sostenible de gestión de plagas y enfermedades a través de la inducción de defensas de las plantas

Las plantas son capaces de activar defensas en respuesta al ataque de herbívoros. Estas defensas pueden ser directas o indirectas, y pueden aprovecharse para su integración en programas de gestión sostenible de plagas y enfermedades. En estudios realizados por el IVIA, se ha demostrado que la exposición de plantas de tomate, pimiento y cítricos a varios volátiles inducidos por herbivoría (HIPV’s) aumentan la sobreexpresión de genes defensivos en comparación con plantas no expuestas. De estos volátiles, se ha seleccionado el (Z)-3-hexenil propanoato [(Z)-3-HP] por su capacidad para activar diversas rutas defensivas en los tres cultivos. Además, se ha confirmado que la exposición a (Z)-3-HP aumenta la producción de compuestos derivados de ácidos grasos y la acumulación de compuestos de defensa específicos. Para su aplicación práctica, y en colaboración con el grupo del CEQA de la UPV, se diseñaron difusores poliméricos de liberación controlada que son capaces de emitir (Z)-3-HP a tasas constantes durante períodos prolongados y que ya han sido probados en condiciones de campo en los tres cultivos mencionados. Los resultados obtenidos sugieren que el uso de HIPV’s puede ser una estrategia prometedora para la gestión sostenible de plagas y enfermedades en agricultura

Enhancing the biocontrol potential of the predator Nesidiocoris tenuis through genetic selection

The zoophytophagous Nesidiocoris tenuis has proven to be a highly effective natural enemy against tomato key pests. It can enhance tomato plants' defenses due to its phytophagous behavior. However, its plant feeding can result in severe plant damage when prey is scarce. Previous studies using an isofemale line demonstrated the dietary habits of N. tenuis are genetically regulated, specifically with regard to phytophagy and zoophagy. In this study, we assessed the life-history traits of the IVIA strain, selected for over 50 generations for its zoophagy and phytophagy, compared to a commercial strain. The IVIA strain developed 3.5% faster, had 34% more offspring, preyed on 34% more Ephestia kuehniella eggs, and caused 50% fewer necrotic rings on tomato plants than the commercial strain. The IVIA strain controlled B. tabaci and T. absoluta in greenhouse experiments at the same level as the commercial strain but produced less damage to the plant. We also studied the capacity of the IVIA strain to induce plant defenses. The IVIA strain increased plant defenses compared to the control, although to a lesser extent than the commercial strain. This finding confirms the reduced phytophagy of the IVIA strain. Interestingly, the use of microsatellite markers revealed genetic differentiation between the IVIA strain and the commercial strain. Our results highlight the potential of selective breeding for improving biocontrol traits of interest in N. tenuis and open the door to differentiating selected races of N. tenuis using molecular techniques

Induction of glandular trichomes to control whitefly-transmitted viruses in tomato crops: modulation by the natural enemy Nesidiocoris tenuis

Whitefly-transmitted viruses are one of the biggest threats to tomato 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 acylsugars-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 trichomes density and acylsugars 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 (Reuter) (Hemiptera: Miridae) displayed an increase (above 50%) in type IV trichomes density. Acylsugars production was consistently increased in N. tenuis-punctured BC5S2 plants, which was more likely associated with upregulated expression of BCKD-E2 gene related to acylsugars 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 B. tabaci and attractiveness to N. tenuis. Thus, by pre-plant 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