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.

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.