Abstract
Simple SummaryDue to the banning of many synthetic pesticides, current intensive farming systems require us to develop new approaches to integrated pest management. Devastating pests rarely occur in the wild and medicinal plants because of effective defense mechanisms. In contrast, only some of these defense mechanisms are found in cultivated crops. Biocidal compounds, derived from various wild and medicinal plants, are bioactive, biodegradable and constitute an ecological method for the successful management of insect pests. Therefore, an extensive study of various wild crops and some weeds is essential to identify new and potential plant species with insecticidal compounds. In this review, we describe the role of plant-derived biochemicals that are toxic to insect pests. Biotic stress in plants caused by insect pests is one of the most significant problems, leading to yield losses. Synthetic pesticides still play a significant role in crop protection. However, the environmental side effects and health issues caused by the overuse or inappropriate application of synthetic pesticides forced authorities to ban some problematic ones. Consequently, there is a strong necessity for novel and alternative insect pest control methods. An interesting source of ecological pesticides are biocidal compounds, naturally occurring in plants as allelochemicals (secondary metabolites), helping plants to resist, tolerate or compensate the stress caused by insect pests. The abovementioned bioactive natural products are the first line of defense in plants against insect herbivores. The large group of secondary plant metabolites, including alkaloids, saponins, phenols and terpenes, are the most promising compounds in the management of insect pests. Secondary metabolites offer sustainable pest control, therefore we can conclude that certain plant species provide numerous promising possibilities for discovering novel and ecologically friendly methods for the control of numerous insect pests.
Highlights
Simple Summary: Due to the banning of many synthetic pesticides, current intensive farming systems require us to develop new approaches to integrated pest management
Insect herbivores feeding on a plant species encounter potentially toxic substances with relatively non-specific effects on proteins, nucleic acids, secondary metabolites, bio-membranes and specific or unspecific interactions with other cellular components [59,60]
Herbivorous insects use different physiological strategies to tolerate noxious and unpalatable toxins. These mechanisms include the involvement of carbohydrates that cover the unpalatable taste of toxins, extended dietary exposure to some unpalatable secondary plant compounds and dietary exposure to toxic compounds that induce the production of P450 detoxication enzymes
Summary
Plants and insect pests are in constant interaction. Plants offer them food, a place for oviposition and shelter [13]. The plant resistance mechanisms that affect insects are constitutive or induced They can be grouped into three main categories: antixenosis or non-preference, tolerance and antibiosis. In the course of evolution, plants have developed many resistance mechanisms to reduce the damage caused by insects [28] Insect adaptations to this defense are mostly related to their biochemical traits [29]. In all of the above cases, specialists have a physiological adaptation to cope with the defense mechanisms of plants It seems that just a small number of insects are immune to the deleterious effects caused by plant toxins. Specialists such as D. plexippus have evolved physiological adaptations for tolerating these steroids [41,42] Their larvae face an interesting tradeoff: feed only on plants containing cardenolides, sequester cardenolides as anti-predator defense. The induction of indirect defenses, such as extrafloral nectar and parasite-attracting volatile organic compounds (VOCs), is strong if the specialist is not actively sequestering toxins
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