Insects

Editorial

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3 pages, 187 KiB

Open AccessEditorial

Special Issue: Natural Substances against Insect Pests: Assets and Liabilities

by Barbara Conti

Insects 2021, 12(3), 244; https://doi.org/10.3390/insects12030244 - 15 Mar 2021

Cited by 1 | Viewed by 1954

Abstract

Many insect pests directly compete with humans for food, damaging several crops in the field and during the processing and storage [...] Full article

(This article belongs to the Special Issue Natural Substances against Insect Pests: Assets and Liabilities)

Research

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13 pages, 1062 KiB

Open AccessArticle

Bioactivity of Different Chemotypes of Oregano Essential Oil against the Blowfly Calliphora vomitoria Vector of Foodborne Pathogens

by Stefano Bedini, Priscilla Farina, Edoardo Napoli, Guido Flamini, Roberta Ascrizzi, Antonella Verzera, Barbara Conti and Lucia Zappalà

Insects 2021, 12(1), 52; https://doi.org/10.3390/insects12010052 - 11 Jan 2021

Cited by 18 | Viewed by 7740

Abstract

Blowflies play a substantial role as vectors of microorganisms, including human pathogens. The control of these insect pests is an important aspect of the prevention of foodborne diseases, which represent a significant public health threat worldwide. Among aromatic plants, spices essential oils (EOs) [...] Read more.

Blowflies play a substantial role as vectors of microorganisms, including human pathogens. The control of these insect pests is an important aspect of the prevention of foodborne diseases, which represent a significant public health threat worldwide. Among aromatic plants, spices essential oils (EOs) are the most suitable to protect food from insect pests. In this study, we determined the chemical composition of three oregano EOs and assessed their toxicity and deterrence to oviposition against the blowfly Calliphora vomitoria L. The chemical analyses showed that the EOs belonged to three chemotypes: one with a prevalence of carvacrol, the carvacrol chemotype (CC; carvacrol, 81.5%), and two with a prevalence of thymol, the thymol/p-cymene and thymol/γ-terpinene chemotypes (TCC and TTC; thymol, 43.8, and 36.7%, respectively). The bioassays showed that although all the three EOs chemotypes are able to exert a toxic activity against C. vomitoria adults (LD₅₀ from 0.14 to 0.31 μL insect⁻¹) and eggs (LC₅₀ from 0.008 to 0.038 μL cm⁻²) as well as deter the oviposition (Oviposition Activity Index, OAI, from 0.40 ± 0.04 to 0.87 ± 0.02), the bioactivity of oregano EOs significantly varies among the chemotypes, with the thymol-rich EOs (TCC and TTC) overall demonstrating more effectiveness than the carvacrol-rich (CC) EO. Full article

(This article belongs to the Special Issue Natural Substances against Insect Pests: Assets and Liabilities)

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11 pages, 1255 KiB

Open AccessArticle

Preliminary Evaluation of a Granite Rock Dust Product for Pest Herbivore Management in Field Conditions

by Nicoletta Faraone and N. Kirk Hillier

Insects 2020, 11(12), 877; https://doi.org/10.3390/insects11120877 - 11 Dec 2020

Cited by 5 | Viewed by 3462

Abstract

The effects of granite rock dust in dry and aqueous formulations were evaluated under field conditions for control of insect pests in different crop systems and ornamental plants. We tested efficacy of crop protection following foliar applications on lily, squash, and cabbage plants [...] Read more.

The effects of granite rock dust in dry and aqueous formulations were evaluated under field conditions for control of insect pests in different crop systems and ornamental plants. We tested efficacy of crop protection following foliar applications on lily, squash, and cabbage plants by evaluating subsequent pest damage, overall plant health, and quantity of crops produced over one season. Lily plants treated with dry and aqueous formulations of rock dust were subject to lower herbivore damage (>1% and 11% herbivory damage, respectively) when compared to the controls (30% herbivory damage). Treatment on cabbage was less effective to protect plants against herbivory damage, and no statistically significant differences were reported within treatments. The foliar applications (dry and aqueous formulations) had positive impacts on growth of squash fruit resulting in a 2.5-fold increase in size relative to the control squash fruit. These results support the potential field application of granite dust to protect ornamental plants against herbivory attack, and reveal an alternative positive effect of the silica-based product on plant growth and development. Full article

(This article belongs to the Special Issue Natural Substances against Insect Pests: Assets and Liabilities)

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13 pages, 767 KiB

Open AccessArticle

Side Effects of Sulfur Dust on the European Grapevine Moth Lobesia botrana and the Predatory Mite Kampimodromus aberrans in Vineyards

by Federico Tacoli, Elena Cargnus, Pietro Zandigiacomo and Francesco Pavan

Insects 2020, 11(11), 825; https://doi.org/10.3390/insects11110825 - 23 Nov 2020

Cited by 11 | Viewed by 3091

Abstract

To reduce the impact of synthetic insecticides on human health and the environment, eco-friendly alternatives must be investigated. Knowledge of the side effects on pests and natural enemies of natural products applied to vineyards is very useful. Sulfur dust, which is used in [...] Read more.

To reduce the impact of synthetic insecticides on human health and the environment, eco-friendly alternatives must be investigated. Knowledge of the side effects on pests and natural enemies of natural products applied to vineyards is very useful. Sulfur dust, which is used in vineyards to control powdery mildew, is investigated in laboratory and field bioassays for its effects on Lobesia botrana egg laying, egg hatching, and larval settlement. In field trials, the efficacy of sulfur dust against the two L. botrana carpophagous generations is compared with that of Bacillus thuringiensis and kaolin, and its side effects on the phytoseiid mite Kampimodromus aberrans are evaluated. In the bioassays, sulfur dust reduced female survival by 43%, egg laying by around 80%, egg hatching by 10%, and larval settlement by 55%. In field trials, sulfur dust caused a significant decrease in the number of L. botrana larval nests of both generations, even though the efficacy was lower than that of B. thuringiensis. No negative effects of sulfur dust on the predatory mite population density was observed. On the basis of these results, in the context of Integrated Pest Management strategies in vineyards, the activity of sulfur dust against L. botrana could be exploited by timing its application to the beginning of egg laying. Full article

(This article belongs to the Special Issue Natural Substances against Insect Pests: Assets and Liabilities)

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12 pages, 758 KiB

Open AccessArticle

Physicochemical Characteristics of Four Limonene-Based Nanoemulsions and Their Larvicidal Properties against Two Mosquito Species, Aedes albopictus and Culex pipiens molestus

by Ioanna Theochari, Athanasios Giatropoulos, Vassiliki Papadimitriou, Vasileios Karras, Georgios Balatsos, Dimitrios Papachristos and Antonios Michaelakis

Insects 2020, 11(11), 740; https://doi.org/10.3390/insects11110740 - 28 Oct 2020

Cited by 20 | Viewed by 3148

Abstract

Negative impacts on the environment from the continuous use of synthetic insecticides against mosquitoes has driven research towards more ecofriendly products. Phytochemicals, classified as low-risk substances, have been recognized as potential larvicides of mosquitoes; however, problems related to water solubility and stability are [...] Read more.

Negative impacts on the environment from the continuous use of synthetic insecticides against mosquitoes has driven research towards more ecofriendly products. Phytochemicals, classified as low-risk substances, have been recognized as potential larvicides of mosquitoes; however, problems related to water solubility and stability are limiting factors for their use in mosquito control programs in the field. In this context, many researchers have focused on formulating essential oils in nanoemulsions, exploiting innovative nanotechnology. In the current study, we prepared 4 (R)-(+)-limonene oil-in-water nanoemulsions using low and high energy methods, and we evaluated their physicochemical characteristics (e.g., viscosity, stability, mean droplet diameter, polydispersity index) and their bioactivity against larvae of two mosquito species of great medical importance, namely, Cx. pipiens molestus and Ae. albopictus. According to the dose–response bioassays with the limonene-based nanoemulsions and pure limonene (dissolved in organic solvent), the tested nanoformulations improved the activity of limonene against Ae. albopictus larvae, while the performance of limonene was either the same or better than limonene against Cx. pipiens molestus, depending on the applied system. Overall, we achieved the production of limonene-based delivery nanosystems, with sufficient lethal properties against mosquito larvae to consider them promising larvicidal formulations applicable to mosquito breeding sites. Full article

(This article belongs to the Special Issue Natural Substances against Insect Pests: Assets and Liabilities)

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13 pages, 2888 KiB

Open AccessArticle

Activity of Ajuga iva Extracts Against the African Cotton Leafworm Spodoptera littoralis

by Leena Taha-Salaime, Galina Lebedev, Jackline Abo-Nassar, Sally Marzouk, Moshe Inbar, Murad Ghanim and Radi Aly

Insects 2020, 11(11), 726; https://doi.org/10.3390/insects11110726 - 23 Oct 2020

Cited by 8 | Viewed by 2895

Abstract

Control of the crop pest African cotton leafworm, Spodoptera littoralis (Boisduval), by chemical insecticides has led to serious resistance problems. Ajuga plants contain phytoecdysteroids (arthropod steroid hormone analogs regulating metamorphosis) and clerodanes (diterpenoids exhibiting antifeedant activity). We analyzed these compounds in leaf extracts [...] Read more.

Control of the crop pest African cotton leafworm, Spodoptera littoralis (Boisduval), by chemical insecticides has led to serious resistance problems. Ajuga plants contain phytoecdysteroids (arthropod steroid hormone analogs regulating metamorphosis) and clerodanes (diterpenoids exhibiting antifeedant activity). We analyzed these compounds in leaf extracts of the Israeli Ajuga iva L. by liquid chromatography time-of-flight mass spectrometry (LC-TOF-MS) and thin-layer chromatography (TLC), and their efficiency at reducing S.littoralis fitness. First and third instars of S. littoralis were fed castor bean leaves (Ricinus communis) smeared with an aqueous suspension of dried methanolic crude extract of A. iva phytoecdysteroids and clerodanes. Mortality, larval weight gain, relative growth rate and survival were compared to feeding on control leaves. We used ‘4’,6-diamidino-2-phenylindole (DAPI, a fluorescent stain) and phalloidin staining to localize A. iva crude leaf extract activity in the insect gut. Ajuga iva crude leaf extract (50, 100 and 250 µg/µL) significantly increased mortality of first-instar S. littoralis (36%, 70%, and 87%, respectively) compared to controls (6%). Third-instar larval weight gain decreased significantly (by 52%, 44% and 30%, respectively), as did relative growth rate (−0.05 g/g per day compared to the relevant controls), ultimately resulting in few survivors. Crude leaf extract (250 µg/µL) reduced gut size, with relocation of nuclei and abnormal actin-filament organization. Ajug iva extract has potential for alternative, environmentally safe insect-pest control. Full article

(This article belongs to the Special Issue Natural Substances against Insect Pests: Assets and Liabilities)

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14 pages, 1076 KiB

Open AccessArticle

Phytochemical Screening and Bioactivity of Ludwigia spp. in the Control of Plutella xylostella (Lepidoptera: Plutellidae)

by Eliana Aparecida Ferreira, Silvana Aparecida de Souza, Alberto Domingues, Matheus Moreno Mareco Da Silva, Isabella Maria Pompeu Monteiro Padial, Emerson Machado de Carvalho, Claudia Andrea Lima Cardoso, Sandra Verza da Silva and Rosilda Mara Mussury

Insects 2020, 11(9), 596; https://doi.org/10.3390/insects11090596 - 3 Sep 2020

Cited by 12 | Viewed by 4219

Abstract

We tested the bioactivity of aqueous extracts of Ludwigia spp. (Myrtales: Onagraceae) on the biological cycle of Plutella xylostella. We assessed the duration of and viability during the larval, pupal and adult phases, as well as the influence of the extracts on [...] Read more.

We tested the bioactivity of aqueous extracts of Ludwigia spp. (Myrtales: Onagraceae) on the biological cycle of Plutella xylostella. We assessed the duration of and viability during the larval, pupal and adult phases, as well as the influence of the extracts on the fecundity and hatching of P. xylostella eggs. Subsequently, we phytochemically screened the extracts. The extracts of L. tomentosa and L. longifolia reduced the pupal weight instead of prolonging the larval stage of P. xylostella. The L. tomentosa effect caused higher larval mortality and reduced the fecundity and hatching of P. xylostella eggs, and L. sericea reduced the egg survival. The phenolic compounds—flavonoids, condensed tannins and alkaloids—were more abundant in L. nervosa, L. tomentosa, L. sericea and L. longifolia. The L. tomentosa, L. longifolia and L. sericea extracts were bioactive, and these species showed the best results regarding their ability to control P. xylostella populations, because these plants produce substances able to inhibit food consumption and interfere with the morphological and physiological transformations of the offspring and the oviposition of adults. Full article

(This article belongs to the Special Issue Natural Substances against Insect Pests: Assets and Liabilities)

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13 pages, 19735 KiB

Open AccessArticle

Plant-Derived Insecticides Under Meta-Analyses: Status, Biases, and Knowledge Gaps

by Leonardo M. Turchen, Lírio Cosme-Júnior and Raul Narciso C. Guedes

Insects 2020, 11(8), 532; https://doi.org/10.3390/insects11080532 - 14 Aug 2020

Cited by 37 | Viewed by 5913

Abstract

Plant-derived or botanical insecticides are biopesticides experiencing substantial ongoing increase in interest. The 74 years of our literature survey tracked over 2500 papers on botanical insecticides published between 1945 and 2019 (Web of Science database). Such a survey allowed meta-analyses to recognize current [...] Read more.

Plant-derived or botanical insecticides are biopesticides experiencing substantial ongoing increase in interest. The 74 years of our literature survey tracked over 2500 papers on botanical insecticides published between 1945 and 2019 (Web of Science database). Such a survey allowed meta-analyses to recognize current status and biases of the studies providing important insights into the research topic. They include the recognition of the exponential growth of such studies since the 1990s, the prevalent interest on the Meliaceae plant species and a dozen additional families, although some 190 families have been investigated. The arthropods targeted by such studies were pest species (ca. 95%) with rather little attention devoted to non-target species (p < 0.001). This bias is followed by another one—mortality assessments are prevalent among target and non-target arthropod species when contrasted with sublethal assessments (p < 0.01). These omissions are pivotal, as they fail to recognize that sublethal effects may be as important or even more important than mortality, and that initial insecticide deposits quickly degrade over time leading to prevailing sublethal exposure. Furthermore, although the target of control is limited to few species, non-target species will be exposed and as such need to be factored into consideration. Thus, these biases in studies of botanical insecticides incur in knowledge gaps with potential consequences for the practical use of these compounds as pest management tools. Full article

(This article belongs to the Special Issue Natural Substances against Insect Pests: Assets and Liabilities)

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17 pages, 2982 KiB

Open AccessFeature PaperArticle

Essential Oils as Post-Harvest Crop Protectants against the Fruit Fly Drosophila suzukii: Bioactivity and Organoleptic Profile

by Stefano Bedini, Francesca Cosci, Camilla Tani, Erika Carla Pierattini, Francesca Venturi, Andrea Lucchi, Claudio Ioriatti, Roberta Ascrizzi, Guido Flamini, Giuseppe Ferroni, Isabella Taglieri and Barbara Conti

Insects 2020, 11(8), 508; https://doi.org/10.3390/insects11080508 - 5 Aug 2020

Cited by 26 | Viewed by 10823

Abstract

The essential oils extracted from mandarin (Citrus reticulata Blanco) fruits, and from tea tree (Maleleuca alternifolia (Maiden and Betche) Cheel) leaves have been chemically analyzed and tested for their bioactivity against D. suzukii. Besides, to estimate consumers’ acceptability of the [...] Read more.

The essential oils extracted from mandarin (Citrus reticulata Blanco) fruits, and from tea tree (Maleleuca alternifolia (Maiden and Betche) Cheel) leaves have been chemically analyzed and tested for their bioactivity against D. suzukii. Besides, to estimate consumers’ acceptability of the essential oil (EO) treatments, we evaluated their impact on the organoleptic characteristics of the EO-treated fruits. The main chemical constituents of the two EOs were 1,8-cineole and 4-terpineol for M. alternifolia (22.4% and 17.6% of the total components, respectively), and limonene (83.6% of the total components) for C. reticulata. The behavioral tests indicate that the two EOs are able to deter D. suzukii oviposition and that D. suzukii shows positive chemotaxis to low concentrations of the EOs and negative chemotaxis when the EO concentration increases. While no negative effects on the organoleptic profiles were detected for fruits treated with C. reticulata EO, the olfactory profile of fruits treated with M. alternifolia EO was so negative that they were defined as “not suitable for consumption” by panellists. Overall, our findings indicate that the use of EOs for the post-harvest protection of small fruits is feasible, provided that the essential oils are selected not only for their bioactivity against the insect pest but also for their affinity with the consumers’ sensorial system. Full article

(This article belongs to the Special Issue Natural Substances against Insect Pests: Assets and Liabilities)

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10 pages, 282 KiB

Open AccessArticle

Evaluation of Five Medicinal Plant Extracts on Aphis craccivora (Hemiptera: Aphididae) and Its Predator, Chrysoperla carnea (Neuroptera: Chrysopidae) under Laboratory Conditions

by Samy M. Sayed, Saqer S. Alotaibi, Nevien Gaber and Sayed-Ashraf Elarrnaouty

Insects 2020, 11(6), 398; https://doi.org/10.3390/insects11060398 - 26 Jun 2020

Cited by 23 | Viewed by 5361

Abstract

Botanical insecticides that degrade rapidly are safer than persistent synthetic chemical insecticides, less harmful to the environment, decrease production costs and are not likely to cause insecticide resistance among pests. This study aimed to evaluate the effect of five different botanical extracts on [...] Read more.

Botanical insecticides that degrade rapidly are safer than persistent synthetic chemical insecticides, less harmful to the environment, decrease production costs and are not likely to cause insecticide resistance among pests. This study aimed to evaluate the effect of five different botanical extracts on the bean aphid, Aphis craccivora and the 2nd larval instar of the green lacewing, Chrysoperla carnea under laboratory conditions. Also, the flavonoids in the methanolic extracts of these tested plants were detected using HPLC analysis. The data from the HPLC analysis indicated that the tested plants differed in their flavonoid components. The total flavonoids were 869.4, 1125.6, 721.4, 1667.8 and 2025.9 mg/kg in Psiadia penninervia, Salvia officinalis, Ochradenus baccatus, Pulicaria crispa and Euryops arabicus, respectively. Moreover, there were many variations among these plants in the amount of each compound. The lethal concentration (LC₅₀) value of P. penninervia extract on aphids was the lowest among all of the plants (128.546 µg/mL) followed by O. baccatus (626.461 µg/mL). Also, the LC₅₀ value of P. penninervia extract on the 2nd larval instar of C. carnea (232.095 µg/mL) was significantly lower than those of all other four plant species extracts, while the other four plants did not show significant differences among them according to relative median potency analyses. Accordingly, O. baccatus extract had a strong effect on aphids and was safest for the predator. This finding suggests that O. baccatus could be exploited and further developed as an effective plant extract-based insecticide to be utilized in integrated pest management (IPM) programs against A. craccivora. Full article

(This article belongs to the Special Issue Natural Substances against Insect Pests: Assets and Liabilities)

13 pages, 2093 KiB

Open AccessArticle

Larvicidal, Ovicidal, Synergistic, and Repellent Activities of Sophora alopecuroides and Its Dominant Constituents Against Aedes albopictus

by Rana Fartab Shoukat, Muhammad Shakeel, Syed Arif Hussain Rizvi, Junaid Zafar, Yuxin Zhang, Shoaib Freed, Xiaoxia Xu and Fengliang Jin

Insects 2020, 11(4), 246; https://doi.org/10.3390/insects11040246 - 15 Apr 2020

Cited by 22 | Viewed by 4209

Abstract

In the current study, to combat insecticide resistance, we explored larvicidal, ovicidal, synergistic, and repellent activities of Sophora alopecuroides extract and its dominant constituents against Aedes albopictus. The results of the toxicity bioassays demonstrated that the extract of S. alopecuroides exerted significant [...] Read more.

In the current study, to combat insecticide resistance, we explored larvicidal, ovicidal, synergistic, and repellent activities of Sophora alopecuroides extract and its dominant constituents against Aedes albopictus. The results of the toxicity bioassays demonstrated that the extract of S. alopecuroides exerted significant larvicidal activity (16.66–86.66%) against the third-instar larvae of Ae. albopictus at different concentrations (5–50 ug/mL) and low hatchability of eggs (2.32–75%) at 5–50 ug/mL. The constituents of S. alopecuroides showed a synergistic effect when applied as a mixture (LC₃₀ + LC₃₀) against larvae, while no synergistic effect was observed against the eggs of Ae. albopictus. S. alopecuroides extract provided 93.11% repellency in the first 90 min and gradually decreased to 53.14% after 240 min, while the positive control DEET (N,N-diethyl-3-methylbenzamide) showed 94.18% in the first 90 min and 55.33% after 240 min. All of the results exhibited a concentration-dependent effect. To the best of our knowledge, this is the first time that a study has identified a highly effective extract of S. alopecuroides, which could be used as an alternative agent to control larvae and eggs and to repel adults of Ae. albopictus. Full article

(This article belongs to the Special Issue Natural Substances against Insect Pests: Assets and Liabilities)

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9 pages, 393 KiB

Open AccessArticle

Larvicidal and Repellent Activity of Mentha arvensis L. Essential Oil against Aedes aegypti

by Ho Dung Manh and Ong Thi Tuyet

Insects 2020, 11(3), 198; https://doi.org/10.3390/insects11030198 - 22 Mar 2020

Cited by 48 | Viewed by 8778

Abstract

Dengue is one of the most dangerous vector-borne diseases transmitted by Aedes mosquitoes. The use of mosquito repellents to protect human hosts and insecticides to reduce the mosquito population is a crucial strategy to prevent the disease. Here, we reported larvicidal and repellent [...] Read more.

Dengue is one of the most dangerous vector-borne diseases transmitted by Aedes mosquitoes. The use of mosquito repellents to protect human hosts and insecticides to reduce the mosquito population is a crucial strategy to prevent the disease. Here, we reported larvicidal and repellent activities of Mentha arvensis L. essential oil against Aedes aegypti, the main vector of the disease. The essential oil was extracted by hydro-distillation from the aromatic plant grown in Vietnam. The yield was 0.67% based on the weight of fresh leaves. The essential oil was analyzed by gas chromatography-mass spectrometry (GC-MS). The main components were menthol (66.04%), menthyl acetate (22.19%), menthone (2.51%), and limonene (2.04%). Toxicity test on Aedes aegypti larvae showed that the median lethal concentrations, LC₅₀ and LC₉₀ were 78.1 ppm (part per million) and 125.7 ppm, respectively. Besides, the essential oil showed excellent repellency on Aedes aegypti mosquitoes. At 25%, 50%, and 100% concentration, the respective complete protection times (CPTs) were 45 min, 90 min, and 165 min. When adding 5% vanillin to the essential oil (25%), the complete protection time of the essential oil increased up to 120 min. In conclusion, the EO from Mentha arvensis L. has been shown to be a promising natural larvicide and repellent against Aedes aegypti mosquitoes. Full article

(This article belongs to the Special Issue Natural Substances against Insect Pests: Assets and Liabilities)

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7 pages, 242 KiB

Open AccessCommunication

The Mosquito Larvicidal Activity of Essential Oils from Cymbopogon and Eucalyptus Species in Vietnam

by Ho Dung Manh, Do Thi Hue, Nguyen Thi Thanh Hieu, Doan Thi Thanh Tuyen and Ong Thi Tuyet

Insects 2020, 11(2), 128; https://doi.org/10.3390/insects11020128 - 17 Feb 2020

Cited by 40 | Viewed by 7550

Abstract

The larvicidal activity of essential oils (EOs) extracted from Cymbopogon citratus, Cymbopogon winterianus, Eucalyptus citriodora, and Eucalyptus camaldulensis aromatic plants grown in Vietnam was evaluated on Aedes aegypti larvae. The EOs were hydro-distilled in a Clevenger-type apparatus. The EOs were analyzed by [...] Read more.

The larvicidal activity of essential oils (EOs) extracted from Cymbopogon citratus, Cymbopogon winterianus, Eucalyptus citriodora, and Eucalyptus camaldulensis aromatic plants grown in Vietnam was evaluated on Aedes aegypti larvae. The EOs were hydro-distilled in a Clevenger-type apparatus. The EOs were analyzed by gas chromatography–mass spectrometry (GC–MS). The mortality rates obtained from the bioassays were used to calculate the lethal concentrations (LC₅₀) of the EOs by the probit analysis method. These essential oils exhibited toxicity to the larvae of Aedes aegypti. Results were obtained for Cymbopogon citratus (LC₅₀ = 120.6 ppm), Cymbopogon winterianus (LC₅₀ = 38.8 ppm), Eucalyptus citriodora (LC₅₀ = 104.4 ppm), and Eucalyptus camaldulensis (LC₅₀ = 33.7 ppm). The essential oils of Eucalyptus camaldulensis and Cymbopogon winterianus were found to be the most efficient, and their respective values of LC₅₀ were 33.7 ppm, 38.8 ppm. In conclusion, this research adds to the growing body of literature on natural larvicides from essential oils against Aedes aegypti mosquitoes. Full article

(This article belongs to the Special Issue Natural Substances against Insect Pests: Assets and Liabilities)

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Review

Jump to: Editorial, Research

21 pages, 670 KiB

Open AccessReview

Plant Allelochemicals as Sources of Insecticides

by Ivana Tlak Gajger and Showket Ahmad Dar

Insects 2021, 12(3), 189; https://doi.org/10.3390/insects12030189 - 24 Feb 2021

Cited by 88 | Viewed by 9646

Abstract

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 [...] Read more.

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. Full article

(This article belongs to the Special Issue Natural Substances against Insect Pests: Assets and Liabilities)

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18 pages, 948 KiB

Open AccessReview

Plants in the Genus Tephrosia: Valuable Resources for Botanical Insecticides

by Peiwen Zhang, Deqiang Qin, Jianjun Chen and Zhixiang Zhang

Insects 2020, 11(10), 721; https://doi.org/10.3390/insects11100721 - 21 Oct 2020

Cited by 36 | Viewed by 5895

Abstract

Synthetic insecticides are effective in controlling insect pests but can also harm nontarget organisms and the environment. During the last 40 years, there has been an increasing interest in alternative insecticides, particularly those derived from plants, commonly known as botanical insecticides. However, commercially [...] Read more.

Synthetic insecticides are effective in controlling insect pests but can also harm nontarget organisms and the environment. During the last 40 years, there has been an increasing interest in alternative insecticides, particularly those derived from plants, commonly known as botanical insecticides. However, commercially available botanical insecticides remain limited. Rotenone is one of the earliest identified compounds and was used as fish poison and pest management. Due to its link with Parkinson disease, the use of rotenone was banned in many developed countries. Rotenone used to be isolated from Derris spp. and Lonchocarpus spp., and it can also be isolated from Tephrosia species. In this article, we present basic botanical information on selected Tephrosia species and their major compounds related to insecticidal activities and highlight the current use of extracts derived from some species, Tephrosia vogelii in particular, for control of insect pests in stored grains and crop production. The crude extracts contain multiple bioactive compounds, mainly rotenone, deguelin, rotenolone, and tephrosin, which act in either additive or synergistic fashion, resulting in effective control of insect pests. There are about 400 species in the genus Tephrosia, and species and even strains or variants vary greatly in these active compounds. We argue that a systematic evaluation of bioactive compounds in different species are needed, and species or strains with high insecticidal activities should be selected for use in the sustainable control of insect pests. Full article

(This article belongs to the Special Issue Natural Substances against Insect Pests: Assets and Liabilities)

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