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Homemade botanical insecticides are widely used by subsistence and transitional farmers in low-income countries. Their use is often driven by the limited availability or cost of commercial pesticides. Homemade botanical insecticides are often recommended by agricultural extension services and some development organizations. However, this could be questioned because scientific evidence of their efficacy and safety may not be available or accessible. Although botanicals with insecticidal properties have been widely studied, a synthesis focusing specifically on homemade preparations used in realistic field or storage conditions is missing. In this paper, we review efficacy assessments of botanicals used to prepare homemade insecticides. This covers twelve botanicals recommended by national extension partners in 20 countries within the global agricultural Plantwise program. These are as follows: garlic ( Allium sativum ), neem ( Azadirachta indica ), chili pepper ( Capsicum spp.), Siam weed ( Chromolaena odorata ), mother of cocoa ( Gliricidia sepium ), chinaberry ( Melia azedarach ), moringa ( Moringa oleifera ), tobacco ( Nicotiana tabacum ), clove basil ( Ocimum gratissimum ), tephrosia ( Tephrosia vogelii ), tree marigold ( Tithonia diversifolia ), and bitter leaf ( Vernonia amygdalina ). This review shows that (1) all the selected botanicals contain active ingredients with insecticidal, antifeedant, or repellent properties, and (2) homemade insecticides based on all the selected botanicals have been used with some success to control pests or prevent damage, although efficacy was variable and often lower than the positive controls (synthetic pesticides). Factors affecting the efficacy of homemade botanical insecticide include variation in active ingredient content and concentration in plant material, as well as variation in the preparation process. In conclusion, there is some evidence that homemade botanical insecticides could contribute to reducing losses in food production. Since further research is needed to better understand their variable efficacy and potential health and environmental risks, those who promote the use of homemade botanical insecticides should also communicate those “unknowns” to the farmers who use such products.

Odontotermes wallonensis is a fungus growing termite species that are abundant inSouth India. Lantana camara leavesextracted with methanol have been found to have repellent and IGR activitiesagainst termites. The extract was also tested on O. wallonensis nymphs and showed significant IGR activity at aconcentration of 1 %.

Jasmonic acid (JA), an important plant hormone, plays a crucial role in defending against herbivorous insects. In this study, we have identified a new Bowman-Birk type protease inhibitor (BBTI) protein in maize that is regulated by the JA pathway and exhibits significant antifeedant activity, which is notably induced by exogenous Methyl Jasmonate and Ostrinia furnacalis feeding treatments. Bioinformatics analysis revealed significant differences in the BBTI protein among different maize inbred lines, except for the conserved domain. Prokaryotic and eukaryotic expression systems were constructed and expressed, and combined with bioassays, it was demonstrated that the antifeedant activity of BBTI is determined by protein modifications and conserved domains. Through RT-qPCR detection of BBTI and JA regulatory pathway-related genes' temporal expression in different maize inbred lines, we identified the regulatory mechanism of BBTI synthesis under the JA pathway. This study successfully cloned and identified the MeJA-induced anti-feedant activity gene BBTI and conducted functional validation in different maize inbred lines, providing valuable insights into the response mechanism of insect resistance induced by the plant JA pathway. The increased expression of the anti-feedant activity gene BBTI through exogenous MeJA induction may offer a potential new strategy for mediating plant defense against Lepidoptan insects.Key messageBBTI was identified as an insect resistance gene up-regulated by MeJA and O. furnacalis feedingNew evidence for JA pathway regulation of insect resistance is presented.The effects of different expression vectors on protein activity were constructed and compared.This study provides a new idea for the ecological control O. furnacalis, and MeJA treatment can be used as a potential pest resistance method to induce maize self-resistance.

The plants of the genus Salvia L. are important medicinal herbs of the Lamiaceae family and some of them such as S. officinalis (sage), S. miltiorrhiza (red sage, Danshen) and S. sclarea (clary sage) have been used as medicinal plants in the folk medicine of several countries. In this review, we discuss the reports that have examined Salvia species with the aim of isolation of pure compounds with different biological activities. The phytochemical analyses of various sage plants have reported 10 monoterpenoids ( 1 – 10 ), 1 sesquiterpenoid ( 11 ), 8 labdane ( 13 – 20 ), 15 ent -kaurane ( 21 – 35 ), 82 abietane, rearranged abietane and tanshinone ( 36 – 117 ), 3 icetexane ( 118 – 120 ), 43 clerodane ( 121 – 163 ), and 3 pimarane ( 164 – 166 ) diterpenoids with cytotoxic and antimicrobial, antiprotozoal, antioxidant, phytotoxic and insecticide effects. The other heavier terpenoids, including 3 sesterterpenes ( 167 – 169 ), 10 triterpenoids and β-sitosterol ( 170 – 180 ) have been introduced as minor bioactive compounds in the sage plants. Sahandinone ( 107 ), 6,7-dehydroroyleanone, 7-α-acetoxyroyleanone ( 40 ), and tanshinone like diterpenoids have been isolated from the roots’ extracts of different Salvia species. On the other hand, several radical scavenger phenolic compounds like simple phenolics and caffeic acid derivatives ( 181 – 201 ) including rosmarinic acid, flavonoids ( 202 – 217 ) as well as phenolic diterpenoids, such as carnosol and carnosic acid have been isolated from the aerial parts of these plants. One pyrrole ( 218 ) and 3 antimicrobial oxylipins ( 219 – 221 ) are among the other less detected constituents in the members of Salvias . Furthermore, sages also synthesize antifungal, antileishmanial and antimalarial phytochemicals in their roots and shoots, which are reviewed in this paper. We also examine the allelopathic phenomena and the ecologically important phytochemicals identified in different parts of the sage plants. Finally, antifeedant and insecticide phenomena, which are due to the presence of volatile monoterpenes and clerodane diterpenes in these plants, are discussed. Considering the presence of diverse biologically active phytochemicals in the sage plants, they can be suggested as suitable candidates for the formulation of valuable natural medicines.

Every year, more than 50 million tons of Helianthus annuus L. are produced mainly for the sunflower oil industry. It is a plant consumed worldwide, due to its use in feeding and traditional medicine for the prevention of some cardiovascular diseases, as anti-inflammatory, antimicrobial, antioxidant and antihypertensive, among others. Sunflower has a great diversity of metabolites, being especially rich in terpene compounds with close to 400 different molecules reported, including volatile mono and sesquiterpenes. Among these terpenic components of sunflower, sesquiterpenes as helibisabonols, helianuols and heliangolides, diterpenes ( ent -kaurenes or ent -trachylobanes and ent -atisarenes compounds) or apocarotenoids (ionone compounds and strigolactones) are worthy to be underlined. Many of these compounds have allelopathic activity. On the other hand, sesquiterpene lactones and diterpene compounds have strong insect antifeedant, antifungal and allelopathic activities. Additionally, the essential oil (rich in α-pinene) has antifungal properties. All these biological activities suggest that Helianthus annuus has great potential for natural crop protection. Since the main sunflower crop residue is the flower head, we have revised the plant-protection properties of flowerhead components to highlight the potential valorization of that residue for the production of biopesticides. Graphical abstract

Plant protection against phytophagous pests still largely relies on the application of synthetic insecticides, which can lead to environmental and health risks that are further exacerbated by the development of resistant pest populations. These are the driving forces behind the current trend of research and the development of new ecological insecticides. The mode of action does not have to rely exclusively on acute or chronic toxicity. Another promising approach is the use of plant antifeedants, which can significantly reduce the food intake of phytophagous insects. However, the information on antifeedant substances has not yet been sufficiently evaluated. The aim of this review was to find the most promising plants that provide potent extracts, essential oils (EOs), or isolated compounds with antifeedant properties. The selection was based on a comparison of effective concentrations or doses. Effective extracts were obtained from 85 plant species belonging to 35 families and the EOs came from 38 aromatic plant species from 11 families. Based on the results, Angelica archangelica, Caesalpinia bonduc, Grindelia camporum, Inula auriculata, Lavandula luisieri, Mentha pulegium, Piper hispidinervum, and Vitis vinifera were selected as promising plants with antifeedant potential. These plants are potent antifeedants, and at the same time provide sufficient biomass for industrial use in the development and production of botanical antifeedants.

The tobacco cutworm, Spodoptera litura , is one of the most important agricultural insect pests. Plant essential oils can be considered potential candidates for eco-friendly control agents, as they exhibit insecticidal and feeding deterrent activity. The present study investigated the antifeedant and insecticidal activity of 29 essential oils. Their potential for habituation and association with the gustatory sensilla were also examined. In no-choice tests and contact-fumigation bioassays on third instar larvae, clove bud, fennel sweet, and lemongrass oils exhibited notable activities. Still, no direct correlation between insecticidal activity and feeding deterrence was observed. Second instar larvae were pre-exposed to those active oils to test the habituation effect. Larvae reared with lemongrass and clove bud oils showed gustatory habituation, whereas those with fennel sweet oil did not show any desensitization compared to the control. Comparable outcomes were observed in individuals exposed to the main constituents of the three oils. Additionally, the mixture of fennel sweet and clove bud oils showed a synergistic feeding deterrent effect. However, although statistically insignificant, potential habituation for the mixture was observed, and only robust inhibition of habituation was expected at physiologically high concentrations (FDI 90  + FDI 90 ). Electrophysiological studies showed that the response of the maxillary palp to citral decreased in the experienced group, while to trans -anethole, it was maintained at levels similar to the naive group. The reduction in feeding deterrence corresponded to the repeated exposure and desensitization of the maxillary palp, varying with the types of essential oils.

Pyrethrum is a botanical insecticide derived from pyrethrum flowers. Feeding deterrence caused by pyrethrum has been reported in several sucking insects; however, there is no account of the cause of deterrence—whether from a single component or the combination of six active ingredients, called pyrethrins. We determined the feeding deterrence of natural pyrethrins, their two main components (pyrethrins I and II), and pyrethroid insecticides on the blowfly, Phormia regina. In a dual-choice feeding assay that minimized tarsal contact with food sources but allowed feeding through proboscises, natural pyrethrins, synthetic pyrethrins I/II, and allethrin were observed to induce deterrence at a concentration 16 times lower than the lowest concentration at which the knockdown rate increased. Feeding bouts were interrupted by intensive grooming of the proboscis at the deterring concentration, but no such grooming was observed to occur while feeding on the unpalatable tastants—NaCl, quinine, and tartaric acid. The underlying mode of action for the feeding deterrence of pyrethrins at sub-lethal concentrations probably occurs on the fly oral gustatory system, while differing from that of unpalatable tastants. The potent feeding deterrence of pyrethrins may provide effective protection for pyrethrum plants by rapidly deterring insects from feeding, before insecticidal activities occur.

Previous research suggested that positively charged zein nanoparticles [(+)ZNP] were toxic to neonates of Anticarsia gemmatalis Hübner and deleterious to noctuid pests. However, specific modes of action for ZNP have not been elucidated. Diet overlay bioassays attempted to rule out the hypothesis that A. gemmatalis mortality was caused by surface charges from component surfactants. Overlay bioassays indicated that negatively charged zein nanoparticles [(–)ZNP] and its anionic surfactant, sodium dodecyl sulfate (SDS), exhibited no toxic effects when compared to the untreated check. Nonionic zein nanoparticles [(N)ZNP] appeared to increase mortality compared to the untreated check, though larval weights were unaffected. Overlay results for (+)ZNP and its cationic surfactant, didodecyldimethylammonium bromide (DDAB), were found to be consistent with former research indicating high mortalities, and thus, dosage response curves were conducted. Concentration response tests found the LC50 for DDAB on A. gemmatalis neonates was 208.82 a.i./ml. To rule out possible antifeedant capabilities, dual choice assays were conducted. Results indicated that neither DDAB nor (+)ZNP were antifeedants, while SDS reduced feeding when compared to other treatment solutions. Oxidative stress was tested as a possible mode of action, with antioxidant levels used as a proxy for reactive oxygen species (ROS) in A. gemmatalis neonates, which were fed diet treated with different concentrations of (+)ZNP and DDAB. Results indicated that both (+)ZNP and DDAB decreased antioxidant levels compared to the untreated check, suggesting that both (+)ZNP and DDAB may inhibit antioxidant levels. This paper adds to the literature on potential modes of action by biopolymeric nanoparticles.

This work has demonstrated the ixodicidal and insect antifeedant effects of essential oils from 14 experimentally cultivated aromatic plants. The strong ixodicidal and antifeedant oils corresponded to Thymus zygis, Thymus vulgaris, Satureja montana, Oreganum virens , and Mentha suaveolens . The moderately active oils were from Lavandula angustifolia, Mentha piperita, Mentha spicata, Artemisa herba-alba , and Rosmarinus officinalis . The most effective larvicidal and antifeedant compounds were piperitenone oxide, carvacrol, piperitenone, and thymol, explaining the effects of the most active essential oils. The rest of the tested compounds were not ixodicidal or antifeedant. Therefore, the activity of moderately active oils cannot be explained by their main components (linalyl acetate, linalool, menthone, menthol, limonene, camphor, 1,8-cineole, p -cymene, α-pìnene, and carvone), suggesting synergistic effects. Considering the ixodicidal and antifeedant effects of these extracts, the plants have been ranked in relation to Thymus vulgare , a commercial biopesticide ingredient, for their potential as botanical pesticides. T. zygis, S. montana , and M. suaveolens ranked over T. vulgaris as ixodicidal agents and S. montana as insecticidal. Therefore, we propose the plant populations of S. montana, T. zygis , and M. suaveolens tested here for further development as biopesticide ingredients.