The ecological and economic contributions of pollinator bees to agricultural production have been threatened by the inappropriate and excessive use of pesticides. These pesticides are often applied in areas with ecological peculiarities (e.g., the Neotropical savannah-like region termed as Cerrado) that were not considered during the product development. Here, we conducted field experiments with melon (i.e., Cucumis melo L.) plants cultivated under Brazilian Cerrado conditions and evaluated the impacts of botanical (i.e., neem-based insecticide) and synthetic (i.e., the pyrethroid insecticide deltamethrin and the fungicides thiophanate-methyl and chlorothalonil) pesticides on the flower visitation rates of naturally occurring pollinator bees. Our results revealed that both honey bees (i.e., Apis mellifera L.) and non-Apis bees visited melon flowers and the intensity of bee visitation was moderately correlated with yield parameters (e.g., number of marketable fruits and fruit yield). Pesticide treatments differentially affected bee species. For instance, Plebeia sp. bees were not affected by any pesticide treatment, whereas both A. mellifera and Halictus sp. bees showed reduced visitation intensity after the application of deltamethrin or neem-based insecticides. Fungicide treatment alone did not influence the bee's visitation intensity. Deltamethrin-treated melon fields produced significantly lighter marketable fruits, and the melon yield was significantly lower in melon fields treated with the neem-based insecticide. Thus, our findings with such pollinator bees reinforce the idea that field applications of botanical pesticides may represent as risky as the applications of synthetic compounds, indicating that these alternative products should be submitted to risk assessments comparable to those required for synthetic products.

The development of “green” alternatives to chemical pesticides could play a crucial role in integrated pest management (IPM). Their use is considered either as a substitution for or in addition to hazardous synthetic products. We analysed the influence of three concentrations of tansy (Tanacetum vulgare L.) essential oil (EO), previously characterised by GC-MS, on the survival and moulting of the 2nd instar and the nutritional indices of the 4th instar gypsy moth (Lymantria dispar L.) larvae. In a residual contact toxicity assessment, the exposure to tansy EO caused low mortality (< 10%) while larval development was significantly slowed down, i.e., the percentage of larvae that moulted into the 3rd instar was reduced. On the other hand, when tansy EO was incorporated into the diet (digestive toxicity assay), high mortality and a lack of moulting after 120 h of eating were recorded for the highest applied concentration of EO. During 48 h of feeding on EO-supplemented food at concentrations of 0.5 and 1% (v/v), the relative growth rate (RGR) of the 4th instar larvae significantly decreased, which can be explained by a significant reduction of the relative consumption rate (RCR) and significantly or marginally significantly lower efficiency of conversion of ingested food into insect biomass (ECI). Although the RCR was also reduced with the lowest applied EO concentration (0.1%), the ECI was not affected which meant the RGR was as high as it was for the control larvae. ECI changes, when two higher EO concentrations were applied, were due to a reduction in the efficiency of conversion of digested food into biomass (ECD), while approximate digestibility was unaffected by the presence of EO in the food. Our results on the significant negative effects of tansy EO on gypsy moth larval survival, development time, and nutritional physiology suggest that it could be considered in future designs for botanical insecticides for gypsy moth control.

The study reports efficacy of Melissa officinalis L. essential oil (MOEO) as a safe plant-based insecticide against Tribolium castaneum Herbst (TC) by induction of oxidative stress. MOEO nanoencapsulation in chitosan matrix was performed to enhance its bioefficacy. GC–MS analysis of MOEO depicted geranial (31.54%), neral (31.08%), and β-caryophyllene (12.42%) as the major components. MOEO showed excellent insecticidal potential in contact (100% mortality at 0.157 μL/cm²) and fumigant bioassays (LC₅₀ = 0.071 μL/mL air) and 100% repellency at concentration ≤ 0.028 μL/cm². Increased reactive oxygen species (ROS), superoxide dismutase (SOD), catalase (CAT), and decreased ratio of reduced glutathione (GSH) to oxidized glutathione (GSSG) at the LC₅₀ dose suggested significant oxidative stress on TC in MOEO treatment sets. The encapsulated MOEO exhibited enhanced activity as fumigant (LC₅₀ = 0.048 μL/mL air) and showed significant antifeedant activity in situ (EC₅₀ = 0.043 μL/mL). High LD₅₀ value (13,956.87 μL/kg body weight of mice) confirmed favorable toxicological profile for non-target mammals. The findings depict potential of nanoencapsulated MOEO as an eco-friendly green pesticide against infestation of stored food by TC.

The western flower thrips (Frankliniella occidentalis Perg.) is one of the most economically important insect pests of greenhouse plants. Plant protection against this pest is based predominantly on synthetic insecticides; however, this form of protection poses problems in terms of thrip resistance to the active substances, along with health risks associated with insecticide residues on the treated plants. Therefore, new active substances need to be sought. Essential oils could be a new, appropriate, and safe alternative for greenhouse culture protection. As greenhouses are enclosed areas, fumigation application of EOs is possible. This paper presents acute toxicity results for 15 commercial EOs applied by fumigation, as well as the effect of sublethal concentrations on fertility of F. occidentalis females. The most efficient EOs were obtained from Mentha pulegium and Thymus mastichina, with LC₅₀₍₉₀₎ estimated as 3.1(3.8) and 3.6 (4.6) mg L⁻¹ air, respectively. As found for the very first time, sublethal concentrations of EOs could result in a significant reduction in the fertility of surviving T. occidentalis females. Among the tested EOs, the EO from Nepeta cataria provided the highest inhibition of fertility, with EC₅₀₍₉₀₎ estimated as 0.18 (0.36) mg L⁻¹ air. Chemical composition of the most efficient EOs and possible applications of the results in practice are discussed. In conclusion, in light of the newly determined facts, EOs can be recommended as active substances for botanical insecticides to be applied against Thysanopteran pests by fumigation.

The control of mosquitoes by means of chemical insecticides has been a problem, mainly due to the possibility of resistance developed by insects to xenobiotics. For this reason, demand for botanical insecticides has increased. In this sense, the present work aims to verify the susceptibility and morphological and biochemical alterations of Culex quinquefasciatus larvae after exposure to essential oil (EO) of leaves of Baccharis dracunculifolia. To observe the larvicidal action, larvae were exposed to EO at concentrations of 25, 50, 100, and 200 mg/L, until their emergence to adults. The control group was exposed to deionized water and dimethyl sulfoxide. Morphological analyses were also carried out using hematoxylin and eosin, mercury bromophenol blue, Nile blue, and periodic acid Schiff. Biochemical analyses of total glucose, triacylglyceride (TAG), protein, and acetylcholinesterase levels were performed. The phytochemical analysis of the EO showed (E)-nerolidol as the major compound (30.62%). Larvae susceptibility results showed a LC₅₀ of 34.45 mg/L for EO. Morphological analysis showed that there were histological changes in midgut. For biochemical analyses, the glucose level in the larvae exposed to EO for 24 h decreased significantly, unlike the TAG levels, which increased. The total protein level of the larvae also increased after exposure for 24 h, and acetylcholinesterase levels decreased significantly. Taking all our data into account, we can conclude that EO causes destabilization in larva, leading to histological changes, metabolic deregulation and, consequently, their death.

In mosquito control programs, insecticides of botanical origin have the potential to eliminate eggs, larvae, and adults. So, the larvicidal, ovicidal, and oviposition-deterrent activities of petroleum ether and ethyl acetate extracts of the leaves of Eugenia jambolana, Solidago canadensis, Euodia ridleyi, and Spilanthes mauritiana were assayed against the three vector mosquito species, namely Anopheles stephensi, Aedes aegypti, and Culex quinquefasciatus. The larval bioassay was conducted following the World Health Organization method. The maximum larval mortality was found with ethyl acetate extract of S. mauritiana against the larvae of A. stephensi, A. aegypti, and C. quinquefasciatus with LC₅₀values of 11.51, 28.1, 14.10 ppm, respectively. The mean percent hatchability of the ovicidal activity was observed at 48-h post-treatment. The percent hatchability was found to be inversely proportional to the concentration of the extract and directly proportional to the number of eggs. The flower head extract of S. mauritiana gave 100 % mortality followed by E. ridleyi, S. canadensis, and E. jambolana against the eggs of the three mosquito vectors. For oviposition-deterrent effect, out of the five concentrations tested (20, 40, 60, 80, and 100 ppm), the concentration of 100 ppm showed a significant egg laying-deterrent capacity. The oviposition activity index value of E. jambolana, E. ridleyi, S. canadensis, and S. mauritiana against A. aegypti, A. stephensi, C. quinquefasciatus at 100 ppm were −0.71, −0.71, −0.90, −0.93, −0.85, −0.91, −1, −1, −0.71, −0.85, −1, and −1, respectively. These results suggest that the leaf/flower extracts of certain local plants have the potential to be developed as possible eco-friendly means for the control of mosquitoes.

Itol A, an isoryanodane diterpene derived from Itoa orientalis Hemsl. (Flacourtiaceae), is a potential plant-based insecticide. However, the effect of itol A on the tobacco cutworm [Spodoptera litura (Fab.) (Lepidoptera: Noctuidae)], an important and widely distributed insect pest, remains unclear. In this study, the toxicity and inhibitory potency of itol A on S. litura were evaluated. The results indicated that itol A exhibited larvicidal activity against the third instar larvae in a concentration-dependent manner (LC₅₀ 875.48 mg/L at 96 h). Antifeedant activity also was observed, and the 24-h AFC₅₀ values were 562.05 and 81.47 mg/L in the no-choice and choice experiments, respectively. The insect growth was inhibited after treatment of itol A, as reflected by long developmental periods, low-quality pupae, and various abnormalities. Itol A exerted ovicidal effect on S. litura, with an estimated LC₅₀ of 759.30 mg/L. Itol A deterred oviposition in the choice experiment (ODI₅₀ 909.60 mg/L). Besides, the activities of α-amylase, general protease, superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD) were inhibited after itol A treatment over time compared to controls, which may be a relevant mechanism underlying the toxicity of itol A toward S. litura. However, the activities of lipase, carboxylesterase (CarE), glutathione S-transferase (GST), and cytochrome P450 monooxygenase (P450) were increased. Taken together, these results suggest that itol A could be a good botanical pesticide to reduce the population of S. litura in integrated pest management programs.

The knockdown and adulticidal activities of individual Cymbopogon citratus and Eucalyptus globulus essential oils (EOs) and their combinations were evaluated against three medical insect pests (Aedes aegypti, Aedes albopictus, and Musca domestica) using a WHO susceptibility test. The knockdown and adulticidal activities against the three medical insect pests of combinations of C. citratus and E. globulus EOs were higher than those of individual EOs alone. Combinations of 7.5% C. citratus + 7.5% E. globulus EOs and 10% C. citratus + 10% E. globulus EOs exhibited the highest efficacy against females of the three species with 100% knockdown and mortality rates at 1 and 24 h after exposure, respectively. Their adulticidal activities were equivalent to that of 10% w/v cypermethrin. In contrast, 70% v/v ethyl alcohol negative control was not effective at all. The combinations of EOs showed a synergistic effect, i.e., their adulticidal activity was improved by 0.2 to 100%, with increased knockdown and mortality rates, compared to individual EOs. The highest synergistic effect on effective knockdown and adulticidal activities against females of the three species was achieved by a combination of 2.5% C. citratus + 2.5% E. globulus EOs, with 36.6 to 100% knockdown rate increase and 33.5 to 98.9% mortality rate increase. This study demonstrates that all tested combinations of C. citratus and E. globulus EOs were effective adulticidal agents against females of Ae. aegypti, Ae. albopictus, and M. domestica and have a high potential for development into a botanical insecticide for controlling populations of Aedes mosquitoes and houseflies.

Essential oils (EOs) extracted from leaves (EL) and fruit pericarp (EFP) of Zanthoxylum planispinum var. dintanensis were analyzed for their chemical composition by GC-MS technique and evaluated for their fumigant, contact toxicity and repellency against three stored-product insects, namely Tribolium castaneum, Lasioderma serricorne, and Liposcelis bostrychophila adults. Results of GC-MS analysis manifested that EL and EFP of Z. planispinum var. dintanensis were mainly composed of oxygenated monoterpenes. Major components included linalool, sylvestrene and terpinen-4-ol. The obvious variation observed between two oil samples was that EL contained 2-dodecanone (11.52%) in addition to the above mentioned components, while this constituent was not detected in EFP. Bioassays of insecticidal and repellent activities were performed for EL, EFP as well as some of their individual compounds (linalool, terpinen-4-ol and 2-dodecanone). Testing results indicated that EL, EFP, linalool, terpinen-4-ol and 2-dodecanone exhibited potent insecticidal and repellent activities against the three target insects selected. Among the three individual compounds, 2-dodecanone was significantly toxic to T. castaneum (LD₅₀ = 5.21 μg/adult), L. serricorne (LD₅₀ = 2.54 μg/adult) and L. bostrychophila (LD₅₀ = 23.41 μg/cm²) in contact assays and had beneficial repellent effects on L. serricorne at 2 and 4 h post-exposure. The anti-insect efficacy of Z. planispinum var. dintanensis EO suggests it has potential to be used as botanical insecticide or repellent to control pest damage in warehouses and grain stores.

The natural and ecologically safe control of stored product insects has gained considerable attention in modern society. In this study of further searching for botanical pesticides from wild-growing plant, the contact toxicity and repellency towards Tribolium castaneum and Liposcelis bostrychophila were assessed for the essential oil (EO) from Ostericum viridiflorum. The EO was distilled from aboveground parts of O. viridiflorum and checked by gas chromatography-mass spectrometry. Twenty-two compounds were identified and the main components were β-caryophyllene (24.3%), α-humulene (21.0%), apiol (10.2%), and carotol (2.5%). For bioactivity tests, results indicated that the EO and its two main compounds (β-caryophyllene and α-humulene) all showed potent contact toxicity towards L. bostrychophila with LD₅₀ values of 44.52 μg/cm², 74.11 μg/cm², and 118.56 μg/cm², respectively. The EO and the two main compounds also exhibited comparable repellency towards T. castaneum and L. bostrychophila. The results evidenced the EO of O. viridiflorum aboveground parts and its major compounds could be considered for the development of eco-friendly botanical insecticides and repellents in controlling stored product insects.