In vitro insecticidal effect of commercial fatty acids, ß-sitosterol and rutin against the sugarcane aphid, Melanaphis sacchari Zehntner (Hemiptera: Aphididae)

The sugarcane aphid, Melanaphis sacchari Zehntner (Hemiptera: Aphididae), is the main pest of sorghum, Sorghum bicolor L. Moench (Poaceae), in Mexico. To control this insect, farmers currently use synthetic chemical insecticides, which are toxic to humans and biodiversity. However, natural products are a promising potential source of safer alternative means to control different agricultural pests. The main objective of this study was to evaluate the insecticidal effect of contact by fumigation of pure molecules of four commercial fatty acids (palmitic, stearic, pentadecanoic and linoleic acids), the phytosterol ß -sitosterol, and the flavonoid rutin. The results showed that fatty acids were the most effective against M. sacchari ; the highest mortality rate (85%) was produced by linoleic acid and the LC 50 was 1,181 ppm, followed by stearic and palmitic acids with mortality percentages of 74 and 63%, respectively, at a concentration of 2,500 ppm at 72 h. The positive control, imidacloprid, had 100% mortality in 24 h and the tween 20 negative control exhibited 4% mortality in 72 h. Our results show that commercial fatty acids are effective against adults of M. sacchari , and can be considered an environmentally friendly alternative to the frequent use of synthetic chemical insecticides.

Synthesis and antiplasmodial activity of regioisomers and epimers of second-generation dual acting ivermectin hybrids

With its strong effect on vector-borne diseases, and insecticidal effect on mosquito vectors of malaria, inhibition of sporogonic and blood-stage development of Plasmodium falciparum, as well as in vitro and in vivo impairment of the P. berghei development inside hepatocytes, ivermectin (IVM) continues to represent an antimalarial therapeutic worthy of investigation. The in vitro activity of the first-generation IVM hybrids synthesized by appending the IVM macrolide with heterocyclic and organometallic antimalarial pharmacophores, against the blood-stage and liver-stage infections by Plasmodium parasites prompted us to design second-generation molecular hybrids of IVM. Here, a structural modification of IVM to produce novel molecular hybrids by using sub-structures of 4- and 8-aminoquinolines, the time-tested antiplasmodial agents used for treating the blood and hepatic stage of Plasmodium infections, respectively, is presented. Successful isolation of regioisomers and epimers has been demonstrated, and the evaluation of their in vitro antiplasmodial activity against both the blood stages of P. falciparum and the hepatic stages of P. berghei have been undertaken. These compounds displayed structure-dependent antiplasmodial activity, in the nM range, which was more potent than that of IVM, its aglycon or primaquine, highlighting the superiority of this hybridization strategy in designing new antiplasmodial agents.

Differential Effects of Abiotic Factors on the Insecticidal Efficacy of Diatomaceous Earth against Three Major Stored Product Beetle Species

This study evaluated the influence of temperature and relative humidity (RH) on the insecticidal effect of diatomaceous earth (DE) at two concentrations, 500 and 1000 ppm, on wheat, for the control of Cryptolestes ferrugineus (Stephens) (Coleoptera: Cucujidae), Oryzaephilus surinamensis (L.) (Coleoptera: Silvanidae), and Tribolium confusum Jacquelin du Val (Coleoptera: Tenebrionidae). These bioassays were carried out in all combinations of four temperature levels (15, 20, 25, and 30 °C), and two relative humidity levels (55 and 75%). Cryptolestes ferrugineus and O. surinamensis were found to be much more susceptible to the DE-treated wheat than T. confusum, but the increase of the DE dose increased the mortality level for all three species. Although the increase of temperature and the decrease of RH increased insect mortality in some of the combinations tested, the reverse was observed in some treatments, suggesting that there are considerable differential effects of these factors in DE efficacy. The increase of insect exposure from 1 to 21 days notably increased insect mortality, suggesting that exposure is a critical factor that may alleviate possible differential effects of certain abiotic conditions. The results of the present work provide data that illustrate the viability of the utilization of DE in stored product protection, as alternatives to chemical control methods.

Antimicrobial and insecticidal effects of essential oil and plant extracts of Myrcia oblongata DC in pathogenic bacteria and Alphitobius diaperinus

The secondary metabolism products of plants have influenced great economic interest, given their chemical diversity and biological activities. Because of this, this study evaluates the phytochemical composition, antimicrobial activity, insecticidal, and antioxidant activity of plant extracts and oil of Myrcia oblongata. Saponins, steroids, triterpenoids, tannins, and flavonoids were detected. The extracts showed antimicrobial capacity on the tested microorganisms, except for the methanolic extract, which showed no activity for P. mirabilis and S. enteritidis. Regarding the analysis of antioxidant compounds, the hexanic, ethyl acetate and acetone extracts showed higher antioxidant activities and also higher insecticidal performance on Alphitobius diaperinus larvae, resulting in 80% adult mortality. The results reported here show that there may be a relationship between antioxidant potential and the insecticidal effect of Myrcia oblongata DC. The components present in both the extract and the oil can be used as natural alternative to synthetic compounds in the biological control of parasites and pathogenic microorganisms.

Evaluation of Applicability to Metofluthrin-based Termiticide for the Traditional Wooden Buildings

In this study, we investigated the applicability of a termiticide based on metofluthrin for termite control on traditional wooden buildings. To evaluate their mortality, termites were exposed to the agent, diluted to various concentrations, for seven days; it was found that it had a sufficient insecticidal effect although there was a difference depending on the degree of agent dilution. Next, the effect on Dancheong, used in traditional wooden structures, was measured based on the color change according to the number of agent treatments. The results showed that only the color difference value of two pigments (i.e., Bun and Juhong) was measured as 3.0 or higher. However, there this varied according to the dilution ratio. Thus, it was found that most pigments had little effect on the color of Dancheong. Finally, the termiticidal efficacy of the agent when applied to wood was evaluated. We found that the specimens coated with 10-fold and 20-fold dilutions exhibited 2.83 and 6.28% mass loss, respectively. The 10-fold dilution satisfied the performance of termiticide as a mass loss of less than 3%. In conclusion, the metofluthrin-based agent used in this study has little effect on various Dancheong pigments and has a termiticidal effect against termites; it is therefore suggested that it may be used in preserving traditional wooden cultural properties in Korea.

Comparative Insecticidal Effects of Dry Ocimum Gratissium (Scent Leaves) and Rambo™ Paper on Mosquitoes in Jos, Nigeria

Insecticides are chemicals or biological substances that are used to kill or disable insects. Blood feeding mosquitoes are responsible for the intolerable biting nuisance and transmission of large number of diseases such as malaria, yellow fever, dengue fever, filarias is amongst others, causing serious health problems to humans and obstacles to socioeconomic development of developing nations like Nigeria. The insecticidal effect of scent leaves (Ocimum gratissum) and Rambo™ paper on mosquitoes was investigated. The study is aimed at comparing the insecticidal effects of Ocimum gratissimum and Rambo™ paper on mosquitoes in Jos. 100 mosquitoes were exposed to dried Ocimum gratissum and Rambo™ paper at different time intervals of 5, 10 and 12 min. Results obtained showed a time dependent insecticidal effect on mosquitoes, which was 54.2%, 54.0% and 55.6% total mortality of mosquitoes at respective time intervals on exposures to both Rambo™ paper insecticide and Osimum gratissum, indicating that there was a significant difference in the lethal effect of Rambo™ paper insecticide and scent leave on mosquitoes at (p<0.05). In comparing the lethal effect of Rambo™ paper insecticide and Ocimum grasstisimum on mosquitoes at differnt locations in Jos, at Dogon Karfe, after 10 min of treatment, Rambo™ paper had the highest lethal effect of 21 (84.0%) compared to scent leaves 6 (24.0%) and at Abattoir Jos, after 12 min of treatment, Rambo™ paper had the highest lethal effect of 17 (94.4%) compared to Ocimum grasstisimum 3 (16.7%). These comparisons were significant at p 0.05. This study provides evidence that Ocimum grasstisimum has a mosquitocidal effect. However, the Rambo™ paper gave a better mosquitocidal effect than Ocimum grasstisimum. There is a need to discover better additive or extract options that could give Ocimum grasstisimum a better effect as a natural product available in Africa towards the malaria eradication programme.

The Valorization of Spent Coffee Grounds Extract as A Prospective Insecticidal Agent Against Some Main Key Pests of Phesolus Vulgaris in Laboratory and Field

Exploiting massive amounts of food and agro-waste represents a severe social, economic, and environmental issue. Under the growing demand toward food products free of toxic synthetic insecticides, the methanolic extract of spent coffee grounds (SCGs), which represent the main by-product of coffee production, was applied in the current study as a bioinsecticide against the main pests of the green bean; Spodoptera littoralis, Agrotis ipsilon, Bemisia tabaci, Empoasca fabi and Aphis craccivora. Deterrent assay, contact bioassay, and lethal concentration analysis were performed to reveal the repellent, antifeedant, and oviposition deterrent effects. Parallel to the above-performed bioassays, the phytochemical composition of the SCGs methanolic extract was investigated via High-Performance Liquid Chromatography (HPLC) analysis. Fourteen phenolic acids and five flavonoids in addition to caffeine (alkaloid) have been identified in the extract. Cinnamic, rosmarinic, and gallic acids were the predominant phenolics, while apigenin-7-glucoside was the main flavonoid, followed by naringin, catechin, and epicatechin. The extract of SCGs showed an insecticidal effect, with mortality between 27.5-76% compared to the control (7.4%) and based on the concentration of the extract used. In the same trend, oviposition efficiency revealed different laid egg batches (0.67, 2.33, 7.33, and 8.67 batch/jar) for 100, 50, 25% of the SCGs extract and control. Finally, the major components of SCGs extract were docked into insecticide acetylcholinesterase enzyme to explore their potential of inhibition, where apigenin-7-glucoside showed a higher binding affinity, followed by catechin, compared to the control (lannate). Obtained findings could be a starting point to develop novel bioinsecticides from SCGs.

Effect of aqueous extracts of three different plants on Myzus persicae Sulzer (Hemiptera: Aphididae) infesting pepper plants under laboratory conditions

This study aimed to determine the percentage infestation and population parameters of the green peach aphid Myzus persicae under laboratory conditions and evaluate the effect of aqueous extracts of three different plants (pot marigold: Calendula officinalis, mint: Mentha viridis and rosemary: Salvia rosmarinus) on the mortality of this aphid. Extracts of these plants were used at three concentrations (C1 = 15%, C2 = 30% and C2 = 45%). Results indicate a percentage infestation of 76.9 ± 9.4%, a mean relative growth rate of 0.062 ± 0.007 and generation time of 11.12 ± 1.42 days. All treatments reduced the numbers of aphids and statistically significantly reduced the number (α < 0.01) recorded after treatment with C1, C2 and C3 of each extract. C. officinalis extract was more effective than those of M. viridis and S. rosmarinus. The highest mortality (69.82 ± 5.23%) and efficacy (61.71 ± 4.46%) were recorded for the C3 of aqueous extract of C. officinalis, whereas the lowest mortality (38.24 ± 2.42%) and efficacy (32.41 ± 1.23%) were recorded for the C1 of extract of M. viridis. The data provided indicate that aqueous extracts of C. officinalis, M. viridis and S. rosmarinus have an insecticidal effect on M. persicae and can be integrated into a pest management strategy to reduce M. persicae abundance on pepper plants.

Insecticidal effect of ethnobotanical plant extracts against Anopheles arabiensis under laboratory conditions

Background The emergence and spread of resistant strains of malaria vectors to chemical insecticides are becoming major problems for malaria vector management. Natural plant products have a vital role to play in the current challenge of malaria control. The current study was conducted to evaluate insecticidal effect of ethnobotanical plant extracts against the primary malaria vector, Anopheles arabiensis in northwestern Ethiopia. Methods Primarily, ethnobotanical plants used for Anopheles mosquito control were surveyed in Dangur district, northwestern Ethiopia. Insecticide-susceptible strains of Anopheles arabiensis mosquito were reared in the insectary of the Tropical and Infectious Diseases Research Centre, Assosa University. After surveying plants used for mosquito control in local people, four frequently used plants were identified for extraction. The larvicidal and adulticidal potential of frequently used plant extracts against susceptible strains of the laboratory colony were evaluated. Results A total of 15 plants were identified as ethnobotanical plants that help local people with mosquito control. Azadirachta indica, Ocimum lamiifolium, Ocimum americanum, Moringa olifeira leaf, and Moringa olifeira seed species of local plants were found to be frequently used to kill and/or repel mosquitoes in the study district. All the plant extracts were found to have potential larvicidal activity against fourth instar larvae of An. arabiensis and only ethanol and methanol extract of Azadirachta indica and Ocimum lamiifolium were found to have potential adulticidal effect against adult of An. arabiensis. The highest larvicidal activity was observed in ethanol extract of Azadirachta indica with 95% larval mortality and lowest Lethal Concentration 50 (LC 50) of 40.73parts per million (ppm) and LC90 of 186.66 ppm. The highest adulticidal activity was observed in methanol extract of Azadirachta indica with 75% adult mortality at 300 ppm and lowest LC50 of 106.65 ppm and LC90 of 1,293 ppm. The lowest larvicidal and adulticidal activity was observed in methanol extracts of Ocimum lamiifolium with 63.35% larval mortality and leaf extract of Moringa olifeira with 50% adult mortality at 300 ppm, respectively. Conclusion Ethanol extract of Azadirachta indica exerted a remarkable larvicidal effect against An. arabiensis and thus it can be used for botanical mosquito insecticide development. Since the current finding is based on susceptible strain of An. arabiensis, further work on wild mosquitoes is recommended.