on Rhipicephalus sanguineus (Latreille, 1806) (Acari: Ixodidae)

A study was undertaken on the ovicidal and larval repellent activity of Tagetes erecta leaf and flower extracts on Rhipicephalus sanguineus (Latreille, 1806), an important tick species in the world from an economic and medical point of view. Ethanol and methanol extracted plant products tested against the eggs and larvae of R. sanguineus indicated that the ethanol extract of flower had maximum ovicidal activity (86.1%), followed by the ethanol extract of leaf (75%) at 25 mg ml-1 concentration. In all analyses, the homogeneity of variance was significant. The probit analysis clearly indicated that the ethanol extract of the flower has a higher ability to kill the eggs. In the case of larval repellency tested, both extracts of leaf showed the highest repellency (83%) at 2.5 mg ml-1. Significant tick repellency (> 90%) was found in both methanol and ethanol extracts of flower at 2.5 mg ml-1. GC-MS analysis of extracts revealed the presence of bioactive insecticidal compounds such as yangambin, cyclohexane and neophytadine.

Oviposition Deterrence and Ovicidal Activity of Birbira (Melletia furrgunia) on Diamondback Moth (Plutella xylostella) (Lepidoptera: Plutellidae)

The efficacy of different polar and non-polar solvent extracts of Birbira, Melletia furrginea (Hochst.) Baker tree seeds namely: Water, Acetic acid, Acetone, Chloroform, Toluene, and Hexane at different rates were evaluated on Diamondback moth, Plutella xylostella L. oviposition and egg mortality under laboratory conditions. The leaf dipping method was used to run both assays. In the assay, full Oviposition deterrence was recorded at the higher rates of polar solvent extracts. Significantly higher egg un-hatchability was recorded only at the higher rates for non-polar extracts. Eggs mortality caused by extracts with Water and Acetone was very high, and have much smaller LC50 values. In contrast, LC50 was higher for the other extracts. However, there was a constant increase in the percent kill of egg mass with the increase in the extract concentration. From this study, it is evident that M. furrgunia extracts with different solvents possess significant oviposition deterrence and ovicidal effect on P. xylostella.

Preparation and Optimization of Peppermint (Mentha Pipertia) Essential Oil Nanoemulsion with Effective Herbal Larvicidal, Pupicidal, and Ovicidal Activity against Anopheles Stephensi

Objectives: The Plasmodium parasite is transmitted directly to humans through the Anopheles mosquito bite and causes vector-borne Malaria disease, which leads to the transmission of the disease in Southeast Asia, including India. The problem of persistent toxicity, along with the growing incidence of insect resistance, has led to the use of green pesticides to control the spread of the disease in a cost-effective and environment-friendly manner. Based on this objective, this work investigated the larvicidal, pupicidal, and ovicidal activity of Mentha pipertia using a natural nanoemulsion technique. Methods: GC-MS characterized essential oils of Mentha pipertia leaves were formulated as a nanoemulsion for herbal larvicidal, pupicidal, and ovicidal activities. Size of the nanoemulsion was analyzed by photon correlation spectroscopy. The herbal activities against Anopheles Stephensi of nanoemulsion were evaluated in terms of the lethal concentration for 50% (LC50) and 90% (LC90) to prove low cost, pollution free active effective formulation. Results: Chiral, keto, and alcohol groups attached Mentha pipertia leaves essential oil nanoemulsions demonstrated good results in the larvicidal probit analysis, with values of LC50=09.67 ppm and LC90=20.60 ppm. Activity results of the most stable nano formulation with 9.89 nm size showed a significant increase when compared to the bulk. Conclusion: The nanoemulsion of Mentha pipertia leaves can be a promising eco-friendly widely available, low-cost herbicide against the Anopheles mosquito.

Activity of terpenes derived from essential oils against Sarcoptes scabiei eggs

Background The limited ovicidal activity of currently available acaricides is a significant obstacle to efficacious scabies treatment. Several essential oils or their respective components have proved to be active against the eggs of arthropods, mainly lice and ticks. Information on the activity of these oils and/or components against the eggs of mites remains very limited. The aim of this study was to assess the activity of six terpenes (carvacrol, eugenol, geraniol, citral, terpinen-4-ol and linalool) commonly found in essential oils against the eggs of Sarcoptes scabiei. Methods Sarcoptes eggs were exposed to paraffin oil containing 1, 2.5, or 5% of each terpene tested. After a 12-h exposure period, the eggs were washed and placed in paraffin oil for hatching. Embryonic development following treatment was assessed every day to determine the stage of developmental arrest. Results The median effective concentration to obtain 50% egg mortality (EC50) was 0.5, 0.9, 2.0, 4.8, 5.1 and 9.8% for carvacrol, eugenol, geraniol, citral, terpinen-4-ol and linalool, respectively. The microscopic images of eggs after each treatment indicated that these six terpenes may act by penetrating through the aeropyles on the egg surface. Conclusions In conclusion, carvacrol, eugenol and geraniol possess significant ovicidal activities, which should be considered as promising ovicidal agents for the treatment of scabies. Graphical Abstract

Evaluation De L’activité Anthelminthique Des Extraits Aqueux De Striga Hermonthica (Del.) Benth Et Ceratotheca Sésamoïdes Endl Sur Deux Stades Biologiques De Haemonchus Contortus

Medicinal plants with anthelmintic properties are an alternative to the chemical fight against small ruminant’s gastrointestinal nematodes. In order to broaden the spectrum of medicinal plants with anthelmintic properties, ovicidal activity and L3 larvae exsheathment of C. sesamoïdes Endl and S. hermonthica (Deli) Benth, aqueous extracts has been done on H contortus egg and L3 larvae. Three concentrations, 3.12 mg / ml, 6.25 mg / ml, 12.5 mg / ml of each plant extract were used to assess the inhibition of fresh egg hatching and larval paralysis as well as the 'inhibition of L3 larvae exsheathment. A negative control (PBS1x) and a positive control (levamisole, 2.5 mg / ml) were constituted for the fresh egg hatching inhibition assessment while only the negative control (PBS1x) was constituted to evaluate the inhibition of L3 Larvae exsheathment.1 ml of each concentration was contacted with 1 ml of the egg solution and then incubated for 48 hours at 27 ° C in petri dishes (60X15 Cm) for hatching test inhibition.1 ml of each extract concentration was contacted with 1 ml of the embryonated egg solution after 24 hours of incubation at 27 ° C for the larval paralysis test.

Ovicidal activity of spirotetramat and its effect on hatching, development and formation of Frankliniella occidentalis egg

Frankliniella occidentalis (Pergande) has become an important vegetable pest worldwide because of its economic damage to crop production. However, it is difficult to control due to its unique living habits. In this study, the eggs of F. occidentalis were used as the target to explore the ovicidal activity of spirotetramat on the thrips and its effect on hatching, development and formation. After the treatment of spirotetramat, the LC50 value descreased with increased egg age using egg dipping method, and showed the same trend as the leaf dipping method verified on living plants. Through ultra-depth-of-field microscopy, scanning electron microscopy and transmission electron microscopy, the egg shell and internal structures of F. occidentalis eggs were studied. Spirotetramat can destroy the egg shells of F. occidentalis, resulting in shrinkage of the egg surface, sunken pores, egg deformities, egg shell rupture and other phenomena. This allows spirotetramat to enter the egg and destroy the egg structure, making the egg internal structure flocculent, fuzzy and unevenly distributed, which affects embryonic development and causes the nymphs to die before hatching. Therefore, the prevention and control of F. occidentalis using spirotetramat before damage is caused to crops should have a better effect.

Andean Plants Essential Oils: A Scented Alternative to Synthetic Insecticides for the Control of Blowflies

Blowflies are vectors of microorganisms and human pathogens, and their maggots cause myiasis in vertebrates and infest and spoil meat and fish products. Essential oils (EOs) from spices were proven to be a safer and more sustainable alternative to synthetic insecticides for the control of blowflies and are suitable for protecting food from such pests. However, some EOs are not acceptable for environmental or topical applications due to their strong, unpleasant odour. In this study, we measured the acute toxicity and the repellence of two EOs extracted from the Andean plants Aloysia citrodora Palau and Bursera graveolens (Kunth) Triana and Planch., both known for their pleasant odour, against the blue blowfly Calliphora vomitoria (L.) (Diptera: Calliphoridae). We also compared their bioactivity with that of the Allium sativum L. EO, which is very effective but bad-smelling. The A. citrodora EO was mainly rich in oxygenated monoterpenes, the most abundant of which were geranial (26.8%) and neral (21.0%). The B. graveolens EO was chiefly composed of monoterpene hydrocarbons, mostly represented by limonene (46.2%). According to the sensory description, the best odour profile was associated with the A. citrodora EO, while the olfactory expression of the EO from B. graveolens was negatively affected by a strong odour of “mouldy lemon”. The behavioural test showed that the A. citrodora EO was more repellent than that of A. sativum and, on the contrary, that the B. graveolens EO was attractive. The toxicity tests showed that the EOs of both Andean plants have a clear toxic effect on the C. vomitoria eggs and adults. In terms of ovicidal activity, there were no significant differences among the effects of the three tested EOs. On the adult flies, the toxicity of the two EOs of the Andean plants was much lower than that of A. sativum (LC50 fumigation = 1.86 μL EO L−1 air; LC50 ingestion = 8.10 μL EO mL−1 gel) both by fumigation (LC50 = 23.66 and 25.30 μL EO L−1 air for A. citrodora and B. graveolens, respectively) and ingestion (LC50 = 36.65 and 44.97 μL EO mL−1 gel for A. citrodora and B. graveolens, respectively), while, by contact, the A. citrodora EO (LD50 = 0.27 μL EO insect−1) was more toxic than the A. sativum EO (LD50 = 0.46 μL EO insect−1).

Ovicidal Activity of 2-Hydroxy-4-Methoxybenzaldehyde, Derivatives and Structural Analogues on Anopheles gambiae eggs

Background Effective remedies for disrupting Anopheles gambiae metamorphosis at the egg stage are crucial in suppression of the malaria vector populations that result in the reduction of disease burden. 2-Hydroxy-4-methoxybenzaldehyde (the major component of Mondia whytei roots), its derivatives, structural analogues and their blends were evaluated against the eggs of An. gambiae in the search for ovicidal compounds with potential use in mosquito control programs. Methods Mature roots were harvested from Mondia whytei plants grown in the Center for African Medicinal & Nutritional Flora and Fauna (CAMNFF) herbal medicinal garden and cleaned with distilled water. 2-Hydroxy-4-methoxybenzaldehyde ( 1 ) was isolated by steam distillation of the chopped roots. The selected derivatives and/or analogues were prepared using established chemical procedures and their structures confirmed by NMR spectroscopy and ESI-MS. Ovicidal activity of the pure compounds, derivatives, structural analogues and/or formulated blends was tested at 1, 10, 25 and 50 ppm on An. gambiae eggs. . Results Eleven mono-substituted ( 3-7 ), di-substituted ( 8-10 ), tri-substituted ( 1-2 ) aromatic compounds were assayed for ovicidal activity against Anopheles gambiae eggs singly or as blends. Benzaldehyde ( 4 ) and 4-methoxybenzaldehyde ( 9 ) were further converted into 2-hydroxy-1, 2-diphenylethanone ( 11 ), 1, 5-diphenylpenta-1, 4-diene-3-one ( 12 ) and 1, 5- bis (4-methoxyphenyl) penta-1, 4-diene-3-one ( 13 ) and evaluated for ovicidal activity individually or as blends. Of the thirteen compounds evaluated individually, 2-hydroxy-4-methoxybenzaldehyde ( 1 ) exhibited the highest ovicidal activity at LC 50 0.7075 ppm while anisole had the lowest activity at LC 50 40.342 ppm. The derivatives exhibited moderate activity: 2-hydroxy-1, 2-diphenylethanone (LC 50 10.599 ppm), 1, 5-diphenylpenta-1, 4-diene-3-one (LC 50 9.019 ppm) and 1, 5-bis (4-methoxyphenyl) penta-1, 4-diene-3-one (LC 50 15.642 ppm). The blends exhibited intriguingly high ovicidal efficacy with the mixture of benzaldehyde and phenol showing the highest (LC 50 0.332 ppm) while phenol and anisole exhibited the lowest activity (LC 50 9.9909 ppm). Conclusion From the activity of the blends, it is evident that anisole is antagonistic to the efficacy of phenol and benzaldehyde. It is also apparent that aldehyde and hydroxyl groups, when directly attached to the phenyl ring, provide the critical structural characteristics that contribute to the ovicidal activity of the aromatic compounds.