The atlas of spectral data of sesquiterpene hydrocarbons; Daniel Joulain & Wilfried A. König. E.B.-Verlag, Hamburg, 1998, ISBN 3-930826-48-8, $700

The two-spotted spider mite, Tetranychus urticae Koch, is a phytophagous pest that can cause significant yield losses in many agricultural crops, including fruits, cotton, vegetables, and ornamentals. To date, 3877 host species have been reported around the world in both outdoor crops and greenhouses. In this paper, we present the common methods to control this pest including chemical and biological practices. While synthetic acaricides have been widely used to manage T. urticae, in recent years, interest in pesticides derived from plants has increased considerably as a result of environmental concerns and pest population resistance to conventional pesticides. Some botanical pesticides can be easily produced, are relatively efficient against pests, and with few exceptions, their mammalian toxicity and persistence in the environment is low. Thus, the use of plant extracts appears to be a promising alternative strategy for pest management. The present paper reviews studies on the biocidal activities of plant extracts, including essential oils, against T. urticae, a plant-feeding mite found worldwide and a serious agricultural and home garden pest.

A review of the major biological approaches to control the worldwide pest Tetranychus urticae (Acari: Tetranychidae) with special reference to natural pesticides

Lamiaceae have traditionally been used in developing countries for their insecticidal and repellent properties against several insect species. In our research, the essential oil (EO) extracted from fresh leaves of Hyptis suaveolens (Lamiaceae), and its main constituents were evaluated for larvicidal and repellent activity against the Asian tiger mosquito, Aedes albopictus Skuse (Diptera: Culicidae), currently the most invasive mosquito worldwide. H. suaveolens EO had insecticidal activity against A. albopictus larvae and mortality was dosage dependent. At the highest dosages of 450 and 400 ppm, there were no significant differences on larval mortality, as mortality ranged between 98.33% and 93.33%, respectively. At dosages ranging from 250 to 350 ppm, mortality rates were lower and not significantly different from each other. Terpinolene was found to be the most effective pure compound. Efficacy protection from H. suaveolens EO, at dosages ranging from 0.03748 to 0.7496 μg cm−2 of skin, was evaluated during 150 min of observation. Results indicated that this EO had a significant repellent activity (RD50 = 0.00035 μg cm−2; RD90 = 0.00048 μg cm−2), with differences in repellency rates, as a function of both concentration and observation time. Protection time ranged from 16 to 135 min. These results clearly evidenced that the larvicidal and repellent activity of H. suaveolens EO could be used for the development of new and safer products against A. albopictus.

Larvicidal and repellent activity of Hyptis suaveolens (Lamiaceae) essential oil against the mosquito Aedes albopictus Skuse (Diptera: Culicidae)

Neem seed oil (NSO) of Azadirachta indica (Meliaceae) contains more than 100 determined biologically active compounds, and many formulations deriving from them showed toxicity, antifeedancy and repellence against a number of arthropod pests. However, it is widely known that botanical products can differ in their chemical composition and bioactivity, as function of the production site and production process. We used high-performance thin layer chromatography (HPTLC) to investigate differences in chemical constituents of NSOs from three production sites. HPTLC analyses showed several differences in chemical abundance and diversity among NSOs, with special reference to limonoids. Furthermore, the three NSOs and their fractions of increasing polarities [i.e. ethyl acetate (EA) fraction and butanol (BU) fraction] were evaluated for larvicidal toxicity and field oviposition deterrence against the Asian tiger mosquito, Aedes albopictus, currently the most invasive mosquito worldwide. Results from bioactivity experiments showed good toxicity of NSOs and EA fractions against A. albopictus fourth instar larvae (with LC50 values ranging from 142.28 to 209.73 ppm), while little toxicity was exerted by BU fractions. A significant effect of the production site and dosage was also found and is probably linked to differences in abundance of constituents among samples, as highlighted by HPTLC analyses. NSOs and EAs were also able to deter A. albopictus oviposition in the field (effective repellence values ranging from 98.55 to 70.10 %), while little effectiveness of BU fractions was found. Concerning ovideterrent activity, no difference due to the production site was found. This is the first report concerning larvicidal toxicity of NSO against A. albopictus and ovideterrence against Culicidae in the field. The chance to use chemicals from the NSO EA fraction seems promising, since they are effective at lower doses, if compared to synthetic products currently marketed, and could be an advantageous alternative to build newer and safer mosquito control tools.

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Larvicidal and ovideterrent properties of neem oil and fractions against the filariasis vector Aedes albopictus (Diptera: Culicidae): a bioactivity survey across production sites

Toxicity of some essential oil formulations against the Mediterranean fruit fly Ceratitis capitata (Wiedemann) (Diptera Tephritidae)

The acute toxicity of essential oils from the whole fruit (EF) or from the fibres of the fruit (FF) of the local aromatic plants Xylopia aethiopica Dunal (Annonaceae) collected in north Cameroon was evaluated on Sitophilus zeamais adults. A concentration of 1 ml of essential oil per 100 g of maize seeds was tested to determine weevil mortality after 24 h of exposure. Under these conditions, the essential oil derived from both EF and FF of X. aethiopica led to 100% mortality. In a second step, proportions of active compounds present in the oil of both EF and FF of X. aethiopica were quantified. The toxicity of the four main compounds was tested against S. zeamais: alpha-pinene, beta-pinene, Delta-3-carene and terpinen-4-ol according to their proportion in the essential oil of the concerned plant part. beta-pinene and terpinen-4-ol were responsible for 50% of the mortality at the proportion found in EF and FF essential oils respectively. When mixed, a synergic effect of the compounds was observed that restored the mortality percentage observed for the crude oil. It appears that X. aethiopica essential oil could be a potential source of natural and low-cost insecticide to control storage pests.

Toxicity Of Some Terpenoids Of Essential Oils Of Xylopia Aethiopica From Cameroon Against Sitophilus Zeamais Motschulsky

Hyptis spicigera essential oils from seven localities in the North-Cameroon (Ngaoundere, Guirvidig, Kodeck, Lara, Toloum, Kaele, Tchecal-baila) were investigated by GC and GC/MS. Results showed differences within harvesting sites and between the different sites of collection but did not revealed clear tendencies in the evolution of the oil composition with regard to the sampling period. The main group of compounds in all the analyzed samples were: alpha-pinene (11.9%-42.1%), beta-pinene + sabinene (6.0%-39.8%) and beta-phellandrene + 1,8-cineole(8.8%-27.4%) except in one oil where beta-caryophyllene (23.4%) was the principal component. The insecticidal activity of H. spicigera and its principal terpenic components was evaluated against the cowpea weevil Callosobruchus maculatus F., the major cause of damages of cowpea (Vigna unguiculata (L.) Walp) in North Cameroon.

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Effect of site location and collecting period on the chemical composition of Hyptis spicigera Lam. an insecticidal essential oil from north-Cameroon

Composition des huiles essentielles de Xylopia aethiopica (Dunal) A. Rich du Cameroun et identification d’un diterpene : ent-13-epi manoyl oxyde. L’huile essentielle des infrutescences de Xylopia aethiopica (Annonacee), de quatre localites du Cameroun, a ete analysee par GC/MS et GC/FID. Plus de soixante composes ont ete identifies avec 47,5–84,0 % de monoterpenes hydrocarbones, principalement le b-pinene et un melange de b-phellandrene et de 1,8-cineole, 6,5–12,9 % de monoterpenes oxygenes, 13,8–30,4 % de sesquiterpenes, et 0,4–0,6 % d’un diterpene non identifie. Les essais de purification sur colonne chromatographique et des analyses par GC/MS et RMN ont permis d’identifier ce diterpene comme etant le ent-13-epi manoyl oxyde qui est rapporte pour la premiere fois dans l’huile essentielle des fruits de X. aethiopica.

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Composition of Xylopia aethiopica (Dunal) A. Rich essential oils from Cameroon and identification of a minor diterpene: ent-13-epi manoyl oxide

The essential oil from the leafets of Steganotaenia araliacea Hochst from the Adamaoua region of North Cameroon was analyzed by GC(FID) and GC/MS. More than 20 compounds have been identifed. Monoterpenes (60.3%) are mainly represented by limonene (31.9%) and α-pinene (17.8%); the main sesquiterpenes were γ-elemene (9.6%) and ar-curcumene (6.6%).

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Papers

Toxicity Of Some Terpenoids Of Essential Oils Of Xylopia Aethiopica From Cameroon Against Sitophilus Zeamais Motschulsky

Effect of site location and collecting period on the chemical composition of Hyptis spicigera Lam. an insecticidal essential oil from north-Cameroon

Composition of Xylopia aethiopica (Dunal) A. Rich essential oils from Cameroon and identification of a minor diterpene: ent-13-epi manoyl oxide

Analysis by GC/FID and GC/MS of essential oil of leaflets of Steganotaenia araliacea hochst from cameroon