Gbénonchi Mawussi

Assessment of average exposure to organochlorine pesticides in southern Togo from water, maize (Zea mays) and cowpea (Vigna unguiculata)

Drinking water, cowpea and maize grains were sampled in some potentially exposed agro-ecological areas in Togo and analysed for their contamination by some common organochlorine pesticides. A total of 19 organochlorine pesticides were investigated in ten subsamples of maize, ten subsamples of cowpea and nine subsamples of drinking water. Analytical methods included solvent extraction of the pesticide residues and their subsequent quantification using gas chromatography-mass spectrometry (GC/MS). Estimated daily intakes (EDIs) of pesticides were also determined. Pesticides residues in drinking water (0.04–0.40 µg l−1) were higher than the maximum residue limit (MRL) (0.03 µg l−1) set by the World Health Organization (WHO). Dieldrin, endrin, heptachlor epoxide and endosulfan levels (13.16–98.79 µg kg−1) in cowpea grains exceeded MRLs applied in France (10–50 µg kg−1). Contaminants’ levels in maize grains (0.53–65.70 µg kg−1) were below the MRLs (20–100 µg kg−1) set by the Food and Agriculture Organization (FAO) and the WHO. EDIs of the tested pesticides ranged from 0.02% to 162.07% of the acceptable daily intakes (ADIs). Population exposure levels of dieldrin and heptachlor epoxide were higher than the FAO/WHO standards. A comprehensive national monitoring programme on organochlorine pesticides should be undertaken to include such other relevant sources like meat, fish, eggs and milk.

Chemical Composition and Insecticidal Activity of Ocimum canum Essential Oil Against Coffee Berry Borer, Hypothenemus hampei (Ferrari) (Coleoptera: Scolytidae)

Abstract The chemical compositions of the essential oils of Ocimum canum Sims (Lamiaceae) areal part cultivated in Togo were investigated by GC-MS and tested for possible insecticidal activity against the coffee berry borer, Hypothenemus hampei (Ferrari) (Coleoptera: Scolytinae) under laboratory. Eighteen constituents (98.5 % of the total oil) were identified in the volatile oil of O. canum leaf. The main constituents found in the oil were terpineol-4 (34.7 %), linalool (22.7 %), λ-terpinene (7.3 %), trans-thujan-4-ol (5.9 %), trans-α-bergamotene (4.9 %) and caryophyllene (4.6 %). Other components were also identified by at minor concentrations ranging from 0.12 % (Thymol) to 2.7 % (Limonene). In the insecticidal activity test, crude essential oil of O. canum emulsions of exhibited adulticidal activity against coffee berry borer and response was being dose-related. The LD50 were 320 ppm for O. canum essential oil and 450 ppm for endosulfan and the conventional insecticide used as standard, respectively. The results indicate that the O. canum essential oil has a potential insecticidal activity and can be used as active ingredient in natural and sustainable pesticide within an Integrated Pest Management approach to combat the coffee berry borer.

Chemical Composition and Insecticidal Activity of Aeollanthus pubescens Essential Oil Against Coffee Berry Borer (Hypothenemus hampei Ferrari) (Coleoptera: Scolytidae)

Abstract Essential oil extracted from aerial parts of Aeollanthus pubescens was analysed for its chemical composition and investigated for possible insecticidal activity against Hypothenemus hampei (Ferrari), the major pest of coffee throughout the world. The GC and GC-MS analyses indicated that linalool (56.4 %) and fenchone (28.6 %) were the main components of the tested A. pubescens oil sample. Emulsions of crude essential oil of A. pubescens exhibited adulticidal activity against coffee berry borer and response was being dose-related. The LD50 were respectively 220 ppm for A. pubescens essential oil and 450 ppm for endosulfan, the conventional insecticide used as standard. These preliminary findings indicate that the tested volatile oil have a potential insecticidal activity and can be used as active ingredient in natural and sustainable pesticide within an Integrated Pest Management approach to combat coffee berry borer.

Investigation of Insecticidal Activity of Blend of Essential Oil of Cymbopogon schoenanthus and neem oil on Plutella xylostella (Lepidoptera: Plutellidae)

Abstract Plant and plant derived materials appear nowadays as a safe alternative to conventional pesticides to fight against crop pests. For this purpose, activity of blend (1:1 weight/weight) of Cymbopogon schoenanthus essential oil and neem (Azadirachta indica) seed oil on diamondback moth (Plutella xylostella) through contact and feeding methods were investigated and compared to each individual botanical. In the contact method, the combination of Cymbopogon schoenanthus/Azadirachta indica (LC50 = 23.3 mg/ml) oils exhibited medium activity showing higher toxicity than neem oil (58.39 mg/ml) and lower toxicity than Cymbopogon schcoenanthus essential oil (LC50 = 12.08 mg/ml). In feeding method, the toxicity resulted from the blend of Cymbopogon schoenanthus/Azadirachta indica (LC50 = 47.02) was slightly higher than both considered separately (LC50 = 52.39 and 53.63 for Cymbopogon schcoenanthus and neem respectively). Neem oil and the blend of Cymbopogon schoenanthus /neem exhibit strong antifeedance effect and inhibition of adult emergence of Plutella xylostella. The interaction between the mixture of Cymbopogon schoenanthus/ neem was additive resulting in increasing of insecticidal spectrum and could be used as an alternative to chemical pesticide in cabbage protection against Plutella xylostella.