Evaluation of 99 pesticide residues in major agricultural products from the Western Highlands zone of Cameroon using QuECHERS method extraction and LC-MS/MS and GC-ECD analyses

There is no information available on pesticide residue levels in major food commodities harvested in Cameroon, especially from the western highlands region, the food basket of the country. Hence, this study evaluated the residues of 99 pesticides in 72 samples of 12 agricultural products collected in the region, using QuEChERS (Quick, Easy, Cheap, Effective, Rugged, and Safe) method extraction, and analyzed by liquid chromatography tandem mass spectrometry (LC-MS/MS) and gas chromatography with electron capture detection (GC-ECD). This method was suitable for detecting the targeted compounds: For 81 pesticides by LC-MS/MS, the limit of quantification (LOQ) was between 0.0004 and 0.0537 mg/kg; and for 18 halogenated pesticides by GC-ECD, it ranged from 0.0012 to 0.2180 mg/kg. The residues of 62 pesticides, including 12 banned compounds, were found in the samples. Insecticides (39.7%) were the most prevalent group, with all the samples containing at least one pesticide. Twenty-one pesticides (34.4%) exceeded their European Union maximum residue limits (MRLs) and 22 pesticides (34.4%) were found in all 6 sampling locations. Malathion and p,p′-DDT were the most distributed pesticides, found in almost all the samples and sampling sites. Food items with the highest rates of positive results were chili pepper (23.2%), white pepper (20.2%), kidney beans (17.3%), and soybeans (17.2%). Samples with residues above their MRLs represented 38% of all the positive analyses; chili pepper (6.4%) and kidney beans (5.5%) were found to have the most residues above their MRLs. The most critical food commodities were kidney beans, soybeans, chili pepper, and maize. This data presents scientific evidence that investigation into continuous monitoring and good regulation of pesticide usage in Cameroon is needed, and paves the way for health risks analysi

Field efficacy of aqueous extracts of Artemisia annua, Commelina benghalensis and Euphorbia hirta on rice growth, yield and brown spot disease incidence

Importance of the work: Brown leaf spot disease is one of the major causes of yield losses in rice production in Cameroon. Objectives: To evaluate the bioactivity of aqueous extracts of three Cameroonian medicinal plants on rice growth, yield and brown spot disease incidence. Materials & Methods: Plant extracts were tested at two doses (1 kg/15 L and 2 kg/15 L sprayed), while water and Mancozeb were used as negative and positive controls, respectively, in a split plot design made up of two factors (variety and plant extract). The varieties were NERICA 8, NERICA L56, Long grain red rice and Toukbem. Results: NERICAs 8 and L56 (exotic) and, Toukbem (local) varieties had the highest number of leaves and tillers while Toukbem had the highest plants and leaf area at 9 wk after transplanting. The numbers of leaves (31.3) and tillers (9.7) were significantly (p < 0.05) higher in plants treated with Euphorbia hirta extract at 67 g/L compared to Artemesia annua and Commelina benghalensis extracts. Brown spot severity was lower with E. hirta at 134 g/L (30%) and not significantly different to Mancozeb (23.6%). The NERICA L56 × E. hirta interaction at 134 g/L had the highest yield (5.8 t/ha) compared to the NERICA L56 × Mancozeb (6.1 t/ha) interaction. Chemical analysis of the E. hirta aqueous extract showed the presence of known bioactive compounds. Main finding: Field application of aqueous extract of E. hirta at 134 g/L could be used as a bioagent for rice brown spot management. The formulation of a natural product with this extract is necessary for large-scale field applications

Identification moleculaire des champignons des semences chez l\u2019Assamela suivi de leur protection a partir des poudres et extraits issus de plantes medicinales

Seedborne fungi constitute one of the major constraints of natural regeneration of Assamela ( Pericopsis elata ) stands in Cameroon\u2019s forest production. The objective of this study was to evaluate the capacity of a botanical ( Vitex doniana , Paullinia pinnata , Citrus sinensis , Ageratum conyzoides and Carica papaya ) to protect Assamela seeds against seedborne fungal pathogens. Fungal DNA extraction was done using the Zymo Research Kit and the internal transcribe spacer (ITS) portions of ribosomal DNA genes were sequenced. Plant powders were tested at 10% (mass/mass) and the efficiency of the aqueous and ethanolic extracts was evaluated at 100 g ml-1 and 48 g ml-1, respectively. Thirame (reference fungicide) was used as positive control. Pathogenic seedborne fungi were found to be Aspergillus niger , Macrophomina phaseolina , Aspergillus flavus and Fusarium equiseti. Seed infection was 67% in the negative control. Seeds stored in plant powders gave infection rates of less than 8% (P&lt;0.05) comparable to those of the synthesis fungicide Thirame (3.33%). The powders had no effect on germination at 10%. Only aqueous extracts of Citrus sinensis, Ageratum conyzoides and Carica papaya gave high germinations of 92, 92 and 97%, respectively. The plant powders tested and the aqueous extract of A. conyzoides could be considered as alternatives to chemical protection of P. elata seeds.Les champignons des semences constituent l\u2019une des contraintes majeures de r\ue9g\ue9n\ue9ration naturelle des peuplements de l\u2019Assamela ( Pericopsis elata ) dans les for\ueats de production au Cameroun. Cette \ue9tude a avait pour objectif de contribuer \ue0 la protection des semences chez l\u2019assamela par l\u2019utilisation des substances naturelles d\u2019origine v\ue9g\ue9tale ( Vitex doniana , Paullinia pinnata , Citrus sinensis , Ageratum conyzoides et Carica papaya ). Le Kit (Zymo Research) a \ue9t\ue9 utilis\ue9 pour l\u2019extraction d\u2019ADN des champignons et les portions ITS des g\ue8nes de l\u2019ADN ribosomial s\ue9quenc\ue9s. Les poudres v\ue9g\ue9tales ont \ue9t\ue9 test\ue9es \ue0 10% (m m-1) et les extraits aqueux et \ue9thanoliques, aux concentrations respectives de 100 g ml-1 et 48 g ml-1. Le fongicide Thirame a \ue9t\ue9 utilis\ue9 comme t\ue9moin positif. Les champignons pathog\ue8nes des semences ont \ue9t\ue9\ua0: Aspergillus niger , Macrophomina phaseolina , Aspergillus flavus et Fusarium equiseti. Le taux d\u2019infection des semences a \ue9t\ue9 de 67% chez le lot t\ue9moin n\ue9gatif. Les semences conserv\ue9es dans les poudres ont donn\ue9 des taux d\u2019infections inf\ue9rieurs \ue0 8% significativement comparable (P&lt;0,05) \ue0 ceux du fongicide de synth\ue8se Thirame (3,33%). Les poudres n\u2019ont pas eu d\u2019effet sur la germination \ue0 la concentration test\ue9e10%. Seuls les extraits aqueux de Citrus sinensis, Ageratum conyzoides et Carica papaya ont offert des taux de germination \ue9l\ue9v\ue9s de 92\ua0; 92 et 97% respectivement. Les poudres test\ue9es et l\u2019extrait aqueux de A. conyzoides pourraient constituer des alternatives \ue0 la protection chimique des semences de P. elata