Sedrick Junior Tsekane

Background: Pollinator-dependent crops such as okra face increasing threats from intensive pesticide use, creating a need for eco-friendly pest management solutions that effectively control pests while preserving pollinator diversity and activity. Aims: Synthetic pesticides pose severe threats to non-target beneficial insects, necessitating eco-friendly alternatives for sustainable agriculture. Study Design: Ecological survey was conducted in 11 trials (four plots each). Place and Duration of Study: Investigations were carried out in Garoua (Bocklé) from June 15 to October 10, 2022. Methods: The study evaluated the comparative impact of a synthetic insecticide (TEMA) and aqueous leaf extracts from three local plants (Azadirachta indica, Eucalyptus camaldulensis and Senna occidentalis) at 5%, 10%, and 15% doses on six pollinators in okra plots across six consecutive days. Data were analysed using the negative binomial generalized linear models (GLM-NB) and the robust permutation ANOVA (5,000 iterations). Results: Out of 991 specimens, Apis mellifera adansonii acted as a keystone species, representing 53.5% of the total pollinators. TEMA triggered an immediate, devastating (90.0%) collapse in pollinators on day 49. Botanical extracts safely sheltered 85.5% pollinators. Permutation procedure unmasked significant triple interactions (P = .011). High-dose extracts (15%) exerted no repellent or toxic effect on Amegilla calens, Megachile cincta, butterflies or hoverflies, optimising and stabilising pollinator residency curves late into the cycle. Conclusion: High-dose extracts offered excellent ecotoxicological safety and non-selective bio-prevention, providing an ecologically sound alternative to conserve biodiversity in sustainable agrosystems.

The exotic Capsicum chinense Jacq., 1776 (Solanaceae) is damaged in farms by insects in Ngaoundere (Cameroon). During ecological survey (from April 25 to August 25, 2024) in 44 neighboring plots of 4x3.5 m each, plants were inspected and adult insects found on stems, leaves, flowers and fruits were counted and captured using either a mouth aspirator or fine forceps for small sized non-flying specimens, or a dip net or butterfly net for large sized flying specimens. Four daily-checks spaced by a five-minute break, were carried out one day per week, four weeks per month and four months. Captured specimens were stored in vials containing 70% alcohol, identified to species level in laboratory and the community structure was characterized. A total of 48,298 specimens belonged to seven orders, 12 families, 14 genera and 14 species. Hemiptera was the most recorded (45.1% of the total collection) followed by Thysanoptera (43.5%), Orthoptera (7.6%), Coleoptera (2.1%), Hymenoptera (1.3%), Lepidoptera (0.2%), and Mantodea (0.2%). Aleyrodidae (Hemiptera) and Thripidae (Thysanoptyera) were mostly recorded. Aleurotrachelus trachoides (Aleyrodidae) was the most recorded (44.7%) followed by Heliothrips haemorrhoidalis (Thripidae) (43.5%), Tagasta marginella (Pyrgomorphidae) (5.8%), and Xenocatantops humilis (Acrididae) (1.3%), other species being rare. Three rare species were natives: Apis mellifera (Apidae), Bagrada hilaris (Pentatomidae), and the pest Lagria villosa (Tenebrionidae). Eleven species (78.6% of the total species richness, 98.3% of the total collection) were exotics. Three useful species were recorded: two pollinator Apidae Amegilla sp. and Ap. mellifera and the eggs-predator Carabidae Laemostenus complanatus. Five exotics were pests: Al. trachoides, Grapholita (Aspila) funebrana (Tortricidae), Gryllus campestris (Gryllidae), H. haemorrhoidalis, and Luprops tristis (Tenebrionidae), A lowspecies richness with a median level of species diversity, median evenness and dominance were detected. Three exotics Al. trachoides, H. haemorrhoidalis, and T. marginella were abundant and co-dominants. Assemblage functioned like a pioneer community and C. chinense appeared to attract naturalized exotic pests. Due to the dominance of non-natives, once they would monopolize available resources and saturate the locality, they would not allow natives the niche opportunities to re-establish themselves. The consequences of loosing natives, which may well interact with the endemic flora and fauna, will be of extreme concern.

Agroforestry leads to the degradation of natural forests, floral and faunal biodiversity. Little information exists on faunal functioning in agroforestry environments invaded by exotic pests compared to natural environments. Ecological survey was conducted from September to November 2023 in Mbalmayo Reserve Forest (Centre-Cameroon), the community structure and functioning of macro-invertebrates in cocoa plantations invaded by the little fire ant, were compared to the situation in neighboring secondary forest. Baits, pitfall, and quadrats allowed collection of 129,916 specimens of seven classes, 18 orders, 39 families, and 82 species. Insecta was mostly abundant (cocoa plantations: 92.7%, secondary forest: 6.97%, pooled sites: 99.7%), as well as Hymenoptera (cocoa plantations: 92.6%, secondary forest: 6.80% of 13 species, pooled sites: 99.4% of 14 species). Cocoa plantations and secondary forest presented each low species richness, diversity, and evenness, and a high dominance by a few species. Cocoa plantations presented more exotic species (92.9%, 25 species) while secondary forest showed mostly natives of unknown pest status and few native pests. The little fire ant was abundant (92.6%) and dominant exclusively in cocoa plantations. In secondary forest, Myrmicaria opaciventris, Crematogaster gabonensis, and Pheidole megacephala were abundant in the dry season, the two former being co-dominants while in the rainy season Cr. gabonensis, Cr. striatula, Craspedophorus bonvouloirii, My. opaciventris, Ph. speculifera, and Paltothyreus tarsatus were abundant, the four former being co-dominants. A low dissimilarity was noted between the two sites. The change in species composition from cocoa plantations to secondary forest was relatively large. Armadillidium vulgare Latreille, 1804 (Armadillidiidae) and Wasmannia auropunctata Roger, 1863 (Formicidae) were good indicators of disturbed environments. Assemblage functioned on the basis of maintaining a multi-species network developed in time and space for the circulation of the information, but with a weak force of regeneration. The secondary forest undergrowth was unfavorable for exotics and in-depth studies would be conducted on the behavior of natives in relation to the progression of invasions, since cases of repellency have been recorded. Policy makers responsible for green space management should take effective measures to prohibit the transfer of plants infested with exotic pest species between invaded and non-invaded areas when creating agroforestry areas.

Aims: Flower-visiting activity in honeybees was compared to that of Xylocopa olivacea on cowpea and sesame. Study Design: Daily activity, weekly activity, floral products and bee behavior were recorded. Place and Duration of Study: Field records (May to July 2016 and 2017) were conducted in Obala Higher Institute of Agriculture and Management campus (Bilone, Obala-Cameroon). Methodology: Thirty neighboring experimental plots (6x5.5 m each) were delimited each year (15 for sesame and cowpea respectively). Bee foragers came naturally from the station During the flowering period, in each year, day, plot and each plant species, two plants were randomly selected. Blooming flowers were checked from 1st to 14th. Daily activity was recorded each day from 6-7 a.m. to 4-5 p.m. Foragers were counted, collected floral products were identified; collection behavior and duration were recorded as well as air temperature and humidity. Results: Bee occurrences could be predicted using a linear combination of bee, plant, and air temperature. Flowers were visited from 2nd flowering day, ceased at 12th day (peak in 6th and 7th day). Daily activity started in sun shining mornings (8-9 a.m.) and stopped at 4-5 p.m., with a slight shift in activity peaks (honeybee:9-10 a.m.; Xy. olivacea: 11 a.m.-12 p.m.). Bees behaved similarly and collected nectar and pollen, with nectar collection lasting longer than pollen, which was in turn, longer in Xy. olivacea on cowpea than honeybee on sesame. Honeybees were interrupted by honeybees, Xy. olivacea and Megachile sp., and Ascalaphus africanus (Neuroptera: Ascalapidae). As for Xy. olivacea, visits were interrupted by Xy. olivacea, honeybees and As. africanus. Honeybees activity was not correlated with the climatic conditions while Xy. olivacea occurrence was positively correlated with air humidity. Conclusion: Sesame more attracted honeybees and cowpea more attracted Xy. olivacea, suggesting a probable difference in quality and/or quantity in floral products.

Aims: Investigations in cowpea fields allowed the characterization of the community structure of flower-visiting insects. Study Design: Seeds were sown in 15 plots (6x5.5 m each). Place and Duration of Study: Campus of Obala Higher Institute of Agriculture and Management (OHIAM), Bilone agroecological farm (Obala-Cameroon), from May to June 2016 and 2017. Methodology: Insects were identified in-situ or captured and stored in papillotes (Lepidoptera adults) or labelled vials containing 70° ethanol (other insects). Abundances allowed the determination of 11 alpha diversity indices. Beta diversity was tested using Bray-Curtis dissimilarity index and the correlation between species occurrences. Results: A total of 929 specimens belonged to five orders, 10 families, 13 species were recorded. Hymenoptera was the most family-rich and abundant (four families, 94.3% of the collection) followed by Diptera and Lepidoptera (two families each). Neuroptera and Orthoptera (one family each). Apidae was the most species-rich and abundant (three species; 72.9%), then Formicidae (one, 10.1%), Megachilidae (two; 9.8%). Apis mellifera (Apidae) was the most abundant (35.5%), then Xylocopa olivacea (Apidae) (22.3%), Amegilla calens (Apidae) (15.1%), Myrmicaria opaciventris (Formicidae) (10.1%), and Megachile (Chalicodoma) cincta (Megachilidae) (8.2%). The afrotropical useful predator Ascalaphus africanus (Ascalapidae) and the phytophagous pest Pteropera carnapi (Acrididae) were recorded. Exotic myasigenic species Calliphora vicina (Calliphoridae) and Musca domestica (Muscidae) were recorded. Acrididae, Nymphalidae and Pieridae cumulatively represented 3.1% pest species in the collection. Assemblages showed low species richness, high species diversity, and highly even community. Numbers of simply abundant species were close to that co-dominants. A negative correlation was noted between Acraea acerata (Nymphalidae) and Apis mellifera adansonii (Apidae), Ap. mellifera and Calliphora vicina (Calliphoridae), Ap. mellifera and Synagris conuta (Vespidae). Several positive correlations were recorded. Conclusion: In Bilone, results highlighted the importance of flower-visiting insects for the cowpea pollination and crop yield. Species were moderately abundant and assemblages functioned on the base of niche partitioning nomocenosis (log-linear model) of more or less disturbed environments with strong competition between pioneer species for the available resources.

Synthetic pesticides present risks of pollution of the environment, humans and livestock and the alternative proposed today is to use botanical extracts in the fields against crop pests. But in North Cameroon, little information exists concerning the effect of these extracts on useful pollinating insects in general and no information exists in particular on foragers of the genus Amegilla Friese, 1897 (Apidae: Apinae: Anthophorini). The frequency and foraging activities of Amegilla , on newly blooming flowers of Vigna unguiculata (L.) Walp., 1843 (Fabales: Fabaceae) were recorded during five consecutive days in 2021 and 2022 planting campaigns. Plants were divided into untreated plots and plots treated using the synthetic insecticide Parastar (l p.c..ha ^-1 ) or 10%, 20% and 30% aqueous leaf extracts of Calotropis procera (Aiton) Aiton, 1811 (Gentianales: Apocynaceae), Eucalyptus camaldulensis Dehnh., 1832 (Myrtales: Myrtaceae) and Tithonia diversifolia (Hemsley) Gray, 1883 (Asterales: Asteraceae) respectively. Among 8,987 insects collected (48.9% in 2021), Amegila calens Le Peletier. 1841 with stockier foragers (2021 campaign: 2.2% of the total collection, entomophily F _{A. calens} =4.5%; 2022 campaign: 0.7%, F _{A. calens} =1.3%; pooled campaigns: 2.9%, F _{A. calens} =2.9%) and Amegilla sp. with slender foragers (2021: 3.8%, F _{Amegilla sp.} =7.7%; 2022: no data) were recorded. Foragers started activity from 6 a.m. and stopped foraging before noon, with a peak of activity in 8 to 9 a.m. time slot for A. calens and 10 to 11 a.m. time slot for Amegilla sp.. During the five consecutive days from the first blooming day of the flowers, 598 visits (89.8% in 2021 and 10.2% in 2022) were recorded with a peak of visits during the 3 ^rd day and then declined until it stopped during the 5 ^th day. Treatments including the synthetic insecticide (which was the most repellent to the wild bees), did not significantly reduce the frequency of visits. But 20% aqueous extract of Ca. procera showed a significant increased of the mean duration of visits of the bees, compare to the results recorded in Parastar-treated plots. Therefore, the tested extracts, especially 20% aqueous leaves extract of Ca. procera may be recommended to control field insect pests and for preservation of foraging activities of Amegilla genus.

A survey was undertaken from July 2021 to January 2022 in South-Cameroon on the biodiversity of micro-arthopods in the Memve’ele dam (Site 1), the tributary river (Site 2) and the adjacent river (Sites 3 and 4). Four abiotic parameters were measured in-situ while nine other abiotic parameters were measured in the laboratory using standard methods. Micro-arthopods were counted and identified. Water quality was determined. BOD ₅ , conductivity, NO ₂ ^- , NO ₃ ^- , pH, PO ₄ ^3- , temperature and suspended solids were on average within the standards for drinking water. Chlorophyll a, color, DO, NH ₄ ⁺ and turbidity values were on average above the standard upper limits. Based on the water quality index (WQI) raw waters were unfit for direct drinking (Dam: WQI=898.864; Site 2: WQI=752.451; Site 3: WQI=883.808; and Site 4: WQI=1,665.883) and presented ideal conditions for fish farming or irrigation for agriculture. A total of 5,487 specimens belonged to three classes, eight orders, 20 families, 57 genera, and 87 species and morphospecies (54 freshwater and 33 tolerant species able to develop in at least two water environments). Ectocyclops sp. was the most recorded species (10.6%), followed by Cyclops sp. (9.1%), Alona costata (8.9%), Mesocyclops sp. (7.9%), Tropocyclops sp. (7.5%), Senecella calanoides (6.8%), Diaphanosoma sarsi (6.1%), while other species were represented each by less than 5.0%. Low species richness, high species diversity and a very low dominance by a few species were noted. Assemblages were highly even (Pielou’s index close to 1). Species exhibited in all sites, a positive global net association. The assemblage recorded during the wet season at Site 3 functioned as a pioneer community (Broken-Stick model) while, the assemblage recorded during the dry season at Site 2 and the one recorded during the dry season at Site 3 functioned as nomocenosis (log-linear or log-normal models) and were therefore little evolved. In contrast, during the two seasons in the dam and Site 4, as well as during the rainy season in Site 2 and the combined seasons in Site 3, the assemblages functioned as highly evolved communities (Zipf or Zipf-models) with significant regenerative force, suggesting that these assemblages maintained a complex information network developed at spatio-temporal scales. The evolved state (close to natural balance) of the micro-arthopods communities should be preserved and protected.

Synthetic pesticides present worldwide risks of contamination of humans, livestock and the environment due to the strong persistence and the toxic residues in fruits and vegetables. Natural biopesticides of local plant origin present low persistence and are the best alternative for the control of crop pests. In the Adamaoua region (Northern Cameroon), few studies exist concerning effects of botanical pesticides on the behavior of beneficial insects. Studies aimed to draw up a list of pollinating insects on flowers of Vigna unguiculata (L.) Walp., 1843 (Fabales: Fabaceae), in situations of treatment with botanical pesticides compared to the situation of the use of synthetic insecticide and to determine the effect of the biopesticides on the behavior of the main floricultural insects. Field investigations were carried out during two cowpea cultivation campaigns (June to September 2021 and June to October 2022) in Dang (suburb of Ngaoundere) on the effect of leaves extracts of local plant origin on the foraging behavior of Apis mellifera Linnaeus, 1758 (Hymenoptera: Apidae) and the main sap-sucking insect Aphis craccivora Koch, 1854 (Hemiptera: Aphididae). Forty-four cowpea plots of 4x3.5 m each distributed according to the randomized complete block model (four untreated plots as negative control, four plots treated with the synthetic insecticide Parastar (40EC 535/ 10/IN, 20 g/l of imidacloprid and 20 g/l of lamda-cyhalothrin) as positive control, and 36 experimental plots treated with three concentrations (10%, 20% and 30%) of aqueous leaves extract of Calotropis procera (Gentianales: Apocynaceae), Eucalyptus camaldulensis (Myrtales: Myrtaceae), and Tithonia diversifolia (Asterales: Asteraceae) respectively, made it possible to conduct four treatments: (1) flowers left to freely pollination, (2) flowers protected against pollinators, (3) flowers visited exclusively by Ap. mellifera and (4) flowers protected against insects. Among eight species (four orders, four families and seven genera) recorded on the flowers of V. unguiculata, the domestic bee Ap. mellifera was the most common and collected nectar and pollen. The control plots and those treated with 10% or 20% aqueous leaves extracts allowed the bee to carry out its activity. Plots treated with 30% extract of each plant and those treated with the synthetic insecticide Parastar, drastically altered the rhythm and speed of activity in Ap. mellifera foragers. This behavior became less coordinated and slow on treated plants. It would be wise to use 10% or 20% aqueous extracts as botanical insecticides and an alternative to the synthetic insecticide Parastar.

A survey was undertaken from March to June 2014 on the biodiversity and the community structure of Chromista Cavalier-Smith, 1981 in Nyong and Kienke River mouths (South-Cameroon). In each river, raw waters were collected from upstream to downstream at four sites. Cells were counted using the Malassez cells procedure and species were identified. A total of 10427.1x10 ⁵ cells corresponded to three phyla, eight classes, 23 orders, 32 genera and 40 species (24 freshwater species (60.0% of total species richness and total collection respectively), three marine species (7.5% and 2.4% of the total species richness; and total collection respectively), and one brackish water specialist in Kienke (2.5% and 5.1%), 13 tolerant species (32.5% and 32.6%)). The trophic diatom index revealed undisturbed conditions with no or little alteration of human origin and a low organic pollution (oligotrophic or mesotrophic state) (Nyong: TDI=52.7; Kienke: TDI=69.7; pooled assemblage: TDI=65.0). A low species richness was detected (richness ratio in Nyong: d=0.008; Kienke: d=0.003; pooled rivers: d=0.004), a high species diversity (Shannon index close to maximum) (Nyong: H’=2.742 and H’ _max =2.996; Kienke: H’=2.685 and H’ _max =2.996; pooled rivers: H’=3.245 and H’ _max =3.689), a very low dominance by a few species (Berger-Parker index close to 0) (Nyong: IBP=0.156; Kienke: IBP=0.175; pooled rivers: IBP=0.134), and Hill’s ratio were close to 1 (Nyong: Hill=0.819; Kienke: Hill=0.803; pooled rivers: Hill=0.722). The community was highly even with a high value of the Pielou’s evenness close to 1 (Nyong: J=0.915; Kienke: J=0.896; pooled rivers: J=0.880). Two useful species and one harmful species to fish were rare in Kienke. Species exhibited in Kienke and pooled data in rainy season, a positive global net association while it was negative in Nyong. Assemblage fitted Preston’s model in Nyong with a high environmental constant in the dry season (m’=1.469), low constant in the rainy season (m’=0.947) and the pooled seasons (m’=0.853). In Kienke constants were low (dry season: m’=0.574; rainy season: m’=0.566; pooled seasons: m’=0.581) suggesting a evolved community in less disturbed environments where the majority of species showed moderate abundances. In the dry season, the pooled assemblage functionned on the basis of maintaining a complex information network (close to ecological balance) developed at spatio-temporal scales (ZM model) and it presented a low force of regeneration (fractal dimension of the distribution of individuals among species (1/γ)=0.925<1). The evolved oligotrophic state (close to natural balance) of the chromists’ community should be preserved and protected and the studied rivers classified as reference.