Insect pests’ incidence and variations due to forest landscape degradation in the humid forest zone of Southern Cameroon: farmers’ perception and need for adopting an integrated pest management strategy

Group surveys were conducted in five villages in each of the three resource-use zones of the humid forest zone of Southern Cameroon, to assess insect pests’ incidence and the variation due to forest landscape degradation in the agricultural production systems. 389 farmers were interviewed. The results show that: (1) In annual crop systems, insect pests in general rank together with vertebrate pests and diseases amongst the most important agronomic constraints. No differences were found between the intensification zones, except for weeds, which appeared to be a greater constraint in the slightly degraded area. Within the insect pest, the greatest damage to crops according to farmers originated from borers and scales, followed by variegated grasshopper. Only the termites showed a difference between zones - the problem being greatest in the high-degraded areas. (2) In the young perennial crop systems, all the categories of agronomic constraints were equally important. Within the insect pest, mirids were identified as the greatest constraint, followed by borers and caterpillars. There were more variations in the responses according to zones compared to annual crops. Termites and scales were relatively more important in the high-degraded area. In term of control strategy, we recommended an integrated pest management.Keywords: Farmers, pest, insect, annual crop, perennial crop, integrated pest managemen

Farmers' perception on the importance of variegated grasshopper (Zonocerus variegatus (L.)) in the agricultural production systems of the humid forest zone of Southern Cameroon

BACKGROUND: Zonocerus variegatus (Linnaeus, 1758) (Orthoptera: Pyrgomorphidae) is known as an agricultural pest in West and Central Africa. However, its importance in the agricultural production system in Cameroon has not been investigated. The study assesses farmers' perception on the importance of Z. variegatus in the agricultural production systems of the humid forest zone of Southern Cameroon. METHODS: Research was carried out in 5 villages of each of three Agro-Ecological, Cultural and Demographic Blocks (AECD-Blocks) of the Forest Margin Benchmark Area (FMBA). In each village, a semi-structured survey was used; male and female groups of farmers were interviewed separately. RESULTS: Z. variegatus is present throughout the humid forest zone of Southern Cameroon, where it is ranked as the third most economically important insect pest of agriculture. In the farmers' opinion, Z. variegatus is a polyphagous insect with little impact on young perennial crops. The length of the pre-farming fallow does not affect Z. variegatus pest pressure in the following crops. The increased impact of the grasshopper observed today in the fields, compared to what existed 10 years ago is as a result of deforestation and increase in surface of herbaceous fallow. The damage caused by Z. variegatus is higher in fields adjacent to C. odorata and herbaceous fallows than in those adjacent to forests and shrubby fallows. The fight against this grasshopper is often done through physical methods carried out by hand, for human consumption. The farmers highlight low usage of the chemical methods and a total absence of biological and ecological methods. CONCLUSION: Farmers' perception have contributed to understanding the status of Z. variegatus in the humid forest zone of Southern Cameroon. The results are in general similar to those obtained in other countries

Redescription and diagnosis of the African genus Gemeneta Karsch, 1892 (Orthoptera: Acrididae: Catantopinae)

The subfamily Catantopinae is a poorly defined subfamily of the Acrididae, having many genera that require taxonomic clarification. The genus Gemeneta from this subfamily is found in African forests and has only two described species, Gemeneta terrea and Gemeneta opilionoides. However, the original descriptions of the genus relied heavily on external female morphology, and a description of male G. opilionoides was completely lacking. The present work provides the first description of the male of G. opilionoides, a morphological description of both species, including internal genitalia, and clarifies the generic diagnosis. This study is a contribution to a better understanding of the taxonomy of Catantopinae in the tropical forests of Africa

Prévalence et abondance de Charletonia cameroonensis Haitlinger & Kekeunou 2014 (Acari : Erythraeidae) parasite de Zonocerus variegatus (Linnaeus 1758) (Orthoptera : Pyrgomorphidae) dans la zone côtière du Cameroun

Objectifs: La recherche d’une stratégie de protection des cultures vivrières contre le criquet ravageur Zonocerus variegatus (Linnaeus 1758) (Orthoptera : Pyrgomorphidae) a consisté à étudier chez cet hôte, la prévalence et l’abondance de Charletonia cameroonensis Haitlinger & Kekeunou 2014 (Acari : Erythraeidae) dans la zone côtière du Cameroun.Méthodologie et résultats: Les captures et observations ont été menées hebdomadairement d’avril 2013 à avril 2014 à Logbessou, un quartier de la banlieue Nord-est de la ville de Douala. Pendant une heure (8h30-9h30), les individus de Z. variegatus ont été capturés et C. cameroonensis a été énuméré sur tout le corps de chacun. Il apparait que C. cameroonensis est un ectoparasite permanent de Z. variegatus, puisqu’il a été rencontré durant toute la période d’étude et sur la quasi-totalité des stades postembryonnaires. Sa prévalence a atteint 21,40 %. Le pourcentage d’infestation a significativement augmenté du stade larvaire 1 (4,14%) au stade adulte (67,58%). Ce pourcentage d’infestation a été plus élevé en saison pluvieuse (31,02%) qu’en saison sèche (7,69%). L’abondance de C. cameroonensis a varié de 0 à 23 individus parasites par individu de Z. variegatus. Cette abondance s’est accrue du stade larvaire1 au stade adulte. C. cameroonensis a été présent sur les trois tagmes de Z. variegatus, avec une charge significativement plus élevée sur le thorax et principalement au niveau des ailes. Une corrélation significativement positive a été obtenue entre l’abondance du parasite et la taille des populations du ravageur.Conclusions et application des résultats: Ces résultats préliminaires apportent des connaissances qui pourraient être approfondies dans le cadre d’études ultérieures pour une exploitation de C. cameroonensis dans une optique de lutte biologique contre Z. variegatus.Mots clés: Abondance, prévalence, C. cameroonensis, Z. variegatus, Zone côtièreEnglish AbstractObjectives: The search for a strategy to protect food crops against Zonocerus variegatus (Linnaeus 1758) (Orthoptera : Pyrgomorphidae) was to investigate the prevalence and abundance of Charletonia cameroonensis Haitlinger & Kekeunou 2014 (Acari : Erythraeidae) in the coastal area of Cameroon.Methodology and results: Catches and observations were conducted weekly from April 2013 to April 2014 in Logbessou, a sub-urban North-East of Douala. For one hour (8:30 to 9:30), individuals of Z. variegatus (all stages combined) were captured and the distribution of C. cameroonensis on each insect was recorded. It appears that C. cameroonensis was a permanent parasite of Z. variegatus. Parasite prevalence reached 21.40 %; this prevalence increased significantly from the stage 1 larva population (4.14%) to adult stage (67.58%). Parasite prevalence was higher during the rainy season (31.02%) than during the dry season (7.69%). C. cameroonensis abundance varied from 0-23 (averagely 0.54±1.65 parasites per host). This abundance also increased significantly from stage 1 larva (0.05±0.24 parasites per host) to adult (2.36±3.4 parasites per individual host). C. cameroonensis was present on the three body regions of the host, with a significantly greater parasite load on the thorax and more precisely on the wings. A significantly and positive correlation has been established between the parasite abundance and the size of Z. variegatus population.Conclusion and application of results: These preliminaries results provides important information that could be explored in future studies in the context of biological control of Z. variegatus by C. cameroonensis.Keywords: Abundance, prevalence, C. cameroonensis, Z. variegatus, Coastal zon

Larval habitats and susceptibility of malaria vectors to insecticides in semi-urban and rural localities of the Coast-Cameroon region: preliminary data

Le choix d’une stratégie appropriée de lutte anti-paludique dans un faciès éco-climatique donné requiert une bonne connaissance de l’écologie des vecteurs, notamment la distribution spatiale et la productivité des gîtes larvaires, et de leur niveau de sensibilité aux insecticides. La présente étude cartographie, caractérise les gîtes de ponte des moustiques et évalue la susceptibilité aux insecticides des vecteurs de paludisme à Banya II et Bodiman, deux localités l’une sub-urbaine et l’autre rurale, de la région du littoral camerounais. Les enquêtes sur le terrain ont été menées en mai 2015. Les gîtes de moustiques ont été géo-réferencés. Pour chaque gîte, les larves ont été prélevées puis élevées et les paramètres physico-chimiques mesurés in situ. La sensibilité des vecteurs au Dichlorodiphényltrichloroéthane (DDT), à la Deltaméthrine et à la Perméthrine a été évaluée sur les anophèles issus de l’élevage des larves. Une diversité de gîtes a été identifiée dans les sites d’étude (mares, cours d’eau, caniveaux, pneus, emballages-plastiques, récipients de réserve d’eau, récipients abandonnés, trous de papayer, trous de bambou). Cependant, Anopheles gambiae s.l., l’espèce la plus abondante à Banya II a été plus fréquente dans les mares, alors que Culex poicilipes, l’espèce la plus abondante à Bodiman a été majoritairement collectée dans des récipients abandonnés. Les deux catégories de gîtes avaient respectivement une conductivité électrique de 167,5 [16,9-305] et 170,43 [11,6-461] µs/cm ; une salinité de 90,5 [23,5-157] et 94,6[15-240] g/l ; un total de solides dissous (TDS) de 119,6 [20,6-215] et 123,3 [7,8-354] ppm. Les trois insecticides testés ont induit des taux de mortalité inférieurs à 85 % pour la souche Banya II d’A. gambiae s.l. et supérieurs à 98 % pour la souche Bodiman d’A. nili. Les présentes informations devraient être prises en compte pour une meilleure orientation des stratégies de lutte si l’on veut contrôler efficacement les vecteurs dans les localités d’étude.Choosing an appropriate strategy for mosquito control in an eco-climatic facies requires knowledge of vector ecology, including the spatial distribution and productivity of larval habitats and their level of susceptibility to insecticides. This study maps, characterizes the mosquito breeding sites and evaluates the susceptibility to insecticides of malaria vectors to Banya II and Bodiman, two semi-urban and rural areas of the coastal region of Cameroon. The field surveys were conducted in May 2015. The mosquito breeding sites were geo-referenced. For each breeding site, larvae were collected then reared and physico-chemical parameters measured in situ. The susceptibility of vectors to dichlorodiphenyltrichloroethane (DDT), deltamethrin and permethrin was evaluated on the anopheline obtained from larva rearing. A variety of breeding sites has been identified in the study sites (ponds, rivers, ditches, tires, plastic wrap, water storage containers, abandoned containers, papaya holes, bamboo holes). However, Anopheles gambiae s.l, the most abundant species in Banya II was more common in the pools, while Culex poicilipes, the most abundant species in Bodiman was mainly collected in abandoned containers. The two categories of breeding sites had respectively electrical conductivity of 167.5 [16.9-305] and 170.43 [11.6-461] µs/cm, salinity of 90.5 [23.5-157] and 94.63[15-240] g/l and total dissolved solids of 119.6 [20.6-215] and 123.3 [7.8-354] ppm. Insecticides tests revealed mortality rates below 85 % for the Banya II Strain of A. gambiae s.l. and over 98 % for the Bodiman strain of A. nili. These informations should be taken into account for a better orientation of control strategies in order to control effectively the vectors in the study localities

Acoustic methods improve the detection of the endangered African manatee

The African manatee (Trichechus senegalensis) is an elusive, data-deficient, and endangered species which inhabits marine and freshwater systems throughout Western and Central Africa. A major challenge in understanding the species ecology and distribution is the difficulty in detecting it using traditional visual surveys. The recent invasion of Giant Salvinia (Salvinia molesta) at the most important site for the species in Cameroon further limits their detectability and may restrict their movements and habitat use. To investigate methods’ effectiveness in detecting African manatees, we conducted monthly vessel surveys from which visual point scans, 360° sonar scans, and passive acoustic monitoring were conducted simultaneously at ten locations and over 12 months in Lake Ossa, Cameroon. Manatee detection frequency was calculated for each method and the influence of some environmental conditions on the methods’ effectiveness and manatee detection likelihood was assessed by fitting a binary logistic regression to our data. Detection frequencies were significantly different between methods (p < 0.01) with passive acoustics being the most successful (24.17%; n = 120), followed by the 360° sonar scan (11.67%; n = 120), and the visual point scan (3.33%; n = 120). The likelihood of detecting manatees in Lake Ossa was significantly influenced by water depth (p = 0.02) and transparency (p < 0.01). It was more likely to detect manatees in shallower water depths and higher water transparency. Passive acoustic detections were more effective in uninvaded areas of the Lake. We recommend using passive acoustics to enhance African manatee detections in future surveys

Urban wild meat and pangolin consumption across southern forested Cameroon: The limited influence of COVID‐19

Overexploitation of wildlife is pervasive in many tropical regions, and in addition to being a significant conservation and sustainability concern, it has received global attention given discussions over the origins of zoonotic disease outbreaks. Where unsustainable, consumption of wild meat by urban residents has been identified as a major socio‐environmental challenge, given it is a significant driver of wildlife declines. Yet, information on urban wild meat consumers and possible ways to target conservation interventions remains lacking. Using one of the largest datasets of urban wild meat consumers (1391) collected through structured questionnaires in 20 towns and cities, we model the demographic, psychographic and spatial factors associated with wild meat consumption patterns in southern Cameroon. We find that nearly half of the sampled consumers ate wild meat once per week or more, and find that the probability of being a frequent consumer was greater among men, those living in smaller towns, and those who do not consider there to be a link between eating wild meat and disease. Threatened pangolin species are highly preferred among urban consumers, and most consumers did not consider there to be a link between COVID‐19 and pangolins. Most respondents had eaten wild meat since the beginning of COVID‐19 and had not reduced their wild meat consumption due to COVID‐19. For the first time, we show that consumers with beliefs against a link between wild meat consumption and disease and those with greater income were less likely to have decreased their wild meat consumption. We identified stakeholders including teachers and religious/community leaders as potentially appropriate messengers for demand‐reduction campaigns, with television and radio being the most trusted communication channels among wild meat consumers. Crucially, our study advances current scientific understanding of the factors that influence wild meat consumption frequency and change due to COVID‐19 by urban consumers (particularly health beliefs and settlement size). We discuss how our results could be used to inform the design of wild meat demand‐reduction interventions to bring the consumption of wild meat towards sustainability in Cameroon, and our approach applied pan‐tropically. Read the free Plain Language Summary for this article on the Journal blog

Larviciding intervention targeting malaria vectors also affects Culex mosquito distribution in the city of Yaoundé, Cameroon

Although Culex species are considered to be equally affected by control measures targeting malaria vectors, there is still not enough evidence of the impact of interventions such as larviciding on the distribution of these mosquito species. The present study assessed the impact of a larviciding trial targeting malaria vectors on Culex mosquito species in the city of Yaoundé, Cameroon. A cluster randomized trial comparing 13 treated clusters and 13 untreated clusters was implemented. Data were collected at baseline and during the larviciding intervention, from March 2017 to November 2020. The microbial larvicide VectoMax G was applied once every 2 weeks in the intervention areas. Adult mosquitoes were collected using CDC light traps in both intervention and non-intervention areas and compared between arms. Globally, larviciding intervention was associated with 69% reduction in aquatic habitats with Culex larvae and 36.65% reduction of adult Culex densities in houses. Adult Culex densities were reduced both indoors (35.26%) and outdoors (42.37%). No change in the composition of Culex species was recorded. The study suggests a high impact of larviciding on Culex mosquito species distribution. The impact of the intervention can be improved if typical Culex breeding habitats including pit latrines are targeted

Knowledge, practices and perceptions of communities during a malaria larviciding randomized trial in the city of Yaoundé, Cameroon

Background Urban malaria is becoming a major public health concern in major cities in Cameroon. To improve malaria vector control, a pilot larviciding trial was conducted to assess its impact on mosquito density and malaria transmission intensity in Yaoundé. The present study investigated perceptions and practices of communities on malaria control during the larviciding trial implemented in Yaoundé. Methods Quantitative and qualitative data were collected in non-intervention and intervention areas. Quantitative data were collected during three cross-sectional surveys using a structured pre-tested questionnaire while qualitative data were obtained through interviews. A total of 26 in-depth interviews and eight focus group discussions with community members were performed. A binary logistic regression model was used to assess the perception of the community on larviciding impact on some malaria or bed nets use indicators. Results People living in intervention areas were 2.64 times more likely to know the mode of malaria transmission (95% CI: 1.82–3.84; p<0.001) and 1.3 time more likely to know mosquito breeding habitats (95% CI: 1.06–1.56; p = 0.009) compared to those living in non-intervention areas. In intervention areas, interviewee opinions on larviciding were generally good i.e. most interviewees reported having noticed a reduction in mosquito nuisance and malaria cases following larviciding implementation; whereas in non-intervention areas no report of reduction of mosquito nuisance was recorded. LLINs were regularly used by the population despite the implementation of larviciding treatments. There was high interest in larviciding program and demand for continuation, even if this needs the community involvement. Conclusion The larviciding program in the city of Yaoundé did not negatively affected community members’ behaviour and practices concerning the use of treated nets. The study indicated the acceptance of larviciding program by the population. This positive environment could favour the implementation of future antilarval control activities in the city of Yaoundé

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