Integrated Management Approach to Citrus Fungal Diseases by Optimizing Cocoa-Based Agroforests Structural Characteristics

The health and productivity of citrus are generally jeopardized by a host of diseases, for which the environmental conditions of the cropping system are critical drivers. Several studies conducted on various diseases of perennial crops have shown the involvement of the structural futures of the cocoa-based agroforestry system (CBAFS) in the spread of pathogens and the epidemics development. This chapter highlights the effect of the CBAFS’s structural characteristics on the intensity of three citrus diseases in the humid forest zones of Cameroon. The involvement of CBAFS structural characteristics in diseases regulation is demonstrated. In particular, the spatial structure of citrus in agroforests shows an effect on the spread of diseases. Moreover, distribution of citrus in the CBAFS, with minimum spacing of 12 m between citrus trees, limits the damage caused by Pseudocercospora leaf and fruit spot disease (PLFSD) and citrus diseases caused by Phytophthora (CDP). Dense shading helps to minimize the intensity of diseases such as CDP and PLFSD and Citrus scab disease. This work may make it possible to contribute to the development of an integrated management tool for citrus diseases in an associated crop context

Farmer’s Perception of Associates Non-Cocoa Tree’s Leaf Litterfall Fertilizing Potential in Cocoa-Based Agroforestry System

Investigations to assess farmer’s perceptions on the fertilizing potential of associated trees species in cocoa agroforest of degraded forest ecology were carried out in southern Cameroon. The perception of the farmers was based on the ability of the trees to maintain or improve soil fertility of their farms. The verification of these perceptions was done through an evaluation of litter fall biomass nutrient content (N, P, K, Ca and Mg) of selected trees. The top 5 associates trees ranked by farmers was: Milicia excelsa, Ceiba pentandra, Ficus mucuso, Asltonia boonei, Terminalia superba. The chemical analysis of the leaf litter from the different tree species revealed a significant different between their chemical components. N appeared to have the highest concentrations varying from 2.82 to 5.57% with a mean value of 4.25 ± 1.065%, P had the lowest concentrations typically around 0.001%. The top 5 tree species based on the chemical analysis ranking were: C. pentandra, M. excelsa, Eribroma oblungum, Alstonia boonei, Zanthoxylum heitzi. Farmer’s perceptions thou holistic, are not completely different from scientific finding. Therefore, they should be taken in consideration in management plans for cocoa- based systems in order to enhance their ecological and economic performance

Microclimatic variations in cocoa-based agroforestry systems affect citrus Phytophthora foot rot disease intensity

International audiencePathogen dynamics in agroforestry systems result from several mechanisms and interactions whose independent effects are difficult to delineate. In recent decades, it has been shown that shade, as a structural feature in agroforestry systems, influences the spread of pathogens through its physical and biological effects. In Cameroon, citrus trees are mainly grown in cocoa-based agroforestry systems (CBAS), and are threatened by a variety of pathogens. This study examines how shading modifies the microclimate in the local environment of citrus trees in CBAS, and the resulting effect on citrus foot rot disease (PFRD). The study was conducted in the Cameroon agroecological zone with bimodal rainfall, where a network of 20 CBAS plots was established. Primary cartographic and structural data were used to perform static simulations with cumulative shadow overlay in ShadeMotion software. A soil sensor was used to quantify the microclimate by measuring air temperature and relative humidity above and in the soil, as well as soil pH. Relationships between shade rate, microclimatic variables, and PFRD intensity were investigated. Results showed that the effect of temperature on PFRD was independent of shade rate. A dependency relationship between relative humidity above and in the soil and PFRD according to shade rate was found. Indeed, a positive correlation of PFRD with relative humidity was observed for citrus trees located in full sunlight, while a negative correlation was observed for citrus trees located under dense and light shade. Optimization of structural characteristics of CBAS would allow ecological management of PFRD and reduction in the use of chemical pesticides