La phaeoramulariose des agrumes au Cameroun due àPhaeoramularia angolensis : expression parasitaire à différentes altitudes

Abstract

Introduction. Citrus leaf and fruit spot due to Phaeoramularia angolensis [De Carvalho & Mendes] P.M. Kirk represents a serious production constraint in tropical Africa. Disease expression may vary greatly from one location to another. Materials and methods. Disease development was studied on young seedlings of grapefruit (Marsh cultivar) inoculated with a conidia suspension and transferred to eight locations at (80 to 1250) m elevation. Temperature (T) and relative humidity (RH) were recorded on the sites during the work. Results and discussion. Disease incidence increased with altitude. The Nyombe Station (80 m elevation, Taverage > 25°C with Tmax above 30°C and RHaverage < 80%, with RHmin often below 60%) was far less conducive to disease development than the rest of the locations, which experienced cooler and more humid climatic conditions (Tmin < 20°C and RHmin > 60%). Conclusion. This study provides preliminary information on characterization of regions that may be invaded by P. angolensis. The work should be pursued, including different ecological situations, to enable the mapping of the risk of this threat.

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

“…Given that shading favors climatic conditions for the development of certain citrus pathogenic fungi such as P. angolensis or many Phytophthora spp. (high relative humidity (>60%) and cool temperature conditions (<25°C)) [18,28,69]. It is assumed that within a plot, trees under shade would have a higher incidence of the disease than those in full sunlight.…”

“…Sorting deviations of up to 100% of the production can be recorded in the case of PLFSD, if no treatment measures are taken [27]. Concerning citrus scab, severe attacks on young C. volcameriana plants, for example in the nursery, result in their death [20,28]. CDP significantly limits citrus production in the plots where it is present [29][30][31][32][33][34].…”

Pest categorisation of Pseudocercospora angolensis

“…PFLS has been reported at altitudes between 80 and 1,800 m (Kuate et al, 2002;Ndo et al, 2010). In Ghana, Cameroon and Guinea, PFLS severity was greater at higher altitudes characterised by cooler (22-26°C) and more humid conditions (Kuate et al, 2002;Ndo et al, 2010;Diallo et al, 2011;Lawson et al, 2017). Field observations in Cameroon, Kenya, Ethiopia and Guinea indicated that infections by P. angolensis occurred mainly during the rainy seasons (Seif and Hillocks, 1993;Kuate et al, 1997;Yesuf, 2007;Diallo et al, 2011).…”

Altitude, tree species and soil type are the main factors influencing the severity of Phaeoramularia leaf and fruit spot disease of citrus in the humid zones of Cameroon

“…Studies conducted in Cameroon to assess the incidence of the disease at different seasons in the humid forest zone and in the highlands (Kuate and Fouré 1988;Kuate et al 1994Kuate et al , 1997 revealed that rainy seasons are conducive for disease development. Other studies have shown that leaf and fruit spot disease incidence increases with altitude and with cooler and more humid climatic conditions (Kuate et al 2002). Furthermore, a series of fungicides have been screened and recommended for the control of PLFSD (Seif and Hillocks 1999;Diallo 2003;Kuate 2003;Yesuf 2007).…”