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Effect of Temperature and Rainfall Variations on Coffee Berry
Disease (Colletotrichum kahawae)
J.A. MOUEN BEDIMO*, D. BIEYSSE, C. CILAS AND J.L. NOTTÉGHEM Institute of Agricultural Research for Development (IRAD), Foumbot Multipurpose Station,
P.O.Box 665 Bafoussam, Cameroon. *E-mail: josephmouen@yahoo.fr INTRODUCTION
Arabica coffee production in Africa is highly affected by Coffee Berry Disease (CBD), due to Colletotrichum kahawae. This disease is specific to green berries and leads to 60-80%harvest losses under conditions favourable to development of the pathogen. Agricultural practices coupled with chemical control with 8 to 12 annual fungicide applications are known to be very effective against CBD, especially in high altitude regions (> 1600 m) where farms sustaining the most damage are found. Temperature and rainfall may be very decisive for development of CBD epidemics. Consequently, an epidemiological study was conducted on smallholders’ farms in Cameroon, to assess disease development dependence upon variations of these factors.
Figure 1. Heavy CBD attack on a Arabica coffee branch. METHODOLOGY
An experiment was carried out in the smallholder’s plantation consisted in coffee trees of Coffea arabica cv. Jamaïca, located at Santa (05°47.190N, 10°09.672E, and 1750 m above sea level), a region with high CBD incidence in North-West Cameroon. 100 vigorous, high-yielding coffee trees were chosen randomly in that plantation for disease monitoring over two successive years (2004-2005). Weekly observations were made on three plagiotropic branches at different positions in each coffee tree canopy (top, middle, and bottom). They consisted in counting (a) the total number of berries, (b) the number of new infected berries, marking them with small labels to avoid counting again in subsequent assessments, and (c) the number of old infected berries.
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Daily climatic data (rainfall, minimum and maximum temperatures) were recorded every year. Weekly climatic parameters obtained from these date were used for cross correlations with disease severity.
Figure 2. Diseased berries labelled during observations. RESULTS
Cross-correlations between disease severity and climatic parameters recorded weekly over two successive years (2004-2005), showed a significant increase of disease severity depending on decreasing temperatures (minimum or maximum).
Figure 3. Correlogram of maximum temperatures with new infected berries (the blue histogram represents the disease severity rate and the red line, the signification level at 5%.
Shifting
of maximum temperature over time
in relation with the rate of
disease
severi
ty
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Figure 4. Changing of disease severity over time depending on maximum temperatures.
They also indicated a high variation of disease severity depending on the number of rainy days during berry growth. However, no significant correlation was found with the quantity of rainfall over the two years of observations.
Figure 5. Correlogram of the number of rainy days with new infected berries (the blue histogram represents the disease severity rate and the red line, the signification level at 5%.
Correlation level
Shifting
of th
e number of rainy days ove
r
time in relati
on with the ra
te of disease
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Figure 6. Changing of disease severity over time depending on the number of rainy days CONCLUSION
Temperatures and rainfall distribution appear to be the key climatic parameters that favour the development of CBD epidemics. The present results suggest that these parameters might be very useful for setting up predictive models enabling optimization of effective control of CBD in areas with high disease incidence.
