An investigation to assess
the spatial structure and severity of Pseudocercospora leaf and fruit spot disease (PLFSD) on citrus trees
in cocoa-based agroforests was carried out in three contrasting ecological
zones in southern Cameroon, viz: 1) the humid forest zone, 2) the degraded
forest zone, and 3) the forest-savannah transition zone. Two main parameters
were investigated viz: 1) the spatial structure of cocoa based agroforests, and
2) the disease severity. In total, the spatial structure of 19 cocoa-based agroforests
was analysed using the Ripley K(r) function, meanwhile the collection of
epidemiological data that consisted of noting the presence of PLFSD spots on
leaves and fruits on 438 citrus trees was used to characterise the severity of
the disease. Results showed that, the spatial structure of citrus trees in
these agroforests investigated were regular in seven plots, random in nine, and
aggregated in three. Aggregated plots presented a significantly higher mean of
disease severity on leaves and fruits (28.55 and 30.37 respectively), as
compared to randomised (20.91
and 16.32 respectively) and regular plots (16.28 and 14.97 respectively), at
P-value < 0.05. These results suggest that the spatial structure of citrus
trees in the cocoa-based agroforests studied influences the severity of PFLSD.
Proper integrated control measures can therefore be initiated, leading to a
considerable reduction of the use of manufactured inputs, and thereby, the cost
of production of citrus fruits.
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