Devouring profit - International Coffee Organization

4.2 Estimation of a loss
function for CBB in India
According to Zadoks (1987) any reduction in quantity and/or quality of yield is called
“damage” which is equivalent to “crop loss”, expressed as reduction in revenue or
income per unit of yield (kg, pound, etc.). As population densities of harmful organisms
can be determined directly by counting (e.g. insects) or indirectly by injury assessment
(e.g. foliar pathogens), the loss function aims to equate losses to damage or
incidence measurements:
Where:
L= Loss
D= Damage
I= Incidence
In a study carried out in India, Prakasan (Central Coffee Research Station, 2001), made
an estimation of crop loss due to CBB. Crop loss was estimated at different levels of
infestation from 0% up to 100%. The study included loss in weight only, because the
internal coffee market in India does not have a clear standard of rules to penalize or
reward coffee depending on low or high quality. However the study is important from
the point of view of CBB-induced yield loss and the findings should be used to teach
the Indian coffee growers about the potential damage caused by CBB. Loss data from
this study is listed in Table 20.
Table 20. Loss due to CBB according to rising levels of infestation 13 .
% infestation Loss in Forlits per 1000
kg of green coffee
13 Study conducted by C.R. Prakasan. Central Coffee Research Institute, India 2001.
14 A forlit = 40 litres
Loss in Percentage
of green coffee
0 0 0
10 2.8 2.7
30 5.2 5.1
50 12.8 12.6
70 23.8 23.4
90 31.6 31.3
100 37.9 37.2
From this information a loss function was estimated (Duque, 2002), using as independent
variable the percentage of infestation caused by CBB and as dependent
variable the loss in percentage of green coffee. A quadratic loss model was obtained
(P < 0.0001; R 2 = 0.992). The main features of the model appear in Table 21.
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