To quantify the perceived severity of pest or disease, respondents
had to rank the selected photographs in descending order of the
damage caused. The respondents were then asked to estimate the
total damage to crop yields by all pests and diseases combined. Next,
they were given ten coins, representing the total damage they just
estimated, and they were asked to allocate these to the photographs.
The purpose of doing the ranking first was to make the coin allocation
easier and to check if it was done in a consistent manner. For
example, if a lower ranked photograph was given more coins than
respondents were asked if they wanted to change the ranking. The
ranking itself was not analyzed as the coin exercise was expected to
give more useful results because it made it possible to disaggregate
the total perceived damage to separate pests and diseases. Ten coins
might offer little discrimination between the various pests and
diseases, but such simplification was necessary given the highly
hypothetical character of the exercise and the low level of pest and
disease knowledge of the respondents. Using ten coins made it
conceptually easy for respondents as each coin represented a 10%
yield loss. Although most farmers were able to separate between
insect problems, they had considerable difficulty seeing the difference
between various bacterial, fungal and viral diseases. The fact
that many disease symptoms look alike is of course part of the
problem why it is so difficult for farmers to manage plant virus
diseases. If respondents could not distinguish between different
photographs, then they were allowed to group these in the ranking
and coins were allocated to the group of photographs rather than to
an individual photograph. The coins were then equally divided over
all photographs in the group.