Abstract:

Sorne 74 years later, the question is equally re 1 evant .
Quantification of yield losses due to specific causes is essential to
the determination of the economic importance of pests (The word pest
is used here to cover plant diseases, insect pests, nematodes and
weeds) . The relative economic importance of a pest should be
considered in setting research priorities and allocating resources.
Establishing the relationship between pest incidence at different
stages of development and subsequent yield loss is needed for decision
making on alternative pest control strategies. Crop 10ss assessment
has received considerable attention (James, 1974; Walker, 1983; Teng,
1987), but the quantification of the effects of insect pests and
diseases on seed yield of beans (Phaseolus vulgaris L.) appears to have
been neglected. Scientists have opted instead to invest resources on
studies of the bio10gy and control of pests that are vaguely perceived
as causing major losses of yield.