Foreword - CCS HAU, Hisar

METHODS OF ESTIMATING CROP LOSSES
DUE TO INSECT-PESTS
Pala Ram
Department of Entomology
CCS Haryana Agricultural University, Hisar
Three groups of people namely, farmers, industry and the government agencies, need
information on insect pest loss. The farmers need the information to decide whether or not
to use control measures, industry for profit governing and decision making, and the government
for general welfare of the whole community. The evaluation of pest damage is helpful in pest
management in several ways. It helps in defining the economic status of a pest species, in
establishing economic threshold and economic injury levels, in estimating effectiveness of
control measures, in allocating funds for research and extension in plant protection, in
evaluation of varieties, and in knowing relative importance of different pests. Pest damage
assessment involves, i) discovery of damage, ii) determination of pest identity and first
appraisal of its seriousness, iii) determination of the effect on the plant and on overall
production, involving some research on the relation between pest abundance and effect,
and; iv) measurement of its local and national effect on production and management with
some estimate in economic terms (Young, 1975).
1. Pest population and damage relationships :
One of the fundamental concepts of integrated pest management is that each pest species
has a definable relationship in terms of damage to the plant or animal host that it attacks.
This relationship is often referred to as the damage curve which is determined relative to
yield loss. Two types of relationships can generally occur between pest attack and yield.
Type one relationship (Fig. 1) occurs where the pest is a vector of disease, or where it
attacks the grain late in the crop, or where crop tolerance and compensation is limited. Type
two relationship (Fig. 2) occurs where the pest attacks at the vegetative stage of the crop
and the crop’s innate tolerance (e.g. more tillers than it can take through to maturity) or
compensation mechanisms result in no loss of yield occurring, up to a threshold level of
pest attack. Yields at a wide range of infestations are needed, to describe the full relationship
and to know how yield is affected at low and high infestation rates. There are several methods
for obtaining these figures (Chiarappa, 1971; Pradhan, 1964; Walker, 1983).
Fig. 1 Fig. 2
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