Methods for Measuring Crop Losses by Insects

Measurement of crop losses that occur within a range of pest insect population densities is fundamental for developing pest management programs. The dynamic and complex relationships between herbivore and host are affected by inherent insect fecundity, the phenology of the pest and crop, and the impact of beneficial organisms such as parasitoids, predators and entomopathogens. Assessments of crop losses are further complicated by soil moisture and nutrient availability that affect plants’ ability to compensate for insect injury. The major reason for quantifying crop yield and/or quality losses is to estimate the pest population density at which crop loss value equals the cost of applied control. This estimate must be precise enough to be meaningful yet sufficiently robust to be useful over range of dynamic field situations.

Several methods have been used to estimate the relationship between insect population density and plant yield response. These include observing naturally occurring...