Defining and Measuring Economic Threshold Levels

Abstract

INTRODUCTIONThe concept of pest thresholds was fmt presented in 1959 by Stem, Smith ,van den Bosch and Hagen as a means to detennine a more rational level of pesticide use. Their development of the concept was in response to what they considered as an excessive and inappropriate use of pesticides. Similar concerns today have renewed the interest in thresholds. Public concerns arise from the possible detrimental environmental and human health impacts associated with the use of synthetic organic compounds while producer concerns relate to the ever increasing costs of pesticides and the growing levels of pest resistance due to extensive pesticide use. Thresholds are a unique management tool which may help alleviate the concerns of all participants since it seeks to both reduce pesticide applications and enhance producer profitability.Corresponding with the increase in threshold applications has been an increase in related terminology such as economic threshold, economic injury level, and action threshold. The terns, although distinct, are often used inter-changeably.

Economic decision rules for postemergence herbicide control of barnyardgrass (Echinochloa crus-galli) in corn (Zea mays)

“…The following economic model proposed by Weersink et al (1991) and modified by Dieleman et al (1996) was used to develop economic decision rules for barnyardgrass control in corn:…”

“…Expected profits are influenced by crop yield that is affected directly by weed interference and indirectly by control provided by postemergence herbicides (Dieleman et al 1996). Therefore, to manage a weed population and maximize profits, two distinct components need to be integrated: the damage function that describes the impact of a weed population on potential crop yield and the control function that describes the affect of postemergence herbicides on a weed population (Moffitt 1988;Pannell 1990a;Weersink et al 1991). Both functions must be calculated, and the information obtained can be incorporated into decision rules for weed control recommendations.…”

Alternative specifications and extensions of the economic threshold concept and the control of livestock pests

“…This point that has been observed by Hall and Moffitt (1985), Moffitt (1986), Plant (1986), Weersink et al (1991), and Higley and Pedigo (1996).…”

“…The dominance of the Stern et al (1959) approach has been explained by Moffitt (1986), Plant (1986) and Weersink et al (1991), who state that the definition simply highlights differences in attitudes between entomologists and economists. This appears unsatisfactory as many economists also continue to define economic thresholds in terms of the Stern et al (1959) concept, for example .…”

Managing Populations with Unimodal Dynamics

“…Threshold concepts provide guidelines to reduce the total amount of pesticides applied, while maintaining or improving farm profitability. More details on economic threshold can be found in [11].…”