Economic thresholds

The primary goals of 1PM are (/) to determine how the life system of the pest needs to be modified to reduce the numbers to tolerable levels, ie, below the economic threshold (2) to apply biological knowledge and current technology to achieve the desired modification, ie, appHed ecology and (2) to devise procedures for pest control compatible with economic and environmental control aspects, ie, economic and social acceptance (9). 

The development of criteria for sound economic thresholds in order to determine when-to-treat is highly complex. Establishing the guidelines for an effective economic threshold for a single pest must take into account the following interacting factors 1) density of the pest, 2) densities of its parasites and predators,... 

Redox-type reactions show by far the worst performance in meeting the golden atom economical threshold. Three reductions meet this criterion with (AE)min values of 1 hydrogenation of olefins using the Lindlar catalyst (1952), Noyori stereoselective hydrogenation reaction (1985), and Zincke disulphide cleavage reaction (1911) whereas, oxidations... 

Bor YJ (1997) Some evidence of the existence of dynamic economic thresholds. Agric Sys... 

Sikkema, P., Van Eerd, L.L., Vyn, R.J. and Weaver, S. (2007) A comparison of reduced rate and economic threshold approaches to weed management in a com—soybean rotation. Weed Technol, 21, 647-655. 

Whenever applied, IPM practices have consistendy resulted in decreases in insecticide applications of 50 to 90% over conventional spray programs. By encouraging natural enemies, IPM practices markedly decrease the rigor of natural selection by pesticides that is responsible for resistance. Natural enemy preservation also prevents the great fluctuations and suiges in insect pest populations observed after the injudicious use of broad-spectrum insecticides. Under the IPM concept, insecticides are generally used when other practices are inadequate and the pest population reaches the economic threshold. In order to make the IPM concept effective, insecticides must be used as selectively as possible, with minimal disturbance to all other elements of the ecosystem. Thus IPM practices are essentially blueprints for the proper use of insecticides in insect pest control. 

Jones, R.E. and R.W. Medd (2000). Economic thresholds and long-term approaches to weed population management. Weed Technol., 14 337-350. 

L.G. Higley and L.P. Pedigo, eds., Economic Thresholds for Integrated Pest Management, University of Nebraska Press, Lincoln, NE, 1996. 

This discrepancy can be attributed to the much lower recoveries during 1987 of parent terbufos (data not shown), which is more toxic than its metabolites (27-28). Root damage ratings were below the economic threshold of 3.0 in all treatments, and yields did not differ significantly from one another nor from the untreated check. 

Energy saving due to variable speed solution depends a lot from thermal loads if at maximum load performances are similar to fixed speed solutions, the main benefit appears at reduced loads. The economical threshold between brushless and asynchronous motors is today around 150 watts under this limit brushless technology is competitive in terms of costs to asynchronous motors above such limits asynchronous motors are used and the motor speed could be changed by inverters. 

Black, I. D. and Dyson, C. D. (1993). An economic threshold model for spraying herbicides in cereals. Weed Research, 33,279-90. 

Use appropriate local economic thresholds and spray intervals... 

Fungicides are used when it is considered that a speeific disease has developed to a point (the economic threshold) which will actually cause a loss of yield that will pay for the eost of treatment and application. There are now many established thresholds for application of fungicides. Often the rate of the fungicide applied will be adjusted depending on the disease risk and variety resistance. This is called an appropriate dose rate. Some computerised models have been or are being developed to aid decision making. 

Economic thresholds have been calculated for many pests and are an important tool in IPM. An eeonomie threshold is the population of pests which if controlled will give a yield return that will pay for the cost of pesticide and application. Where available these have been ineluded in Table 7.1. Another important tool to help with deeision making for appheation of a pesticide is the use of forecasts of pest populations. A number of oiganisations run forecasting services for some important crop pests sueh as eutworm, pea moth and carrot fly. These forecasts combined with erop monitoring and use of traps including pheromone traps can all help to reduee the requirement for pestieide applications. 

Yearian and Young (41) point out that in short term comparisons most viruses do not compare favorably with chemical insecticides, from either an economic or effectiveness standpoint, in terms of crop protection or productivity. However, insect viruses are ideally suited for IPM systems. Their host specificity limits their direct effects to target pests or closely related species. This minimizes the chances of pest population resurgence or release of secondary pests as a result of reduction in parasitoids and predators, as often occurs with the use of broad-spectrum insecticides. In IPM systems, where the objective is maintenance of pest populations below the economic threshold, not total elimination of the pest, the efficacy of many NPVs may be quite adequate. The biggest impediment to incorporation of insect viruses into IPM systems is the lack of an adequate supply of formulated virus (1,16,41). 

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