Date: 3/31/99

Time: 10:05

Type: Symposium

Number: 234

Insurance to encourage adoption of IPM: the case of corn rootworm

*P. Mitchell, Department of Economics, Iowa State University, Ames, IA 50011
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Previous evaluations of corn rootworm scouting and the use of root ratings to assess yield losses have traditionally relied on expected values (averages) or ratios of correct and incorrect predictions (frequencies) (e.g. Stamm et al. 1985, Foster et al. 1986, Gray and Steffey 1998). An alternative method of analysis utilizes the theory of decision making under uncertainty to fully incorporate the stochastic nature of the scouting process and the evaluation of yield losses by root ratings. This method requires the estimation of conditional probability density functions that describe the distribution of root ratings given a scouting observation and the distribution of yield losses given an observed root rating. For the analysis presented here, these density functions are estimated using data from two sources: (1) a stochastic population model created by linking the population model developed by Naranjo and Sawyer (1989) with a stochastic weather generator and (2) data on yield loss, lodging and root ratings from artificial infestation experiments conducted near Brookings, SD (Riedell et al. 1996). These conditional density functions are then used to derive the optimal economic injury level (EIL) for adult scouting and to determine how this EIL changes under different decision rules and to isolate how the different sources of uncertainty influence this EIL. These conditional density functions are also used to evaluate the potential for insurance to reduce the uncertainty faced when using scouting and thus encourage the adoption of scouting. Lastly, how such insurance affects the EIL and overall insecticide use is evaluated.

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